摘要:
土岩组合基坑的安全风险预警标准目前主要沿用现有相关规范中的监控标准,这种做法缺乏针对性。为了更有效地指导土岩组合基坑施工,对土岩组合基坑的破坏模式进行了定性分析,并对依托工程典型施工断面进行了三维有限元分析和现场监测,然后,深入对比分析了有限元分析结果和现场监测结果。研究指出：①围护墙的水平位移可作为主要的安全风险预警指标,支撑/土钉/锚杆轴力可作为辅助指标;②围护墙水平位移最大值、水平位移最大值变化速率、水平位移最大值与基坑开挖深度的比值、支撑/土钉/锚杆轴力值与开挖深度范围内土压力的比值等四个特征参数可作为土岩组合基坑安全风险预警指标特征参数;③建立了相应的安全风险预警标准体系,同时认为该依托工程土岩基坑的设计过于保守,从而导致过高的施工成本,因此有必要进行优化设计。
Abstract:
For the foundation pit consisting of soil and weathered rock stratum, at present, the warning standards of safety risk follow the existing related specifications. They lack pertinence. To more effectively guide the construction of the foundation pit consisting of soil and weathered rock stratum, the failure modes are qualitatively analyzed. Based on an related project, a typical cross section is computed using the three-dimensional finite element method and field monitoring. After synthetic analysis of the monitoring and calculated results, it is pointed out that: (1) the horizontal displacement of retaining structures is a major warning index, and the axial force of inner bracing / soil nailing / anchor bar is auxiliary; (2) the characteristic parameters of warning indexes are the maximum horizontal displacement of retaining structures, the maximum rate, the ratio of the maximum horizontal displacement to excavation depth, the ratio of axial force to earth pressure in the range of excavation depth; (3) the appropriate warning system is established, and compared with the existing related warning index, the design of the above-mentioned foundation pit is too conservative, resulting in high cost of construction, so it is necessary to optimize the design.
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