针对基坑宽度对围护结构嵌固稳定性的影响问题,将滑动面假定为直线与对数螺旋线状组合形式,按照对数螺旋线滑移面能否在基坑宽度内完全展开,将基坑定量地划分为普通基坑与窄型基坑.运用能量法分别推导出普通基坑与窄型基坑主、被动土压力对围护结构最下道支撑点的力矩,进而推导出考虑基坑宽度的嵌固稳定性安全系数计算公式,并开展对比验证及参数分析.结果表明:临界宽度既受围护结构布置形式影响又受土体参数影响;考虑基坑宽度的新嵌固稳定性计算方法在普通基坑范畴与现行规程计算结果较为接近,但对于窄型基坑,二者相差较大,基坑宽度越小差异越大;新方法得到的嵌固稳定性安全系数随着最下道支撑点距坑底距离的增大而减小,随着土体粘聚力、内摩擦角和土体与围护结构间摩擦角的增大而增大.

To investigate the influence of excavation width on the embedment stability of retaining structures, the slip surface is assumed to be a combination of a straight line and a logarithmic spiral. According to whether the logarithmic spiral slip surface can fully develop within the excavation width, excavations are quantitatively classified into ordinary excavations and narrow excavations. The energy method is employed to derive the moments of active and passive earth pressures about the lowest support point of the retaining structure for both ordinary and narrow excavations, respectively. Based on these derivations, a calculation formula for the embedment stability factor of safety that accounts for excavation width is established, followed by comparative verification and parametric analyses. The results indicate that the critical width is influenced by both the layout of the retaining structure and the soil parameters. The proposed method, which incorporates the excavation width, yields results comparable to those of current code specifications for ordinary excavations; however, for narrow excavations, significant discrepancies are observed, and the difference becomes more pronounced as the excavation width decreases. Furthermore, the factor of safety obtained by the new method decreases with increasing distance from the lowest support point to the excavation bottom, while it increases with increasing soil cohesion, internal friction angle, and friction angle between the soil and the retaining structure.