Preferred Discontinuity Distribution Characteristics Of Mining Entry Roof And Its Impact On Stability Of Surrounding Rock In Yangquan Mining Area

The distribution characteristics of roof preferred discontinuity,as one of principal influence factors which directly influences the characteristics of roof deformation and failure.The rock pressure behaviors is not the same on different distribution characteristics of roof preferred discontinuity,which can arouse serious deformation and failure of roadway surrounding rock.Therefore,it is highly important to research the stability roles of roadway surrounding rock under different distribution characteristics of roof preferred discontinuity.Taking the mining roadway in Yangquan mining area as the engineering background,the methods of field measurements,similar material simulation experiments,theoretical analysis and laboratory tests are used to investigate the distribution characteristics of roof discontinuity and stability roles of roadway surrounding rock.The Main research achievements of this thesis are mainly embodied in the following.(1)Field measurement and statistical analysis showed that there are multiple types of roof discontinuity in Yangquan mining area.The preferred discontinuity separated from the discontinuity by applying preferred plane theory.According to different bedding dip angle divide roof preferred discontinuity into horizontal bedding groups and tilt bedding groups.Analysis were put forward,and there were three kinds of preferred discontinuity in horizontal bedding groups,which were single horizontal bedding,combination of horizontal beddings and cross joints,irregularity cracks.The first two types was included in the tilt bedding groups.(2)Roadway similar model tests showed that the stability of roof most sensitive to the interlayer spacing of roof,and two sides takes second place,floor takes third place.The smaller of the interlayer spacing of roof,the weaker of shearing strength and extension strength.The change of damage mode of two sides from shear compression failure towards sliding failure with increasing extent of the damage of roof,then the deformation and failure degree of the floor increases.(3)According to similar model tests results,as angle of roof structural planes gradually increased from 0 to 30,45 and 60,the deformation and failure of roof showed obvious asymmetric characteristics that mainly reflected in different of the opening and slip extent of structural planes in both ends of the roof,which directlylead to the deformation and failure of two sides and floor heave losing symmetry.Roadway surrounding rock deformation and failure undergo an crease line process of decreased first and then increased.It is 45 degree at the turning point of decreasing and increasing.(4)Large scale similar model tests of roof showed that the cross section of broken roof contains three different regions,which are stable region,tilted region and subsidence area,respectively.There are four distinct phases of the three regions in the deformation process of roof roughly,which are initiation phase,developmental phase,formative phase and instability phase.It is brittle shear failure in horizontal stratification model.The deformation process of block model was obviously controlled by vertical joint.The instability process of stable intermediate layer that is the deformation failure process of loose block model,The main features are loosening and slippage of loose block in stable intermediate layer.