某盾构施工岩溶场地地面塌陷机理和数值分析

Mechanism Analysis and Numerical Simulation of Ground Collapse in a Karst Site under Shield Tunneling Construction

归纳和分类了岩溶地区地面塌陷的必备条件、诱发因素和致塌机制。针对广州某盾构施工岩溶场地地面连续两次塌陷事故,梳理工程场地条件及塌陷过程,结合现场情况对首次塌陷、局部地面冒浆及二次塌陷进行了定性的机理分析。并使用有限元软件Plaxis2D建立了事故现场的概化模型,土层选用能更好计算地基变形的硬化土模型,进行了施工开挖、环境变化等全过程的分步数值模拟,基本复原了事故过程,验证了机理分析。分析表明,多种诱因、多种形成机制的综合叠加导致了最终的地面塌陷,水动力条件变化可能是主要因素。工程施工中,需结合现场情况,综合考虑防护措施以降低地面塌陷风险。

The essential conditions,factors and catastrophe mechanisms were summarized and categorized. The case study of two continuous ground collapse accidents in the karst site under shield tunneling construction in Guangzhou presents the engineering geological condition and the collapse process. The qualitative analysis was carried out to study the catastrophe mechanisms of the two sinkholes and local mud spillover based on the site investigation.And the finite element code Plaxis2 D was used to conceptually model the accident site and the advanced hardening soil model was adopted to calculate the ground subsidence accurately. By the staged whole process numerical simulation of excavation and environmental changes,the accidents course was reappeared and the mechanism analysis was verified. The study shows that this ground collapse was caused by comprehensive superposition of multiple inducing factors and catastrophe mechanisms,in which the change of hydrodynamic condition may be the most important issue. In the construction of the project,it is necessary to combine the site conditions and comprehensively consider the protective measures to reduce the risk of ground collapse.