地铁车站交叠式群洞结构施工过程动态安全变化对比研究

Comparative Study on Dynamic Safety Changes during Construction Process of Metro Station Overlapping Tunnel-group Structure

目的:由于对隧道的稳定性评价缺乏合理的评判标准,传统有限元方法无法得到隧道工程的安全系数和围岩破坏面,为解决此问题,将有限元强度折减法引入到隧道施工稳定性分析与控制中。方法:以青岛某地铁车站为例,尝试将强度折减法应用于研究该车站隧道施工过程中的各阶段安全系数动态变化,并对关键施工工序围岩塑性区进行分析。将施工现场的监测数据与数值模型进行对比,验证模型的准确性。通过等效塑性应变和围岩位移,研究叠式群洞地铁车站典型开挖工况下的整体极限状态,指出施工过程中的围岩潜在破坏面,同时研究了站台的水平极限间距和站厅与站台的垂直极限间距,以期为这类地下结构的初步设计和施工过程评价提供依据。结果及结论:各开挖步中初期支护的施作都会对围岩整体稳定安全系数有不同程度的提高,其中区域3的开挖为最不利施工步骤,围岩会产生塑性区贯通现象,加剧围岩变形,增加站台层衬砌受力,此时车站整体安全系数达到最小;站台层水平极限间距和站厅-站台垂直极限间距分别为4.5 m和1.8 m,此时整体安全系数的最小值为1.0。

Objective:Due to the lack of reasonable judgment criteria for tunnel stability assessment and the inability of conventional finite element methods to obtain safety factor and surrounding rock failure surface for tunnel engineering,the finite element strength reduction method is introduced into tunnel construction stability analysis and control to address this issue.Method:Taking a metro station in Qingdao as example,the strength reduction method is applied to study the dynamic changes in safety factors during various stages of station tunnel construction.An analysis of surrounding rock plastic zone of key construction procedures is conducted.Monitoring data from the construction site is compared with the numerical model to verify the accuracy.By studying equivalent plastic strain and surrounding rock displacement,the overall limit state under typical excavation working conditions for overlapping tunnel-group metro stations is investigated.Potential failure surfaces of the surrounding rock during construction process are identified.Additionally,the horizontal and vertical limit distances between the platform and the station hall are studied,aiming to provide reference for the preliminary design and construction process evaluation of such underground structures.Result&Conclusion:The construction of initial supports in each excavation step contributes to varying degrees of improvement in the overall stability safety factor of the surrounding rock.The excavation in Area 3 is identified as the least favorable construction step,leading to plastic zone breakthrough and exacerbated deformation in surrounding rock,increasing the stress on platform lining.At this point,the station overall safety factor reaches the minimum.The platform-platform horizontal and station hall-platform vertical limit distances are 4.5 m and 1.8 m,respectively,with a minimum overall safety factor of 1.0.