Research On Ground Settlement Induced By Excavation Of Urban Shallow-Buried Small Clearance Tunnels And Control Methods

In recent years,municipal tunnel engineering has developed vigorously,but many urban highway tunnels are restricted by factors such as construction and pipelines.At the same time,in order to save land and construction period,most of them are designed as shallow-buried small-distance tunnels.Shallow buried tunnels with small clear distances are likely to cause uneven settlement of the overlying surface during the excavation process,and cause irreversible effects on overlying buildings,roads and other facilities.In this paper,relying on the construction of the Yuhan Road small-distance tunnel construction project of the second phase of the southern extension of the Shunhe Elevated Project in Jinan,through model tests,indoor tests,numerical simulations and other methods,the overlying surface settlement induced during the excavation of shallow-buried small-distance tunnels The law has been systematically studied,and a three-stage four-sequence settlement control method is proposed for the shallow ground surface settlement.The specific research results are as follows:(1)A physical model test system for surface settlement induced by shallow-buried small-distance tunnel excavation was established.By testing the physical and mechanical performance parameters of a large number of materials with different proportions,a soil-like material suitable for the small-distance tunnel excavation test was developed.Carry out tunnel excavation-induced ground settlement test,process and analyze the stress,displacement and other data collected during the test excavation process,study the catastrophic evolution process of the rock stress field and displacement field around the tunnel during the excavation process,revealing The settlement,displacement and deformation laws of the overlying stratum during different stages of excavation of small-distance tunnels.(2)Based on the finite difference principle,the numerical simulation was verified according to the model test results,and the settlement and displacement information of the ground surface over the small clear distance tunnel under different buried depths,clear distances and soil properties were analyzed.The settlement and deformation characteristics of the overlying surface under these factors have explored the inducing process of the ground settlement caused by the excavation of the small clear distance tunnel and the influence form of the settlement deformation.At the same time,based on the influencing factors of surface settlement and deformation,a multi-condition surface settlement numerical simulation was carried out,and the prediction equation of the overlying surface settlement induced by the Yuhan Road tunnel excavation was established.(3)Aiming at the problems of surface settlement induced by the excavation of urban shallow-buried small-distance tunnels and the existing problems of grouting reinforcement methods,a three-stage four-sequence grouting control method was proposed,and the indoor film bag grouting was designed and carried out separately Pressure isolation and suppression of surface uplift model test,three-stage foursequence grouting reinforcement to control surface settlement model test,systematically studied the development law of surface uplift displacement caused by subsequent grouting after the shallow grouting layer membrane bag grouting reinforcement,and three The law of surface settlement and displacement caused by tunnel excavation after the section four sequential grouting reinforcement reveals the suppression mechanism of film bag grouting on the surface uplift and the control mechanism of the three section four sequential grouting reinforcement method on the surface settlement.The project case verifies the results of the indoor model test.