平动模式下考虑剪应力作用的刚性挡土墙主动土压力计算

以墙后为无黏性填土的刚性挡土墙为研究对象,假定破裂面为通过墙踵的平面,且墙后土体中形成圆弧形土拱,考虑滑动土楔内水平土层间的平均剪应力,修正水平层分析法,得到平动模式下主动土压力的表达式。通过与文献中模型试验结果和现有理论成果的对比分析证明了修正方法的合理性。参数分析表明,水平土层间的平均剪应力和主动土压力一样,沿墙高为非线性分布,主要受墙背倾角、墙土摩擦角、填土内摩擦角等因素的影响。对于墙背竖直或墙背较陡且比较粗糙的挡土墙,考虑水平土层间平均剪应力作用算得的主动土压力合力作用点位置高于库仑解且低于不考虑剪应力作用的理论解答,而对墙背较缓且比较光滑的挡土墙,情况则正好相反。而且,不论是否考虑水平土层间的平均剪应力,主动土压力合力作用点位置都会随墙背变缓而降低。

Active earth pressure against rigid retaining wall considering shear stress under translation mode

Taking a rigid retaining wall with granular backfill for example, it is assumed that the failure surface is a plane through the wall heel and the soil arch in the backfill takes the form of a circle, the differential level layer method is modified considering the mean shear stress between level soil layers in the failure wedge, and then a new formulation is proposed for calculating the active earth pressure on the retaining wall undergoing horizontal translation. In order to verify the accuracy of the proposed formulation, the predictions from the equation are compared with both the existing full-scale test results and the values from the existing equations. The calculated results show that the mean shear stress between level soil layers is related to the inclination of wall back face, the angle of wall friction and the internal friction angle of backfill, and its distribution along the wall height is nonlinear like that of active earth pressure. For the wall with a vertical back face or a steep and rough one, the point of application of the resultant active earth pressure by the proposed formulation considering the mean shear stress between level soil layers is higher than that by the Coulomb’s theory, and lower than that by the existing theories which the mean shear stress between level soil layers is negligible. But the conclusion will be just the opposite for the wall with a relatively gentle and smooth back face. In addition, whether the mean shear stress between level soil layers is taken into consideration or not, the height of the resultant active earth pressure will decrease with the increase of the inclination of the back face.