挡墙后土体应力状态与主动土压力计算分析

Calculation and analysis of soil stress state and active earth pressure behind retaining wall

为探究土压力理论中挡墙背后土体所处的应力状态,完善对于土体力学条件的考虑,在相关研究成果的基础上,提出在主动土压力条件下,滑移面上土体单元达到极限应力状态时,墙土界面和土楔体内部单元未达到极限应力状态的观点。采用非极限参数对土体的非极限应力状态进行描述,基于二维微分方程对问题进行求解。通过一定假设得到挡墙上土压力和滑裂面上土反力的分布,并进一步考虑滑楔体整体的静力平衡条件和力矩平衡条件,反向求解平面滑移边界的倾角和表征墙背土体非极限状态的参数,从而得到考虑土体非完全极限应力状态,并符合所有力学条件的主动土压力解答。通过实例验证理论的可靠性与合理性,并分析土体内摩擦角与外摩擦角对于土压力分布及有关参数的影响。理论分析结果表明,极限应力状态仅出现在滑裂面上,位于墙面和土楔内部的土体均未完全达到极限状态,而将土体近似视作极限状态并不会对土压力计算结果产生很大影响。相同参数条件下,理论计算滑移面倾角要大于朗肯解和库伦解。内摩擦角和外摩擦角对于土压力分布、合力作用点位置、应力状态参数、土体主应力偏转角度等均会产生不同程度的影响。

In order to explore the stress state of the soil behind the retaining wall in the earth pressure theory and improvethe consideration of the mechanical conditions of the soil,based on the relevant research results,it was proposed that the soil element on the slip surface reaches the limit stress state,while the wall-soil interface and the internal element of the soil wedge do not reach the limit stress state,under the condition of active earth pressure.The unlimited stress state of soil was described by unlimited parameters,the problem was solved based on two-dimensional differential equation.The distribution of earth pressure on the retaining wall and earth reaction force on the sliding surface were obtained through certain assumptions,and the inclination of the plane slip boundary and the parameters representing the unlimited state of the soil behind the wall were inversely solved by further considering the static balance condition and moment balance condition of the whole sliding wedge.Thus the active earth pressure solution considering the incompletely limit stress state of the soil and satisfying all mechanical conditions was obtained.Finally,the reliability and rationality of the theory were verified by case study examples,and the effects of soil internal friction angle and external friction angle on earth pressure distribution and related parameters were analyzed.The theoretical results show that the limit stress state only appears on the sliding surface,and the soil located in the wall and soil wedge does not fully reach the limit state,and the approximate treatment of the soil as the limit state does not have a great impact on the calculation results of earth pressure.Under the same parameters,the dip angle of the slip surface calculated theoretically is greater than that of Rankine solution and Coulomb solution.The internal friction angle and external friction anglehave different effects on the distribution of earth pressure,the position of resultant force action point,stress state parameters,principal stress deflection angle of soil and so on.