Numerical Simulation Of Loose Circle Thickness In Deep Weak Coal And Rock Roadway

With the gradual depletion of shallow coal resources,deep coal mining is also increasingly important,especially in deep and complex environment under the conditions of the roadway,the weak coal and the two gangs and roof displacement deformation,easy to control.Based on the analysis of the loosening circle around the coal and rock,the distribution characteristics of the loosening circle are obtained.The result is the theoretical basis for the calculation of the thickness of the loosening zone and the design of the parameter.In this paper,the influence of looseness thickness and its distribution on the stability of roadway in Xinji No.2 Mine of Huainan mining area in Anhui Province is analyzed.The strain softening SS constitutive model is selected and the numerical simulation of FLAC3 D is carried out.Distribution.FLAC3 D numerical simulation method is characterized by its lack of time,space,conditions,with strong flexibility and mobility.First,to the scene sampling,sent back to the laboratory to do the experiment,the determination of the mechanical parameters of the surrounding rock(elastic modulus,Poisson's ratio,cohesion and internal friction angle,etc.),select the seven directions(Figure 4-1(Ground stress: 10 MPa,14MPa,18 MPa,20MPa),the cross-sectional dimension(4.5),and the depth of the roadway in the medium-hard coal lithology condition,and to determine the cohesive force of the grid,m × 3.0m,5.5m × 4.5m,6.0m × 5.5m)on the thickness of loose loops and their distribution characteristics.The thickness of the loosening circle of the roadway is measured by borehole imaging method,which is basically consistent with the numerical simulation results.And draw the following conclusions:(1)Under the same conditions in the cross-section,when the local stress is small,the two sides of the roadway's cohesive force shows a relatively large state,will lead to relatively large degree of broken,so that the division of the grid showing partial elastic-plastic state,The two gangs of the roadway were first destroyed and needed to be first strengthened.With the increase of the ground stress,the loose circle also showed a gradual increase trend,while the change of the plastic zone is larger than that of the loose circle.At the bottom of the roadway,the stress on the loose circle and the plastic area is not much impact,only the local stress is large,will occur under thedrum damage.(2)Under the same conditions of geostress,the area where the variation of the loosening circle is relatively large is at the center of the two lanes of the roadway,and the area where the plastic zone is relatively large is in the four corners of the roadway.Rectangular roadway to help the loose circle will produce some changes in the column,the greater the depth,V-type trend is more obvious,arch effect is less and less obvious.The smaller the cross-section,the more prominent the arch effect.With the increase of the ground stress,the curvature of the loose circle is more full and the arch effect is more obvious.When the roadway section is 4.5m × 3.0m and 5.5m ×4.5m,the change value of loosening circle is gradually increasing,and the distance of6.0m × 5.5m is the most sensitive to the change of the distance of loosening circle.