复杂条件下挡土墙塑性临界深度极限上限分析

Upper Bound Limit Analysis of Plastic Critical Depth of Retaining Wall under Complicated Conditions

塑性临界深度计算是黏性土主动土压力计算中一项重要的内容,目前规范中给出的计算公式仅适用一些特殊情况。因此,应用极限上限分析理论,将与挡墙顶部相邻滑裂面为折线的滑楔体作为研究对象,针对多种因素对塑性临界深度的影响,推导了平移模式下挡墙塑性临界深度计算公式。研究结果表明:极限破裂角并不是定值,而是随计算参数变化而变化;塑性临界深度不仅受填土黏聚力、内摩擦角的影响,而且与墙-土黏聚力、墙背倾角、填土倾角和裂缝深度有关;经典朗肯塑性临界计算公式为文中计算公式的一个特例,文中计算公式相比其他计算公式适用性更广,计算结果更接近实测值。

The plastic critical depth is one of the most important part in the calculation of active earth pressure of cohesive soils in retaining walls. The formulas given in the current standards are only applicable to some special cases. In this paper, the external work rate and internal energy dissipation rate of the sliding wedge adjacent to the top of the retaining wall is studied. Based on the upper bound limit analysis method, the calculation formula of the plastic critical depth of the retaining wall is derived in the panning mode by considering the influence of various factors on the plastic critical depth. The results show that the limit rupture angle varies with the calculation parameters. The plastic critical depth is influenced not only by the cohesion and the internal friction angle of the backfill soil, but also by the cohesion of wall-soil interface, wall batter angle, ground slope and the tension cracks. The classic Rankine plastic critical calculation formula is only a specific case of the derived method, which indicates the wide applicability of the formula. Compared with the measured values, the results of the derived formula are more accurate than those obtained from other formulas.