Research On Fissure-water Burst Mechanism And Treatment Measures In Highway Tunnels

With the rapid development of the national economy，as an important basic industry，roadconstruction has also been a large degree of development.On the one hand due to themulti-country highway was built in the mountains， on the other hand highway graderequirements are increased，tunnels were asked to adopt as much as possible when the highwaythrough the mountains.It not only ensures optimal road alignment，but also effectively preventgeological disasters caused by the steep mountain road，which improves the safety andreliability of the highway.Complex and diverse engineering geological problems become amajor factor restricting mountain highway construction.Frequent engineering disasters are themajor problems affecting the normal construction and operations of the tunnelengineering.Variety of problems such as landslides，rock burst， large deformation，followedgushing water in the tunnel construction process.Gushing water in tunnel is likely to causeinterruption in tunnel construction，and even causes damage to the tunnel after tunnel support oroperations which results in large economic losses.Firstly，the flow characteristics of fractured rock was analyzed theoretically.Then theengineering geological conditions and gushing water features of the Shizizhai tunnel and othertunnels were clarified.Gushing law of fracture water in tunnels and mechanism analysis weredone in a more systematic study through the use of theoretical analysis，mechanics analyticalcalculation and other means.Finally treatment measures had been proposed based on differentgushing mechanisms of fracture water.The paper mainly achieved the following results：(1) Structural characteristics of fractured rock and fissured were extensively studied bytheoretical analysis in order to analyze the flow characteristics of fractured rock. flowcharacteristics of fractured rock were summarized as follows: fissures composed of rock arenon-uniform distribution.Adjacent crack propagation and mutual destruction are the main waysthrough rock in geological and engineering disturbances. The movement of fissure water is inline with Darcy’s law, and fracture flow is generally laminar flow state. The flowing of fissurewater is in line fracture network model. rock blocks are impermeable low permeability materialcompared with the structure of the surface. Fissure water flows only in the fissures.Instability infractured rock fracture process as crack initiation and propagation, it gradually and nativestructures that already exist with each other through the surface, resulting in the destruction ofrock eventually happens.(2) Through to our country western region of several tunnel fracture water surged bytypical case analysis, to illustrates the background, process and mechanism of flood waterbursting, it is concluded that the fracture distribution and combination of different tunnel fissure-waterburst of four main types:①r eveal water-bearing fracture cause fissure-waterburst,②osmotic pressure ceiling surrounding rock damage caused to fissure-waterburst,③osmoticpressure constraints surrounding rock damage caused to fissure-waterburst,④osmotic pressurewater plugging caused by rock damage caused to fissure-waterburst.(3) More in-depth studies the mechanics on the four kinds of tunnel fissure-waterburst. Touncover water-bearing fracture caused by fissure-waterburst, calculating the water inflow andwater pressure; The others are established three types of simplified mechanical model, throughdeduction and analysis, to be addressed to the osmotic pressure of surrounding rock roofdamage caused by flood water inrush simplified as a cantilever beam, the constraints to beaddressed to the osmotic pressure of surrounding rock damage caused by flood water inrushsimplified as the simply supported beam, the osmotic pressure water plugging caused by rockdamage cause flood water inrush is simplified to concentrated load and uniform load on thesurrounding rock,it is concluded that the fracture criterion of fissure-waterburst happened, keyfactors and water pressure under the action of tunnel surrounding rock failure criteria, andsafety constraints airport length and safety thickness.(4) Different mechanisms for fissure-waterburst are carried treatment measures. Treatmentmeasures are mainly based on the design of the calculated water pressure, safe overhead lengthand safe working face thickness. For expose fissures caused fissure-waterburst, mainly to blockthe flow path grouting way; for damage caused by the tunnel wall rock fissure-waterburst, drainbolt mainly taken the way while rock drainage reinforcement; for rock tunnel face destruction,use for drainage scuppers in advance to ensure the normal construction.