Theoretical And Applied Analysis On Hydrochemical-Hydraulic Damage In Tunnel Surrounding Rock

Carbonate rock is widely distributed in China both in depth and in area. A large number of tunnels are excavated and built in it. Carbonate rock is distinguished from the other fracture rock in that most of it has bored hydro-chemical and hydraulic erosion in groundwater environment. To study the mechanism,course and evolution of hydro-chemical and hydraulic erosion in carbonate rock,together with the coupling of seepage field and mechanics in it is significant both in theory and application.The damage caused by hydro-chemical and hydraulic erosion in groundwater environment for carbonate rock is defined as rock erosion damage by author. The hydro-chemical damage is caused by the chemical reaction between groundwater and carbonate rock,while hydraulic damage by hydraulic fracture action. The erosion effect damage variable can be defined in many ways,while the one defined in wave velocity by author is more appropriate for deep buried tunnel surrounding rock. For the evolution of hydraulic damage under complex mechanics environment,the extension of branch fracture means the initiation of evolution,and the hydraulic damage evolution equation can be deduced by the method of Fracture Mechanics. The hydro-chemical damage evolution equation is deduced by cross board model established by author by the method of chemical kinetics (PWP Equation). The hydro-chemical damage evolution of a fracture is defined by the variation of board geometry dimension caused by chemical reaction,while a channel by the cross pipe of the board. Hydro-chemical damage increases the width of a fracture,while hydraulic damage increasesfractures' connectedness,which means that improve the seepage character of erosion rock. For erosion damage rock,its seepage field can be described by multi-medium mathematical seepagemodel. Erosion damage decreases rock load area,after defining damage variable,the damage stress in rock can be calculated by the method bring forward by Lemaitre conveniently. For surrounding rock of a deep buried tunnel under the condition of drained,its seepage character is not only controlled by the high stress in rock,but also influenced by the development of erosion damage. In the whole course of rock' s deformation and failure,its seepage character decreases with the increment of stress in elastic stage,while 'increases with the development of failure. Stress decreases rock seepage character in elastic stage,while erosion damage increases it. Under some conditions,the influence of stress to seepage may be shielded by erosion damage.Obtaining the distribution of seepage field,tunnel external water pressure can be calculated in two ways:1. If lining is separated from surrounding rock,it can be calculated alone with the method of coefficient or elastic;2. If lining combine with surrounding rock closely,it can be calculated together with rock pressure with coupling model. The lining of a tunnel in the area with high groundwater table does not bear high external water pressure in-normal,the surrounding rock reinforced by intrusion concrete does it. In the case,the groundwater through reinforced rock accumulated in the space between lining and rock must be drained in time.