Closure of "Measured and Computed Lateral Response of a Pile Group in Sand"

Lateral load test was performed on a full-scale pile group following blast-induced liquefaction to evaluate pile–soil–pile interaction effects. The 3×3 pile group at 3.3 pile diameter spacing was driven into loose to medium dense sand. A single pile test was conducted for comparison. In contrast to preliquefaction tests, group interaction effects were insignificant after liquefaction. The lateral resistance of each pile in the group was similar and about the same as that for the single pile test. p–y curves were developed based on the bending moment versus depth data for Ru values of 95%. While the slope of p–y curves for nonliquefied sand typically decreases with continued deflection, the slope of the backcalculated p–y curves for liquefied sand increases with deflection. This phenomenon appears to be connected with load-induced dilation and a decrease in excess pore pressure locally around the pile. The p–y curves stiffened with depth and as the excess pore pressure ratio decreased. Equations were devel...

Lateral Resistance of a Full-Scale Pile Group in Liquefied Sand

A lateral load test was performed on a full-scale pile group to evaluate pile–soil–pile interaction effects. The 3×3 pile group at 3.3 pile diameter spacing was driven opened ended into a profile consisting of loose to medium dense sand underlain by clay. The load carried by each pile was measured and strain gages were attached to determine bending moment. A single pile test was conducted for comparison. Group effects significantly reduced lateral resistance for all rows relative to single pile behavior. Trailing rows carried less load than the leading row. In contrast to tests in clay, lateral resistance was also consistently lower for middle piles within each row. Backcalculated p -multipliers were 0.8 for the front row and 0.4 for the trailing row piles which is consistent with results from previous centrifuge tests and full-scale tests where different installation methods were used. Good agreement between measured and computed pile group response was obtained using the p -multiplier approach. Based on...

Measured and Computed Lateral Response of a Pile Group in Sand

A series of centrifuge model tests has been conducted to examine the behavior of laterally loaded pile groups in normally consolidated and overconsolidated kaolin clay. The pile groups have a symmetrical plan layout consisting of 2, 2 32, 233, 333, and 434 piles with a center-to-center spacing of three or five times the pile width. The piles are connected by a solid aluminum pile cap placed just above the ground level. The pile load test results are expressed in terms of lateral load-pile head displacement response of the pile group, load experienced by individual piles in the group, and bending moment profile along individual pile shafts. It is established that the pile group efficiency reduces significantly with increasing number of piles in a group. The tests also reveal the shadowing effect phenomenon in which the front piles experience larger load and bending moment than that of the trailing piles. The shadowing effect is most significant for the lead row piles and considerably less significant for subsequent rows of trailing piles. The approach adopted by many researchers of taking the average performance of piles in the same row is found to be inappropriate for the middle rows, of piles for large pile groups as the outer piles in the row carry significantly more load and experience considerably higher bending moment than those of the inner piles.

Centrifuge Model Study of Laterally Loaded Pile Groups in Clay

Using the results from three full-scale lateral pile group load tests in stiff clay with spacing ranging from 3.3 to 5.65, computer analyses were performed to back-calculate p multipliers. The p mu...

Pile Spacing Effects on Lateral Pile Group Behavior: Analysis

A static lateral load test was performed on a full-scale pile group to determine the resulting pile-soil-pile interaction effects. The 3 × 3 pile group at three-diameter spacing was driven into a profile consisting of soft to medium-stiff clays and silts underlain by sand. The piles were instrumented with inclinometers and strain gages. The load carried by each pile was measured. A single pile test was conducted for comparison. The pile group deflected over two times more than the single pile under the same average load. Group effects significantly reduced load capacity for all rows relative to single pile behavior. Trailing rows carried less than the leading row, and middle row piles carried the lowest loads. Maximum moments in the group piles were 50–100% higher than in the single pile. P-multipliers were 0.6, 0.38, and 0.43 for the front, middle, and back row piles, respectively. Good agreement between the measured and computed pile group responses was obtained using the p-multiplier approach. Design c...

Lateral Load Behavior of Full-Scale Pile Group in Clay

Static and dynamic (statnamic) lateral load tests were performed on a full-scale 3 x 3 pile group driven in saturated low-plasticity silts and clays. The 324-mm outside diameter steel pipe piles were attached to a reinforced concrete pile cap (2.74 m square in plan and 1.21 m high), which created an essentially fixed-head end constraint. A gravel backfill was compacted in place on the back side of the cap. Lateral resistance was therefore provided by pile-soil-pile interaction as well as by base friction and passive pressure on the cap. In this case, passive resistance contributed about 40 percent of the measured static capacity. The measured resistance was compared with that computed by several techniques. The log-spiral method provided the best agreement with measured resistance. Estimates of passive pressure computed using the Rankine or GROUP p-y curve methods significantly underestimated the resistance, whereas the Coulomb method overestimated resistance. The wall movement required to fully mobilize ...

Kris T. Peterson

Papers

Lateral Load Behavior of Full-Scale Pile Group in Clay

Lateral Load Capacity and Passive Resistance of Full-Scale Pile Group and Cap

Lateral Statnamic Load Testing and Analysis of a Pile Group