基于平面应变统一强度公式的结构性黄土填料挡墙地震被动土压力研究

Seismic passive earth pressure against the retaining wall of structural loess based on plane strain unified strength formula

基于结构性黄土不同含水率方形试样的三轴剪切试验,研究了非饱和黄土的残余强度效应和构度与强度参数的关系,引入两种效应修正了平面应变统一强度公式,分析了地震荷载作用下墙后土应力摩尔圆的变化规律,采用水平层分析法,建立了综合考虑中主应力、土结构性、残余强度的黄土填料被动动土压力公式。研究表明:平面应变统一强度公式计算得到的峰值或残余黏聚力和摩擦角随统一强度参数b值增大而增大,结构性对黏聚力的增幅较大,而对摩擦角影响则不明显;结构性黄土的地震被动土压力系数随b值、构度指标的增大而增大,而随水平地震系数的增大而减小;结构性较大时残余强度计算的地震被动土压力系数较峰值强度大,结构性较小时,两者计算结果接近。

Based on triaxial shear tests of structural cube loess samples with different water contents,residual strength effect and relationships between structural indexes and strength parameters are studied,based on which the uniform strength formula for plane strain is corrected.Variations of Mohr circle of soil stress behind the wall under the seismic conditions are analysed.By using the method of level layer element,calculating seismic passive earth pressure of loess filler considering intermediate principal stress,structure and residual strength effects is established.The results indicate that cohesions and friction angles calculated by unified strength theory increase with unified strength parameter b.The structure of loess has a huge influence on cohesion while the effect of friction angles is not obvious.The total seismic passive earth pressure coefficient increases with the increase of b value and structural index,while it decreases with the increase of horizontal seismic coefficient.The residual strength makes a more contribution to seismic passive earth pressure coefficient for large structure than for small structure.