Experimental Investigation On Grouting In Rough Single Fracture And Fracture Network With Flowing Water

Groundwater inrush in mine seriously threatens the safe production of coal.Grouting technology plays an important role as one of the effective measures to control mine water hazards.Therefore,the research of grouting in fractured rock mass with flowing water is necessary.In this study,the grouting simulation experiments were carried out in the laboratory by using the grouting experimental platform for simulating rough single fracture and fracture network with flowing water.The grout propagation process,the variation of grouting pressure,the variation of seepage pressure and the effect of water plugging were also obtained.The influence of various factors on water plugging of grouting was analyzed.The main contents and results are as follows:(1)The main effect of influence factors on grouting efficiency of flowing water in rough single fracture is obtained.The orthogonal experimental of simulated rough single fracture on grouting with flowing water was carried out in the laboratory.According to Bardon’s standard roughness curve,the JRC values of 2-4,6-8,12-14 and 18-20 were selected to simulate a rough single fracture for the orthogonal test on grouting with flowing water.The value of JRC(A),the gel time of grout(B),the initial water flow speed(C)and the fracture-opening(D)were taken as four factors in the orthogonal experimental.The results show that the factors affecting the grouting efficiency in rough single fracture with flowing water are the value of JRC,the fracture opening,initial water flow speed and the gel time of grout.(2)The characteristics of seepage pressure field of grouting in a rough single fracture with flowing water are obtained.The seepage pressure of grouting in the rough single fracture with flowing water can be divided into three types: single-peak type,multi-peak type,and platform type,the seepage pressure curves of six measuring points had a good regularity in the same test.The “single peak type" seepage pressure curve was mostly found in grouting when the JRC value of the fracture surface was large and the fracture-opening was small.The “multi-peak type” seepage pressure curve was more common in grouting when the initial water flow speed was large and the JRC value of the fracture surface was small.The “platform type” seepage pressure curve was often found in grouting when the initial water flow speed was small and the JRC value of the fracture surface was large.(3)The relationship between grout propagation pattern and roughness of grouting in a rough single fracture with flowing water is obtained.The test found that grout propagation pattern was related to the roughness of the fracture surface.The smaller the JRC value,the easier the grout propagation,which results in the difficulty of grout cementation.The larger the initial water flow speed,the more incomplete of the final grout morphology.(4)The test system of grouting in rough fracture networks with flowing water is established,the relationship between grouting efficiency and the JRC value was obtained by parallel tests.According to 10 Bardon’s standard roughness curves,10 different fracture network models with Barton’s standard roughness curve were processed.A parallel experimental investigation was carried out under the same conditions,the initial water flow speed,the gel time of grout,the grout take were selected as factors and controlled at the same level.The results show that the larger the JRC value,the better the water plugging effect and the more complete of the grout propagation shape.(5)The main effect of influencing factors on sealing efficiency of grouting in rough network with flowing water is obtained.The orthogonal experimental investigation of grouting in rough fracture network with flowing water was carried out with four factors and four levels.The results show that the factors affecting the sealing efficiency ranked as initial water flow speed(B),JRC(A),grout take(D)and the gel time of grout(C).(6)The characteristics of seepage pressure field of grouting in rough network with flowing water are obtained.During the grouting process,the varation of seepage pressure kept a good consistency.The change forms of eight measuring points were basically the same.According to the shape of the seepage pressure curve,it can be divided into four types: multi-peak type,single-peak type,platform type,and overall rising type.