Model Test Research About The Fixing Methods Of Tunnel's Water-tight Layer

With the perfection of domestic traffic network continuously, a mass of tunnel projects were needed to build. The problem of tunnel enduring water pressure was inevitable in the area which has abundant groundwater. In the condition of think much of environmental protection nowadays, changing the former groundwater controlling methods from "mainly drainage, combining drainage and plugging" to "mainly plugging, setting limits to evacuate", so the pressure action causing by groundwater was needed to consider when building tunnel's lining. Therefore, it has prominent engineering experience application value to determine whether the tunnel enduring groundwater pressure, how much pressure it was endured, and the groundwater pressure distribution regular in the surrounding rock and back of tunnel's lining.In this thesis, a couple of principal problems were settled about tunnels' groundwater pressure mainly through the model test methods, they were:1. If there has water-tight stratum above the tunnel, what the relationship between the thickness of water-tight stratum and head pressure when the tunnel enduring none groundwater pressure.2. If the water-tight stratum had already existed, what the groundwater pressure distribution regular in it.Model test mainly divided into three parts, there were clay soil's permeability coefficient test, clay soil's initialized hydraulic slope test and groundwater pressure distribution regular test in water-tight clay soil stratum. In this thesis, detailed formulation combining theory research methods was made out to clay soil's initialized hydraulic slope, the application scope of Darcy's law and detailed definition of water-resisting layer.Initialized hydraulic slope of tested clay soil, the relationship among clay soil's Initialized hydraulic slope and clay soil's moisture content and permeability coefficient, testing water pressure distribution regular in water-tight clay soil were gained through model test methods in this thesis. The test results show us: testing water pressure in clay soil is greater less than the hydrostatic-pressure in theory, when the permeability coefficient of clay soil fall down one class rating, the fall down of testing water pressure was greatly remarkable accordingly. The conclusion gained from this thesis was the same with any seepage mediator which the permeability coefficient was equivalent with the clay soil in this thesis, such asclose-grained surrounding rock, integrate surrounding rock or early shot-concreting, so the conclusion from this thesis has definite guidance value towards practice engineering.