Study On The Relationship Between Grouting Parameters And Stress Field And Seepage Field Of Water-rich Fissure Surrounding Rock Tunnel

In tunnel construction,it has become a common construction method to reinforce the surrounding rock by grouting water plugging and grouting,The reasonable selection of grouting parameters was the key factor of water plugging effect and surrounding rock reinforcement effect,In order to better achieve the effect of grouting,theoretically better guide the grouting construction and tunnel lining drainage design.In this paper,Newtonian fluid was analyzed as the grouting object,and the fluid characteristics and the diffusion pattern in fractured rock mass are investigated.Based on the theoretical basis,the calculation formula of rock mass permeability coefficient and grouting pressure in the grouting area was deduced,and the water inflow prediction model was put into.The engineering feasibility of the prediction model was verified by the tunnel grouting water plugging construction case,Through the fluid-structure coupling theory,the field of seepage and stress change law in the grouting influence range after the excavation of water-rich tunnel provides some theoretical support for this type of grouting case.The main research contents of this paper are as follows:(1)The analysis of the influence factors of fluid in fractured rock mass,the movement mode of fluid inside and the characteristics of grout were the premise to explore the seepage characteristics and the feasibility of grouting.From the flow pattern of fluid in fractures and the special seepage characteristics of fractured rock mass,The fluid characteristics,three kinds of permeation and diffusion laws and diffusion formulas of Newtonian fluid were analyzed.The coupling mechanism of seepage field and stress field was explored,and the influencing factors and degrees of the seepage and stress field were comprehensively analyzed.(2)Taking Newtonian fluid as the grouting fluid,a simplified grouting model within the scope of the grouting domain was established,A single crack in surrounding rock was selected as the research object,and the effect of slurry on the change of filling degree in the crack was considered,The theoretical relationship between the porosity before and after grouting was deduced by the cube law,and the calculating relationship between the grouting pressure and the permeability coefficient of the grouting circle was established.(3)Based on the simplified grouting water plugging model,the calculation formula of seepage water flow per meter of tunnel is obtained,so as to establish the forecast model of water inflow,Therefore,the relationship between the estimated water inflow after grouting and the permeability coefficient is obtained.The project is based on inflow stion of Junchang Tunnel of Baomao Expressway,According to the comparison between the actual water inflow before and after field grouting and the theoretical analytical water blocking,the error between the theoretical water blocking and the actual grouting water blocking is the acceptable(within 10%),it can provide theoretical reference for other grouting water plugging processes in the later stage.(4)The fracture model was established by Rhino software and imported into FLAC3 D to establish the grouting model of fractured rock mass.The influence of different grouting circle thickness and permeability coefficient on the stress field and seepage field of fractured rock mass after the grouting process was studied and analyzed.Under different permeability coefficient conditions,the influence of permeability coefficient on seepage field is direct,and the change step of permeability coefficient is equal to the change amount of pore water pressure.The relationship between the thickness of the grouting ring and the thickness of the water barrier is determined when the thickness of the grouting ring is different.With the increase of the thickness of the grouting circle,the improvement effect of grouting construction on the formation seepage field gradually increases,but when the thickness of the grouting circle is too large,the length of the grouting pipe,the grouting pressure and the amount of grout will increase.It shows that when the thickness is greater than a certain value,the improvement effect of grouting on the seepage field and stress field of surrounding rock is not obvious.