| Driven by my country’s economic development in the new era,the construction and development of highway tunnels is getting faster and faster.At the same time,more and more weak surrounding rock tunnels appear in tunnel construction.Due to the low strength and poor stability of the surrounding rock in soft rock tunnel engineering,the evolution of the surrounding rock displacement field during the tunnel excavation is often unclear.Will cause a landslide accident.The surrounding rock displacement field is an intuitive evaluation index for judging the stability of the tunnel.Exploring the evolution law and characteristics of the surrounding rock displacement field during the collapse of soft rock tunnels is of great significance to the safe construction and early warning of tunnel engineering.Based on a soft rock highway tunnel in Northwest my country,this paper uses comprehensive research methods such as theoretical analysis,field monitoring,data analysis and numerical simulation to study the evolution laws and characteristics of surrounding rock displacements in the collapse of soft rock tunnels.The main research content and The results are as follows.(1)Analyzed and summarized the displacement form of the surrounding rock instability collapse of the soft rock tunnel and the factors affecting the displacement;discussed two displacement field calculation methods: one is based on the boundary conditions combined with Schwarz alternating method and Cauchy integral method for double-hole tunnel surrounding Theoretical calculation of rock displacement field;the second is to calculate and solve the discontinuous displacement field of surrounding rock through the combination of smooth functions.(2)Five typical monitoring sections are selected for real-time monitoring of the surrounding rock displacement,and the monitoring data are sorted and analyzed to obtain the temporal curve of clearance convergence and arch settlement.By analyzing the monitoring results and temporal curve,the surrounding rock in the process of tunnel surrounding rock destruction The characteristics of the displacement field change are summarized,and the most unfavorable position of the tunnel surrounding rock displacement field is obtained,so as to reveal the evolution law and characteristics of the surrounding rock displacement field before the collapse of the soft rock tunnel.(3)Using the 3DEC discrete element software,the three-step seven-step method was used to excavate the tunnel under the two support parameters.One is that when the original support parameters cannot meet the support requirements,the tunnel’s instability and collapse of the arch settlement and clearance are simulated and analyzed.The convergent displacement laws and characteristics reveal the evolution laws and characteristics of the displacement field of the surrounding rock at various stages during the collapse of soft rock tunnels,and provide early warning of a series of disasters caused by the collapse of tunnels.The second is to simulate the tunnel excavation and support based on the modified parameters,and the obtained tunnel surrounding rock displacement change law is consistent with the actual project,further verifying the importance of the support parameters to the stability of the tunnel. |
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