紧邻既有建筑基坑有限土体主动土压力计算方法

CALCLULATION OF ACTIVE EARTH PRESSURE FOR LIMITED SOIL BETWEEN EXISTING BUILDING AND EXCAVATION

当拟开挖基坑周边存在既有建筑物时,在基坑支护的挡土构件与既有建筑基础间土体宽度有限,此时土压力不能采用传统的朗肯理论或库伦理论进行计算。由于采用滑移土体为刚性体、墙土界面光滑等假设,此前针对该问题进行研究的文献未能很好反映实际情况。该文通过对挡土墙与既有建筑基础间的有限土体进行完整的受力分析,考虑了既有建筑基础与有限土体间的法向及切向相互作用力,建立了求解有限土体主动土压力的计算公式,并进行了适当的简化。与有限元计算结果的比较表明,该公式较以往的算法更接近于有限元结果,同时它还能考虑对墙土界面强度折减系数的不同取值。该文给出的简化公式形式较为简捷,精度较高,可方便工程技术人员对此类土压力问题进行初步计算。

In the situation of a deep excavation adjacent to an existing building, the soil between the retaining wall and the existing basement is limited. Active earth pressure in this case cannot be exactly calculated by using classical Rankine or Coulomb theory. Because of the assumption that sliding soil is rigid and that wall-soil interface is smooth, the methods proposed in current literatures cannot reflect the real mechanism. In this paper, a complete mechanical analysis of the limited soil is conducted, which has considered the lateral and tangential forces between the limited soil and the wall. Then the equations for calculating the active earth pressure are established, and a simplified formula for this case is presented finally. Compared with finite element analysis results, it is found that this formula can give more accurate results than those of previous methods. Meanwhile, it can deal with situations that the strength reduction factor differs in a wall-soil interface. The simplified formula derived has a relatively simple form and a high precision, which make it possible for engineers to get preliminary results of earth pressure under such conditions conveniently.