基于联合强度理论的主动土压力计算方法

考虑结构性黄土的抗拉强度和有限土体对土压力的影响,推导了抛物线加直线形式的联合强度理论。基于此强度理论,建立了土体主动极限平衡状态,推导了无限土体主动土压力的计算公式;通过滑动块体理论推导了有限土体主动土压力的计算公式。通过算例对公式进行了验证比较,研究结果表明:基于联合强度理论计算的土体开裂深度明显小于朗肯土压力理论的开裂深度,且基于联合强度理论土体应存在拉应力区,在此区域内,挡土墙与土体存在胶合力的情况下,需考虑挡土墙受到的拉力和因此导致的局部应力集中;有限土体的土压力小于朗肯主动土压力,且随着挡土墙与既有构筑物距离的增加,有限土体土压力趋近于无限土体土压力。基于联合强度理论和有限土体理论建立的主动土压力计算方法能更合理地评价黄土的主动土压力。

Calculation Method of Active Earth Pressure Based on Joint Strength Theory

Considering the influence of the tensile strength of structural loess and finite soil mass on soil pressure, the joint strength theory of parabola plus linear form was derived. Based on this strength theory, the active limit equilibrium state of soil was established, and the calculation formula of active soil pressure of infinite soil was derived; the calculation formula of active soil pressure of finite soil mass was deduced by sliding block theory. The formula was verified and compared through an example. The results show that the cracking depth of soil based on the calculation of joint strength theory is obviously smaller than that of Rankine's earth pressure theory, and there is tensile stress zone in soil based on joint strength theory. In this area, when there is a bonding force between the retaining wall and the soil body, the tensile force of the retaining wall and the local stress concentration caused by it must be considered; and the earth pressure of the finite soil mass is less than the Rankine active earth pressure, and with the distance between the retaining wall and the existing structure increase, the earth pressure of the finite soil mass infinitely approaches the that of the infinite soil body. The calculation method of active soil pressure based on joint strength theory and finite soil theory can evaluate the active soil pressure of loess more reasonably.