Analysis And Prevention Of Tunnel Drainage Pipe Blockage Effect In Water Rich Region

Focusing on the drainage pipe blockage problem of tunnel in the water rich region,two drainage pipe blockage simulation methods are adopted to build a numerical modeling for the Zhongliangshan Tunnel in Chengyu Expressway based on the basic theory of fluid solid coupling.Considering the coupling analysis of the seepage field and stress field of the blocked drainage pipe in tunnel,it is mainly studied the spatial evolution law of the seepage field inside the surrounding rock of tunnel site and the mechanical response of the tunnel surrounding rock and bracing structure under different blocking conditions of drainage pipe as per the quantitative evaluation of various indexes,such as the groundwater level,pore water pressure,lining water pressure,stress and deformation of lining in the process of drainage pipe blocking.The rational assumption under the actual conditions is put forward as well as the study of the blockage effect of the tunnel drainage pipe under different water levels is carried out.In the last chapter,a series of prevention and mitigation measures for drainage pipe blockage are introduced from various aspects and the main study results are as follows:(1)The constitutive model and parameters of various materials are reasonably selected and the numerical model is generalized so as to develop the study of the blockage effect of the drainage blind pipe in the tunnel as well as analyze the results in different water levels,and the following conclusions are drawn:(1)The distribution pattern of the groundwater level in the tunnel site might be changed accordingly when the blocking condition or the initial groundwater level changes.Under the condition of unobvious blockage,a remarkable hydraulic gradient is noticed near the tunnel structure when the initial groundwater level rises,the maximum water level falls to 33 m and the water level near the tunnel structure changes slightly.Under the condition of obvious blockage,the water level varies significantly everywhere in the tunnel site when the initial groundwater level rises.(2)As the groundwater level rises,the maximum difference of the pore water pressure of the rock mass on a horizontal plane of the tunnel site is 360 kPa when the pipe is drained normally;on the contrary,the difference of the pore water pressure on a horizontal plane is relatively small when the drainage pipe is obviously blocked;the hydraulic load on the lining of the tunnel decreases in pulse nearby the longitudinal drainage pipe when the pipe is drained normally;the variation amplitude of waterpressure near the drainage pipe decreases as the increase of the blocking level of the drainage pipe.(3)The rising of initial groundwater level or the increase of drainage pipe blockage lead to the floating upward of the tunnel structure accompanied by horizontal movement and rotation.Specifically,the tunnel structure moves outwards the adjacent tunnel with the increase of the blocking level of the drainage pipe under the same initial groundwater level;the tunnel structure moves towards the adjacent tunnel with the rise of the groundwater level under the same blocking level.(4)The principal stress of tunnel lining ascends with the rising of the drainage pipe blocking or the initial groundwater,the greatest growth of the maximum principal stress is 0.4 MPa,the greatest growth of the minimum principal stress is 2.6 MPa and the position of the maximum growth is near the arch springing.The axial force of the bolt increases with the rise of the initial groundwater level,and there is a slight difference in the axial force of the bolt in the local area when the blocking level of drainage pipe is relatively low;the axial force of the bolt decreases with the rise of the initial groundwater level when the drainage pipe blocking onto a certain degree.(2)The seepage coefficient reduction method and the substitute hole with plate method for the drainage pipe simulation are used to analyze the Zhongliangshan tunnel,and evaluated the applicable conditions of the two methods: the seepage coefficient reduction method can directly express the spatial distribution regulation of the local seepage field of the drainage pipe,however it cannot accurately simulate the blocking level of the drainage pipe;on the contrary,the conditions of the substitute hole with plate method is opposite.(3)From the point of view of physics,chemistry and biology,a series of prevention and mitigation measures for drainage pipe blockage are introduced.Measures should be taken to prevent and mitigate the blockage of the tunnel drainage pipe from multiple aspects according to the specific conditions of different projects.