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15 N Silt Fence Test Site (150 ft x 40 feet approx.) Figure 3-1. Aerial view of the test site and surrounding area. Torvane test and are not likely to be representative of the soil Figure 3-5 provides plots of the cone tip resistance, friction in-situ. The undrained shear strength was also computed from ratio, and pore pressure versus depth as a function of depth for the cone tip resistance using the following correlation equation: all four of the CPT soundings. The measured parameters and layering are generally very consistent for all four soundings, (qc - ) which indicates that the lateral pile load tests can be fairly com- su = (2) Nk pared from one site to the next. Figure 3-6 provides a plot of the shear wave velocity as a where qc is the cone tip resistance, is the total vertical stress, function of depth obtained from the downhole seismic cone and Nk is a variable which was taken to be 15 for this study. The testing. The interpreted soil profile and cone tip resistance are undrained shear strength obtained from Equation 2 also is also provided in Figure 3-6 for reference. The shear wave veloc- plotted versus depth in Figure 3-3(c) and the agreement with ity in the upper 10 ft of the profile is between 300 and 400 ft/sec, the strengths obtained from the Torvane and unconfined com- which is relatively low, and suggests a low shear strength. pression tests is reasonably good. Nevertheless, there is much Between a depth of 10 to 20 ft, the velocity increases to about greater variability and the drained strength in the interbedded 550 ft/sec. This increase in velocity is likely associated with the sand layers is ignored. A summary of laboratory test results is interbedded layer that contains significant sand layers. Below provided Table 3-1. 20 ft, the velocity drops to a value of around 500 ft/sec and Four cone penetration tests were performed across the test remains relatively constant to a depth of 45 ft. site and plots of cone tip resistance, friction ratio, and pore pressure are provided as a function of depth in Figure 3-4. In addition, the interpreted soil profile also is shown. From the 3.3 Single Pile Test in ground surface to a depth of about 15 ft the soil profile appears Untreated Soil to be relatively consistent with a cone tip resistance of about Test Pile Properties 6 tons per square foot (tsf) and a friction ratio of about 1%. However, one thin sand layer is clearly evident between 6 and A 12.75-in. OD pipe pile with a 0.375-in. wall thickness was 8 ft. The cone tip resistance, friction ratio, and pore pressure driven closed-ended with a hydraulic hammer to a depth of plots clearly show the interbedded silt and sand layering in the 45 ft below the excavated ground surface on June 15, 2007. soil profile between 15 and 27 ft. below the ground surface. The test pile had a beveled end that allowed a 1.5-in. thick

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N Pile Cap 4 Pile Cap 3 Pile Cap 2 Pile Cap 1 Geopiers Compacted Fill Flowable Fill Compacted Fill Flowable Fill Jet Grouting Jet Grouting Mass Mixing 5ft x 9ft x 10ft 5ft x 9ft x 5ft Virgin Soil Virgin Virgin Virgin 9ft x 9ft x 5ft 5ft x 9ft x 5ft 9ft x 9ft x 10ft 5ft x 9ft x 10ft 5ft x 9ft x 10ft 9 ft 32 ft 9 ft 32 ft 9 ft 32 ft 9 ft Figure 3-2. Generalized layout of test pile groups at the test site.

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17 (b) Moisture Content (%) (c) Undrained Shear Strength, su (psf) (a) Soil Profile 0 20 40 60 0 20 40 60 0 250 500 750 1000 1250 0 0 0 LEAN CLAY (CL) w/ Sand Lenses 5 FAT CLAY (CH) w/ Sand Lenses 5 5 10 LEAN CLAY (CL) w/ Silt Lenses 10 10 Depth Below Excavation (ft) Depth Below Excavation (ft) Depth Below Excavation (ft) 15 15 15 SANDY SILT (ML) with Silty 20 Sand and Lean Clay Layers 20 20 PL LL wn 25 25 25 SANDY LEAN CLAY (CL) w/ 30 Sand Lenses 30 30 35 35 35 Unconfined LEAN CLAY (CL) w/ Sand Lenses Torvane CPT 40 40 40 45 Interbedded LEAN CLAY (CL) 45 45 and SANDY SILT (ML) 50 50 50 Figure 3-3. Borehole log, plot of Atterberg limits and natural water content vs depth, and plot of undrained shear strength vs depth. plate to be welded flush with the edge of the pile at the bottom. 10 ft. The steel pipe pile was filled with concrete that had an The steel conformed to ASTM A252 Grade 3 specifications average unconfined compressive strength of 5150 psi based on and had a yield strength of 58,700 psi based on the 0.2% tests of four specimens. A drawing of the cross-section for the offset criteria. The moment of inertia of the pile itself was test pile is provided in Figure 3-7. 279 in.4; however, angle irons were welded on opposite sides of the test pile, which increased the moment of inertia to Test Layout, Instrumentation, 342 in.4. A steel reinforcing cage was installed at the top of the and Procedure test pile to replicate the reinforcing cages in the test piles within the pile groups. The reinforcing cage consisted of six #8 The lateral load test was conducted on October 10, 2007, reinforcing bars that were confined within a #4 bar spiral with after the pile had been in the ground for about 4 months. The a diameter of 8 in. The reinforcing cage extended to a depth of ground around the test pile was excavated to the elevation of Table 3-1. Summary of laboratory soil test data. In-Place Atterberg Limits Miniature Dry Natural Liquid Plastic Plasticity Unconfined Vane Unified Soil Depth Unit Moisture Limit Limit Index Compressive Shear Classification (ft) Weight Content (LL) (PL) (PI) Strength Strength System d wn (%) (%) (%) (lb/ft2) (Torvane) Symbol (lb/ft3) (%) (lb/ft2) 1.25 117.6 34.2 39 18 21 1104 - CL 2.75 117.4 34.4 38 18 20 626 620 CL 5.75 104.6 56.0 51 21 30 384 320 CH 8.5 112.4 41.5 38 18 20 684 534 CL 11.5 110.8 44.1 38 19 19 741 500 CL 16.5 126.6 24.2 19 18 1 1081 560 ML 26.75 116.9 35.0 27 14 13 237 780 CL 33.5 124.6 26.1 27 14 13 1306 780 CL 36.75 117.1 34.8 35 17 18 1381 840 CL 41.75 112.0 42.1 46 17 29 1037 520 CL 48 117.2 34.6 33 16 17 297 660 CL

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Cone Tip Resistance, qt (tsf) Friction Ratio, Rf (%) Pore Pressure, u (ft) Soil Profile 0 20 40 60 0 50 100 150 0 2 4 6 0 100 200 300 0 0 0 0 LEAN CLAY (CL) w/ Sand Lenses CPT 2 5 5 5 5 FAT CLAY (CH) w/ Sand Lenses Hydrostatic 10 10 10 10 LEAN CLAY (CL) w/ Silt Lenses Depth Below Excavation (ft) Depth Below Excavation (ft) Depth Below Excavation (ft) Depth Below Excavation (ft) 15 15 15 15 SANDY SILT (ML) with Silty Sand 20 and Lean Clay Lenses 20 20 20 25 25 25 25 SANDY LEAN CLAY (CL) w/ 30 Sand Lenses 30 30 30 35 35 35 35 LEAN CLAY (CL) w/ Sand Lenses 40 40 40 40 CPT 2 CPT 2 45 Interbedded LEAN CLAY (CL) and 45 45 45 SANDY SILT (ML) 50 50 50 50 Figure 3-4. Plots of cone tip resistance, friction ratio and pore pressure vs depth curves from cone penetration test (CPT) Sounding 2 near the center of the site along with soil profile.

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Cone Tip Resistance, qt (tsf) Friction Ratio, Rf (%) Pore Pressure, u (ft) Soil Profile 0 20 40 60 0 50 100 150 0 2 4 6 0 100 200 300 0 0 0 0 LEAN CLAY (CL) w/ Sand Lenses CPT 1 5 FAT CLAY (CH) w/ Sand Lenses 5 5 5 CPT 2 CPT 3 10 LEAN CLAY (CL) w/ Silt Lenses 10 10 10 CPT 4 Hydrostatic Depth Below Excavation (ft) Depth Below Excavation (ft) Depth Below Excavation (ft) Depth Below Excavation (ft) 15 15 15 15 SANDY SILT (ML) with Silty Sand 20 and Lean Clay Lenses 20 20 20 25 25 25 25 SANDY LEAN CLAY (CL) w/ 30 Sand Lenses 30 30 30 CPT 1 CPT 1 35 35 35 35 LEAN CLAY (CL) w/ Sand Lenses CPT 2 CPT 2 CPT 3 CPT 3 40 40 40 40 CPT 4 CPT 4 45 Interbedded LEAN CLAY (CL) and 45 45 45 SANDY SILT (ML) 50 50 50 50 Figure 3-5. Plots of cone tip resistance, friction ratio, and pore pressure vs depth curves from all CPT soundings at the site along with soil profile.

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20 Cone Tip Resistance, qT (tsf) Shear Wave Velocity (fps) Soil Profile 0 20 40 60 0 50 100 150 0 200 400 600 800 1000 0 0 0 LEAN CLAY (CL) w/ Sand Lenses 5 FAT CLAY (CH) w/ Sand Lenses 5 5 10 LEAN CLAY (CL) w/ Silt Lenses 10 10 Depth Below Excavation (ft) Depth Below Excavation (ft) Depth Below Excavation (ft) 15 15 15 SANDY SILT (ML) with Silty 20 Sand (SM) and Lean Clay (CL) 20 20 Layers 25 25 25 SANDY LEAN CLAY (CL) w/ Sand Lenses 30 30 30 35 35 35 LEAN CLAY (CL) w/ Sand Lenses 40 40 40 45 Interbedded LEAN CLAY (CL) 45 45 and SANDY SILT (ML) 50 50 50 Figure 3-6. Plots of cone tip resistance and shear wave velocity versus depth from seismic cone testing along with soil profile. 12.75 inch OD pipe pile with 0.375 in wall thickness (fy=58.6 ksi) 6-#8 longitudinal bars (fy=60 ksi) with 8 inch diameter #4 bar spiral at 4 inch pitch Concrete in-fill (f'c=5150 psi) 1.5"x1.5"x0.25" angles (fy=36 ksi) (rotated 18 from line of loading) Direction of Loading Figure 3-7. Cross-section of single pipe pile.

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21 head fixity condition than whether it was a free-head or fixed- head. The boundary condition can be changed easily for sub- sequent analyses once the soil model is established. The load was applied to the test pile using a hydraulic jack attached to an electric pump. Hemispherical plates were used to prevent the application of moment to the pile and account for any eccentricity in the loading. Load was measured using a resistance-type strain gauge load cell that had been calibrated previously in the laboratory. Pile head deflection was measured at the elevation of the load point with a string potentiometer attached to an independent reference frame. In addition, pile head deflection was measured at an elevation 3.31 ft above the load point so that pile head rotation could be computed. Prior to placing concrete in the test pile, a 1-in. diameter conduit was installed to a depth of 30 ft. A shape accelerometer array was Figure 3-8. Photograph of lateral load test on single inserted into this conduit at the beginning of the load test so pipe pile. that deflection versus depth profiles could be determined at various load increments. Data was recorded using computer data acquisition systems. A photograph of the test pile during the base of the pile caps used in the pile group testing, which testing is provided in Figure 3-8. was approximately 2.5 ft below the ground surface shown in The load test was performed incrementally using a deflec- Figure 3-9. Load was applied at a height of 1.5 ft above the sur- tion control approach. The load in the hydraulic jack was rounding ground surface. In contrast to the pile group tests increased to deflection increments of 0.125, 0.25, 0.50, 0.75, where the pile head was restrained (fixed-head), the pile head 1.0, 1.5, 2.0, and 2.5 in. The maximum deflection was some- for the single pile test was unrestrained (free-head). A free- what larger than that used for the pile group testing to facili- head lateral load test for a single pile is common because it is tate calibration of the numerical models. After reaching each very difficult to create a truly fixed-head condition for a single target deflection, the deflection was maintained for 3 minutes pile. Because the purpose of the test was to calibrate the analy- and then load was reduced to zero prior to loading the pile to sis model, it was considered more important to know the pile the next increment. 35 30 25 Pile Head Load (kips) 20 15 10 5 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Pile Head Deflection (in) Figure 3-9. Complete pile head load vs pile head deflection curve.

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22 35 30 25 Pile Head Load (kips) 20 15 10 Pipe Pile 5 0 0.0 0.5 1.0 1.5 2.0 2.5 3.0 Pile Head Deflection (in) Figure 3-10. Peak pile head load vs pile head deflection. Test Results values and eliminating the unload and reload segments. The curve exhibits the conventional hyperbolic shape that would be A plot of the complete pile head load versus deflection expected for a pile in soft clay. The peak pile head load versus curve for the entire test is presented in Figure 3-9. This curve rotation curve is also plotted in Figure 3-11. The rotation, , provides the load path taken during loading, unloading, and was determined using the following equation: reloading for each cycle. While the load was decreased to zero after each increment, the pile did not return to its initial zero ( 1 - 2 ) = tan -1 (3) deflection level, but exhibited a residual deflection. This may H have been due to side friction and soil falling into the gap behind the pile. During reloading, the load-defection curve where 1 is the pile deflection 3 ft above the load point, 2 is the was stiffer than that observed during virgin loading at the pile deflection at the load point, and H is the distance between same deflection. the measurements (3.31 ft). The virgin pile head load versus deflection curve is plotted Deflection versus depth curves obtained from the shape in Figure 3-10. This plot was developed by plotting the peak accelerometer arrays are provided in Figure 3-12 for a number 35 30 25 Pile Head Load (kips) 20 15 10 Pipe Pile 5 0 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 Pile Head Rotation (Degrees) Figure 3-11. Peak pile head load vs pile head rotation.