| With the continuous increase of underground minerals and underground engineering excavation,the reinforcement of fractured coal and rock mass is increasingly important in the geotechnical construction of high geostress,surrounding rock fissure development and complex geological conditions.Grouting can fill fractured rock mass,prevent leakage and increase surrounding rock strength.At present,the grouting reinforcement methods are mainly divided into two categories,respectively,using high-strength anchor rods with grouting tubes or ordinary grouting anchor rods.The above grouting reinforcement method only pays attention to the effect of grouting,and the combination of high-strength pre-stress anchoring and grouting cannot be realized.For grouting materials,most of them are chemical and polymer fiber grouting materials,which have serious pollution to groundwater and coal quality,and the reinforcement effect of a few cement-based grouting materials is not obvious.The key of the new prestressed grouting reinforcement technology proposed in this paper is the strength characteristics of the consolidation body formed under the prestressing conditions of the grouting anchor cable prestressing combined with the new grouting material.The self-supporting capacity of the surrounding rock of the roadway is determined by the strength of the solid body formed in different time and range.Therefore,the mechanical properties of prestressed grouting material and grouted solidified body are explored,and environmentally friendly cement-based prestressed grouting material and prestressed grouting anchor cable support members are developed.The research results effectively solve the problem of chemical grouting materials polluting the underground environment,and provide a new reinforcement method for prestressed anchoring combined grouting of fractured coal rock mass.(1)The mechanism of surrounding rock failure and support in mine roadway is analyzed,and the reinforcement mechanism of anchor cable and grouting material in prestressed grouting reinforcement technology is explained.Based on the reaction principle of cement-based concrete slurry,the optimal ratio of new grouting materials was determined by orthogonal test method.The amount of expansion agent is 8%,the amount of early strength agent is 2%,the amount of water reducing agent is 1.5%,and the water-cement ratio is 0.45.Through the coal block grouting test,the strength of the coal block solidified body is increased by 17.1%compared with the original coal sample,and the performance of the slurry is preliminarily verified.(2)The thread structure,torque stress ratio and material of the rod body were analyzed,and the high-strength prestressed grouting anchor rod and supporting support members were developed.According to the uniaxial compressive strength test of the consolidated core,the compressive strength of the mudstone and sandstone consolidated body is 25.4Mpa and 126.4Mpa,respectively,and the mudstone strength is increased by 25.1%compared with the original.The SEM test shows that the flaky calcium hydroxide and acicular ettringite crystals at the rock-slurry interface are intertwined to increase the compactness of the cemented surface.The internal hydration reaction product gel increases the cementation force at the magma interface.,improve the interface strength.(3)The prestressed grouting support scheme was designed for the test roadway of Daxing Coal Mine.The effect of prestressed grouting reinforcement under mining conditions was studied by numerical simulation.The new grouting materials and supporting supporting members have been applied in the test section roadway.According to the mine pressure observation data and the results of drilling TV,the reliable application of the new supporting materials has been verified,and good economic and social benefits have been achieved.The industrial trial production of new grouting materials and supporting support members has been realized. |
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