Investigation on 3D ground deformation and response of active and passive piles in loose sand

Two scaled-model tests were carried out to investigate the pile–soil–pile interaction during a lateral loading process. Two instrumented piles, termed the active pile and the passive pile, were installed into loose sand. The active pile head was subjected to lateral loads, and the passive pile was set at twice pile width away from the active pile center. To study the effect of the direction of lateral loading on the pile–soil–pile interaction, the passive pile was set in front of and behind the active pile in Tests 1 and 2, respectively. Experimental results showed that the leading passive pile produced much stronger effects on surrounding ground deformation and on response of active pile as compared with the trailing passive pile. The intermediate soil between the active and passive piles was the most susceptible to be affected by the leading passive pile. Within this zone, the larger magnitude of ground heave (by up to 50 %) was caused by the leading passive pile. The leading passive pile also enhanced the lateral resistance of the active pile by up to 70 %. The underlying reason is that the leading passive pile was located in the passive influence zone of the active pile and hence restrained the intermediate soil between the two piles. As a result, the relative stiffness ratio between soil and pile increased, leading to a stronger soil resistance.