Abstract
Due to poor engineering geological conditions of Liujiazhuang tunnel on Shanghai-Kunming Passenger Dedicated Line, the large deformation of weak rock occurs repeatedly during tunnel construction. In this paper, the large-scale finite element software ABAQUS is used to simulate the construction process of a large-section tunnel in weak surrounding rock. It is found that when tunnel face passes through the coal seam, the displacement and stress simulated by the bench method increase abruptly. The maximum stress reaches up to 18 MPa, and displacement reaches 45 mm, which is about twice when without crossing coal seam. It is technically feasible to use the bench method for tunnel construction, under the condition when large settlements is allowed; additionally, the bench method has better technical and economic benefits than that of the CD method. Through the comparative analysis of onsite monitoring data and numerical simulation results, it can be seen that the tunnel is in a dangerous state when passing through the coal seam and measures such as strengthening support or auxiliary advance support should be taken immediately to control the surrounding rock and to ensure tunnel construction safety.
Highlights
Due to many active faults, wide distribution of weak rock, high ground stress, karst development, and abundant groundwater, the tunnel in weak surrounding rock may produce many disasters such as large deformation, mud outburst and gushing water, collapsem and harmful gas [1,2,3]
The analysis shows that construction process of the bench method is relatively simple compared with the CD method
Based on the project of the Liujiazhuang tunnel exit section of Shanghai-Kunming Passenger Dedicated Line, large-scale finite element software ABAQUS is used to simulate the excavation of large section tunnel in weak surrounding rock and the construction process when crossing coal seam
Summary
Due to many active faults, wide distribution of weak rock, high ground stress, karst development, and abundant groundwater, the tunnel in weak surrounding rock may produce many disasters such as large deformation, mud outburst and gushing water, collapsem and harmful gas [1,2,3]. Domestic and foreign methods for tunnel research in weak surrounding rock mainly include numerical simulation analysis, field monitoring measurement, and model test [9]. Combined with the monitoring and measurement practice of the Shilong tunnel, the influence of initial support on the stability and displacement of surrounding rock was analyzed [15]. When tunnel traverses the soft surrounding rock section and large-section excavation construction technology that were carried out, unlike in the section with good geological conditions, rapid mechanized construction of tunnel lining can be used, and we must analyze the poor geological conditions of the section with weak surrounding rock, through comparative analysis of multiple construction technical plans, to obtain the optimist method. In view of the large deformation problem caused by large section tunnel under such adverse geological conditions, the strengthening support measures are given
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