Research On The Seepage Characteristic Of Fractured Rocks And The Mechanical Properties Of Grouting And Fillings Of High-Temperature Water-Rich Broken Rock Masses

In recent years,tunnels and other underground projects have developed rapidly,and the scale and number of tunnels in China have become a major tunnel country.Due to the limitation of terrain conditions,the engineering geology and construction environment encountered in tunnel construction are complex and changeable,and high ground temperature,high ground stress,high osmotic pressure and strong excavation disturbance have become a normal state.The high ground stress makes the tectonic stress more complex,the fracture occurrence more random.The surrounding rock of tunnel is subject to repeated load disturbance and trench flow which can cause diversity in internal fracture width,filling condition and penetration rate.The high ground temperature environment not only affects the design and construction of the tunnel,but also puts forward higher requirements on the temperature tolerance of the grouting materials,and makes the diffusion law of the slurry and the mixed structural state of the surrounding rock after grouting more complicated.Therefore,the research on the seepage characteristic of fractured rocks and the mechanical properties of grouting and fillings of high-temperature water-rich broken rock masses has important theoretical significance and engineering practical value.This paper takes the Gaoligongshan Tunnel as the engineering background,and the seepage test of filling fractured rock mass with different occurrences under cyclic loading and the grouting test of high-temperature water-rich fractured rock mass are designed.The method of combining COMSOL Multiphysics numerical simulation with THM coupling rock grouting theoretical analysis are adopted.From the seepage law of filling fractured rock mass with different occurrences,grouting material selection,equipment development and filling physical and mechanical properties,the research on the seepage characteristic of fractured rocks and the mechanical properties of grouting and fillings of high-temperature water-rich broken rock masses have been studied,the main research contents are as follows:(1)The types of underground rock fractures and the degree of filling penetration were summarized,and the fully filled fractured test samples with different penetration rates were further prepared,the multi-stage confining pressure cyclic loading-unloading confining pressure-seepage coupling test was designed.The variation characteristics of permeability and stress sensitivity coefficient with confining pressure of fully filled fractured test samples with different penetration rates were revealed,and the effects of penetration rate on permeability and stress sensitivity coefficient of fully filled fractured rock were quantified.It is found that the stress sensitivity coefficients recover poorly after the first circumferential pressure unloading of fully penetrated rock masses,while the incompletely penetrated test samples show a stress sensitivity coefficient greater than that in the unloading phase than in the loading phase.(2)The test samples with different equal-width ratios fully penetrated filling fractures were prepared,and the expressions for the permeability coefficients of fracture rock mass with non-equal width filling were derived.Which is proportional to the sum of the squares of the entrance and outlet width in the uncoupled state.The confining pressure-seepage coupling test under multistage high-low confining pressure cyclic loading and unloading was carried out,and revealed the variation law of permeability and stress sensitivity coefficients with confining pressure for fully penetrated filling fractured test samples with different equal-width ratios under cyclic loading and unloading.(3)The rational selection test of grouting materials under high geothermal water-rich environment was carried out.The cement-based slurry containing diatomaceous earth and glass beads was denied as the grouting material under high geothermal environment.Finally,the modified cement-based grouting materials suitable for high ground temperature environment were preferred as metakaolin(8% of cement dosage)and Na OH(1% of metakaolin dosage),the strength of the slurry stone body under this ratio was greater than that of pure cement slurry,the thermal conductivity and permeability were less than that of pure cement slurry.(4)The indoor grouting test device for fracture-developed rock formations in a high ground temperature water-rich environment was developed,and the feasibility of the device was demonstrated from both experimental and theoretical perspectives.The diffusion law of slurry in broken rock mass under high temperature water-rich environment is revealed,and the influence of formation temperature on diffusion law of slurry is clarified.With the dynamic permeability as the coupling factors,Comsol was used to make a useful discussion on the grouting effect of fractured rock bodies under the consideration of temperature field.(5)The grouting tests on fractured rock masses under high temperature water-rich environment were carried out.With formation temperature and maintenance time as the dominant variables,the variation laws of strength,permeability,thermal conductivity and acoustic properties of the filling body were revealed.The relationship equations of physical and mechanical properties of the filler under the effect of multiple factors of temperature,grouting pressure and water-cement ratio were obtained,the degradation mechanism of the physical and mechanical properties of the filling body under the long-term action of formation temperature and maintenance time were revealed from the macro and micro perspective.The paper contains 114 pictures,31 tables and 221 references.