Research On Shallow Large-span Railway Tunnel Excavation Methods Under Urban Complex Environmental Conditions

The construction of Huo-Feng Mountain tunnel of Chongqing Railway facesshallow burial depth, large cross section, poor geological conditions, complexengineering environment, unpredictability of risk factors and difficult constructionproblems, which may cause adverse impact on the surrounding environmentconstruction. The paper is based on Huo-Feng Mountain tunnel under the3rd light railline, and makes researches on shallow large-span railway tunnel excavation methodsunder urban complex environmental conditions, which obtains some achievements andhas a certain theoretical significance and use value. The paper makes research on thefeasible excavation method, and presents the optimal excavation method which isapplied in the project, and the rationality of the excavation method is finally to beverified through monitoring. In this paper, the main work is:①Analyzing and summarizing the main factors that affect the stability of thetunnel and the mechanical behavior of surrounding rock during excavation.②Comparing suitable excavation methods in local engineering geologicalconditions, and gets several feasible excavation methods of the tunnel.③Simulating the three excavation method numerically by using finite elementsoftware, and gets the displacement, internal force, deformation of surrounding rock ofthe excavation area, and analyzes mechanics characteristic of support structure of thecorresponding branch to propose feasible excavation scheme through the comparative analysis.④Analyzing monitoring data and comparing it with the results of numericalsimulation, which verifies the scientific rationality of forepoling upper and lower benchexcavation scheme.