Mechanical characteristics of lining structure under different blocking conditions of drainage system of Karst tunnel
The blockage of drainage system often occurs in the operation of Karst tunnels,and the water pressure behind the lining will increase rapidly,if the groundwater cannot be discharged in time,which will directly affect the mechanical characteristics of the tunnel lining and endanger the normal operation of the tunnel in serious cases.In order to explore the distribution law of water pressure and the stress of lining structure when the drainage system of Karst tunnel was blocked,the FLAC3D software was used to analyze the mechanical characteristics of the lining structure under different blockage rates of the drainage system based on the Karst tunnel of Zhejiang Lin-Jian(Linan to Jiande)Expressway Project.The results show that the water pressure behind the lining is increases nonlinearly with the increase of blockage rate,and can be divided into three growth rate intervals.The blockage rate of 0%to 40%is the first rapid growth interval,the blockage rate of 40%to 80%is the stable interval,and the blockage rate of 80%to 100%is the second sudden increase interval.Compared with the normal working state of the drainage system,the maximum water pressure behind the lining increases by 162%under the condition of complete blockage,so the blockage rate of the drainage system is 40%as the control threshold of the water pressure behind the lining.The stress growth of lining structure has no obvious stage division,and the stress of lining structure changes linearly with the increase of blockage rate.The maximum values of minimum and maximum principal stresses is increase by 149%and 83%respectively under the condition of complete blockage,and there is no obvious threshold of blockage rate in the drainage system.Under different blockage conditions,the mechanical characteristics of the common section lining are symmetrical,while the mechanical characteristics of the Karst cave lining are asymmetrical,and the stress characteristics of the Karst cave location are more sensitive to the blockage rate.Therefore,when the Karst tunnel drainage system is blocked,the drainage capacity of the drainage system will be significantly reduced,and the mechanical characteristics of the tunnel lining will be significantly increased,especially at the location of the cavity.In order to ensure the safety of the lining structure of Karst tunnel,the drainage system should be cleaned and maintained before the blockage rate of 40%.It can provide theoretical basis and technical reference for the management and maintenance opportunity of drainage system of Karst tunnel.3 tabs,21 figs,25 refs.
tunnel engineeringblocking condition of drainage systemnumerical simulationblockage ratemechanical characteristiccontrol threshold