砂卵石地层条件下台阶式基坑的地表变形特点及地层补偿法应用
Surface subsidence features of pit in pit foundation and application of stratum compensation theory in sand cobble stratum

摘要 台阶式基坑在基坑工程中应用较为普遍，其内坑开挖形态、位置的不同将使周围地层的应力场、位移场更为复杂，也给设计和施工带来一定的难度.以北京地区典型的砂卵石地层为研究背景，利用数值模型分析了台阶式基坑地表变形特点.通过地表沉降量比较了影响台阶式基坑工程地表变形的3个主要因素：内坑边距、深度和宽度.同时，进一步讨论了地层补偿法在北京地区砂卵石地层条件下的适应性，并对其他地域的相似工程提出了边墙侧移估算深度的方法.研究结果表明：造成台阶式基坑两侧地表变形差异的本质原因在于内、外坑之间土层形态的不同；地层补偿法可用于描述台阶式基坑地表变形与墙体侧移之间的相互关系.研究成果对北京地区及类似的砂卵石地层条件下台阶式基坑的监控量测与施工精细化控制提供了参考.
Abstract：Pit in pit is a common excavation problem, and its excavation form and different locations increase the complexity of stress and displacement field of surrounding stratums, bringing about a certain difficulty for design and construction. Based on the typical sandy cobble stratum of Beijing, deformation features of pit in pit foundation are analyzed by applying the numerical model, and three factors are compared with ground deformation, which aredistance, depth and widthof inner pit edge. Meanwhile, the adaptability of stratum compensation method in sand cobble stratum in Beijing is discussed, and suggestions for similar engineering in other fields in terms of the estimation of depth of wall lateral displacement are also provided. The results show that shape of soil mass between inner pit and outer pit mainly causes the different surface deformations of both sides.Stratum compensation methodis applicable for describing the relation ship between the ground surface deformation of pit in pit foundation and wall lateral displacement.The research achievements can provide references for monitoring measurement of pit in pit foundation and construction fine control under sand cobble stratum in Beijing and other similar areas.