Experimental Study On Superfine Cement Grouting Of Micro-fracture Of Surrounding Rock In Deep Mine

The grouting technology can effectively block the rock fracture and improve the stability of the surrounding rock,which is of great significance to ensure the safe production of underground engineering such as mine shaft construction.With the increase of construction depth of coal mine,the complex geological environment such as high ground stress,high ground water and so on has put forward new challenges to the rock mass micro fracture grouting water plugging technology.In this paper,in order to study the water plugging of micro fracture cement grouting in deep well surrounding rock,the simulation test of micro fracture cement grouting in sandstone is carried out.Combined with numerical simulation,the grouting law of micro fracture cement grouting in sandstone under different roughness conditions is analyzed and discussed.The main study contents are as follows:(1)Using laser particle size meter,Digital Viscometer,measuring cylinder and other instruments,the paper tests and coMPares the material particle size,viscosity,stability and other properties of ultra-fine cement slurry.Taking the water cement ratio as the main factor,the paper analyzes its influence on the viscosity and water evolution rate of ultra-fine cement slurry,theoretically analyzes the injectability of ultra-fine cement slurry,and determines the ultra-fine cement used in grouting test Grout mix.(2)Based on the analysis and summary of the grouting test model of fractured rock mass at the present stage,combined with the research and test conditions of this test,a self-designed method for the preparation of samples for monitoring the micro fracture seepage is designed.According to this method,a group of molds are made.For the grouting test,three kinds of micro fracture sandstone with initial opening of 0.2mm and roughness of JRC=0-2,JRC=4-6 and JRC=10-12 are prepared Grouting the test block,and embedding the FBG sensor in the test block as the monitoring mode.(3)Using the triaxial stress grouting seepage model test system of micro fracture,under the confining pressure of 6MPa and 7MPa respectively,three kinds of sandstone like micro fracture test blocks with different roughness were tested under different grouting pressure to record the volume flow of slurry in different stages,and at the same time,the fiber Bragg grating sensor was used to monitor the different injection Based on the test results,the influence of roughness,grouting pressure,confining pressure and other factors on the grouting law of sandstone micro fracture is analyzed.After grouting,the test block is cut to observe the slurry stone body and fracture sealing.(4)In this paper,COMSOL multiphysics is used to establish three kinds of micro fracture models with different roughness.Under the condition of considering the slurry rock interaction,the influence of different roughness on the flow law of slurry in the micro fracture and the stress effect of slurry on the fracture surface are analyzed.