Delong Pier Tests at Fort Eustis, Virginia

TA .7 .W34 n o.3- 4 5 0 DELONG PIER TESTS AT FORT EUSTIS, VIRGINIA

TECHNICAL REPORT NO. 3.450

February 1957

U. S. Army Engineer Waterways Experiment Station CORPS OF ENGINEERS Vicksburg, Mississippi

ARMY.MNC VICKSBUR. MIS. iii

PREFACE

The Waterways Experiment Station was requested by the Philadelphia District, CE, on 28 January 1955, to make soils foundation investigations and analyses of two sites on the James River at Fort Eustis, Virginia, where an Engineer Test Unit from the Engineer Center, CE, U. S. Army, planned to install a DeLong pier tramway system for use by the Transporta- tion Research and Development Command, Transportation Corps, U. S. Army, for conducting offshore cargo-discharge exercises. The Office, Chief of Engineers, had previously assigned primary responsibility for coordinating all phases of the tests to the Philadelphia District. Basic responsibility for installation of the tramway system, operational tests, and for the foundation tests and analyses were assigned, respectively, to the Engineer Center, Fort Belvoir, Virginia, the Trans- portation Research and Development Command (TRADCOM), Fort Eustis, Virginia, and the Waterways Experiment Station (WES), Vicksburg, Mississippi. The soils investigations were conducted in February, March, and April 1955 by personnel of WES assisted by military personnel of TRADCOM. TRADCOM furnished the floating plant required for the offshore work and personnel to assist WES personnel in the field exploration. Personnel of the Soils Division, Waterways Experiment Station, connected with the investigation were Messrs. W. J. Turnbull, W. G. Shockley, C. I. Mansur, T. B. Goode, and A. L. Mathews. This report was prepared by Mr. Mathews. CONTENTS Page

PREFACE ...... iii SUMMARY ...... vii PART I: INTRODUCTION ...... Purpose and Scope ...... Pier and Tramway Details ... .. 2 PART II: CAMP WALLACE SITE ...... 4

Foundation Explorations ...... " 4 Laboratory Tests ...... Required Spud Penetrations and Bearing Capacity . Analysis of Foundation Conditions ...... 10 Conclusions ...... 17 PART III: RED BEACH SITE ...... 19 Foundation Explorations ...... 19 Laboratory Tests ...... 21 Required Spud Penetrations and Bearing Capacity ...... 21 Analysis of Foundation Conditions ...... 26 Summary of Findings and Conclusions ...... 36 vi

List of Tables

Table Title Page

Camp Wallace Site

1 Summary of Soil Test Data 2 Comparison of Spud Penetrations and Dynamic Cone Penetration Resistance 13 3 Computed Spud Bearing 16

Red Beach Site

4 Summary of Soil Test Data 23-24 5 Comparison of Spud Penetrations and Dynamic Cone Penetration Resistance 29 6 Computed Spud Bearing 32 7 Computed Bearing for Land Towers 35

List of Figures

F1igure

Camp Wallace Site Plan and soil profile 5 Dynamic cone soundings 7 Comparison of spud bearing and dynamic cone penetration 12

Red Beach Site

4 Plan and soil profile 20 5 Dynamic cone soundings 22 6 Comparison of spud bearing and dynamic cone penetration 28 vii

SUMMARY

Soils investigations were made in February, March, and April 1955 at two sites, Camp Wallace and Red Beach, on the left bank of the James River near Fort Eustis, Virginia. These sites had been selected for the installation of a DeLong pier tramway system to be operated by the Trans- portation Research and Development Command during offshore cargo-discharge exercises. The investigations were made to determine the suitability of the sites for the installation of a pier and tramway system.

Borings and dynamic cone penetration tests were made at both sites. Laboratory tests were made on representative samples of the various soil strata encountered. The tests performed on the foundation soils showed that sufficient spud bearing could be obtained to raise the DeLong pier barges to the required elevations by using 150-ft spuds on the barges at Camp Wallace and 100-ft spuds on the pier barges and 50-ft spuds on the platform barges at the Red Beach site. An analysis was made of the foundation requirements for the land towers and the land anchor installed during the tests at the Red Beach site. DELONG PIER FOUNDATION TESTS, FORT EUSTIS, VA.

PART I: INTRODUCTION

Purpose and Scope

1. The Armed Forces testing program for DeLong piers included the installation and operational testing of a DeLong pier tramway system at two sites, designated Camp Wallace and Red Beach, selected by TRADCOM on the left bank of the James River at Fort Eustis, Va. The purpose of the testing program was to train personnel in the installation and operation of these tramway systems. 2. Before the system was installed soils tests and analysis were made to determine the suitability of the foundation soils at the sites for the installation and operation of the pier and tramway system, and to estimate the depth of spud penetration and length of spuds required to raise and support the pier and platform barges. 3. Dynamic cone penetration tests were made to obtain data for estimating spud penetrations by correlation with similar data obtained during DeLong pier foundation tests conducted at Norfolk, Va.* Some borings were made to obtain undisturbed soil samples from which shear strengths could be determined for use in computing spud load capacity for the depths of penetration obtained, for estimating spud penetrations for a known driving force, and for analyzing foundation requirements for the land towers and land anchor. 4. This report presents only the foundation phase of the tests at the Camp Wallace and Red Beach test sites. A report on the installation of the tramway system has been prepared by the Engineer Center** and a report on its operation is to be prepared by TRADCOM.

* Corps of Engineers, Waterways Experiment Station, DeLon Pier Founda- tion Tests. Miscellaneous Paper 3-78, Vicksburg, Miss. (February 1954). ** Corps of Engineers, Engineer Center, Engineer Test Unit, Tramway Aerial, Ship-to-shore, Project No. 8-71-10-001. Fort Belvoir, Va. (30 July 1955). 2

Pier and Tramway Details

5. The pier and tramway system used in the testing program con- sisted of two self-elevating pier barges, 300 by 90 by 13 ft, designated as F and G barges; two platform barges, 45 by 56 by 6 ft, designated as H and I barges; four monotube land towers, a land anchor, tramway cables, sky cars for transporting cargo, and auxiliary equipment and supplies necessary for the erection and operation of the system. The F and G barges are each equipped with 22 spuds; the H and I barges are each equipped with 4 spuds. The spuds are raised and lowered through wells located inside the outer perimeter of the barges, and are 6 ft in diameter and hollow. They are constructed of 3/4-in. steel plate in 50-ft sections with a quick-coupling arrangement to permit the lengths of the spuds to be varied in multiples of 50 ft. The bottom section of each spud has a reinforcing ring 1/2 in. thick and 9 in. high welded to the inside at the bottom, and a solid diaphragm welded inside 15 ft above the bottom. Two 2-in.-diameter vent holes are located in the spud wall diametrically opposite each other just below the diaphragm. These holes prevent air and water from being trapped in the spuds below the diaphragm during driving and also facilitate the pulling of the spuds. In addition, two plugs are located 1 ft and 7 ft above the diaphragm. These plugs can be re- moved externally after the spuds are raised sufficiently to allow access to them; they are used to drain the water from above the diaphragm during pulling operations before final removal of the spuds in the event the installation is dismantled. Each spud is operated by means of an air jack of 250-ton capacity at an air pressure of 150 psi. 6. The tramway cables over which the sky cars operate are supported on a series of two-leg monotube towers extending from a terminal tower on the offshore end of the F barge to the land anchor on shore in the unloading and intratransit area. One tower is located on the inshore end of the G barge and one on each of the platform barges. Other land- based towers as required are installed in the system to extend it to the land anchor. The machinery for operation of the tramway cables is housed in the base of the terminal tower on the F barge. Details of the system 3 are shown in General Information Book for 300-ft Barge Tramway Pier, prepared by G. E. Sudrow, Inc., 29 Broadway, New York 6, N. Y., and other related drawings prepared for the Transportation Corps by various commercial agencies. 4

PART II: CAMP WALlACE SITE

7. The first site at which tests were conducted was Camp Wallace, an outlying test camp for Fort Eustis, located about 5 miles upstream from Fort Eustis on the left bank of the James River. The limited plan of tests at this site required installation of the F barge and two platform barges only. The land anchor and land towers of an aerial tramway system previously tested at the site were utilized as part of the new system.

Foundation Explorations

8. A program for foundation exploration and testing was developed after available foundation data were reviewed. Eight dynamic cone soundings and four undisturbed sample borings were made with a drill rig mounted on a barge at the sites to be occupied by the F, H, and I barges. All samples were visually classified in the field. A plan of the locations of the F, H, and I barges, borings and cone soundings, and a soil profile of the foundation under the barges are shown on fig. 1. Foundation soils 9. The river bottom at the F and H barge locations is composed of about 105 ft of soft gray clay down to approximately el -116 to -122 ft mlw, and at the I barge location it consists of about 81 ft (to el -97) of similar material. This clay gradually increases in strength with depth and is underlain by a firm greenish-gray clay with lenses of sand and shell extending for at least 30 ft below the soft clay at the F and H barges and is underlain by a firm, greenish-gray silty sand with shells at the I barge. Dynamic cone penetration tests 10. Eight dynamic cone penetration tests were made with a cone assembly consisting of 5-ft lengths of "E" drill rods (1-5/16 in. in diameter) fitted on the bottom with a 60-degree solid cone point 1-5/16 in. in diameter and on top with a drive head. The cone was driven by means of a 140-lb hammer with a drop of 30 in. Penetration resistance C-5 C-3 C-1 C-e C-7 • . . TRAMWAY C U-3 U-2 - 4 '* BARGE "w" BARGE ce ' C-a "F"* BARGE

LEGEND W DYNAMIC CONE SOUNDING

UNDISTURBED SAMPLE BORING 7 PLAN

STATION

J 3L

I 1- w

O zI-

-J hiJ

SOIL PROFILE

LEGENa

f o ANGLE Of INTERNAL FRICTION SILTY SAND SM CONSOLIDATED-DRAINEO DIRECT SHEAR TEST UC = COHESION IN TONS/SQ FT FROM UNCONFINED INORGANIC CLAY COMPRESSION TEST ON UNDISTURBED SAMPLE HIGH PLASTICITY CH UCRsCOHESION IN TONS/SQ FT PROM UNCONFINED COMPRESSION TEST ON REMOLDED SAMPLE INDICATES BOTTOM ELEV OF SPUOD: w WATER CONTENT 0 ON UPSTREAM SIDE Of ARGE = x ON DOWNSTREAM SIDE OI ARGE ib UIOYANT WEIGHT OF SOIL IN LS/CU FT

FIGURES TO SIDE OF BORING LOGS REPRESENT RESULTS OF SOIL TESTS, EXCEPT THOSE DESIGNATED BY WHICHARE ASSUMr VALutES

Fig. 1. Plan and soil profile, Camp Wallace site 6 was measured as the number of blows of the hammer required to advance the cone 1 ft. Soundings C-2 and C-3 were not completed to the planned depths but were suspended after reaching el -98 and -110 ft mlw, respectively, to avoid interference with pier and tramway installation operations. The cone penetration resistances in blows per foot are plotted versus the elevation of the cone point in feet mlw on fig. 2. Undisturbed borings 11. Four undisturbed sample borings were made with a thin-wall, fixed-piston sampler driven by the hydraulic feed on the rig in one continuous thrust. The samples were 3 in. in diameter and 30 in. long. The borings were cased from the top of the drilling barge down into the soil for a sufficient distance to obtain a seal that would prevent surface water from entering the borings. The bore holes were advanced with a baffled fishtail bit after each sampling operation and were kept open below the bottom of the casing through the use of drilling fluid composed of salt water and commercial drilling mud. Graphic logs of the borings are shown in profile on fig. 1. 12. A split-spoon sample of the greenish-gray clay was taken from the bottom of borings U-l, U-2, and U-3 for identification and classification. The split-spoon samples were taken with a 2-in. OD, 1-3/8-in. ID, split-spoon sampler, which was driven 18 in. for each sample by a 140-lb hammer with a drop of 30 in.

Laboratory Tests

Classification 13. Laboratory classification tests including mechanical analyses and Atterberg limits, and water-content determinations were made on all soil samples obtained. These data are shown in table 1. Unconfined compression tests 14i. Unconfined compression tests were made on undisturbed and remolded samples of the clays to obtain shear strengths for computing the penetration and final bearing capacity of the spuds. The tests on remolded samples were made at essentially the same water content as that 0

SOIL SURFACES SOIL SURFACES

-40 -40

J J 2 I H -so- w w

-120 - -- 1- z W 0

w w -160

**.***** CONE SOUNDING C-I .- *- " CONE SOUNDING C-2 CONE SOUNDING C-5 CONE SOUNDING C-3 - CONE SOUNDING C-S CONE SOUNDING C-4 -200

-240 -24 - 0 20 40 60 bC 0 20 40 60 C D 2 BLOWS PER FOOT BLOWS PER FOOT

-JW

W 0

SOIL SURFACES

-40 - --

NOTE: SEE FIG.I FOR LOCATION OF CONE I- SOUNDINGS. hi hi - 0"...... z> W J z W 0

-J hi -160

---- CONE SOUNDING C-7

- CONE SOUNDING C-8

-200

-240 - i 0 20 40 60 *O

SLOWS PER FOOT

Fig. 2. Dynamic cone soundings, Camp Wallace site 8

of the companion undisturbed samples. The cohesive shear strength of the upper soft gray clay layer ranged from 0.05 to 0.50 ton per sq ft for the undisturbed samples and from 0.015 to 0.14 ton per sq ft for the remolded samples. The strength of the soft gray clay increased with depth. The cohesive strength of the underlying firm gray clay containing shells and sand lenses ranged from 0.82 to 0.9 ton per sq ft for undisturbed samples and 0.55 to 0.66 ton per sq ft for remolded samples. All values obtained from these tests are shown in table 1.

Required Spud Penetrations and Bearing Capacity

Pier barge 15. The limited operational tests conducted at the Camp Wallace site involved a maximum operating load of 50 kip per spud on the F barge. The total load to be supported by the spuds during the operation was as follows : Kip/Spud Operating load...... 50 Dead weight of barge and equipment .... . 250 Weight of 150-ft spud ...... 90 Weight of soil plug in spud below diaphragm. 15 Total . . 0

16. Instrumentation was not available for measuring a spud bearing capacity of 405 kip. The only method available for determining the spud penetration resistance was to jack the spuds down to refusal with a known air pressure and then add the weight of the spud and soil plug to the total force exerted by the air jack. In order to do this the spuds were individually jacked to refusal after the F barge had been raised clear of the water, using the available air pressure (133 psi) on the jacks. The driving force per spud thus obtained was: Kip/Spud Capacity of jacks with 133-psi air supply . 443 Weight of 150-ft spud ...... 90 Weight of soil plug in spud below diaphragm. 15 Total .. 5 Table 1

Suamary of Soil Test Data, Cam Wallace Site

Atterberg or est Bor- Sam- Elevation, ft nly ing ple Stratum Limits Test 'd Cohesion No. No. Sale From To Classification L~ PI T L lb/cu ft tons/sq ft u-1 1A -33.3 -11.6 -42.0 Clay CH 128 39 87 UC 124 39 0.06 UCR 117 39 0.02 1 -67.0 -42.0 -72.0 Clay CH 98 3266 UC 99 44 0.09 UCR 90 16 0.06 2 -75.5 -72.0 -78.0 Clay CH 87 30 57 UC 85 49 0.11 ucR 86 50 0.06 3 -98.0 -78.0 -104.0 Clay CH 92 28 64 UC 87 50 0.32 UCR 85 49 0.10 4 -105.0 -104.0 -116.0 Clay CH 87 33 54 UC 79 53 0.50 UCR 75 54 0.12 5 -120.0 -116.0 -146.2 Clay w/shell CH 76 19 57 UC 30 94 0.82 UCR 29 95 0.55

U-2 1 -23.3 -11.8 -38.0 Clay CH 107 33 74 Uc 124 38 0.06 UCR 117 39 0.02 2 -43.5 -38.0 -67.0 Clay CE 87 29 58 UC 109 42 0.19 UCR 104 44 0.03 3 -69.3 -67.0 -92.0 Clay CH 100 34 66 uc 96 46 0.27 uca 94 46 0.07 4 -93.6 -92.0 Clay CH 79 31 48 uc 76 54 0.42 ucR 72 56 0.09 5 -108.7 -116.3 Clay CR 89 32 57 UC 75 55 0.42 UCR 74 55 0.14 6 -119.0 -116.3 -120.4 Clay v/sand layers CEH 94 33 61 UC 74 55 0.19* UCR 71 56 0.13* 7 -127.7 -120.4 Clay v/shells CH 63 22 41 UC 34 88 0.94 UCR 33 88 0.66 8 -136.8 -147.5 Clay w/shells CH 76 30 46 --- 44 --

U-3 1 -24.9 -12.5 -41.0 Clay CH 128 39 89 UC 128 37 0.05 UCR 127 37 0.015 2 -46.3 -41.0 -56.0 Clay cH 103 37 66 UC 100 45 0.11 UCR 100 44 0.04 3 -60.9 -56.0 -73.0 Clay CH 98 35 63 UC 97 46 0.23 UCR 93 47 0.05 4 -80.7 -73.0 -93.0 Clay CH 103 36 67 UC 93 47 0.31 UCR 90 48 0o.o07 5 -103.2 -93.0 -122.0 Clay CH 63 23 40 UC 73 56 0.32 UCR 76 55 0.09 6 -123.5 -122.0 -124.0 Clay v/sand lenses CH 58 22 36 --- 34 -- and shell

U- 1 -63.4 -10.4 -77.0 Clay CH 112 37 75 UC 102 45 0.25 UCR 101 44 0.05 2 -82.3 -77.0 -97.0 Clay CH 97 34 63 UC 93 47 0.35 UCR 85 50 0.08 3 -99.5 -97.0 -100.9 Silty sand v/shell SM Nonplastic --- 22 --

Wote: v denotes iater content. UC denotes unconfined compression test on undisturbed sample. UCR denotes unconfined compresion test on remolded rsqle. V, denotes dry unit eight. * T'at on elayey portion of samuple, not representative of stratum. 10

Platform barge 17. The spuds of the platform barges were required to support a total operating load as follows: Kip/Spud Dead weight of barge and equipment. .... 80 Operating load ...... 87 Weight of 150-ft spud ...... 90 Weight of soil plug in spud below diaphragm. 15 Total . . 272

The jacking force available after raising the barge without additional load was as follows: Kip/Spud Dead weight of barge and equipment ..... 80 Weight of 150-ft spud ...... 90 Weight of soil plug in spud below diaphragm. 15 Total . . 10 18. As the 185-kip jacking force was not sufficient to provide the jacking force required to obtain enough spud penetration for adequate support of a 272-kip load, the barges were filled with approximately 540 kip of water before they were raised. The jacking force thus available was: Kip/Spud Dead weight of barge and equipment ..... 80 Weight of water added ...... 135 Weight of 150-ft spud ...... 90 Weight of soil plug below diaphragm . .. . 15 Total . . 320

The spuds were driven to refusal under this jacking force after the barges were raised out of the water, and the load was maintained until it was ascertained that additional spud penetration would not occur. The barges then were drained.

Analysis of Foundation Conditions

Estimated spud penetrations 19. The depths of spud penetration and the lengths of spuds required at the Camp Wallace site were estimated by comparison of the 11 dynamic cone sounding data obtained at the site and the dynamic cone sounding data and spud penetration data obtained in similar foundation soils encountered at site 4 of the DeLong pier tests conducted at Norfolk, Va., in 1953.* The Norfolk penetration and spud bearing data together with minimum and maximum bracketing lines of cone penetration resistance versus spud bearing are plotted on fig. 3. These data indicate that a cone penetration resistance of 38 to 46 blows per foot would be required to support a pier-barge spud load of 548 kip, and that a cone penetration resistance of 18 to 25 blows per foot would be required to support a platform-barge spud load of 320 kip. 20. Dynamic cone soundings C-1 and C-4 (fig. 2) at the F barge location (Camp Wallace) show that a cone penetration resistance of 38 blows per foot was first encountered at an average elevation of -114 ft and a penetration resistance of 46 blows per foot was encountered at an average elevation of -118 ft. Soundings C-2 and C-3 did not penetrate to sufficient depths to give resistances of 38 blows per ft. Thus, on the basis of previous correlations, the spuds of the F barge should penetrate to between el -114 and -118 ft under a load of 548 kip. Dynamic cone sounding C-7 shows that at the H barge location cone penetration resistances of 18 and 25 blows per foot were encountered at el -100 and -110 ft, respectively, and cone sounding C-8 shows these resistances encountered at el -94 and -97 ft, respectively, at the I barge location. This indicated that with a load of 320 kip per spud the H barge spuds should penetrate to between el -100 and -110 ft and the I barge spuds would penetrate to between el -94 and -97 ft. A comparison of the estimated and actual spud penetrations obtained under the three barges at the Camp Wallace site is shown in table 2 (page 13). 21. The dynamic cone penetrations at the F barge location (fig. 2) show that the cone penetrated the soft clay to about el -100 ft mlw under a relatively low resistance of about 20 blows per ft with a rapid increase in resistance to 60 blows at about el -120 in the firm clay. This indicates a stratum of soil of increasing strength in the transition zone

* Corps of Engineers, Waterways Experiment Station, op. cit. 800

58 K/P

500 /NMU /

NORFOLK DATA / BRACKET/NG L/NE FAX/MUA

.__ I I / 400 -- - / /

30JO K/P (3 3010 300 ...... ,

Z w / /n 0na Y '/ n 2/6 / I /0

77 _ _ _ 100

0 10 20 30 40 50 BLOWS PER FOOT PENETRATION DYNAMIC CONE

LEGEND

0 NORFOLK SITE 4 A CAMP WALL ACE

Fig. 3. Comparison of spud bearing and dynamic cone penetration, Camp Wallace site 13

Table 2 Coaparison of Spud Penetrations and Dynamic Cone Penetration Resistance Camp Wallace Site

Actual Dynamic Cone Penetration Applied Estimated Dynamic Estimated Resistance No. of Driving Cone Penetration Spud at Maximum Actual Spuds Force Resistance Required Penetration Spud Penetration Spud Penetration Repre- per Spud Blows per ft el, ft mlW Blows per ft el ft mlw Barge sented kip Minimum Maximu* in ax Minom Maximum Minim= Mximu

F 22 548 38 46 -114 -118 32 50 -110 -117

H 4 320 18 25 -100 -110 17 21 -98 -106 I 4 320 18 25 -94 -97 13 16 -79 -92

* Taken from minimum and maximum bracketing lines, fig. 3. * Taken from fig. 2. between the soft clay and the firm clay encountered at el -116 in boring U-i and at el -120 in boring U-2 (fig. 1). The above cone resistances indicate that the F barge spuds should penetrate into the transition zone stratum just above the firm clay. Variations in the spud penetrations that were obtained represent variations in the strength and/or thickness of the transition stratum. In view of natural variations in soil stratum, the spud penetrations estimated from the dynamic cone soundings and the actual spud penetrations are considered in good agreement. The percentage of error for the estimated penetrations is only 2 per cent of the average actual penetrations. 22. The comparison of the cone penetrations at the locations of the platform barges at Camp Wallace with those obtained at Norfolk indicated that the spuds on the platform barges would not penetrate the soft clays to the underlying firm clay at the H barge location but would penetrate to the underlying silty sand at the I barge location. The flat portion of the cone resistance curve for cone sounding C-8 (fig. 2) begins at el -94 ft mlw and indicates the top of the silty sand encountered in adjacent boring U-4 (fig. 1) at el -98 ft. Since the top of the silty sand varies 4 ft in elevation within a 10-ft distance from U-4 to C-8, it is possible that the bottom elevations of the I barge spuds correctly reflect the elevation of the top of the silty sand at those locations or an increase in the strength of the clay, as the spud locations are from 35 to 100 ft from the location of the cone sounding. The average actual spud penetrations obtained at both platform barge locations were less than those estimated, but the percentage of error for the estimated penetrations is only 3 per cent of the average of the actual spud penetration at the H barge and 12 per cent for the I barge. These variations are within the expected range of accuracy of dynamic cone data. 23. The actual dynamic cone penetration resistances in blows per foot at maximum spud penetrations, as shown in table 2, are plotted on fig. 3. The points based on I barge data plotted at 13 and 16 blows per foot for a spud bearing of 320 kip do not agree as well with the extrapolated limits of the Norfolk data as the points based on the other Camp Wallace data. This difference may be due to the conditions discussed in the preceding paragraph and, consequently, the points based on the I barge data should not be given too much weight if the Camp Wallace data are used in future comparisons.

Computation of spud penetration resistance 24. In computing the bearing capacity of the spuds based on soil strength data and estimating the depth of spud penetration that would be obtained, the assumption was made that the spuds act in the same manner as large piles or cylindrical piers. The very soft clays under all of the barge locations at the Camp Wallace site would allow the spuds to penetrate to a depth of at least 15 ft, at which depth a soil plug should be formed beneath the diaphragm and full end bearing should be developed. The spud penetration resistance below 15 ft would be composed of skin friction on the outside walls of the spud plus end bearing of the spud bottom. 25. The spud penetration resistance was computed by the semiempirical formula for large piles or caissons given by Terzaghi and Peck* as follows:

* Karl von Terzaghi and Ralph B. Peck, Soil Mechanics in Engineering Practice. New York, John Wiley & Sons, Inc. (1943). 215

2 6 rN) + 2 r f Df d = r (13 cN + 7 Df Nq + 0. where Qd = bearing capacity r = radius of spud c = cohesion of the soil 7 = unit weight of the soil f = skin friction s D = depth of embedment of spud Nc, Nq, N = factors dependent upon shearing strength of the soil 7 and evaluated in charts in the referenced publication.

The first term on the right-hand side of the equation evaluates the end bearing; the second term, the skin friction. 26. The soil values from laboratory tests shown in table 1 were used in computing the spud bearing capacities, with the exception of values for the stratum represented by sample 6 from boring U-2. The unconfined compression tests were run on a clayey portion of this sample, which was not a representative specimen of the stratum; an examination of the entire sample showed the material to be predominantly sandy clay and sand. Assumed values of 0 = 250, c = 0, and yd = 104 lb per cu ft were used for this stratum. Values of cohesion from unconfined compression tests on undisturbed and remolded samples were used, respectively, for determining end bearing and skin friction. Soil test data from samples within each stratum were considered representative of the stratum and were used in computing that portion of spud bearing affected by the stratum.

Comparison of estimated and actual spud penetrations 27. Table 3 shows the estimated spud penetrations derived from computations and the actual penetrations obtained at the Camp Wallace site, together with a breakdown of the computed bearing values for the estimated and average actual penetrations. The last column in the table gives the actual driving force applied to the spud and transmitted to the foundation during final driving. Table 3 Computed Spud Bearing Camp Wallace Site

Estimated Average Actual Depth Computed Computed Computed Applied Elevation Bottom Eleva- of Spud Skin End Total Driving Force Bottom of Spud tion of Spuds Embedment Friction Bearing Bearing per Spud Barge Boring ft mlw ft mlw ft kip kip kip kip

F U-1 -115 103.4 252 295 547 548 -116 104.4 257 430 687 548 -i12 100.4 239 292 531 548

F U-2 -115 103.2 224 245 469 548 -116 104.2 227 477 704 548 -116* 104.2 227 477 704 548

H U-3 -93 80.5 124 195 319 320 * -99 86.5 144 201 345 320 -104t 91.5 161 206 367 320

I U-4 -77 66.6 126 200 326 320 -83" 72.6 144 203 347 320 -89t 78.6 162 210 372 320

* Four spuds nearest boring. ** Two spuds nearest boring. t Two spuds farthest from boring. 28. The estimated spud penetrations for the F pier barge given in table 3 were based on soil test data from undisturbed sample borings U-l and U-2 (table 1) and a driving force of 548 kip. Both borings show the top of firm soil (firm clay or clay with sand lenses) at approximate el -116 ft mlw. The computed spud bearing for an estimated elevation of -115 ft mlw for the bottom of the spud (table 3) using soil strength values of the soft clay in determining the spud end bearing gave values equal to or less than the driving force of 548 kip which was transmitted to the foundation soils. The computed bearing for an estimated elevation of -116 ft mlw for the bottom of the spud using soil strength values of the firm soil formations in determining the spud end bearing gave values greater than the driving force of 548 kip. The spud bearing values computed for el -112 and -116 ft mlw as the average elevations obtained for spuds near borings U-l and U-2, respectively, also gave computed values respectively below and above the driving force of 548 kip. A variation in the elevation of the top of the firm soil formation encountered at approximately el -116 ft in both borings or a variation in the strength of the soil in the transition zone between the soft clay and the firm clay would account for the difference obtained in the spud penetrations. 17

Bearing values computed for the higher elevations of the actual penetrations using soil strength values of the firm stratum in determining the spud end bearing show that the spuds would reach refusal under the applied driving force at the higher elevations if the top of the firm soil was reached at that depth. The percentage of error of the estimated penetrations based on actual spud embedment in the soil is 3 per cent for the average of the spuds nearest boring U-l and 0 per cent for the average of the spuds nearest boring U-2. 29. The estimated spud penetrations for the platform barges (table 3) were based on soil test data from undisturbed sample borings U-3 and U-4 (table 1) and a driving force of 320 kip per spud. The borings, made after the barges were on location, were located on the tramway center line 30 ft and 38 ft from the edge of the barges (fig. 1). The actual spud penetrations are greater than those estimated and they increase with distance away from the borings, which could indicate a change in soil strength with change in location. However, the percentage of error of the estimated penetrations based on spud embedment in the soil is 4 per cent for the shallowest and 18 per cent for the deepest actual spud penetrations obtained, which is within the expected range of accuracy of the formula used in making the computations.

Conclusions

30. Both the correlations of the dynamic cone penetration test results with the Norfolk data, and the computations of bearing capacity based on the soil strength values obtained from laboratory tests on undisturbed samples of foundation soils at the Camp Wallace site indicated that the installation could be made satisfactorily. The depth of spud penetrations estimated both from the dynamic cone penetration tests and from the computations based on soil strength values checked reasonably well with the actual penetrations obtained. Thus it is apparent that either method is satisfactory for estimating spud penetrations in soil similar to that at the Camp Wallace site. 31. The dynamic cone penetration tests and computations based on 18 soil strength values indicated that spuds 150 ft long would be required to raise the barges to the desired height and obtain sufficient penetration and bearing capacity. 19

PART III: RED BEACH SITE

32. The second site at which tests were conducted was at Red Beach on the left bank of the James River at Fort Eustis. The plan of tests at this site required the installation of two pier barges, two platform barges, one offshore tower on a pile foundation, three land towers on spread footings, and a land anchor. The pier and tramway installed and tested at Camp Wallace were dismantled after completion of limited tests and installed at the Red Beach site as a semipermanent installation.

Foundation Explorations

33. A program for foundation exploration and testing was developed after the available foundation data were reviewed. Fourteen dynamic cone soundings and nine undisturbed sample borings were made at the site. A plan of the locations of the F, G, H, and I barges, land-based towers, land anchor, undisturbed borings, cone soundings, and a soil profile of the foundation at the site are shown on fig. 4. Foundation soils 34. The river bottom under the F and G barges is composed of a stratum of very soft gray clay. At the inshore end of the G barge this clay exists from el -7 to -23; at the offshore end of the F barge it exists from el -13 to -52, the lower 9 ft of which is composed of soft lean clay. The lower portion of this stratum of soft clay contains some lenses of clayey sand. The clays are underlain by a 3- to 4-ft stratum of sand and sandy gravel. Available data are not sufficient to establish whether this latter stratum is continuous or consists of isolated pockets. This stratum is underlain by firm greenish-gray clay with lenses of sand and shell extending to at least el -75 ft mlw. The river bottom between the pier barges and the shore is covered by irregular deposits of silty sand, clayey sand, and sand to approximately el -28 ft mlw. These deposits are underlain by firm greenish-gray clay with lenses of sand and shell to an unknown depth. The immediate beach area is covered by sand placed as hydraulic fill during channel dredging operations. The area LEGND * DYNAMIC CONE SOUNDINGS * UNDISTURBED SAMPLE BORINGS PLAN

- --0 E S --.

-ro o

r =-ac•c [ - -o -"J'UC -,

-70 -

-80 LEGCEN SOIL PROFILE

O* ANGLEOF INTERNALFRICTIONCONSOUOATED-ODAINED C CONESIONIN TONS/SQ FT JIRECT SHEARTEST SAND OR GRAVLLY M UC. COHESIONIN TONSQFT FRO UNCONFINEDD SCOMPRESSIONl TESt ONUNOISTUREO SAMPLE ND OR GRELLY CC ON INTONSASQ rT ROM UNCONFINED AMPRESSION TES o IONIEMOLOED SAMPLE w ISTERCOENT INOAGANICLAYS OR FIGUREi$3TO SE Or BORINGLOGS REPRESENTRESULTS GRAVELLYCLAY OF SOILTESTS, EXCEPTTHO E OESIGNATEoDIY IANDYCLAY CL WICH AREASSUEL VALUES SILTY CLAY CN

INORGANICSILTML

SIOICATESBOTTOM ELEVTItoNS OF SPUOS: 0 ONUPSTREAM SOE OF BARGE RON OOWNSTREAMSIDE OF BARGE

Fig. 4. Plan and soil profile, Red Beach site 21

landward of the sand beach consists of firm to hard, tan, sandy clay to a depth of 8 to 10 ft underlain by sand, silty sand, and clay with sand lenses. Dynamic cone penetration tests 35. Dynamic cone penetration tests were made with the same equipment and in the same manner as those at the Camp Wallace site. Cone penetration resistances plotted versus elevation of the cone point are shown on fig. 5. Undisturbed borings 36. Undisturbed sample borings were made with the same equipment and in the same manner as those at the Camp Wallace site. The graphic logs of the borings are shown in profile on fig. 4.

Laboratory Tests

Classification 37. Laboratory classification tests including mechanical analyses and Atterberg limits, and water-content determinations were made on all soil samples obtained. These data are shown in table 4. Shear strength tests 38. Unconfined compression tests were made on undisturbed and remolded samples of the clays to obtain shear strengths for computing the depth of penetration of the spuds and the final bearing capacity of the spuds. 39. Consolidated-drained direct shear tests were performed on selected undisturbed samples of the sands to determine the angle of internal friction for use in making computations of bearing capacity where sand occurred in the foundation. 40. Values obtained from the unconfined compression tests and the direct shear tests are shown in table 4.

Required Spud Penetrations and Bearing Capacity Pier barge 41. The schedule of operations indicated that cargo of unknown SOIL SURFACES SOIL SURFACES-

-20 -20

J J

W -40 - - - - - w -40

z 02 -60

-80 - - -- J W -0 ------

-CONESOUNDING C-3 --- .CONE SOUNDING C-4 100 -0 20 40 60 80 000 20 40 60o 80 BLOWS PER FOOT BLOWS PER FOOT

+20 +20

SOIL SURFACE o-20 0 SOIL SURFACE

W w -20 I' z

2w -40 0 -40 -60 5- -8 Wa.J ------CONE SOUNDING C-S .CONESOUNDING C-6 --- CONE SOUNDING C-IO -- - CONE SOUNDING C- - CONE SOUNDING C-II CONE SOUNDING C-9 -So 0 20 40 60 60 0 20 40 80 so80 BLOWS PER FOOT BLOWS PER FOOT +20

SOIL SURFACES S--20

NOTE: SEE FIG. 4 FOR LOCATION OF CONE SOUNDINGS.

O -40

"""... CONE SOUNDING....- C-12 ----- CONE SOUNDING C-13 - CONE SOUNDING C-14 -. I I I I s0 0 20 40 sO !e BLOWS PER FOOT

Fig. 5. Dynamic cone soundings, Red Beach site 8! M of 8Soil Test Data Red ach Site

Bor- Sam- Elevation, ft ly Atterberg 1efore bst ing ple Stratum Limits Test d C so so. No. SWle S To Classification LI 'T L PI lb/cu ft toms/!ft U-1 1 -20.6 -12.7 Clay CI 93 31 62 UC 103 44 0 0.05 UCR 96 49 0 0.02 2 -30.5 -43.5 Clay Ca 87 28 59 uc 101 45 o 0.05 UCR 87 50 0 0.02 3 -44.8 -43.5 -46.8 Clay, sandy CL 37 19 18 UC 63 62 0 0.13 uCR 40 80 0 0.06 4 -49.2 -46.8 -52.0 Clay, silty ML-CL 25 20 5 UC 22 103 0 0.24 uCR 22 o109 0 0.16 5 -54.5 -52.0 -56.0 Gravel, sandy OP Nonplastic --- 1W 10* 30* 0.00* 6 -62.1 -56.0 -63.0 clay v/shell CR 52 20 32 tC 35 84 0 0.91 frasgent s UCR 34 86 0 0.35 7 -73.5 -63.0 -74.5 Clay v/shell CH 62 21 41 UC 35 83 0 1.25 fragments UCR 36 85 0 0.47 U-2 1 -6.3 -5.6 -6.9 Sand, fine SP Nonplastic --- 1W --- 2 -13.0 -6.9 -14.2 Clay CH 56 23 33 UCR 89 55 0 0.02 3 -18.0 -14.2 -23.0 Clay CH 56 22 314 U 66 6o 0 0.16 UCa 69 58 0 0.0k 4 -24.4 -23.0 -26.0 Sand SP Nonplutic CDB 32 92 33 0.05 5 -29.9 -26.o clay, sandy CL 37 26 11 --- 33 86 20* 0.20* v/shells 6 -34.2 -12.9 Clay, sandy CL 46 22 23 --- 33 --- v/shells 7 -43.7 -42.9 -53.0 Clay v/shell CH 55 21 3 tC 35 84 0 0.92 UCR 35 85 0 0.37 8 -63.8 -53.0 -64.8 Clay v/shell CL 4, 22 22 --- 32 --- U-3 1 -7.3 -3.8 -10.0 Sand, silty SM Nonplastic --- 27 94 25* 0.00* 2 -18.0 -10.0 -20.0 Sand, gravelly SP Nonplastic --- -- 104* 30* 0.00* 3 -23.0 -20.0 -27.6 sand 8P Nonplastic --- -- 104* 30* 0.00* 4 -34.0 -27.6 -35.1 Clay v/shell CL 37 22 15 --- 34 85 25* 0.00* 0.00* U-4 1 -4.5 -2.1 -9.0 Sand, silty SM Nonplastic --- 23 104 25* 0.00* 2 -14.0 -9.0 -23.0 Sand, clayey SC Nonplastic --- 13 104 25' 0.00* 3 -26.0 -23.0 -29.2 Sand, silty SM Nonplautic --- 21 104 30* 4 -37.0 -29.2 -38.2 Clay, sandy CL 49 24 25 UC 36 84 0 0.261.13 UCR 35 86 0 v/shell 0.13 U-5 1 -3.6 -0.4 -12.1 Clay, sandy CL 26 17 9 UC 22 103 0 UCR 22 014 0 0.19 2 -19.0 -12.1 -22.0 Sand, gravelly SP Nonplatic --- -- 104* 30* 0.00* v/silty sand layers o 3 -24.0 -22.0 -25.9 Sand, silty SM Nonplastie --- -- 104* 25* 0.00* 4 -35.4 -25.9 -38.5 clay CH 72 31 41 tC 58 64 0 1.00 UCR 59 64 0 0.21 5 -46.4 -38.5 -17.4 Clay CR 54 21 33 UC 31 86 0 1.99 ucR 35 84 0 0.37

(Continued)

Note: v denotes water content. UC denotes unconfined compression test on undisturbed samples. UCR denotes unconfined compression test on remolded samples. CD6 denotes consolidated-drained direct shear test. 7 denotes dry unit w ight. * Asumed values. Table 4 (continued)

Bor- Bam- Elevation ft mal Atterberg Before Test7 Shear Strenth ing ple tratu Limits Test d ohesion Wo. NO. S le Froma To . Classification Lt Pt PI lbcu ft eg tons/sq ft u-6 1 -2.0 +4.2 Sand SP Nonplastic CDB --- 89 34 0.00 2 -11.0 -15.8 Sand SP Nonplastic CI --- 96 37 0.00 3 -20.0 -15.8 -29.0 and, silty v/clay SM Nonplastic ------layers 4 -29.2 -29.0 -30.0 Sand, gravelly SP Nonplastic ------5 -47.o -30.0 clay v/sand lenses CB 77 31 46 --- 55 ------6 -56.0 -56.6 Clay v/sand lenses C 76 31 45 --- 62 ------U-7 1 +2.8 +6.7 -1.3 clay CL 49 25 24 UC 22 101 O 0.97 ucR 22 98 0 1.59 2 -6.8 -1.3 -10.3 Sand SP Nonplastic --- -- 104* 30* 0.00 3 -13.8 -10.3 -14.3 Clay, sandy CL 35 17 18 ------4 -14.6 -14.3 Sand SP Nonplastic ------5 -17.5 -17.8 Sand SP Nonplastic ------U-8 1 0.0 +5.0 -2.3 Clay CH 54 29 25 UC 27 95 o 0.67 UCR 28 90 0 0.79 2 -14.4 -2.3 -5.8 Sand, silty SM Nonplastic --- 27 105 -- 3 -10.0 -5.8 -18.0 Sand, silty SM Nonplastic --- 23 ------4 -19.0 -18.0 -22.0 Sand, gravelly SP Nonplastic ------5 -29.0 -22.0 -29.5 Sand SW Nonplastic ------U-9 1 +0.8 +4.3 -1.3 Clay CH 57 27 30 UC 27 94 0 0.52 UCR 28 94 0 0.9 2 -4.1 -1.3 Sand SP Nonplastic --- -- 104* 25* 0.00 3 -9.2 -9.7 Sand SP Nonplastic --- -- 104* 25* 0.00 -10.0 -9.7 -10.2 Clay, stiff CH --- 37 ------4 -15.7 -10.2 -16.4 Clay, stiff CL 38 21 17 --- 38 ------5 -25.0 -16.4 -25.4 Clay, sandy CL 29 17 12 --- 36 ------6 -26.0 -25.4 -26.2 Sand, silty SM Nonplastic --- 25 ------

Note: w denotes water content. UC denotes unconfined cqpression test on undisturbed saples. UCR denotes unconfined ccpression test on resolded asqples. CDB denotes consolidateddrsaid direct shear test. 7 denotes dry unit ieight. * ALsmed values. 25 weight might be allowed to accumulate on the F and G barges during the operational tests. Therefore, it was considered necessary for the spuds to penetrate sufficiently deep at the time of installation to mobilize the maximum possible bearing capacity obtainable with the spud-driving force available, which was: Kip/Spud Capacity of jacks with 140-psi air supply . . 466 Weight of 100-ft spud ...... 60 Weight of soil plug below diaphragm ..... 15 Total .... 541 This driving force limited the allowable deck load to 216 kip per spud or 176 lb per sq ft of deck surface; otherwise, the barges might settle. Large differential settlements that would tip the barges laterally would be objectionable as the tramway cannot be operated if any of the cable support towers are out of line more than 18 in. 42. The spuds are watertight from the diaphragm to the joint at the top of the first 50-ft section. Until this joint penetrates below the water surface, the buoyancy of the spud is a factor of the depth of submergence of the spud less the 15 ft below the diaphragm, and must be subtracted from the applied driving force in determining the spud bearing capacity at the completion of spud-driving operations. None of the spuds penetrated to sufficient depth for water to fill them during the spud-driving operations and the buoyancy did apply. Correcting for the buoyancy of the submerged portion of the spuds, based on the water surface at 0.0 ft mlw, the driving force resisted by the soil was 526 kip for the spuds with the least penetration which was to el -23 and 478 kip for the spuds with the greatest penetration which was to el -50. Platform barge 43. The spuds of the platform barges are required to support a total operating load as follows: Kip/Spud Dead weight of barge, operating load and equipment ...... 167 Weight of 50-ft spud ...... 30 Weight of soil plug in spud below diaphragm . 27 Total .. 221 26

The barges were filled with 540 kip of water before raising to provide sufficient jacking force so that the spuds would penetrate deep enough to obtain safe bearing for the 224-kip load. The jacking force thus available was: Kip/Spud Dead weight of barge filled with water .... 215 Weight of 50-ft spud ...... 30 Weight of soil plug in spud below diaphragm. . 27 Total . . . 272 The spuds were driven to refusal under this jacking force after the barges were raised to the required elevation, and the load was maintained until it was ascertained that additional penetration would not occur. Overnight, after the I barge had been raised, one spud showed additional penetration. This spud again was jacked to refusal at a final depth 6 ft greater than the other three spuds of the I barge. This indicated a local soft pocket in the foundation soils, which is to be expected oc- casionally in alluvial soil deposits. The barges were drained after maximum penetration of the spuds had been obtained. 44. The spuds on the platform barges did not penetrate to sufficient depth for the buoyancy of the submerged portion above the diaphragm to affect the penetration materially. The spuds on the H platform barge did not have vent holes in the walls below the diaphragm and air undoubt- edly was trapped in the 15-ft section below the diaphragm. Under the jacking force of 272 kip this column of air would compress to a length of about 3 ft and the spud should develop full end bearing after penetrating about 12 ft into the soil.

Analysis of Foundation Conditions

Estimated spud penetrations 45. The depths of spud penetration that would be obtained and the lengths of spuds required at the Red Beach site were estimated by comparison of the dynamic cone sounding data obtained at the site and the dynamic cone sounding and spud penetration data obtained in similar foundation soils encountered at sites 1 and 3 of the DeLong pier tests conducted at Norfolk in 1953. The Norfolk cone penetration and spud 27

bearing data obtained in silty sand, with a curve of the cone penetration resistance extrapolated to the Red Beach spud resistances, are plotted on fig. 6. It was concluded from these data that the soil would have to have a cone penetration resistance of 33 blows per foot to support a pier barge spud load of 541 kip and a cone penetration resistance of 15 blows per foot to support a platform barge spud load of 272 kip. This conclusion was based on the assumption that the spuds would develop end bearing as a result of a soil plug forming in the spud under the diaphragm after 15 ft of penetration into the soil. 46. Dynamic cone soundings C-1 through C-7 (fig. 5) at the F and G barge locations show that a cone penetration resistance of 33 blows per ft was encountered at about the following elevation: -70 ft at the offshore end of the F barge (C-1 and C-2), -59 ft at the mid-point of the F barge (C-7), -55 ft at the inshore end of the F barge (C-3 and C-4), and an average elevation of -29 ft at the inshore end of the G barge (C-5 and C-6). Dynamic cone soundings C-8 and C-9 showed that a cone penetration resistance of 15 blows per foot was encountered at el -13 and -16 ft, respectively, at the H and I barge locations. Had the H barge spuds been vented below the diaphragm they would not have been filled with soil until they reached el -19 ft. As they were not vented below the diaphragm, it was estimated that the spuds should penetrate until end bearing developed as a result of the column of air trapped below the diaphragm reaching maximum compression under the applied load of 272 kip. This should occur when the bottom of the spud reached about el -16 ft. The spuds penetrated to el -15 ft. A spud penetration at this location to any depth below el -13 ft, which was based on a cone penetration resistance of 15 blows per ft, would give a cone penetration resistance greater than the 15 blows required to support the spuds after end bearing developed. Therefore, no attempt was made to correlate these spud penetrations with the cone sounding, as the additional penetration would be dependent solely upon that depth at which end bearing developed. A comparison of estimated spud penetrations and actual spud penetrations under the barges at the Red Beach site,with the exception of the H barge, is given in table 5. 500

= 400 - / '1-I U NORFOLK DA TA CURVE AND z / RED BEACH MAX/IMUM URVE I

300 .. - Z a

S200

100

O 10 20 30 40 50 BLOWS PER FOOT PENETRATION DYNAMIC CONE

LEGEND

0 RED BEACH SITE O NORFOLK SITE I A NORFOLK SITE 3

Fig. 6. Comparison of spud bearing and dynamic cone penetration, Red Beach site 29

Table 5 Comparison of Spud Penetrations and Dynamic Cone Penetration Resistance Red Beach Site

Actual Dynamic Cone Applied Penetration No. of Driving Estimated Dynamic Estimated Resistance Spuds Force Cone Penetration Spud at Maximum Average Actual Repre- per Spud Resistance Required Penetration Spud Penetration Spud Penetration Barge sented kip* blows per ft** el, ft mlwt blows per ft el, ft mlw

F 6tt 483 29 -59 22 -48

G 2$ 483 29 -55 25 -48

G 4** 526 32 -29 21 -28

I 4 272 15 -16 15 -18

* Corrected for spud buoyancy to give applied force resisted by soil. * Taken from Norfolk data curve, fig. 6. t Taken from fig. 5 and based on estimated dynamic cone penetration resistance required. tt Spuds at mid-point of barge. * Spuds at offshore end of barge. $# Spuds at inshore end of barge. 47. The dynamic cone penetrations at the pier barge locations (fig. 5) show that the cone penetrated the very soft clays under a resistance of less than 4 blows per foot, developed some resistance in the soft clay containing sand lenses, and began developing resistance rapidly upon contact with the sand and sandy gravel layer overlying the firm clay (fig. L). A decrease in cone resistance occurred at the boundary between the sand or sandy gravel stratum and firm clay, but the resistance increased rapidly after about 2-ft penetration in the firm clay. Sixty blows per foot resistance had been developed within 23 ft after reaching the top of the sandy gravel shown by boring U-1, and within 10 ft after reaching the top of sand shown by boring U-2. The F and G barge spuds should penetrate the very soft clays to at least the top of the sand or sandy gravel stratum as the cone penetration resistances obtained in the very soft clays do not indicate sufficient resistance to support the spuds under a driving force of 272 kip. However, some of the spuds did not penetrate the very soft clay and stopped at elevations less than those to which the cone penetrated under its own weight. This behavior indicates that these spuds might not have been driven to refusal under the available Jacking force. It is possible that mechanical difficulties 30 in the air Jacking system, when several spuds were being driven simulta- neously, prevented proper operation of the jacks. Also, it is possible for the spuds to bind in the spud wells, and for apparent spud refusal to occur when actually the full jacking force is not being applied to the spud below the barge. .Therefore, spuds that did not penetrate below the elevations to which the cone penetrated under its own weight were not considered in comparison of spud penetrations and dynamic cone penetration resistance. The estimated penetrations are greater than the actual penetrations and the percentage of error varies from 4 per cent to 23 per cent. 48. A comparison of the cone penetration resistances obtained at the location of the I platform barge at Red Beach with those obtained in the Norfolk tests indicated that the spuds on the I barge should penetrate through the silty sand stratum into the underlying clayey sand to el -16 ft mlw. Cone sounding C-9 at the I barge location (fig. 4) shows cone penetration resistances varying from 7 to 19 blows per foot between el -10 and -25 ft mlw. A resistance of 15 blows per foot was reached at el -12, -16, -22, and -25 ft mlw with resistances both greater and less than 15 blows per foot between these elevations, which indicated soft and firm stratified soil. Immediately below el -12 ft the cone resistance only reached 16 blows per foot, and then decreased to 12 blows per foot at el -14 ft. The resistance at this point was not considered sufficient to support the spuds under a spud load of 272 kip, as the spud diaphragm would not contact the soil surface at this depth of penetration and allow end bearing to develop. Below el -16 and -22 ft the resistance increased to 19 blows per foot before decreasing, which was considered sufficient to support the spuds, as the diaphragm would have been filled with soil at about el -16 ft and spud end bearing would develop. Below el -25 ft the cone resistance increased to 60 blows per foot at el -28 ft, which is considered more than adequate to support the spuds. 49. Three of the spuds stopped at el -16 ft and the fourth penetrated to el -22 ft after first stopping at el -16 ft. The spuds are located 40 to 80 ft from cone sounding C-9 and the spud which penetrated to el -22 is located 80 ft from the cone sounding. The spud penetrations 31 obtained and the estimated penetrations are considered to be in good agreement. The percentage of error of the estimated penetrations is 14 per cent for the one deep spud and 0 per cent for the other three. 50. The actual dynamic cone penetration resistances in blows per foot at maximum spud penetration as shown in table 5 have been plotted on fig. 6. Using these data, curves were drawn for minimum and maximum cone penetration resistance in blows per foot versus spud penetrations and are considered reasonable for use in estimating spud penetrations in similar soils.

Computation of spud penetration resistance 51. The bearing capacity of the spuds was computed using the formula given in paragraph 25. Values from laboratory tests shown in table 4 were used in the computations. Values of cohesion obtained from unconfined compression tests on undisturbed soil samples were used to determine end bearing, and values from unconfined compression tests on remolded samples were used to determine skin friction. Soil test data from samples within each stratum were considered representative of the stratum and were used in computing that portion of spud bearing affected by the stratum. As the spud is pushed into the soil, disturbance will take place and the remolded strength of the soil is effective in developing skin friction at the time the penetration is made. The skin friction portion of the bearing capacity should increase with time owing to a regain in shear strength of the soil disturbed during penetration, as the sensitivity ratio of the clay soils at the site ranges from 1.5 to 4.0.

Comparison of estimated and actual spud penetration 52. Table 6 lists the estimated depths of penetration of the spuds determined from computations and the actual depths of penetration obtained at the Red Beach site, together with a breakdown of the computed bearing values for estimated penetrations and the average actual penetrations. The last column in the table gives the actual driving force applied to the spud and transmitted to the foundation during final driving. 32

Table 6 Computed Spud Bearing Red Beach Site

... Estimated Average Actual Depth Comp)uted- - Computed- Computed Elevation Bottom Eleva- of Spud Skyin End Total Applied Bottom of Spud tion of Spuds Embedment Friction Bearing Bearing Driving Force B4 g Boring ft mlw ft miw ft hi kip hip per Spud, kip

F U-1 -51 38.3 5;6 136 192 478* -52 39.3 6)2 915 977 478* 46** 33.3 29 128 157 485*

G U-2 -22 16.4 1L8 84 102 528* -23 17.4 2?0 637 657 526* * -23 17.4 20 637 657 526*

H U-3 -15 11.2 38 506 544 272 -15t 11.2 338 506 5 44 272

I U-4 -17 15.0 633 386 449 272 -17.5t 15.5 63 396 459 272

* Driving force of 541 kip corrected for buoyancy of spud. ** Four spuds nearest boring. t All four spuds on barge.

53. The estimated spud penetrations of the F and G barges (table 6) were based on test data from undisturbed sample borings U-I and U-2 at the Red Beach site (table 4) and a driving force of 541 kip corrected for the buoyancy of the submerged portion of the spud. The borings show that the various soil strata occur at different elevations in borings U-i and U-2 and that the strata dip sharply toward the offshore end of the barges. The elevations of strata changes at intermediate points between borings U-i and U-2 were estimated from cone soundings C-3, C-4, and C-7. 54. The computed spud bearings for the estimated penetrations (table 6) show that the spuds should penetrate the very soft clays to within 1 ft or less of the top of the sand (shown by boring U-2 at el -23 ft) or sandy gravel (shown by boring U-1 at el -52 ft) under a low penetration resistance of 102 to 192 kip, and then develop a penetration resistance higher than the spud driving force of 541 kip upon contact with the sand or sandy gravel. Therefore, the spuds should penetrate Just to the top of the sand or sandy gravel stratum. The actual penetrations varied from el -23 to -29 ft at the shore end of the G barge near boring U-2 and from el -41 to -50 ft at the offshore end of the F barge 33 near boring U-I. Variations in the elevation of the sand or sandy gravel stratum could account for the difference in the estimated depth of spud penetration and the actual penetrations obtained. However, one of the spuds near the offshore end of the F barge was located immediately adjacent to boring U-l, and the spud did not penetrate through the soft clay. The error of the estimated penetrations based on spud embedment in the soil is 18 per cent for the average of the four spuds nearest boring U-1 and 0 per cent for the average of the four spuds nearest boring U-2. 55. The estimated spud penetrations computed for the platform barges (table 6) are based on test data from undisturbed sample borings U-3 and U-4, table 4, and a driving force of 272 kip per spud. The computations showed that a spud penetration of 272 kip would not be mobilized until the spuds penetrated sufficiently to develop end bearing, at which point more than sufficient penetration resistance would develop than required to resist a driving force of 272 kip. The H barge spuds did not have vent holes below the diaphragm and the spuds should have developed end bearing after penetrating only 12 ft into the soil (el -15.4 ft) for, at this depth, the air trapped under the diaphragm would be compressed to a maximum under the driving force of 272 kip and end bearing in excess of 272 kip would develop immediately. They penetrated to el -15.0 ft. On the I barge the spuds should penetrate 15 ft into the soil, at which depth (el -17.0 ft) end bearing would develop in excess of 272 kip. Three of the I barge spuds penetrated 14 ft and one to a depth of 20 ft. The error in the estimated penetrations averaged 4 per cent for the H barge spuds, and 3 per cent for the I barge spuds.

Determination of pile penetration resistance 56. Tower 4 at the Red Beach site was installed on two hollow steel pipe piles in very shallow water just off the beach. The piles were 30 in. in diameter, had a wall thickness of 3/8 in., and were 50 ft long. They were driven to refusal at el -38 ft mlw with a 5-ton, double-acting, steam hammer developing on energy of 38,000 ft-lb. Each pile was required to support a total load of 150 kip. Depth of penetraticx 34 required to support the tower was determined by the formula given in paragraph 25. The computations showed that each pile would develop a bearing capacity of 186 kip at el -26 ft (top of stiff clay) and 302 kip at el -38 ft (top of firm clay), the maximum depth of penetration, thus giving a safety factor of 2.0, which is considered adequate. Land tower footings 57. Towers 1, 2, and 3 at Red Beach were installed on spread footings. With a wind velocity of 30 mph, each footing will be subjected to a vertical load of 148 kip during capacity operations, with one 40-kip cable car at the tower and one each at the center of the adjacent cable spans. The size of footings required to support the towers under the maximum vertical load conditions was computed by the semiempirical formula for square footings given in Terzaghi and Peck* as follows:

Q = 7 (Df N + 0.4 B N) + 1.3 c N q y c where

Qd = bearing capacity per unit area 7 = unit weight of the soil c = cohesion of the soil Df = depth of embedment of footing B = width of footing N , N , N = factors dependent upon the shearing strength of the q c soil and evaluated in charts in the referenced publication.

Footings 6 ft by 6 ft are supplied with the tower units and may be set at a maximum depth of 2 ft without cribbing. The tower footings will be subjected to a maximum horizontal load of 2750 lb during hurricane winds of 125 mph. A 2-ft depth of embedment would give more than adequate resistance against this horizontal load. Soil strength values from borings U-6, U-7, and U-8 (table 4) were used in the computations of bearing capacity for towers 3, 2, and 1, respectively. The computed bearing

* Op. cit. 35

Table 7 Computed Bearing for Land Towers Red Beach Site

Footing Bearing Capacity, kip at 2-ft Depth with Safety Tower Maximum Load Factor of 2 Number kip/footing 6 ft by 6 ft 8 ft by 8 ft

1 148 183 -

2 148 263 ---

3 148 93 193 capacities are shown in table 7. Tower 3 located just onshore in the filled beach area was erected on 8- by 8-ft footings. Although embedment of 2 ft would have been adequate for bearing, the footings were set on cribbing to a depth of 7 ft to afford protection against scour by wave action. Land anchor stability 58. The land anchor is a floored steel frame 30 ft wide by 40 ft long with a braced retaining wall 30 ft wide by 12 ft high located 10 ft back of the forward end of the anchor. Eyes for securing guy ropes, track ropes, and traction ropes are located at the top of the wall section of the anchor. The anchor is designed to be buried to a depth of 11-12 ft in a pit and is required to withstand a maximum horizontal pull of 607 kip. The stability of the anchor was determined by summating the sliding resistance of the loaded frame and the resistance of the passive earth pressure of the soil in front of the frame. The computations showed that if the anchor was embedded to a depth of 11 ft and the ex- cavation was backfilled to the ground surface, it would develop a resistance to sliding of 890 kip under submerged soil conditions, neglect- ing the weight of the anchor. This gives a factor of safety of 1.5, which is considered sufficient. Also, the ground-water table at the anchor was 4 ft below the ground surface. This will increase the effective weight of the soil above the ground water by about 83 per cent 36 over completely submerged conditions, resulting in a factor of safety above 1.5.

Summary of Findings and Conclusions

Pier barges 59. The tests performed on the foundation soils at Red Beach showed that the required bearing for the pier barges would not be developed until the spuds reached the firm sandy gravel or sand layer overlying the firm clays at el -23 ft mlw at the landward end of the G barge, el -48 ft mlw at the offshore end of the G barge, and el -52 ft mlw at the offshore end of the F barge, and that the spuds would penetrate to these elevations under the applied driving force and then develop more than the required bearing. All dynamic cone penetration test data and computations based on soil strength values indicated that spuds 100 ft long would be required to raise the F and G barges to the desired height and obtain the required penetration and bearing. 60. Some of the spuds did not penetrate to the sand or sandy gravel stratum and five of the spuds did not penetrate through the upper stratum of very soft clay (see fig. 4). Some differential settlement of the pier barges, particularly the F barge, could possibly occur under the maximum loading indicated in paragraph 41. However, since bearing computations were based on the strength data from remolded soil samples used for determining skin friction values, and since the sensitivity ratio of the soil ranges from 1.5 to 4.0, a regain in soil strength will occur with time. This regain of soil strength, together with the fact that the spuds reaching the sand or sandy gravel stratum mobilized more than the required bearing, should offset to some degree the lack of bearing support of some of the spuds and minimize settlement. Platform barges 61. The tests showed that the required bearing would not be obtained on the H and I platform barge spuds until full end bearing developed, and then more than adequate bearing would be mobilized. The platform barge spuds penetrated to sufficient depths to develop full end 37 bearing and 50-ft length spuds were sufficient to obtain the required bearing and raise the barges to the desired height. Land-based towers and land anchor 62. Tower 4, just offshore, was installed on two 30-in.-diameter pipe piles driven to el 38.0 ft mlw in the firm clay, which gave more than adequate bearing. Towers 1 and 2 were installed on standard 6- by 6-ft footings embedded to a depth of 2 ft, and tower 3 was installed on 8- by 8-ft footings embedded to a depth of 7 ft, which the computations indicated as being adequate. 63. The land anchor was embedded to a depth of 11 ft and the ex- cavation was backfilled to the ground surface, which gave sufficient resistance to sliding to withstand the maximum operating load.