Study On The Seepage Mechanism And The Prevention From Seepage Disease Of Multiple-arch Tunnel

A number of tunnels have been built with the development of transportation. Andfor some special location, in order to improve the line type, save space and save theproject cost and so on, the multiple-archtunnels have appeared. Due to the reasons aboutthe complex geological conditions, the disturbance of construction and the loss ofwaterproof measure, the seepage has become the one of general diseases of tunnelprojects, what is called “Nine seepage tunnels in ten tunnels” indicated this meaningvividly. But the multiple-archtunnel, especially for the integrated multiple-archtunnel,has very bad seepage disease. Based on the expressways from Hang Zhou to An Huiand from Jin Hua to Wen Zhou, the researches on the seepage mechanism and theprevention have been carried out in terms of the theories, the investigations, the modeltest and the numerical simulation systematically. The main study contents and resultsare as follows:①The seepage type has been classified based on the field tests and the seepagelocations of multiple-archtunnel. The seepage location mainly concentrates on themiddle wall, the slots and the entrance, and at the surface of second liner the seepagehas existed; the seepage types are mainly point type and face type, the magnitude ofseepage inflow is different for different tunnel.②the causes of formation and the properties of seepage have been analyzedbased on the field tests, and the impact factors of seepage disease have been also studiedas follows:(1) By the advanced AHP, there eighteen factors inducing seepage have beenstudied, and the significance analysis has indicated that the type of multiple-archtunnelis the main factor inducing seepage.(2) Analyzed the effect of rainfall and groundwater level on the seepage ofmultiple-archtunnel, and derived the equations of seepage inflow related to the crack onthe liner, the point type of seepage, the face type of seepage and the construction joint;the results have indicated that the seepage inflow will increase with increasing thegroundwater level, and decrease with increasing the thickness of liner; the seepageinflow related to the crack will become large with increasing the width of crack and theface inflow of seepage will become large with increasing the radius magnitude of face.(3) Used the finite element software to simulate the effect of construction on the seepage field and the rule of construction mechanics response; the results have indicatedthat, after excavation, the seepage occurs at the crown, the side wall, the top of middlewall, the joint between two tunnels and the joint between middle wall and invertgenerally. When constructing the tunnel, the seepage will also occur at these locations,so the waterproof measures should be improved at these locations when designing andconstructing tunnel, which will provide the theoretical proof to the prevention fromseepage disease.(4) Based on the physical-chemical reaction of groundwater in ground, thephysical-chemical mathematical programming model has been established, and then thesimple Monte Carlo method has been used to solve this problem, the results havedescribed the eroded grade of rock by the groundwater around tunnel, the more seriousthe rock has been eroded, the better the passage for the groundwater is in the rock, andthe more easily the seepage disease occurs.(5) By studying the frost heave in tunnel, the relationship between the fault frostheave force behind multiple-archtunnel and the stiffness rate of rock stiffness to linerstiffness has been established; the results have indicated that the fault frost heave forcebehind multiple-archtunnel related to the size of the fault and the filled mass by water,and with increasing the size, the frost heave force will become larger.(6) Proposed the effect of hidden block on the seepage of multiple-archtunnel, andobtained that the period of the deformation and the displacement of hidden block is verylong; and induced the destruction of second liner and flashing due to self-balance andstress release, finally, the seepage occurs.③The seepage has been simulated by the finite element software Midas/GTS atthe working period of the integrated multiple-archtunnel. For the different groundwaterlevel and the good drain and waterproof systems, the drainage pipe, the constructionjoint and the seepage rule of liner have been simulated numerically; the study hasindicated that the higher the groundwater level is, the more disadvantage it is to theworking of multiple-archtunnel, the seepage drive force and the loss of total head haveappeared at the seepage location. The effect of groundwater replenishment near the hillis more significant on the seepage, and the seepage induced by construction joint andthe point seepage on the liner is more serious; the hydraulic gradient is larger and thenthe seepage inflow is larger at these locations. The drain-waterproof construction andthe drain-waterproof measure should be improved at these locations.④Investigated the effect of seven types of filled materials by water on the radar signal by the model test, and indicated that the higher the rate of water content of thefilled material is, the stronger the reflection to the wave is and the larger the intensity ofreflection wave is; based on the field test, the small wave data have been transformedand the properties of atlases have been visualized by MATLAB and small wave analysis,and simulated the various crack atlases by the three-dimensional model, which haveprovided the proof to the leakage prevention, the leakage design and the leakageconstruction.⑤From the discussion about seepage mechanism of multiple-archtunnel, theprevention measures from seepage induced by the construction, the rainfall, the frostheave and the hidden block have been proposed, and then the practical technicalmeasures and the construction process have also been proposed for the seepageprevention of multiple-archtunnel depended by this study; the treatment measures arefeasible and the results are well.