Layout Discussion On Drain Hole Design Of Deepburied Tunnel In Rich Water Area With High Water Level

The main problems in the construction and operation of high water level and rich water deep-buried tunnel are high water pressure and gushing water.In order to ensure the safety of tunnel construction and operation and to meet the seepage drainage capacity permitted by the surrounding environment of the tunnel,the design concept of water blocking and drainage is usually adopted.However,due to the failure of surrounding rock and the uncertainty of construction quality of grouting and plugging,the lining will undoubtedly bear great external water pressure,thereby threatening the safety of the lining structure.Therefore,high water level and rich water tunnel must take effective drainage measures to reduce the high water pressure on the outer surface of the lining,and ensure the safety and stability of the lining structure.The drainage holes due to their hollow structure become the rock with strong permeability of hydraulic structure,seepage field in groundwater seepage basin directly to the outside,and has a great influence on the distribution of the head,is in the actual engineering,especially in underground cavern is one of the important measures to control seepage.In this paper,Aiming at the area of high groundwater level of deep buried tunnel drainage hole,drainage hole will simplify the three-dimensional unsteady seepage problem for planar unsteady seepage problem,the groundwater dynamics theory of single hole drainage hole drawdown and flow formula,and were in constant drawdown and flow control conditions,combined with the engineering example,analysis effect of drainage hole on seepage field.By studying the effect of drainage and depressurization of drainage holes at different distances,the spacing of holes in accordance with the requirements of different precipitation time is put forward.The main contents of this paper are as follows:(1)Through the analysis of the drainage hole drainage principle,the drainage hole of three dimensional unsteady seepage plane unsteady seepage problem,and establish the mathematical model with constant drawdown and flow formula for drainage hole drawdown under the control of the single hole seepage of groundwater level is deduced.(2)Taking the setting depth and constant flow as control conditions,the calculation of the water level drawdown,seepage,influence radius and flow rate at the top of the drainage hole under different conditions is analyzed.(3)With the constant drawdown as control conditions,using the principle of superposition of the hypotensive effect of drainage tunnel longitudinal arrangement holes were calculated.The results show that the longitudinal drainage holes spacing on seepage drawdown significantly affect the spacing between drainage holes stated in the specification is reasonable,according to the requirements of different construction period by calculating the best choice straight out of the drainage hole spacing layout.