Through applying horizontal loads on pile top in model test

the displacement distributions of soils on the upper-surface and around piles are analyzed by the non-target digital photography deformation measure system. The surface horizontal displacement of sand around dual-piles is observed. The effect of space between piles on the interaction of piles is studied combining the relationship between displacement of pile top and horizontal load. Particle flow code in two dimensions (PFC2D) is introduced to simulate the displacement of sand at some given depth. The particle flowing behavior of sand around active pile and the effect of space between piles on the pile-soil interaction are revealed. The results show that the displacement field of sand around piles seems two fusiform bodies; the deformation region of sand in front of pile extends with the increasing of compactness of sand; the effect of interaction between piles is obvious with small pile space.