挡土墙地震主动土压力的库仑解

传统的Mononobe-Okabe法在实际工程中有着广泛应用,但它仅适用于无黏性土的极限土压力计算,且不能给出土压力分布。基于极限平衡理论,视墙后填土为服从Mohr-Coulomb屈服准则的理想弹塑性材料,假定墙后塑性区的一簇滑移线为直线即平面滑裂面,考虑墙背倾角、地面倾角、土黏聚力和内摩擦角、墙土之间黏结力和外摩擦角、地面均布超载、塑性临界深度以及水平和竖向地震系数等因素的影响,建立较为完善的塑性滑楔分析模型,进而采用极限平衡法求解挡土墙地震主动土压力、滑裂面土反力及其分布,并且通过量纲一化的分析首次提出几何力学相似原理。研究结果表明,总地震主动土压力随水平地震系数代数值的增大而增大;但随竖向地震系数代数值的增大并非总是减小,当水平地震系数较大时,可能出现先减后增的情况。

COULOMB S SOLUTION TO SEISMIC ACTIVE EARTH PRESSURE ON RETAINING WALLS

Although the conventional Mononobe-Okabe method is widely used in practice,it is only applicable for calculating total limit earth pressure of non-cohesive soil,and not for solving earth pressure distribution.Based on the limit equilibrium theory in this paper,the backfill is treated as a perfectly elastoplastic material which follows the Mohr-Coulomb yield criterion,and a family of slip-lines in the plastic zone is assumed as straight lines,i.e.the plane slip surfaces.The influence factors including inclination of wall,slope angle of backfill,cohesion and internal friction angle of soil,adhesion and external friction angle between wall and soil,surface uniform surcharge,plastic critical depth,horizontal and vertical seismic coefficients are considered.And a more reasonable plastic slip wedge analysis model is established to solve the seismic active earth pressure on retaining wall,the reaction force on slip surface and their distributions by using limit equilibrium method.Furthermore,the geometric and mechanical similarity principle is first presented by means of dimensional analysis.The results show that the total seismic active earth pressure increases with the increasing algebraic value of the horizontal seismic coefficient;but it does not always decrease with the increase of the algebraic value of the vertical seismic coefficient;and it may decrease first and then increase when the horizontal seismic coefficient is rather large.