Research On Collapse Mechanism And Control Of Shallow Buried Roadway Surrounding Rock With Mudstone-clay Compound Roof

There are a large number of mudstone-clay dual-soft compound roof occurrence conditions in shallow coal seams in Shanxi,Shaanxi and Western Inner Mongolia in China.which have a very unfavorable impact on roadway excavation and support.Therefore,the mechanical response characteristics of mudstone-clay compound specimen under the influence of multiple factors were experimentally analyzed based on the deformation and support of surrounding rock in mudstone-clay compound roadway in shallow buried seam of Xishan Xiegou Coal Mine,Shanxi Province;The stress deformation expression of roadway surrounding rock in mudstone-clay compound strata is obtained by theoretical research,and the deformation mechanism of roadway surrounding rock in compound strata is revealed,and a reasonable deformation roadway control strategy is proposed.The stress and deformation law of roadway surrounding rock under the influence of multiple factors was simulated and analyzed,and the sensitive factors of roadway deformation control in compound strata were determined.The support method of bolt + short anchor cable + long anchor cable was adopted,and good roadway support effect was achieved.The main results of this study are as follows:(1)The existence of mudstone-clay layer has a significant weakening effect on the strength of compound specimens.Finally,the elastic modulus is used as the key parameter to characterize the macroscopic mechanical properties of compound specimens.The results show that,the stress-strain curve of compound specimens becomes gentle from high to steep and the elastic modulus of specimens decreases with the increase of thickness,layer number and moisture content of clay layer.The increase of water content accelerates the failure mode of mudstone-clay compound specimens from brittleness to plasticity.Affected by the uneven deformation of clay layer,the macro failure modes of compound specimens are mainly tension fracture,tension + shear fracture and shear fracture.The low strength of clay layer and the deformation transient response have no significant effect on the deformation curve shape of the compound specimen in the elastic stage,but the elastic modulus changes obviously.(2)Based on the occurrence conditions and mechanical response characteristics of mudstone-clay compound material,the elastic modulus is used as the key parameter to characterize the compound strata,and the transverse isotropic equivalent mechanical model of roadway surrounding rock is established.The deformation mechanism of roadway in mudstone-clay compound strata is revealed,and the reasonable roadway deformation control strategy is proposed.Firstly,according to the transversely isotropic constitutive assumption of mudstone-clay compound strata,the equivalent stress model of roadway surrounding rock is established by using the unified macroscopic characterization parameter of compound strata – elastic modulus,and the stress deformation analytical expression of roadway surrounding rock is obtained.Secondly,the stress and deformation characteristics of roadway surrounding rock in typical position are further discussed.It is concluded that the deformation of roadway surrounding rock is affected by the elastic modulus of compound strata.Finally,it is proposed that the manual intervention in elastic modulus of mudstone-clay is an effective way to realize the orderly control in the deformation of roadway surrounding rock.The coordinated deformation of roadway surrounding rock in the horizontal and vertical directions can be obtained by controlling the elastic modulus configuration of the mudstone-clay material in different directions,which provides the basis for the control measures such as the hydrophobic drying of roadway surrounding rock,the enhancement of the mudstone-clay layer,and the strong anchor cable support.(3)The influence law on the stress deformation of roadway surrounding rock in mudstone-clay compound strata caused by multiple factors is simulated and analyzed.It is determined that the moisture content is a sensitive factor in multiple factors,and a reasonable roadway surrounding rock support method is proposed.The research shows that,under dry conditions,the clay layer is the main influencing factor of roadway surrounding rock deformation,and the layer depth is negatively correlated with the maximum subsidence of roadway roof,which is the main factor affecting roof separation.Under the condition of water content,moisture is the main factor affecting the deformation of roadway surrounding rock.The higher the water content,the wider the plastic zone distribution,and the greater the deformation in roadway surrounding rock.Based on this theory,the support method of bolt + short anchor cable + long anchor cable is put forward,and the appropriate time for long anchor cable delaying secondary support is 25 m from the head of excavation,and the delaying time is about 10 days.The application effect of material roadway in 18511 working face of Xiegou Coal Mine is good.The cumulative displacement to get closer of roof and floor was 141 mm,and the cumulative displacement to get closer of two sides was 135 mm in roadway.This paper has 79 figures,12 tables and 127 references.