Abstract: A series of 1g model tests was carried out using a motor servo horizontal cyclic loading equipment to study the stiffness and cumulative displacement of the large-diameter single pile in sand under horizontal cyclic loading. The test results indicated that the residual displacement generated by one loading and unloading cycle is about 80% of the peak displacement. As the number of cycles increases, the area of the cyclic loading hysteresis curve gradually decreases, indicating that the behavior of soil around the pile changes from elastoplastic to elastic stage. The secant stiffness of the hysteretic curve increases firstly and then decreases with the increase of the number of cycles, which is caused by the trend that the soil around the pile is gradually dense, and the resistance of the soil around the pile is developing from shallow to deep. The secant stiffness of the hysteretic curve increases firstly and then decreases with the increase of the number of cycles, which is caused by the progressive compaction of the soil around the pile in the shallow layer and the tendency of the resistance of the soil around the pile to transfer from the shallow layer to the deep layer. The cumulative displacement of the pile top decreases to approximately the same extent as the pile diameter increases. However, with the increase of burial depth, the reduction of displacement also gradually decreases, revealing the existence of critical burial depth. An empirical model of cyclic cumulative displacement is proposed by linear fitting in a double logarithmic coordinate system based on the exponential model. It is found that the effect of increasing the pile diameter on the reduction of cyclic cumulative displacement is better than that of increasing the buried depth.

Key words: large-diameter single pile foundation, horizontal cyclic loading, 1g model test, cumulative displacement