| During the construction of a long continuous tunnel with a large cross-section in the karst cave,if the support is not timely after the excavation,it is easy to cause safety problems such as collapse and collapse.In the southwest region,many highways often pass through the karst cave(clay filling)area when constructing highways.Therefore,how to ensure the safe passage of these bad geological sections during tunnel construction has become particularly prominent and important.In this paper,a highway tunnel at Yizhao Expressway is taken as an engineering case.First,the stability analysis of the tunnel and the study of the supporting method are carried out.Second,the rock mechanics and soil mechanics tests are carried out on the samples in the laboratory to obtain more accurate data;Pre-support analysis of the stability of the tunnel,combined with the actual situation on the spot,analyzed and researched the relevant support parameters,and at the same time compared the monitoring data with the simulation results to verify the rationality of the FLAC3 D simulation and obtain better support parameters.(1)Experimental analysis of tunnel geomechanics and rock mechanicsRelying on the engineering background of the highway tunnel,through the on-site sampling,the indoor related mechanical tests are carried out to obtain the accurate data required by the FLAC3 D numerical simulation.(2)Study on the stability of the tunnel with advanced pre-supportCombined with the geological characteristics of the highway engineering that is relied on,through FLAC3 D numerical simulation,the displacement and mechanical changes of the tunnel when it passes through the karst cave(clay filler)section with filler are obtained.The safety analysis of the tunnel supporting structure was carried out,and it was obtained that the supporting safety factors are all greater than 3,which satisfies the design specification and verifies the necessity of advanced pre-supporting.(3)Research on optimization of supporting parameters of tunnels passing through karst caves(clay fillers)Taking Yizhao Expressway tunnel as an engineering case,through FLAC3 D numerical simulation,comparative analysis of tunnel support structure deformation and safety was performed,parameters such as arch support distance,grouting mix ratio were determined,and better support parameters(support The spacing is 0.6m and the water-cement ratio is 1: 1).(4)Tunnel section monitoring and result analysisAccording to the monitoring data at the junction of the soft and hard rocks of the highway tunnel,the contribution of the excavation and support of the construction sections 1,2,3,4 on the left and right sides of the CRD method to the deformation is first analyzed,and then the results of the numerical simulation of FLAC3 D simulation software are analyzed It was then compared with the data monitored at the junction of soft and hard rocks.The measured settlement of the vault after the bracing was 15.2mm,the convergence of the arch waist was 65.2mm,the simulated numerical results were the settlement value of the arch vault was 60.2mm,and the convergence value of the arch waist was 60.2mm,thus ensuring the accuracy of the FLAC3 D numerical simulation.The construction provides reference significance.This paper analyzes the influence law of tunnel excavation in the karst cave with fillings from various aspects,verifies the rationality of "pipe advance,short footage,strong support",and also provides reference for this project and similar projects. |
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