复合地基侧向开挖上覆荷载影响规律离心机试验研究

进行了三组临近复合地基开挖的离心机模型试验,对比分析了相同开挖工况、不同上覆荷载下的桩轴力、桩侧摩阻力、桩土应力比以及桩弯矩的变化规律。结果表明,当复合地基上覆荷载增加时:①桩轴力及其因开挖产生的增量明显增大,桩侧摩阻力数值增大,但方向不变;②桩土应力比及其增量明显增大,其变化趋势与桩轴力曲线一致;③各级开挖工况下的桩体弯矩也会相应增加,而且随着与基坑距离的增加,弯矩值逐渐变小,荷载的影响也逐渐降低;④随着复合地基上覆荷载的增加,高应力水平下的桩间土更容易受到临近基坑开挖的扰动,荷载更多地向刚性桩转移,桩轴力增加,同时伴随着更大的桩体弯矩,进而加快桩体的破坏趋势。研究成果可为既有复合地基临近基坑开挖支护设计提供参考。

Centrifugal model tests on lateral mechanical properties of composite foundation under different additional loads

Three centrifugal model tests are carried out, and the axial force of piles, side friction resistance, pile-soil stress ratio and moment of piles under different loads are compared. The test results show that when the additional loads on the composite foundation increase: (1) The axial force of piles and the increments caused by the excavation increase obviously, and the value of pile side friction increases under the same direction. (2) The pile-soil stress ratio and its increment obviously increase. (3) The bending moment of piles under the excavation conditions increases correspondingly, and the effect of the load is gradually reduced as the distance from the foundation pit increases. (4) With the heavier additional load, the soil between piles is more susceptible to the disturbance of the excavation, and the load is more transferred to the rigid pile, so the axial force of piles increases, with the larger bending moment of piles, the demolition tendency of the piles is accelerated. The conclusions can provide reference for the design of retaining structures adjacent to the existing composite foundation, and the lateral displacement of the composite foundation should be strictly controlled.