被动区溶洞对地铁车站深基坑稳定性的影响

为研究被动区溶洞对地铁车站深基坑稳定性影响规律,依托大连某地铁车站深基坑工程,基于弹性地基梁理论和尖点突变理论建立了被动区溶洞侧板最小安全厚度表达式,并进行了工程计算。采用FLAC3D软件建立数值模型,分别模拟了被动区溶洞不同侧板厚度、长度、埋深对基坑稳定性的影响。以桩体最大水平位移的模拟结果为具体数据,应用灰色关联分析法对影响基坑稳定的各因素进行了敏感性分析。结果表明：以溶洞侧板厚度为指标,根据数值模拟结果验证了被动区溶洞侧板最小安全厚度表达式的合理性,并可将溶洞侧板厚度对基坑稳定性的影响分为平缓区、明显区和剧烈区,剧烈区内的溶洞须对其进行加固处理；随着溶洞长度的增大,桩体最大水平位移和地表最大沉降位移的增值将加速增大；溶洞埋深与桩体嵌固深度相同时,桩体最大水平位移和地表最大沉降位移变化剧烈,应采取相应的处理措施；在影响基坑稳定性的各因素中,敏感性大小排序为：溶洞长度＞溶洞侧板厚度＞溶洞埋深。可见,在施工前通过理论分析、数值计算、统计分析等方法研究被动区溶洞对基坑稳定性的影响是必要的。

Influence of Karst Cave in Passive Zone on Stability of Deep Foundation Pit of Subway Station

In order to study the influence of the karst cave in the passive zone on the stability of the deep foundation pit of a subway station, relying on the deep foundation pit project of a subway station in Dalian, the expression of the minimum safe thickness of the karst cave side slab in the passive zone was established based on the elastic foundation beam theory and the cusp catastrophe theory. FLAC3D software was used to establish a numerical model to simulate the influence of different side slab thickness, length and buried depth of the passive zone on the stability of the foundation pit. Taking the simulation result of the maximum horizontal displacement of the pile as the concrete data, the sensitivity analysis of the factors affecting the stability of the foundation pit is carried out using the grey relational analysis method. The results are listed as follows. First of all, taking the thickness of the side slab of the karst cave as an indicator, the rationality of the expression of the minimum safe thickness of the side slab of the karst in the passive zone is verified by the numerical simulation results, and the influence of the thickness of the side slab of the karst cave on the stability of the foundation pit can be divided into a gentle zone, an obvious zone and a severe zone, and the caves in the severe zone must be reinforced. Secondly, as the length of the karst cave increases, the increase in the maximum horizontal displacement of the pile and the maximum settlement displacement of the ground will increase at an accelerated rate. Thirdly, when the buried depth of the karst cave is the same as the embedded depth of the pile, the maximum horizontal displacement of the pile and the maximum settlement displacement of the ground change drastically, and corresponding treatment measures should be taken. Fourthly, among the factors that affect the stability of foundation pits, the order of sensitivity from largest to smallest is the length of the cave, the thickness of the side plate of the cave, and the depth of the cave. It can be seen that it is necessary to study the influence of karst caves in the passive zone on the stability of foundation pits through theoretical analysis, numerical calculation, and statistical analysis before construction.