液化场地浅埋钢筋混凝土结构物变形及动土压力分析

ANALYSIS OF DEFORMATIONS OF SHALLOW-BURIED REINFORCED CONCRETE STRUCTURES AND DYNAMIC EARTH PRESSURES IN LIQUEFIABLE SOILS

基于多重剪切机构塑性模型和液化前缘面的有效应力分析方法,分析不同地震强度下液化场地中浅埋大断面矩形钢筋混凝土结构物变形与地震动土压力分布特征,进而探索0.85g输入地震波条件下结构物与液化土间的相对位移差、结构物侧壁和顶底板土体的动土压力、剪切应力、有效应力和超孔隙水压力的变化规律。研究得出结构物的最大变形、弯矩和曲率值随着地震强度的加大而增大,结构物最先发生屈服变形部位位于拐角处,并逐步向周围扩展;场地发生液化模型中的结构物–液化土相互作用系数数值小于场地未发生液化模型,结构物与土体间的相对位移差值随着场地液化而剧增到一定值;作用于结构物侧壁的动土压力最大值和震后值随地震强度加大而增加,但不是简单的线性增长;结构物侧壁动土压力随着振动持续而增长,而作用于顶底板土层的剪切应力和侧壁有效应力随着土体液化而剧减。研究结论可为液化场地浅埋结构物的抗震设计提供可靠的依据和参考。

Based on the method of effective stress analysis using a multiple shear plasticity model and the concept of liquefaction front, numerical modeling for deformations and dynamic earth pressures acting on the shallow duct-type reinforced concrete（RC） structures subjected to earthquake motions is presented. Moreover, the change rules of the relative displacement between the underground structures and liquefiable soils, dynamic earth pressures acting on the sidewall of RC structures, shear stress and excess pore water pressures in liquefiable soil during earthquake for the cases with a crest input motion of 0.85 g are further investigated. The results indicate that the values of deformations and bending moments, curvatures of RC structures increase with the level of input motions. And plastic yield area firstly occurs on the comers of structure and expands to other areas. The interaction factors in liquefied models with strong motions are less than those of non-liquefied models with a motion of 0.1 g. The values of relative displacement between ground and structure increase sharply up to a stable value after the soil is liquefied during earthquakes. The maximum and residual values of dynamic earth pressures acting on sidewalls increase with shaking. However, the growth is not a simple linear relationship with the input motion. On the contrary, the shear stresses acting on the top and the bottom slab, and the horizontal effective stresses acting on sidewall decrease sharply when the soil is liquefied. These results provide the foundation and references for the seismic design of shallow underground structures in the liquefiable soils.