绕墙趾转动挡土墙主动土压力的确定

Determination of active earth pressure behind retaining wall rotating about wall toe

墙背土压力分布和挡土墙变位模式、位移大小密切相关。考虑位移影响的土压力分析方法是在已知挡土墙位移大小的情况下,方可计算墙背土压力分布。对于绕墙趾向外转动的刚性挡土墙,从满足倾覆稳定性和基底压应力偏心距要求的角度,提出了确定主动平衡状态时墙顶位移大小和墙背土压力分布的方法,并分析挡土墙宽度和墙背摩擦系数对墙背土压力分布的影响。分析结果表明:主动平衡状态时,墙背土压力均大于库仑主动土压力,墙背土压力产生绕墙趾的倾覆弯矩同样大于由库仑主动土压力计算的倾覆弯矩;挡土墙宽度越大,墙背土压力越接近静止土压力;随着宽度的减小,墙背土压力由静止土压力分布向库仑主动土压力逐渐过渡;摩擦系数主要影响倾覆弯矩,对于墙背光滑的挡土墙,满足倾覆稳定性要求的墙宽显著提高。

Distribution of earth pressure of rigid retaining wall is closely related with mode of rotation and wall movement. Analytical method of earth pressure considering displacement can be used to calculate the distribution of active earth pressure only when the wall movement is known. The method of determining wall top displacement of active equilibrium condition and earth pressure distribution behind rigid retaining wall rotating about wall toe is put forward from the aspect of satisfying the requirement of overturning stability and eccentricity of wall base compressive stress. Influence of wall width and frictional coefficient behind retaining wall on earth pressure distribution is analyzed. Analytical results show that the earth pressure of active equilibrium condition is larger than Coulomb active earth pressure. The overturning moment rotating about wall toe induced by active earth pressure with working condition is also larger than it calculated by Coulomb active earth pressure. Active earth pressure distribution is more close to static earth pressure with increasing of wall width, and as the decrease of it the distribution of earth pressure will be transferred from static earth pressure to Coulomb active earth pressure. Frictional coefficient is closely related with overturning moment. The width of smooth wall back satisfying the requirement of overturning stability is increased distinctively compared with rough wall back.