| Grouting is an effectively reinforcement method for broken coal-rock mass and widely-used in surrounding rock control in coal mine underground.But,because it's complexity of broken coal-rock mass geological situation and influence factors of grouting reinforcement are variety,so the grouting project practice is always ahead of the grouting theoretical studying all the time,grouting parameters were mostly determined by experience,so the characters that scientificity,rationality and reliability of grouting reinforcement were influenced obviously.The paper taking broken coal-rock mass grouting reinforcement of Lu'an mining district as project background,then following methods that theoretical analysis,laboratory test,numerical simulation,underground testing and grouting results detection were used,then grouting reinforcement mechanism,grouting material,grouting parameters and technology and so on were studied,then the following achievement were obtained.(1)The cement modified liquid was developed,then the following characters viscosity,stone ratio and bonding strength of modified cement liquid were tested.When water cement ratio was 0.7:1,the bonding strength(7d)reached the maximal value as modified liquid dosage was 20% approximately,improved about 42.36% than without modified liquid.So it advised cement modified liquid dosage for deeply hole and high pressure grouting was about 15%-20%.(2)Planar fractured grouting simulator test rig and bundled software were developed,the grouting simulator tests were done in the following different situations,which include different fracture aperture,different fracture dip angle,different grouting pressure.After the experiments of chemical grouting,cement grouting and cement modified liquid grouting under smooth and coarse fractures with aperture 2mm and 3mm.The following results could be put forward,all pressure curves all appeared pressure rise stage-steady pressure stage-pressure decay stage after grouting,with grout viscosity increase,the pressure value of measure point appeared the variation features that firstly rise then decay,the pressure value of the same measure point was the maximum as grout viscosity between 50-150mPa·s,the stability of steady pressure stage of single grout was better then chemical pulp,the influence that fracture incline angle variation to grouting pressure was small.(3)The experiment results of multiple fractures grouting results showed that with grout viscosity increase,the time of the main fracture pressure reached the maximal value was extended,fractures incline angle variation was fuzzy for pressure variation.Through fracture grouting simulation experiments,the linear relationship between measure point pressure and grouting initial pressure was obtained,and the relationship between chemical grouting and grouting pressure was in accordance with the exponential relationship.The best viscosity of chemical grouting for engineering was 50-150mPa·s,and the best water cement ratio was about 0.7:1.(4)The diffusion shape and scope and it's main influence factors of shallow hole and low pressure grouting and deeply hole and high pressure grouting were analyzed by UDEC numerical simulation software,then the relationship between grouting pressure and grout diffusion distance appeared as two parabolic functional relationship,and advised water cement ratio of high pressure and deeply hole grouting should be as 0.7:1,grouting pressure was approximately 30 MPa.(5)The high pressure and deeply hole grouting was applied in underground during N1-3 isolated working face ending of Changcun coal mine of Lu'an coal district,then reasonable grouting reinforcement method,scheme,technology and parameters were determined,and grouting result was detected also.The validity of the research achievement in the paper were verified by the practical results in underground,grouting results in underground was good,the working face ending time was compressed,and engineering cost was decreased,then good technical economy benefits were achieved. |
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