Block A-56Galveston Area
1. PLAN OF BORINGS

INote: Roman numerals refer to the stratigraphy as I
ENTERPRISE FIELD SERVICES, LLC
ENTERPRISE FIELD SERVICES, LLC
SOIL BORINGS
ENTERPRISE FIELD SERVICES, LLC

EXECUTIVE SUMMARY

Fugro-McCleliand Marine Geosciences, Inc. (FMMG) performed geotechnical investigations for

proposed offshore structures across the Texas Offshore Port System (TOPS), located

in Block A-56, of the

Galveston Area

in the Gulf of Mexico. The primary purpose of the investigation was to obtain soil data to

develop foundation design recommendations for the Single Point Mooring (SPM) facility, designated

SPM #1 and SPM #2, of the proposed TOPS facility in Block A-56:

The field investigation was performed on June 30, July 2 and

3, 2008, from the RN

Seaprobe.

The

soil conditions were determined by performing a total

of four exploratory borings, with one boring at a

selected anchor leg location and one boring

at the proposed Pipe Line End Termination (PLET) location at

each

of the SPM locations. These borings were drilled to a penetration of 131-ft below mudline. The water

depths ranged from 117

to 121 ft at the soil boring locations across Block A-56. An exploratory boring was

also drilled at the Offshore Terminal location

in Block A-56 and is presented in FMMG's Report

No. 0201-6502.

Field and laboratory tests were conducted to determine the pertinent index

and engineering

properties of the soils encountered. Engineering analyses were then performed to develop the required

design information. For the purposes

of discussion and presentation, "driven pipe pile" is used in this report

to represent foundation piles, caissons and conductors, unless otherwise specified.

This report presents axial and lateral design data for 24-in.-diameter driven pipe piles

at the two

PLET locations and 42-in.-diameter driven pipe piles for the two anchor leg locations. This data was

developed using methods and recommendations presented

in API RP 2A (2000). Pile penetrations should

be based on allowable capacities with appropriate safety

or load resistance factors.

The ultimate seafloor bearing capacity for mud mat and tubular members bearing

on the seafloor at

the PLET locations were computed using general bearing capacity methods and recommendations

presented

in API RP 2A-WSD (2000). Seafloor bearing capacity equations are presented in the appropriate

sections

of the main text of this report to facilitate design of the PLET foundations, if required.

A review of the geotechnical data indicates that the soil stratigraphy

in the top 34-ft penetration is

variable across the block, alluding to channel features across the investigation area. The exploratory boring

revealed clay layers interbedded with silt, sandy silt, or silty fine sand layers of varying thickness within

approximately the upper 34-ft of sediments. The underlying soils to at least 131-ft penetration consists

firm to stiff lean clay to clay, with a shear strength profile that increases with depth. Soil variability is

demonstrated

in a comparison of the log of boring and test results presented in Section 3 with the

subbottom geophysical data at each

of the boring locations. The geophysical survey was performed by

Fugro Geoservices, Inc. (FGSI) of Lafayette,

LA and is presented in detail in FGSI Report No. 2407-1298.

The information revealed

in this investigation suggests that the piles can be driven with a properly

sized hammer to a sufficient depth

in the above stratigraphy to achieve the desired pile capacity.

Supplementary installation procedures,

if necessary, should be applied under close engineering supervision

to determine the impact of the procedures on pile capacity.

Report No. 0201-6503

1-1

------------------_.---.

GENERAL PROJECT INFORMATION

2.1 INTRODUCTION

2.1.1

Purpose and

Scope

Fugro-McClelland Marine Geosciences, Inc. (FMMG) performed a geotechnical investigation

program to investigate soil conditions at the proposed Single Point Mooring (SPM) facility locations

in the

Texas Offshore Port System (TOPS), located

in Block A-56, of the Galveston Area in the Gulf of Mexico.

The primary purpose of the investigation was to obtain data to develop foundation design recommendations

for anchor leg and Pipe Line End Termination (PLET) locations at the facility sites designated

as SPM #1

and SPM #2. To accomplish this objective, the following tasks were performed:

(1) Four soil borings, with one boring at a selected anchor leg location and one boring

at the

proposed PLET location at each

of the SPM locations, were drilled to 131-ft penetration

below seafloor

to explore the subsurface stratigraphy and obtain soil samples for laboratory

testing;

(2) Field and laboratory tests were conducted to evaluate pertinent index and engineering

properties of the foundation materials;

(3) A comparison of the geotechnical and geophysical data was performed to investigate soil

variability

to help in selecting soil parameters; and

(4) Engineering analyses were performed

to develop pile design information, seafloor bearing

capacity, and a general pile installation assessment.

Enterprise Field Services, LLC specified the boring locations and designations. A plan

of borings

presenting the relative positions

of the four borings is presented on Plate 2-1.

2.1.2

Report Format

The results

of the geotechnical investigations completed for the TOPS campaign are presented in

the following reports:

0201-6500:

0201-6501:

0201-6502:

0201-6503:

0201-6504:

0201-6505:

Offshore Terminal Location, Block A-36, Galveston Area;

SPM

#1 and SPM #2 PLET and Anchor Leg locations, Block A-36, Galveston Area;

Offshore Terminal Location, Block A-56, Galveston Area;

SPM

#1 and SPM #2 PLET and Anchor Leg locations, Block A-56, Galveston Area

(this report);

Offshore Terminal Location, Block A-59, Galveston Area; and

SPM

#1 and SPM #2 PLET and Anchor Leg locations, Block A-59, Galveston Area.

The initial section

of this report contains brief descriptions of the field and laboratory phases of the

study, including a general description

of the soil stratigraphy and a summary of the findings of the

geophysical survey across Block A-56.

Also included

in this section is a general discussion of the

engineering methods, axial and lateral pile design, used at all the boring locations. Section 3 presents a

detailed description

of the site-specific conditions encountered at each boring location followed by brief

discussions of axial pile design, lateral pile analyses, seafloor bearing capacity, and pile installation

recommendations. Discussions

of the field and laboratory investigations are presented in Appendix A.

Report No. 0201-6503

2-1

-@---------------------------------

Appendix B contains discussions of analytical procedures used in our engineering analyses. Appendix C

contains a positioning report by Fugro Chance, Inc., of Lafayette, Louisiana.

For the purposes of discussion and presentation, "driven pipe pile" is used in this report to represent

foundation piles, caissons and conductors, unless otherwise specified.

2.2 FIELD AND LABORATORY INVESTIGATIONS

The field investigation was performed

on June 3D, July 2 and 3, 2008, from the RN

Seaprobe.

The

soil conditions were determined by performing four exploratory borings, two at each SPM location with one

boring at a selected anchor leg location, and one boring at the proposed PLET location. Enterprise Field

Services selected the boring locations. These borings were drilled

to a penetration of 131-ft below mudline.

The water depths

at the boring locations ranged from 117 to 121 ft. A chronological summary of field

operations

is presented in Appendix A.

2.2.1

Exploratory

Borings

FMMG personnel drilled the soil borings with a DMX drill rig positioned over the centerwell of the

Seaprobe.

The vessel was anchored at the boring location by a 4-point mooring system.

Soil

conditions at the site were explored by drilling a group of four soil borings to 131-ft penetration below the

seafloor. The final coordinates for the boring locations are presented in Table 2-1. A plan of borings within

Block A-56, of the Galveston Area

is presented on Plate 2-1. Fugro Chance, Inc., of Lafayette, Louisiana,

conducted surveying utilizing STARFIX and DGPS,

and performed a 360-degree scanning sonar survey at

each of the boring locations. The positioning report, prepared by Fugro Chance, is presented

in Appendix

C. The scanning sonar reports are available from Fugro Chance upon request.

FMMG

Boring

Designation

SPM#1 PLET

SPM

#1 ANCHOR

LEG #2

SPM#2 PLET

SPM #2 ANCHOR

LEG

Table 2-1: Final Boring Coordinates

(Texas South Central Zone Coordinates)

Fugro Chance

Proposed Boring

Final Boring

Boring

Coordinates

Designation

Core 3

3,258,627.75 ft

3,258,639 ft

252,334.60 ft

252,312 ft

Core 1

3,257,224.19 ft

3,257,199 ft

251,897.66 ft

251,890 ft

Core 4

3,265,632.42 ft

3,265,650 ft

256,177.08 ft

256,155 ft

Core 2

3,266,735.50 ft

3,266,759 ft

257,148.73 ft

257,169 ft

Boring

Termination

Depth

(tt)

131

Samples were obtained through 5.0-in.-OD, 4.5-in.-IF drill pipe at all the locations. Samples were

generally spaced at 3-ft intervals to 20-ft penetration, at 5-ft intervals to 68-ft penetration, and at 10-ft

intervals thereafter to the final boring depth at all the locations. The drilling and sampling techniques used

to complete this boring are explained

in detail in Appendix A.

Report No. 0201-6503

2-2

(

---.---------

Two water depths were measured at each boring location using a seafloor sensor seated in the drill

bit. The water depth measurements are tabulated

in Table 2-2. The water depth measurements are

intended for the purpose

of the geotechnical investigation only, and are not corrected for tidal or other

variations.

If utilized for other purposes, the water depth measurement should be adjusted to account for

meteorological tide and datum corrections. The water depths measuring procedures are explained

in detail

in Appendix B.

Table 2-2: Measured Water Depths

Boring

Water Depth

Time and Date

Supplemental

Time and Date

Designation

(tt)

of Measurement

Water Depth

of Measurement

Jft)

SPM #1 PLET

118

2125 hours on

119

0245 hours on

July 2,2008

July 3,2008

SPM #1 ANCHOR

121

0650 hours on

121

1105 hours on

LEG #2

July 3,2008

SPM#2 PLET

118

1205 hours on

117

1725 hours on

July

2,2008

July 2,2008

SPM #2 ANCHOR

117

0345 hours on

117

0945 hours

LEG #6

June 30, 2008

June

30, 2008

2.2.2

Field and

Laboratory Tests

The soil testing program was designed to evaluate pertinent index and engineering properties of the

foundation soils. During the field operation, all samples were extruded from the sampler and classified by

the soil technician or field engineer.

Unit weight, Torvane, pocket penetrometer, miniature vane and

unconsolidated-undrained triaxial compression tests were performed

in the field on selected cohesive

samples. All of the samples were shipped to Fugro's Houston laboratory where Atterberg limit tests, water

content tests, and grain-size analyses,

as well as additional density tests, unconsolidated-undrained triaxial

compression tests, and miniature vane tests, were performed.

A description of relevant laboratory procedures is provided

in Appendix A.

The strength and

classification test results are presented graphically

on the Logs of Boring and Test Results in Section 3.

Grain-size distribution curves from sieve-analysis and stress-strain curves from triaxial compression tests

are presented

in Appendix A.

2.3 GENERAL SOIL CONDITIONS

2.3.1

Soil Stratigraphy

The soil stratigraphy at each of the boring locations disclosed by the field and laboratory

investigations is presented

in Section 3. The soil stratigraphy is based on the classification of soil samples

recovered from the boring and observations made during drilling operations

.. Detailed soil descriptions, for

each location, that include textural variations and inclusions are noted

on the respective boring log

presented

in Section 3. A key to the terms and symbols used on the boring log is presented on Plate 2-2.

Report No. 0201.6503

2-3

--------.--~-------------------------------------

The Roman numeral representing each stratum is also shown on the respective boring log and on relevant

plates.

In general, the exploratory borings revealed stratified cohesive and granular soil profiles with clay

layers interbedded with silt, sandy silt, or silty fine sand layers

of varying thickness, within approximately the

upper 34 ft of sediments. Alternating clay and silty fine sand layers were also encountered at the Offshore

Terminal boring location

in Block A-59 (FMMG Report No. 0201-6502) to a depth of about 46-ft penetration.

The soil below the interlayered zone consists predominately of firm

to stiff clay with a shear strength profile

that increases

with increasing depth.

2.3.2 Interpretation

of Soil Properties

The shear strength and submerged unit weight profiles best represent the assembled test results

plotted

on the boring logs are shown on the respective "Design Strength Parameters" and "Design

Submerged Unit

Weighf plots in Section 3. These profiles were used in the engineering analyses.

In developing the shear strength profile for the cohesive soils, undrained shear strength test results

from miniature vane and unconsolidated-undrained triaxial compression tests were analyzed. The selection

of shear strength profiles for clay soils and the effects

of the type of sampling procedure on the profiles are

discussed by Dennis and Olson (1983) and Quiros, et

al. (1983). Strength parameters for granular soils

were selected based

on their gradation and relative density estimated from sampler blow count information.

The submerged unit weight profile was developed from actual density measurements and calculated unit

weight values based on sample moisture content and the assumption of 100 percent sample saturation.

The

recommendations for foundation design and installation were developed with the

assumption that the soil conditions revealed by the borings are continuous throughout the general

area

of the proposed foundation structure. Consideration of possible stratigraphic changes, faulting, or

geologic conditions which may influence foundation design were beyond the scope of this investigation.

Variations in soil

conditions may become evident during PLET or pile installation. If variations are

found, a re-evaluation of the recommendations

in this report may be necessary. We recommend that

additional soil borings be obtained

to determine the site-specific conditions within the immediate proximity of

the remaining proposed PLET and anchor locations.

2.4 GEOPHYSICAL SURVEY SUMMARY

2.4.1

Introduction

The purpose of this section is to briefly summarize the results and findings of the high-resolution

geophysical survey conducted

in the area encompassing Block A-56 in the Galveston Area as related to the

proposed

SPM locations. A map indicating the subbottom profiler data lines is presented in Plate 2-3, with

the geophysical lines used for interpretation of the highlighted soil borings. Section 3 contains cross-section

plots

of integrated data that compares the soil stratigraphy from the borings and geophysical data within the

immediate vicinity of each boring. A detailed assessment

of the seafloor and shallow geological conditions

in Block A-56 is presented in the geophysical report, FGSI Report No. 2407-1298 (Fugro Geoservices, Inc.,

2008).

2.4.2

Water Depth and Seafloor Topography

Water depths across the survey area range from -111 feet MLLW in the northwest corner to -122 feet

MLLW

in the southeast corner, with zero datum equal to Mean Lower Low Water. Bathymetric contours

within Block A-56 define a seafloor that slopes gently to the southeast at a gradient of 4 feet per mile

(0.04°).

I __

Report No. 0201-6503

2-4

2.4.3 Soil Conditions

Five geotechnical borings across the project field indicate an upper unit of very soft to stiff gray clay

to lean clay

to greenish gray stiff to hard clay up to 11 feet Below Mud Line (BML). Underlying these soils, a

gray lean clay to silty fine sand to silt unit extends to approximately 20 to 34 feet

BML. From 34 feet BML, a

firm to stiff lean clay

is present to approximately 131 feet BML. The borings represent the generalized soil

stratigraphy for the study area, but soil properties vary between boring locations

as revealed by the mapped

channel features

and acoustic voids indicated in the geophysical data.

2.4.4

Geological Features and Hazards

Biogenic gas accumulations "acoustic voids" attenuated the subbottom profiler records

in some

locations result

in reduced penetration and resolution within those areas. Extra caution should be exercised

in these areas.

However, the soil borings could be used as an indicator that shallow gas was not

encountered at the boring locations.

Channels buried 2 to

18 feet below the seafloor were noted throughout the survey area. Where

discernable, thalweg depths range from 18 to 113 feet BML. Areas

of channelized sediment represent

seafloor locations where geotechnical sediment properties may vary significantly. Site-specific soil borings

would be necessary

to determine the specific geotechnical properties of the sediments within the channels.

2.5 PILE DESIGN INFORMATION

The pile design information developed for this study inclUdes ultimate axial capacities, axial load-

pile movement data, and lateral soil reSistance-pile deflection (p-y) characteristics. The analytical methods

used to develop this information are presented briefly

in the following paragraphs and in more detail in

Appendix B.

2.5.1

Axial Pile Design

Method

of Analysis. The ultimate axial capacity of piles was computed using the static method of

analysis described in API RP 2A (2000). In this method, the ultimate compressive capacity of a pile for a

given penetration

is taken as the sum of the skin friction on the pile wall and the end bearing on the pile tip.

The weight

of the pile and soil plug is neglected in the computations. When computing the ultimate tensile

capacity

of piles, as well as the compressive capacity of conductors or caissons, the end bearing

component is also neglected.

Ultimate Axial Capacity. The unit skin friction and unit end bearing values are presented

Section 3, and were calculated using the API RP 2A methods described in Appendix B. These values were

used to calculate the ultimate axial compressive and tensile capacities for 24-in.-diameter pipe piles at the

PLET locations and 42-in.-diameter pipe piles at the anchor leg locations, driven to final penetration.

Capacity curves for driven pipe piles (conductors, caissons, anchor

and foundation piles) are also presented

in Section 3.

API RP 2A recommends that pile penetrations be selected using appropriate factors of safety or

pile resistance factors. For working stress design (WSD), API

RP 2A recommends that pile penetrations be

selected to provide factors

of safety of at least 2.0 with respect to normal operating loads and at least 1.5

with respect to maximum design storm loads. These factors

of safety should be applied to the design

compre.ssive and tensile loads. For load and resistance factor design (LRFD),

API RP 2A recommends pile

resistance factors

of 0.7 and 0.8 for operating and maximum storm loads, respectively. Also, appropriate

load factors

shOUld be used to determine operating and maximum storm loads for LRFD design.

Report No. 0201-6503

-@----_.

2.5

------------------------------

---~

Axial Load Transfer Data. Axial load-pile movement analyses are usually performed using a

computer solution based

on methods developed by Reese (1964) or Matlock, et al. (1976).

These

programs treat the pile as a series of discrete elements, represented by linear springs that are acted upon

by nonlinear springs representing the soil. The nonlinear soil springs are referred to as t-z and Q-z curves.

Input data for the program include: (1) pile dimensions and material properties, (2) load transfer

characteristics of the soil surrounding the pile, and (3) the pile tip load-tip movement relationship. The axial

load transfer curves were computed using procedures described

in API RP 2A and outlined in Appendix B.

The results of side load-side movement (t-z) and tip load-tip movement (Q-z) data for 24-in.-

diameter driven pipe piles at the PLET locations and 42-in.-diameter driven pipe piles at the anchor leg

locations are presented

in Section 3. The presented Q-z data should be used for foundation piles and

neglected for caissons and conductor design.

In developing the axial load transfer data in the cohesive

soils, a post-peak adhesion ratio of 0.90 was utilized.

2.5.2

Lateral Pile Design Data

The soil resistance-pile deflection (p-y) characteristics of the soils at the boring locations were

developed for individual 24-in.-diameter driven pipe piles at the PLET locations and 42-in.-diameter driven

pipe piles at the anchor leg locations. These data may be used

in lateral load analyses of driven piles,

conductors and caissons. The p-y data for cyclic loading were developed to 1

DO-It

penetration using the

procedures proposed by Matlock (1970) for soft clays

and O'Neill and Murchison (1983) for sands. These

procedures have been outlined

in API RP 2A and briefly explained in Appendix B. The stratigraphy and

parameters used

to develop the p-y data at the boring locations are presented in Section 3, together with

the p-y data for 24-in.-diameter driven pipe piles at the PLET locations and 42-in.-diameter driven pipe piles

at the anchor leg locations.

P-y values presented

at 100-ft penetration may be used for lateral load

analyses at greater depths.

2,5.3

Pile

Group Effects

API

RP 2A recommends that a pile spacing of less than eight pile diameters be evaluated for group

effects. This additional analysis can

be performed by FMMG when pile spacing has been selected.

2.5.4 Pile and Spud Can Interaction

When a spud can penetrates into the seafloor, a cylindrical zone of remolded and lower (degraded)

shear strength

is created. This zone of lower shear strength soil is called a spud can depression or

pockmark.

Piles located near existing,

or future, spud can depressions may have degraded axial and

lateral capacities.

This degradation

is a function of spud can and pile diameter, depth of spud can

penetration, distance between spud can depression and pile, and soil type. Consideration should also be

given to the effects

on pile performance associated with the potential use of jack-up rigs and the formation

of future spud can depressions. FMMG can perform this additional evaluation when the geometry and

layout of the piles and spud can depressions are determined.

2.6 SEAFLOOR BEARING CAPACITY

2.6.1

Bearing Capacity

Ultimate bearing capacity equations for the surface soils were taken from a design method

developed by Skempton (1951) based on undisturbed shear strength. Equations are presented

in Section 3

for each PLET boring location and can be used to determine the ultimate bearing capacity for horizontal

tubular members and mud mats resting

on the seaftoor.

Report No. 0201-6503

2-6

The ultimate bearing capacity of the near-seafloor soils is a function of the size and configuration of

the mud mats. A more detailed analysis of soil deformation and bearing capacity can be undertaken when

the actual configuration and loading conditions are determined.

For Working Stress Design (WSD), API

RP 2A recommends that a safety factor of at least 2.0 be

used with the ultimate bearing capacity determined from the above equations. For Load and Resistance

Factor Design (LRFD), a resistance factor of 0.67

is recommended. Also, an appropriate load factor should

be used to determine the jacket load in the LRFD design procedure. The ultimate bearing (load-carrying)

capacity of a horizontal tubular member or mud mat may be calculated

as the ultimate bearing capacity of

the soil multiplied by the base area of the mat or member. The equations for ultimate bearing capacity

presented above are based on static bearing capacity conditions. Significant vertical PLET velocities at the

time of its placement could cause large or uneven foundation settlements.

2.6.2 Degraded Bearing

Capacity

When a spud can penetrates into the seafloor, a cylindrical zone of remolded and lower (degraded)

shear strength

is created.

This zone of lower shear strength soil is called a spud can depression or

pockmark.

Mud mats located in, or near, existing depressions may have reduced (degraded) bearing

capacity. This degradation is a function of spudcan diameter, depth of penetration, distance between spud

can depression and mud mat, and soil type.

FMMG can perform this additional evaluation when the

geometry and layout

of the mud mats and' spudcan depressions have been determined.

2.7 PILE INSTALLATION CONSIDERATIONS

Pile driving problems are not expected at these boring sites.

The information

in this site

investigation suggests that the piles can likely be driven with a properly sized hammer to a sufficient depth

in the stratigraphies, presented in Section 3, to achieve the desired pile capacity. A pile drivability analysis

can be used to evaluate the proper hammer-pile system. Unfavorable soil conditions

or driving eqUipment

problems may prevent piles from being driven to the desired penetration. Interruptions

in driving should be

as short as possible to reduce set-up of the soil around the piles. Supplementary installation procedures, if

necessary, should be applied under close engineering supervision to determine the impact

of the

procedures

on pile capacity.

2.B SERVICE WARRANTY

The section entitled "Service Warranty" at the end

of Appendix B outlines the limitations and

constraints

of this report in terms of a range of considerations including, but not limited to, its purpose, its

scope, the data

on which it is based, its use by third parties, possible future changes in design procedures

and possible changes

in the conditions at the site with time. This section represents a clear description of

the constraints, which apply to all reports issued by FMMG. It should

be noted that the Service Warranty

does not

in any way supersede the terms and conditions of the contract between FMMG and the Client.

Report No. 0201-6503

2-7

-@------~-----------------

..!!i

, i!i

x =

3,256,400ft

x =

3,261,400ft

x =

3,266,400ft

262,500 ft

Block A-56

Galveston Area

257,500 ft

..........

Offshore

•

Terminal

Y =

252,500

I SPM #1 PLET \

SPM #1

Anch~

Leg #2£

1,470 ftl

............

Y =

247,500 ft

Projection: Texas South Central Zone Coordinates

PLAN OF BORINGS

SPMJRAnchof Leg #6

......

...

SPM #2 PLET \

1,470ft~

....

.... _ ....

Texas Offshore Port System

Block A-56, Galveston Area

_@HeportNo. 0201-6503

PLATE

2-1

TERMS AND SYMBOLS USED ON BORING LOG

SOIL TYPES

SAMPLER TYPES

[tnd

Siit

~Clay

~GraVel

c:lJDebriS

~Llner

~In

Situ

.....

••

6.6.'1

•

~Thin-

Walled

Test

Tube

[j]Silly

mSandY

~SandY

~peator

9,.V"

Coral

. Sand

. Silt

. Clay

Highly

•

Organic

••

~Piston

~Clayey

mClayey

Silly

Rock

~Shell

~ROCk

~NO

•

Sand

Silt

Clay

Core

Recovery

SOIL GRAIN SIZE

u.s. STANDARD SIEVE

314"

200

COBBLES

GRAVEL

SAND

SILT

CLAY

COARSE

FINE

COARSE

MEDIUM

FINE

152

76.2

19.1

4.76

2.00

0.420

0.074

0,002

SOil GRAIN SIZE IN MILLIMETERS

STRENGTH OF COHESIVE SOILS(1)

Undrained

DENSITY OF GRANULAR SOILS

2,3)

Consistency

Very Soft..................................................

Soft............................................................

Finn...........................................................

Shear Strength,

Kips Per Sq Ft

Descriptive

Term

Very Loose.................................................

loose..............................................................

Medium Dense.................................................

'"'Relative

Density.

less than 15

15 to 35

to 65

StilL.........................................................

Very Stiff....................................................

Hard.....................................................

less Ihan 0.25

0.25 to 0.50

0.50 to 1.00

1.00

to 2.00

2.00

to 4.00

greater than 4.00

Dense.............................................................

65 to 85

Very Dense............................................

greater than 85

*Estimated from sampler driving record

SOIL STRUCTURE(1)

Slickensided..........................

Having planes of weakness lhal appear slick and glossy. The degree of slickensided ness depends

upon the spacing

of slickensides and the ease of breaking along these planes.

Fissured...............................:

Containing shrinkage

or relief cracks, often filled with fine sand or silt, usually more or less vertical.

Pocket............ ...................... Inclusion

of material of different texture that is smaller than the diameter of the sample.

Parting..................................

inclusion less than

1/8

inch thick extending through the sample.

Seam....................................

Inclusion

1/8

inch to 3 inches thick extending through the sample.

Layer....................................

Inclusion greater than 3 inches thick extending through the sample.

Laminated.............................

Soil

sample composed of alternating partings or seams of different soil types.

Interlayered...........................

Soil sample composed

of alternating layers of different soil types.

Intermixed.............................

Soil

sample composed of pockets of different soil types and layered or laminated structure is not

evident.

Calcareous............................

REFERENCES:

(1) ASTM D 2488

(2) ASCE Manual 56 (1976)

(3) ASTM D 2049

Having appreciable quantities of carbonate.

Information on each boring log is a compilation

of subsurface conditions and soil or rock

classifications obtained from the field

as well as from laboratory testing of samples. Strata have been

Interpreted by commonly accepted procedures.

The stratum lines on the log may be transitional and

approximate in nature. Water level measurements refer

only to those observed at the times and

places indicated in the text, and

may vary with time, geologic condition or construction activity.

Report No. 0201-6503

PLATE 2-2

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---------------------

«., LINE

52402

•

Y-260,000

L/Nr= 82401

".,.,.

•

LINES211~"""

•

,..

L'NE

:;2112 ...

~,..

,",

•

Y-255,000

-t

...

"'..,.

UNE

8211 f

•

Y-250,000

-I

•

..,

•

-t

;

•

iJ2!

Report No. 0201-6503

-0-9

•

-y

11 ••

11,.

,,"

"'0

•

r...

,,.

PM#21 LET

•

',"

shore T

rminal

,..

...

j\iI#1

••

•

SPM

~Ancl

or Leg j

II-

..,

Fr-

•

,,,

MAP OF SOIL BORINGS AND SUBBOTTOM PROFILE LINES

Texas Offshore Port System

Block A-56, Galveston Area

•

"00

•

"5O

SPM#2

'""

000

•

iii

"..

,,,;

Anchor

•

iii

•

~eg

'-.

H--

I-

•

I--f-.

"f-

PLATE

2-3

3.2 SPM #1 ANCHOR LEG #2 LOCATION

3.2.1

Introduction

The field investigation at the location designated as SPM #1 ANCHOR LEG #2 was performed on

July 3,2008. Soil sampling was performed to 131-ft penetration at Texas South Central Zone Coordinates

3,257,199 ft and Y

251,890 ft. The measured water depth was 121

ft.

3.2.2

Soil Stratigraphy

The soil stratigraphy disclosed by the field and laboratory investigations is presented on the boring

log, Plate 3-12. The soil stratigraphy is based

on the classification of soil samples recovered from the

boring and observations made during drilling operations. A generalized summary of the major soil strata is

tabulated below.

Stratum

III

Penetration, ft

From

131

Description

Soft to stiff lean clay

Medium dense silt with sand

Firm to stiff clay

Detailed soil descriptions that include textural variations and inclusions are noted

on the boring log.

A key to the terms

and symbols used on the boring log is presented on Plate 2-2. The Roman numeral

representing each stratum

is also shown on the boring log and on relevant plates. The variation in soil

stratigraphy across this site

is indicated in a comparison (integration) of the geophysical and geotechnical

soil information presented

on Plate 3-13.

3.2.2.1 Interpretation

of Soil Properties

The shear strength and submerged unit weight profiles shown

on Plates 3-14 and 3-15,

respectively, best represent the assembled test results plotted

on the boring log. These profiles were used

in the engineering analyses.

3.2.3

Pile Design Information

The pile design information developed for this study includes ultimate axial capacities, axial load-

pile movement data, and lateral soil resistance-pile deflection (p-y) characteristics. The analytical methods

used to develop this information are presented briefly

in Section 2.5 and in more detail in Appendix B.

3.2.3.1 Axial Pile Design

Ultimate Axial Capacity. The unit skin friction and unit end bearing values plotted

on Plates 3-16

and 3-17, respectively, was calculated using the API

RP 2A methods described in Appendix B. These

values were used to calculate the ultimate axial compressive and tensile capacities for 42-in.-diameter pipe

piles, driven

to final penetration at the boring location. Capacity curves for driven pipe piles (conductors,

caissons and foundation piles) are presented on Plate 3-18.

API

RP 2A recommends that pile penetrations be selected using appropriate factors of safety or

pile resistance factors. These factors are discussed in Section 2.5.1 of this report.

Axial Load Transfer Data. Axial load-pile movement analyses are usually performed using a

computer solution based on methods developed by Reese (1964) or Matlock, et

al. (1976). Plates 3-19 and

Report No. 0201.6503

3.4

-~---------------------------------

3-20 present the results as side load-side movement (t-z) and tip load-tip movement (Q-z) data for 42-in.-

diameter driven pipe piles, respectively. The Q-z data should be used for foundation piles and neglected for

caissons and conductor design.

In developing the axial load transfer data in the cohesive soils, a post-peak

adhesion ratio of 0.90 was utilized.

3.2.3.2

Lateral Pile Design Data

The soil resistance-pile defiection (p-y) characteristics of the soils at the boring location were

developed for individual 42-in.-diameter driven pipe piles. These data

may be used in lateral load analyses

of driven piles, conductors and caissons.

The p-y data for cyclic loading were developed to WO-f!

penetration using procedures that have been outlined

in API RP 2A and briefiy explained in Appendix B.

The stratigraphy and parameters used to develop the p-y data are presented on Plate 3-21. The p-y data

for 42-in.-diameter driven pipe piles are presented on Plate 3-22. P-y values presented at 100-fI penetration

may

be used for lateral load analyses at greater depths.

I_@

Report No. 0201-6503

3-5

9-£

SNOI.lV~:IlSnlll

en:

N0I1::l3S

@-I

1 ,

r '

cr,

..:

(f)

tIl

a..

Checl,_~

-I'

It... ",

Approved By:

.tJ~

"-,- 1 ['i.:",'

.,~;,.)

u,awnBy:

"v,~cl

..... d".,.9/"'/ ....... o

X=3,257,199'

251,a90'

Texas South Central Zone Coordinates

SEAFLOOR AT

EL. -121'

Date:

IDENTIFICATION TESTS,

[%J

UNDRAINED SHEAR STRENGTH

SUBMERGED UNIT WEIGHT,

[Kef]

[ksf]

BLOW

COUNT

0.03

0.04

0,05

0,06

0.5

1 0

1 5

t::.U

SOFT TO STIFF GRAY LEAN CLAY

WOH

+-- --- +

WOH

+- ______ ..

•

WOH

_.__

I-

Note:

See PLATE 3-12b for detailed soil

stratigraphy to 34-ft penetration

PUSH

-. ---, -

.~.

,~""

...

~J:*I

111

H---+I

(28.0')

30t

IMEDIUM DENSE OLIVE GRAY SILT WITH

SAND

PUSH

- 1

10. 1

(34.0')

I-

FIRM TO STIFF GRAY CLAY

.[ean to 64

-with a few shell fragments

55'

PUSH

+r--

I [TIn I

'"[:.!

140

•

PUSH

...

50 I-

PUSH

+-+______

01 0

1<j>.A

<1><1>+

-with sand, 58' to 63'

60 J----

-expansive, with a few light gray bands at 59'.

PUSH

I I

..!

0 I

-with a sandy silt layer.

WITh

a few mica and wood

fragments al64'

-with many silt pockets, partings. and seams, and .Ii

PUSH

t~~~t:--t

I-

few pockets of organic matter, 65' to 78'

~--+---~---+---4--~11

170

-expansive,

76' to 98'

-platy at 77'

t--~

PUSH

Jt.

-I-

I80

100

I-

110

I-

120

I-

130 t=-

140

I-

150 I-

160

I-

170

I-

180

t--

190

t--

-with silt pockets and partings, and a few light gray

bands, 86' to 98'

-blocky below 96'

-with gas blisters below 106'

-with a few claystones at 101'

-brown, mottled

with gray below 116'

-with a

few sand and silt seams at 117'

--expansive.

with silt pockets, partings, and seams

[

below 126'

-with a few claystones at 127'

-with a few pockets of organic matter at 130'

________ --1)31.0')

PUSH

+1---___ --+

PUSH

J:J

PUSH

+--e_+---+

PUSH

f--

<1>'

[.t.

®

<1>.

<1><1>

: .A.--

200

SAMPLING TECHNIQUES

CLASSIFICATION TESTS

STRENGTH TESTS

Number ofb!ows of a 175-lb weight (hammer) dropped approximately 5 fllo produce a

... SOLUBILITY IN HCl,

[%}

POCKET PENETROMETER (PP)

maximum of 24

In. of penelration of a 2.25-in...QD. 2.125-1n.-ID thin..walted tube

•

PERCENT PASSING -200 SIEVE, [%}

•

TORVANE

(TV)

sampler. 'PUSH" denotes a 3.00-in...QD, 2.B3-in.-ID thin-waited tube sampler was

•

WATER CONTENT (W). [%}

REMOTE VANE (RV)

in. with the weight of the dnll siring. "WOH" denotes a 2.50..jn.-OD,

SUBMERGED UNIT WEIGHT (SUW)

+ MINIATURE VANE (MV)

RESIDUAL (MVres) VALUE)

liner sampler was advanced 24

in. with the weight of the hammer.

... UNCONSOLIDATED UNDRAINED TRIAXIAL (UU)

PLASTIC LIMIT (PL)

LIQUID LlMrT (LL)

LOG OF BORING AND TEST RESULTS

Texas Offshore Port System, SPM #1 Anchor Leg #2

Blo.ck A-56, Galveston Area

(Open symbols i

100

110

120

130

140

150

160

170

180

190

200

..:

(f),

a..

il'

..:

(f)

0..

--Ch.,,_--

A~ D~f5,t:=-

Approved By:

j?A

Date:

r7ff4

---0 By' '-'-'---

-("'-~

"'-

X=3,257,199'

251,890'

Texas South Central Zone Coordinates

'r'-----------------------------------,

IDENTIFICATION TESTS,

[%1

BLOW /I

COUNT

SUBMERGED UNIT WEIGHT,

[kef]

0.05

0.06

UNDRAINED SHEAR STRENGTH

[i<sf)

•

....... I SEAFLOOR AT

-121'

0.03

0.04

I'------..:r'-----'T'------'i'-----=r-----;

SOFT TO STIFF GRAY LEAN CLAY

-mottled with yellowish red, with a few pockets of

+_+___ - _-1-4-

51-

I-

organic matter to 12'

-with a few sand pockets and shell fragments to 5'

-olive gray at

mudHne

-with

few

s:!lt

pockets. 6' to 12'

;r-, -mottled with greenish gray at 6'

-mottled with brownish yellow,

with a

few

sand

pockets, 9' to 12'

-fat

at 10'

.with

a few sheJi fragments.

13' to 17'

-with

many sand pockets, partings. and seams

at 15'

-dark gray and fat, mottled with gray and yellowish

red, with many pockets of organic matter at 19'

-with mica, 23' to 33'

-with a few

sand seams at 23'

28.0'

MEDIUM DENSE OLIVE GRAY SILT WITH

SAND

-with clay pockets, partings, and seams

-with a

few shell fragments at 33'

34.0'

WOH

-. -+

WOH

..L.-~

_____

'~-f

---=-

•

PUSH

•

PUSH

I.L

DDD

PUSH

+-~--+I

PUSH

Ll.....

Ll.

....

o .....

1..1>.

I I "I

I -d Ilr

....

FIRM TO STIFF GRAY eLAY

11 __, I

-lean to 64'

-with

few shell fragments

55'

Ll.

....

--------S-A-M-P-L-'N-G-TE--C-H-N-'Q-U-E-5-------I------I

CLASSIFICATION TESTS

STRENGTH TESTS

Number of blows of a 175-1b weight (hammer) dropped approXimately 5

to prodUCB a

..,

SOLUBILITY IN HCL,

[%]

POCKET PENETROMETER (PP)

maximum of 24 In. of penetration of a 225-ln.-OD, 2.12S-in.-ID thin-walled IIJbe

•

PERCENT PASSING -200 SIEVE, [%j

•

TORVANE

(TV)

sampler. -PUSH" denotes a 3.00-in.-OO, 2.83-in.-ID thin.walled rube sampler was

•

WATER CONTENT

(W),

[%]

<j) REMOTE VANE (RY)

advanced 24

In. with the weight of the drill slrlng.

-v-JOW

denotes a 2.50-in.-OD,

SUBMERGED UNIT WEIGHT (SUW)

•

MINIATURE VANE (MV) (.e- RESIDUAL (MVl'lls) VALUE)

2.125-in..ID liner sampler

was advanced 24 in.

v.ith

the weight of the hammer.

... UNCONSOLIDATED UNDRAINED TRIAXIAL {UU}

PLASTIC

UMlT

(PL)

LIQUID LIMIT (LL)

---- +

LOG OF BORING AND TEST RESULTS

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

(Open symbols I

(f)

"'I

0..

PI..ASnc lJl,!1l

~PiJ

LIQUIGUMiT (tt.)

+----------------------+

Report No. 0201-6503

-........

~.,.

-,..,

.....................

_ ................................

,,~

L"T

GEOPHYSICAL AND GEOTECHNICAL INTEGRATION

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A56, Galveston Area

-.-.----

------------------===~

125 METERS

Line 2003

PLATE 3-13

-~-----------------------------------------------------------------------------------------------~-----------

[

;;;

Shear Strength Profile, [ksf]

0.0

0.5

1.0

1.5

2.0

2.5

0:;:;'

..:

'iii

.(1)

0..

100

120

140

r---.

;----

----

--_.-

---

20., 1)

5., N

8.0, I

1.0 ksl, qma,

oksl

r----.-

---\

----

--_.-

---

III

INote: Roman numerals refer to the stratigraphy as

described in the text and on the boring log.

------

------------

-_\_-

-----

DESIGN STRENGTH PARAMETERS

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

Report No. 0201-6503

PLATE 3-14

-~-----------------------------------------

Submerged Unit Weight, [kcf)

0.00

O.~

O.M

0.00

0.08

0.10

I ii

•

I~ ~

•

!;::'

<;::::

til

(/)

(jj

:;:::;

.....

til

c..

100

120

140

1----.-

----

f------

---

1---_.-

----

--.~

f------

---

III

Note: Roman numerats refer to the stratigraphy as

described in the text and on the boring log.

---------------- -- ------

-----

DESIGN SUBMERGED UNIT WEIGHT

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

Report No. 0201-6503

-@------------------

PLATE 3-15

- ---- -----------

Unit Skin Friction, [ksf]

1 0

1 5

1if

..:

'1ii

(J)

Cf)

(jj

(J)

0...

100

120

140

--~-

----

--_.-

\ -

---.-

--_.-

Notes:

1. Roman numerals refer to the stratigraphy as

described in the text and on the boring log.

2. Tension and compression curves coincide.

1------------

------

_\_--

UNIT SKIN FRICTION

API RP

2A (2000) Method

---

III

-----

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

[

Report No. 0201-6503

-@---~-

PLATE 3-16

~\I\;

•

Unit End Bearing, [ksf]

...:-

'iij

(J)

r:::

D.,.

100

120

140

......

............

[;7

~.-

1---.---

1------

1---

----

Noles:

1. Roman numerals refer to the stratigraphy as

described-in the text and on the boring log.

2. Dashed line represents equivalent unit end

bearing available from frictional resistance

I-

of soil plug inside the indicated pile size.

3. End bearing component is neglected for

~----

caissons and conductors.

1-------------------

UNIT END BEARING

API RP 2A (2000) Method

---

III

-----

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

Report No. 0201-6503

PLATE 3-17

-~----------------------------------

I~~

~ ~

&i-

,'"

Ultimate Axial Capacity, [kips]

500

1000

1500

2000

2500

:'~.=

--------

---,-

---'-

----

--_.-

f----

---'-

'af

..:

'iii

III

1il

100

120

140

Note: Roman numerals refer to the stratigraphy as

described in

the

text and on the

borirg

log,

Compression for piles

Tension for piles, or tension and compression

for caissons and conductors

III

------------

-----'-

~-----

------

ULTIMATE AXIAL CAPACITY

API RP 2A (2000) Method

42-in.-Diameter Driven Pipe Piles

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

Report No, 0201-6503

-@---------------------------------

PLATE 3-18

\~~

[

[~ ~

•

PENETRATION

BELOW

CURVE POINTS

MUDLINE

(feel)

0.0

0.00

0.07

0.13

0.24

0.34

1.0

0.00

0.10

0.16

0.24

0.29

0.00

0.07

0.13

0.24

0.34

9.0

0.00

0.14

0.23

0.34

0.41

0.00

0.07

0.13

0.24

0.34

15.0

0.00

0.13

0.21

0.32

0.38

0.00

0.07

0.13

0.24

0.34

16.0

0.00

0.13

0.21

0.32

0.38

0.00

0.07

0.13

0.24

. 0.34

20.0

0.00

0.13

0.21

0.32

0.38

0.00

0.07

0.13

0.24

0.34

24.0

0.00

0.12

0.20

0.30

0.36

0.00

0.07

0.13

0.24

0.34

28.0

0.00

0.11

0.18

0.26

0.32

0.00

0.07

0.13

0.24

0.34

28.0

0.00

0.31

0.00

0.10

42.00

34.0

0.00

0.38

0.00

0.10

42.00

34.0

0.00

0.19

0.32

0.48

0.57

0.00

0.07

0.13

0.24

0.34

68.0

0.00

0.31

0.52

0.79

0.94

0.00

0.07

0.13

0.24

0.34'

96.0

0.00

0.41

0.68

1.03

1.23

0.00

0.07

0.13

0.24

0.34

107.0

0.00

0.45

0.74

1.12

1.34

0.00

0.07

0.13

0.24

0.34

117.0

0.00

0.48

0.80

1.20

1.44

0.00

0.07

0.13

0.24

0.34

131.0

0.00

0.53

0.89

1.33

1.60

0.00

0.07

0.13

0.24

0.34

Notes: 1. "t" is mobilized SOil-pile adhesion, [ksf].

2. "z" is axial pile displacement, [in.].

3. Data for tension and compression coincide.

AXIAL LOAD TRANSFER DATA

(T-Z DATA)

API RP

2A (2000) Method

42-in.-Diameter Driven Pipe Piles

0.00

0.42

0.32

0.42

0.45

0.42

0.43

0.42

0.43

0.42

0-40

0.42

0.35

0.42

0.63

0.42

1.05

0.42

1.37

0.42

1.49

0.42

1.60

0.42

1.77

0.42

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

0.00

0.84

42.00

0.29

0.84

42.00

0.41

0.84

42.00

0.38

0.84

42.00

0.38

0.84

42.00

0.38

0.84

42.00

0.36

0.84

42.00

0.32

0.84

42.00

0.57

0.84

42.00

0.94

0.84

42.00

1.23

0.84

42.00

1.34

0.84

42.00

1.44

0.84

42.00

1.60

0.84

42.00

[

Report

No. 0201-6503

PLATE

3-19

-@----------------------

PENETRATION

BELOW

CURVE POINTS

MUDLINE

(feet)

34.0

0.00

0.08

0.55

1.76

3.07

4.20

131.0

120

144

160

0.00

0.08

0.55

1.76

3.07

4.20

Notes: 1.

"Q"

is mobilized end bearing capacity, [kips].

2. "z" is axial

tip

displacement, [in.].

AXIAL LOAD TRANSFER DATA

(Q-Z

DATA)

API RP 2A (2000) Method

42-in.-Diameter Driven Pipe Piles

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

I_@

Report No. 0201-6503

42.00

160

42.00

PLATE 3-20

'>.

Seafloor

Soft

T'"

cl",

Medium dense silt with sand

Firm

to stiff clay

Penetration

28'

34'

= 1.5 %

k=10pci

850 =

1.5

at 34'

decreasing linearly to

= 1.0 % at 100'

100' -

Notes:

1. Eso is axial strain at half of peak deviator stress for cohesive soils.

2. Soil strength parameters are shown on Plate 3-14.

3. Submerged unit weight profile is shown on Plate 3-15.

4. k is the modulus of horizontal subgrade reaction for granular soils.

STRATIGRAPHY AND PARAMETERS FOR P-Y DATA

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

_@e

portNo.0201-6S03

PLATE 3-21

1,,--

1:(

"'-

,~~

•

(

•

PENETRATION

BELOW

MUDLINE

(feet)

0.0

0.00

3.0

0.00

7.0

0.00

10.0

0.00

13.0

0.00

16.0

0.00

20.0

0.00

25.0

0.00

28.0

0.00

28.0

0.00

33.0

0.00

34.0

0.00

34.0

0.00

100.0

(and below)

0.00

Notes: 1. "p" is soil resistance, [Iblin.].

'Y'

is lateral deflection, [in.].

CURVE POINTS

190

292

431

634

0.04

0.16

0.47

1.57

208

318

471

692

0.04

0.16

0.47

1.57

223

342

506

745

0.04

0.16

0.47

1.57

230

352

521

766

0.04

0.16

0.47

1.57

232

355

525

772

0.04

0.16

0.47

1.57

229

351

518

762

0.04

0.16

0.47

1;57

217

333

492

723

0.04

0.16

0.47

1.57

184

282

417

614

0.04

0.16

0.47

1.57

138

211

312

459

0.04

0.16

0.47

1.57

870

1450

1914

2407

0.27

0.47

0.68

1.03

1174

1957

2584

3249

0.31

0.54

0.78

1.17

1212

2020

2667

3354

0.31

0.54

0.79

1.18

354

543

803

1181

0.04

0.16

0.47

1.57

609

933

1380

2029

0.03

0.10

0.31

1.05

P-YDATA

(CYCLIC LOADING)

API RP 2A (2000) Method

42-in.-Diameter Driven Pipe Piles

914

4.72

996

4.72

1072

4.72

1103

4.72

1112

4.72

1098

4.72

1041

4.72

884

4.72

662

4.72

2755

1.58

3719

1.81

3839

1.81

1701

4.72

2922

3.15

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

23.62

42.00

23.62

42.00

240

23.62

42.00

362

23.62

42.00

489

23.62

42.00

616

23.62

42.00

776

23.62

42.00

884

42.00

662

42.00

2871

2900

2.28

42.00

3875

3915

2.62

42.00

4001

4041

2.62

42.00

1701

42.00

2922

42.00

I __

~_R_e_po_rt_N_O_._02_0_1-_6_50_3

_____________________________________________________________P_LA

T_E_3_~_2

CONCLUSIONS AND RECOMMENDATIONS

The TOPS geotechnical investigation program to investigate soil conditions at the proposed SPM

#1 and SPM #2 facility locations located in Block A-56, of the Galveston Area in the Gulf of Mexico

consisted of four soil borings, field and laboratory testing,

and engineering analyses. A summary of the

pertinent conclusions and recommendations follows:

•

Soil borings across the proposed facility locations indicate a significant degree

near-surface soil variability.

Soil conditions above 34-ft penetration show channel

features within the block. These channel features vary both

in depth and width across

the block and result

in variable soil stratigraphy and properties. FMMG recommends

that a site-specific soil boring be completed at each

of the anchor and PLET locations

prior to design

of the foundation elements.

•

A scanning sonar survey was performed at each boring location and is available upon

request from Fugro Chance.

•

The water depth ranged from 117 ft to

121 ft across the boring locations within

Block A-56

in the Galveston Area.

•

Final engineering design data are presented for 24-

and 42-in.-diameter driven pipe

piles for the PLET and anchor locations, respectively.

•

The safety

and load resistance factors should be carefully reviewed based on

API RP 2A guidelines and appropriately applied to the engineering analyses presented

in this report.

•

Pile group effects and pile interaction with spud

can depressions should be evaluated

when the geometry and location

of these elements are determined.

•

Mud mat bearing capacities at the PLET locations should be reviewed when the final

size and configurations

and proximity to spudcan depressions are determined.

•

Pile driving problems are not expected based

on the soil information presented in this

study but a drivability study could be performed to select

an appropriate hammer-pile

combination.

FMMG would be pleased to assist

in re-evaluations and additional analyses.

:!l

(T1

l.--

log

Drawn By:

-r[""",o'

Date:

9/¥

Job No.: 0201-6503-1

04-Sep-2008

(Ver. #4)

Summary of Test Results

Boring: Texas Offshore Port System, SPM #1 Anchor Leg

Block: A-56

Area: Galveston

Identification Tests

Strength Estimate

Miniature Vane Tests

Compression Tests

P;sslng

(ksf)

Liquid

PLlIstic

Moisture

Submerged

No. 200

Moisture

Conflnlng

Undlstllrbed

Remolded

Submerged

FaUure

Sample

Depth

liquIdIty

Limit

LimIt

Content

UnIt Walght

Slev.

Type

Content

Pra5&ure

Strenllth

Strength

Strain

UnltWelllht

Strain

Type

No.

1ft)

Index

(%)

(')

(%)

"01)

(%)

Penetrometer

TOIVlIne

Unc!lsturbed

Remolded

Residual

T'"

(%)

(psi)

("'"

(""l

(%)

(,01)

I'M

Failure

1.00

1.50

1.70

.50

1.70

1.39

3.70

4.30

1.34

4.50

.33

4.50

1.31

6.50

1.50

1.26

6.50

.57

•

10.00

1.50

1.08

10.50

120

1.07

1.0

10.50

1.11

11.00

.28

1.50

1.48

1.28

12.50

1.00

1.10

13.00

0.46

13.50

120

0.15

13.50

120

0.25

1.9

14.00

0.50

14.00

.81

15.50

16.00

0.30

NOTES:

TYPE OF TEST

TYPE OF FAILURE

Plus Signs I+] denote tests which exceeded the

- Unconfined Compression

A - Bulge

capacity of the measuring device.

UU- Unconsolidated-Undrained Triaxial

- Single Shear Plane

CU- Consolidated-Undrained Triaxial

C - Multiple Shear Plane

NP = Non Plastic Material

0- Vertical Fracture

-u

Checked By:

Date:

tJ/L!/o8"

Drawn

By:

f/on-.-li'l

Date:

9/'1

(oy

Approved By:

P ..

Date:

~ffi

Job No.: 0201-6503-1

04-Sep-2008 IYer.

#4)

Summary of Test Results

Boring: Texas Offshore Port System. SPM #1 Anchor Leg #2

Btock: A-56

Area: Galveston

Identification Tests

Strength Estimate

Miniature Vane Tests

Compression Tests

POIlIsi"1J

(ksf)

Liquid

Plastic

Moisture

Submerged

No. 200

MolstLire

Confining

Undisturbed

Remolded

SubmBfliIsd

Failure

Sample

Depth

LIquidity

Limit

LImit

Conlant

UnltWalllht

Sieve

Typo

Content

Pl'lIssura

Strvnlllh

Strength

Slndn

Unit Welllht

Strain

Type or

N••

(0)

Inda:.:

f%J

1%)

(pel}

I%)

Pamtlromel.r

Torvana

Undlsturbad

Remolded

Residual

Test

!'I.)

(psi)

'''''

[kaf)

,%,

',d)

('10)

Failure

16.00

0.70

117

0.49

0.9

16.50

17.00

.84

0.60

0.53

19.00

0.90

19.50

120

0.69

0.5

19.50

120

0.31

20.00

0.90

0.77

20,00

.68

102

23.50

117

0.35

4.4

23.50

0.15

24.00

1.26

0.43

30.00

34.00

0.68

34.50

0.11

34.50

117

0.43

3.1

34.50

0.10

35.00

.91

0.80

0.55

39.00

1.00

39.50

120

0.74

1.4

39.50

120

0.21

40.00

1.00

0.64

40.00

.79

NOTES:

TYPE OF TEST

TYPE OF FAILURE

Plus Signs

[+) denote tests which exceeded the

Unconfined Compression

A - Bulge

capacity of the measuring device.

UU- Unoonsolidated-Undrained Triaxial

B - Single Shear Plane

CU- Consolidated-Undrained Triaxial

C - Multiple Shear Plane

NP = Non Plastic Material

Vertical Fracture

-g

""Q

./t;/o!)

Drawn By:

'"1(0

hi " /

Date:

ql'ffoS

... ,. -,

Job No.: 0201.6503.1

04.Sep.2008 (Ver. #4)

Summary of Test Results

Boring: Texas Offshore 'Port System, SPM #1 Anchor Leg #2

Block: A.56

Area: Galveston

Identification Tests

Strength Estimate

Miniature Vane Tests

Compression Tests

Passin"

(ksf)

Liquid

Plastll;

Moisture

Submarvad

No. 200

Type

Molslure

Confining

Undisturbed

RemOlded

Subm"I'Vad

Filnur.

SlImpl,

Dopth

Llquldlty

Limit

Content

Unit Weight

S[eve

Content

Praasura

StrengCh

Stran'ilth

Str.liln

UnltWalghf

Stlllin

Type

N,.

,ft)

Inde.

,%)

(%)

(pol)

(%)

penelroma!8r

Torvana

Undl8lurbud

Remolded

ResIdual

T."

(%)

(psO

,...,

('"

,%)

(PI:f)

,%)

FallllF1l

44.00

0.92

44.50

122

0.29

44.50

117

1.15

1.1

45.00

.63

1.06

0.68

48.50

0.92

49.00

1.08

1.25

49.00

54.00

1.00

1.20

54.50

122

0.41

54.50

117

1.24

1.2

55.00

.91

1.25

1.57

59.00

0.95

59.50

60.00

1.00

1.55

60.00

.79

64.50

65.00

1.00

65.00

.80

67.00

1.00

1.25

67.50

68.00

.62

68.00

1.00

1.66

NOTES:

TYPE OF TEST

TYPE OF FAILURE

Plus Signs

[+1 denate tests which exceeded the

- Unconfined Compression

A. Bulge

capacity of the measuring device.

UU- Unconsolidated-Undrained Triaxial

- Single Shear Plane

CU- Consolidated-Undrained Triaxial

C. Multiple Shear Plane

NP = Non Plastic Material

- Vertical Fracture

fIeJ

Summary of Test Results

Identification Tests

Passing

LIquid

PI..stlc:

Molstu"'

Submwrged

No.2DO

Sample

OapUi

LIquidity

Limit

COl1Wnt

UnllWall1ht

SIllY'

'ft)

Index

,.,

"d}

'%J

77.00

77.50

77.50,

78.00

87.00

87.50

88.00

.62

97.00

97.50

96.00

107.00

107.50

106.00

.43

117.00

117.50

118.00

127.00

127.50

NOTES:

TYPE OF TEST

- Unconfined Compression

UU. L,Lnconsolidated-Undrained Triaxial

CU- Consolidated-Undrained Triaxial

,/q/eK

Drawn By: -rio

no. /

Date:

'l/4/0?

Job No.: 0201-6503-1

04-Sep-2008 01er.

#4)

Boring: Texas Offshore Port System, SPM #1 Anchor Leg

Block: A-56

Area: Galveston

Strength Estimate

Miniature Vane Tests

Compression Tests

(ksf)

Moishlro

Conlln!n"

Undisturbed

Remolded

",.

Submerged

Fillura

Typo

Contell1

Pressure

Strength

Stf"iln

UnltWellilht

Strain

Type of

Penetrometer

Torvana

Undisturbed

Ramolded

RasJdL/.illI

Test

,.,

(psi)

,...

,,.,,

,.,

"d}

,.,

Filliura

1.00

1.25

121

0.36

118

1.55

1.0

1.00

1.25

1.47

1.00

1.50

1.25

1.40

1.21

1.25

118

2.05

0.7

121

0.43

1.25

1.50

1.34

1.75

1.65

1.50

1.25

1.51

1.50

1.65

121

1.72

1.5

122

0.40

1.25

1.50

1.70

1.50

1.80

TYPE OF FAILURE

Plus Signs

[+]

denote lesls which exceeded the

A- Bulge

capacity of the measuring device.

B - Single Shear Plane

- Multiple Shear Plane

NP = Non Plastic Material

- Vertical Fracture

i:'

100

rf.

100

"tJ

-/V,-

--,heeke,..

Approved by;

u.s. STANDARD

SIEVE SIZES IN INCHES

1 314

I I

GRAVEL

Coarse

318

Fine

Da~~

Date:

fifr"'-

u.S. STANDARD SIEVE NUMBERS

100

200

0.1 .075

GRAIN SIZE IN MILLIMETERS

SAND

Coarse

Medium

Fine

SAMPLE NO.

DEPTH, Ff

SYMBOL

CLASSIFICATION

30.00

SILT (ML)";th sand, clay pockets, partings and seams

GRAIN-SIZE DISTRIBUTION CURVES

Texas Offshore Port System, SPM #1 Anchor Leg #2

Block A-56, Galveston Area

--c.

_____.by:

.- • -#) ;

_. ___.

-'?

Iq-,

_ ..

HYDROMETER

;;:;

60 !z

70 If

100

0.Q1

0.002

0.001

SILTorCLAY

._---

•

<t-

•

(

CI)

....

.;;

-0

....

, J

t~ ~

" "

....

~ ~

-{i [

1.25

.---------~--------~--------~--------r_------__,i

1.00

~:::::!t!I<;;;:::~i§ir ~ot&z§6 ~,

0.75 I 11

0,50

I."

0.25 mt

0.000

Strain in Percent

Maximum

Confining

Deviator

Curve

Sample

Depth.

Test

Pressure

Stress

E50

No.

[It]

Type

[psi]

[ksf]

[%]

e>----tl

10.50

120.5

2.14

1.0

13.50

120.0

0.50

1.9

•

16.00

117.0

0.99

0.9

•

19.50

120.2

1.38

0.5

• Normalized with respect to maximum deviator stress.

STRESS-STRAIN CURVES

Unconsolidated-Undrained Triaxial Compression Test

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

PLATEA-14a

Report No. 0201-6503

-~---------------------------------

--------------------

I..

,':J-

•

\f-

I'"

, 1

.~~

\ iii

iii

1t~

-I~

1.25

1.00

•

III

r.::.

....

0.75

.s;:

""0

0.50

....

0.25

0.000

Strain in Percent

Maximum

Confining

Deviator

Curve

Sample

Depth

Test

Pressure

Stress

1:50

No.

[ft]

Type

[psi]

[ksf]

[%]

23.50

117.2

0.70

4.4

[T----f]

34.50

116.9

0.87

3.1

•

39.50

120.1

1.48

1.4

•

44.50

117.0

2.30

1.1

• Normalized with respect to maximum deviator stress.

STRESS-STRAIN CURVES

Unconsolidated-Undrained Triaxial Compression Test

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

Report No. 0201-6503

-@----

PLATEA-14b

I..

, 1

•

'~~

----l~

I-

itj

1.25

1.00

rJl

(])

.....

L-

0.75

.....

(])

(1l

(])

0.50

(1l

L-

0.25

0.000

Strain in Percent

Maximum

Confining

Deviator

Depth

Test

Pressure

Stress

E50

[ttl

Type

[psi]

[ks!]

[%]

Curve

Sample

No.

54.50

116.8

2.48

1.2

B----fl

77.50

117.5

3.10

1.0

•

97.50

118.1

4.09

0.7

• Normalized with respect to maximum deviator stress.

STRESS-STRAIN CURVES

Unconsolidated-Undrained Triaxial Compression Test

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

PLATE A-14c

Report No. 0201-6503

-@----------------------

1.25

1.00

rJ)

0.75

.s:

Cl.l

-a

Cl.l

.t::!

0.50

)

0.25

0.000

)

iii

'Iii

" "

{fi

{fi

-l~

.1_@Report No.

0201-6503

Strain in Percent

Maximum

Confining

Deviator

Curve

Sample

Depth

Test

Pressure

Stress

eSO

No.

[ft]

Type

[psi]

[ksf]

[%]

<r---t>

117.50

121.0

3.43

1.5

B----fl

130.50

120.5

4.33

0.7

• Normalized with respect to maximum deviator stress.

STRESS-STRAIN CURVES

Unconsolidated-Undrained Triaxial Compression Test

Texas Offshore Port System, SPM

#1 Anchor Leg #2

Block A-56, Galveston Area

PLATE

A-14d

ANALYTICAL PROCEDURES

CONTENTS

Page

CRITERIA FOR AXIAL PILE LOAD ANALYSIS ..........................................................................................8-1

Method of Analysis ..........................................................................................................................8-1

Unit Skin Friction .............................................................................................................................

8-1

Cohesive Soils ...................................................................................................................8-1

Granular Soils ....................................................................................................................

8-2

Unit End Bearing .............................................................................................................................8-2

Cohesive Soils ...................................................................................................................

8-2

Granular Soils ....................................................................................................................8-2

Equivalent Unit End Bearing ..............................................................................................8-2

CRITERIA FOR AXIAL LOAD TRANSFER DATA ......................................................................................8-3

Side Friction Versus Pile Movement Data ......................................................................................8-3

Cohesive Soils ...................................................................................................................B-3

Granular Soils ........

...........................................................................................................B-3

Tip Load Versus Tip Movement Data .............................................................................................B-3

CRITERIA FOR LATERAL SOIL RESISTANCE-PILE DEFLECTION DATA ..............................................B-3

Cohesive Soils ....................................................................................................'...........................

8-3

Granular Soils .................................................................................................................................8-4

SCOUR EFFECTS .......................................................................................................................................B-5

SERVICE WARRANTY ................................................................................................................................

8-6

ILLUSTRATIONS

Plate

Summary of Recommended Design Parameters (API RP 2A, 2000) for

Cohesionless Siliceous Soils ..........................................................................................................8-1

Typical Side Load Transfer (t-z) Curves .......................................................................................................

8-2

Typical Pile Tip Load Transfer (Q-z) Curves ................................................................................................8-3

Typical Lateral Load-Pile Deflection (p-y) curves .........................................................................................8-4

Report No. 0201-6503

-~--------------------------------------

CRITERIA FOR AXIAL PILE LOAD ANALYSIS

In this report, the word "pile" is used as a generic term for foundation piles, caissons and

conductors. The installation

of caissons and conductors is the same as that of foundation piles, except that

the soil plug

is later removed or disturbed, thus reducing the end bearing component. For this reason, the

end bearing of caissons

and conductors is neglected in capacity computations.

Method of Analysis

The static method of computing axial pile capacity described

in API RP 2A (2000) is used to

compute ultimate compressive and tensile capacities

of pipe piles installed to a given penetration. In this

method, the ultimate compressive capacity,

Q, for a given penetration is taken as the sum of the skin

friction

on the pile wall, Q" and the end bearing on the pile tip, Qp, so that:

Q,+ Q

fA, + qAp

where A, and Ap represent, respectively, the embedded surface area and pile end area; f and q represent,

respectively, the unit skin friction and unit end bearing. Procedures used to compute values of f and q are

discussed

in the following paragraphs. When computing ultimate tensile capacity or compressive capacity

of conductors and caissons, the end bearing term in the above equation is neglected.

Unit Skin Friction

Cohesive Soils.

Computation

of Q, for pipe piles embedded in cohesive soils is done in

accordance with the API RP 2A recommendations. According to API RP 2A-WSD (2000), Sec. 6.4.2 or

API RP 2A-LRFD (1993), Sec. G.4.2, the unit skin friction may be expressed as:

where:

a dimensionless factor; and

undrained shear strength of the soil at the point in question.

The factor a

is computed by:

0.5 IV

-0.5

for IV ,;; 1.0, or

0.5 IV

-0.25

for IV > 1.0

with the constraint that a

,;; 1.0,

where:

SJcr', for the point in question, and

cr',

effective vertical stress at the point in question.

The undrained shear strength used

in our computations and the values of submerged unit weight used to

compute effective vertical stress are presented

in the main report along with the resulting skin friction

values.

I_@Report No. 0201-6503

B-1

Granular Soils.

The procedure recommended by API RP 2A-WSD (2000), Sec.

6A.3

API

RP 2A-LRFD (1993), Sec.

GA.3

is used to determine unit skin friction in granular soils.

Unit skin

friction,

f, for granular soils is computed from the expression:

Ko-',tano

where:

coefficient of lateral earth pressure,

effective vertical stress, and

angle of friction between soil and pile.

API RP 2A recommends values for K of 0.8 for open-ended pipe piles driven unplugged, and 1.0 for

full displacement piles (plugged or close-ended).

API RP 2A presents recommended values for 0, the angle of friction acting between the soil and

pile and specifies limiting values

of skin friction. The recommended values for granular deposits composed

primarily

of silica are related to the density and composition of the granular deposits, and are presented on

Plate B-1.

Unit End Bearing

Cohesive Soils.

The procedure recommended by API

RP 2A-WSD (2000), Sec.

6A.2

API

RP 2A-LRFD (1993), Sec.

GA.2

is used to determine unit end bearing, q, in clays. Unit end bearing in

clays can be estimated by the following equation:

9 Su

where:

undrained shear strength.

Granular Soils. Unit end bearing

in granular soils is computed by API RP 2A-WSD (2000),

Sec. 6.4.3 or API

RP 2A-LRFD (1993), Sec.

GA.3

using the expression:

where:

a'v

a'v

effective vertical stress, and

a dimensionless bearing capacity factor that is a function of q" the angle of internal

friction of the material.

Recommended bearing capacity factors,

N., for granular soils composed primarily of silica are given in

API RP 2A and are presented on Plate B-1. Also shown on Plate B-1 are limiting unit end bearing values.

Equivalent

Unit End Bearing. For open-ended driven pipe piles, the end bearing is limited to the

frictional resistance of a soil plug developed inside the pile. The total skin friction on the inside

of the pile is

assumed equal to the total skin friction on the outside of the pile. Any influence

of the driving shoe on the

internal skin friction

is neglected. The end bearing on the steel end area of the pile is also neglected. The

assumptions made

in the analyses make no difference in the unit end bearing below the point where the

pile plugs (I.e., equivalent unit end bearing becomes equal to unit end bearing). Above this point, the unit

end bearing

is limited by the frictional resistance of the soil plug.

Report No. 0201-6503

~@---~

8-2

CRITERIA FOR AXIAL LOAD TRANSFER DATA

An axial load-pile movement analysis requires load transfer data on the skin friction along the side

of the pile (t-z data) and the end bearing

on the pile tip (Q-z data). Recommended procedures are given in

API RP 2A-WSD (2000), Sec. 6.7 or API RP 2A-LRFD (1993), Sec. G.7.

Side

Friction Versus Pile Movement Data

Axial side load transfer curves are different for cohesive soils (clay) and granular soils (sand).

Typical axial side load transfer-displacement (t-z) curves for both material types are illustrated on Plate B-2

and discussed below.

Cohesive Soils, The side friction versus pile movement (t-z) curve for cohesive soils is given

API RP 2A-WSD (2000), Sec.6.7.2 or API RP 2A-LRFD (1993), Sec. G.7.2, and is the same for

compressive

and tensile loading. The maximum side friction, t

ma"

at the pile-soil interface is taken as the

ultimate skin friction,

f, as determined by API RP 2A-WSD (2000), Sec. 6.4.2 or API RP 2A-LRFD (1993),

Sec. G.4.2.

The post peak adhesion ratio for clays can range from 0.90 to 0.70 for highly plastic, normally

consolidated clays, to

as low as 0.50 for low plasticity, highly overconsolidated clays. The recommended

adhesion ratios beyond peak values for static loading conditions are given

in the report text.

Granular Soils. The side friction versus pile

movement

(t-z) curve for granular soils is presented in

API RP 2A-WSD (2000), Sec. 6.7.2 or API RP 2A-LRFD (1993), Sec. G.7.2. The maximum side friction,

max,

at the pile-soil interface is the ultimate unit skin friction, f, determined by API RP 2A-WSD (2000),

Sec. 6.4.3

or API RP 2A-LRFD (1993), Sec. G.4.3.

Tip Load Versus Tip Movement Data

Relatively large axial

movements

may be required to mobilize full end bearing resistance. End

bearing or tip load increases with displacement of the pile tip. The development of full end bearing occurs

at a displacement equal to 10 percent

of the pile diameter according to API RP 2A. The tip load versus tip

movement

curve is given in API RP 2A-WSD (2000), Sec. 6.7.3 or API RP 2A-LRFD (1993), Sec. G.7.3.

The end bearing component should not

be considered when tensile loads are applied to a pile. Typical pile

tip-load-displacement (Q-z) curves are presented

in Plate B-3.

CRITERIA FOR LATERAL SOIL RESISTANCE-PILE DEFLECTION DATA

API RP 2A recommends that pile foundations be designed for lateral loading conditions. The lateral

soil structure interaction is complex and the soil response

to lateral loading is generally nonlinear. To

analyze this complex interaction, a computer program based

on the finite difference or finite element

method is normally used.

The nonlinear soil response

is input into these methods with lateral soil

resistance-pile deflection (p-y) curves. The methods for constructing p-y curves follow.

Cohesive

Soils

Soil resistance-pile deflection (p-y) data for cohesive soils are developed using the procedure

outlined by Matlock (1970) for soft clays subjected to cyclic loads and adopted by API

RP 2A-WSD (2000),

Sections 6.8.2 and 6.8.3. Interpreted shear strengths, submerged unit weights, and strain

values

at one-

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Report No. 0201-6503

B.3

I I

half the maximum deviator stress

(E50)

used in our computations are presented in the text illustrations.

These strain values were selected based on data from unconsolidated-undrained triaxial compression tests.

The ultimate lateral soil resistance

(Pus) increases from 3SuD to 9S

D as X increases from 0 to X

according to:

Pus

and

Pud

where:

D +

yXD + JSuX

9SuD for X

ultimate resistance (s

shallow, d

deep),

undrained shear strength for undisturbed clay soil samples,

pile diameter,

effective unit weight of soil,

dimensionless empirical constant with values ranging from 0.25 to 0.5

having been determined by field testing. A value of 0.5 is appropriate for

Gulf of Mexico clays,

depth below soil surface, and

depth below soil surface to bottom of reduced resistance zone.

The deflection values

(y)

are a function of the pile diameter and

E50.

Typical curve shapes are

shown

on Plate B-4.

Granular

Soils

Soil resistance-pile deflection (p-y) data for granular soils are developed using the procedure

outlined by O'Neill and Murchison (1983) for sands subjected to cyclic loading and adopted by API

RP 2A-

WSD (2000)

in Sections 6.8.6 and 6.8.7. Input parameters include submerged unit weight, angle of internal

friction,

and the initial modulus of horizontal subgrade reaction. These values are presented in the text

illustrations. Values of initial modulus of subgrade reaction are selected from the recommendations

API RP 2A based on our interpretation of the soil relative density from sampler driving resistance records

and grain size analyses.

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At a given depth, the following equation giving the smallest

value

of Pu should be used as the

ultimate lateral bearing capacity in granular soils.

Pu,

(C, H + C

0) YH

and

Pud

0y H

where:

ultimate resistance (s

shallow, d

deep),

effective

unit weight of soil,

depth,

coefficients, and

average

pile diameter from surface to depth.

The shape

of the p-y curve in granular soil is defined by the following equation:

[

k H

]

= Apu tanh

--y

A Pu

where:

factor to account for cyclic or static loading condition,

ultimate bearing capacity at depth H,

initial modulus of subgrade reaction,

lateral deflection, and

depth.

The shape of typical granular p-y curves is illustrated on Plate 8-4.

SCOUR EFFECTS

Whenever the near-surface soils are comprised

of granular material, they may be susceptible to

scour. Scour effects are considered insignificant to axial capacity but can

have

a large influence on lateral

capacity. When scour

is considered likely, the p-y data are reduced to reflect the potential loss of lateral

support from the material scoured away near the seafloor around the pile. General scour indicates that

installation of the structure may cause a layer of material to be removed throughout the area of the platform.

Local scour indicates that scour is likely to occur only

in the near vicinity of the piles.

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