考虑填土侧向变形的地震土压力计算方法

Evaluation of Seismic Earth Pressure Considering Lateral Deformation

摘要:

地震土压力评价是挡土墙抗震设计的关键问题之一。以往的研究结果表明,挡墙上地震土压力的大小及分布与墙体的侧向位移或者墙后填土的侧向变形密切相关。经典的物部-冈部地震土压力公式可计算填土处于主动与被动状态的极限平衡条件下的土压力,未考虑挡墙侧向位移或填土侧向变形对土压力的影响。在研究土压力系数随应变增量比变化规律的基础上,本文指出土压力系数与挡土墙位移量之间不存在唯一性关系,发现正常固结填土的土压力系数与以应变增量比表述的填土侧向应变约束条件之间具有良好的唯一性,揭示了压剪耦合效应是土压力形成的物理本质;基于上述的唯一性关系和中间土楔等概念,提出了可考虑填土侧向变形的地震土压力实用计算方法,并通过土压力模型试验结果初步验证了该方法的合理性。

Abstract:

Evaluation of seismic earth pressure is one of the key items in the earthquake-resistant design of retaining structures.Previous studies indicate that seismic earth pressure is closely related to the lateral deformation of the backfill.Classic Mononobe-Okabe earth pressure theories can be used to compute the earth pressure at the active and passive limit states only,ignoring the effect of lateral deformation on earth pressure change.In this paper,the variation of earth pressure coefficient with the strain increment ratio is investigated.The earth pressure coefficient is experimentally confirmed to have no unique relationship with the wall displacement,but it has a unique one with the strain increment ratio.The compression-dilatancy coupling effect is found to be responsible for the dependency of the earth pressure change on the strain increment ratio and also the lateral strain constraint of the backfill.From this finding and new concept of intermediate soil wedge,a new method is then developed for the evaluation of the seismic earth pressure under any lateral deformation.Furthermore,Its essential effectiveness is preliminarily checked through comparing the calculated results with model test data.