Failure Characteristics And Grouting Support Of Surrounding Rock In Soft Rock Roadway

In the process of coal mining in western China,soft rock characterized by low strength,poor cementing,and degradation and softening in water is often encountered,which results in the failure of anchorage support methods to maintain roadway stability for a long period of time,and roadway deformation and destruction.It is of great theoretical significance and engineering practical value to carry out research on deformation,failing mechanism of surrounding rock in soft rock roadway and grouting support.This article takes the Hongqingliang Coal Mine as the engineering background,and uses a combination of theoretical analysis,numerical simulation,indoor test and field test to conduct systematic research.The main work is as follows:Firstly,the mechanical properties of the roadway roof coal and rock were tested.The strength of the coal was greater than that of the sandy mudstone.Sandy mudstone belongs to soft rock and has an average uniaxial compressive strength under 20 MPa and analyzes the influence law of sandstone bedding on its strength and deformation during loading,and analyzes the physical components and water physical characteristics of sandy mudstone.the effect of water on the strength of sandy mudstone was analyzed and the fracture characteristics were revealed.Secondly,the characteristics of roadway deformation and failure are explored,the roof rock bedding,crack development and damage scope,roof cracking,drastic droop,and frequent roof fall accidents;coal wall is prone to rib spalling and internal extrusion;The anchor bolts(cables)of the roadway roof are insufficient for anchorage,and the roadway support structure is seriously damaged.Combining engineering geological conditions and FLAC numerical simulation software to analyze the influence of tunnel excavation width,horizontal stress magnitude,and strata bedding on roadway stability.analysis shows that as the width of the roadway increases,the stress concentration point moves to the deep rock mass,the range of plastic zone in the rock strata expands;as the horizontal stress increases,the plastic zone of the rock mass decreases,and transfer to the roof and floor of the tunnel;the shear strength between bedding decreases,which leads to a significant increase in the plastic zone of strata in both the horizontal and vertical directions.Finally,the grouting reinforcement governing project was proposed according to the failure mechanism of surrounding rock.The results of grouting reinforcement test showed that the basic performance of cement slurry,water glass-cement slurry was greatly influenced by the ratio of water to cement,volume ratio,etc.The cohesive strength,internal friction angle and other strength parameters are all higher than those of sandy mudstone.The damage of consolidation body is mainly based on the interface between stone body and rock mass and the destruction of grout stone structure.The results of numerical simulation show that the grouting reinforcement of the roof rock strata in the roadway,the width of the grouting layer of the roof should not be less than 1.4 times the width of the roadway;under the condition of small horizontal stress,the effect of the control of the roadway surrounding rock can be improved by increasing the width of the grouting rock.In the case of high-level stress,it is necessary to increase the height to 6m and improve strength of the grouting area to achieve the control effect.Through grouting,the anchorage supporting performance is effectively improved,and the roadway roof and floor movement is reduced by more than 50%compared with the non-grouting section.The supporting effect is good.