| Luling coal mine, huaibei mining area two level of the main development and preparation of roadway is not affected by mining, roadway maintenance in good condition, but by coal bed mining disturbance, deformation, advance roadway affected not only the distance is long, but also big influence degree, deformation and failure of tunnel is very serious, almost all floor roadway after many renovations, cause roadway maintenance difficulties, seriously affected the normal production order of mine.Based on the theoretical analysis, laboratory test, numerical simulation and industrial test the integrated research methods of combining systematic analysis of the dynamic pressure influence mechanism of large deformation mechanics, stope floor of roadway surrounding rock stress distribution and floor damage depth, the dynamic pressure influence floor of roadway surrounding rock deformation and failure regularity, under different supporting method and the dynamic pressure influence the space-time evolution of floor roadway surrounding rock stability.The major achievements of this thesis are given as below:(1)By introducing rock mass strength softening modulus Q=σc-σbc/εpb0-εep0, the elastic-plastic mechanical analysis model of round roadway surrounding rock with consideration of strain softening condition under static pressure and mining pressure was set up. Then, the stress and new displacement explanation of elastic-plastic three area of roadway surrounding rock under static pressure and dynamic pressure were deduced. The new explanation example shows that strain softening modulus has remarkable impact on surrounding rock "three areas" scope, which can objectively reflect the features of roadway surrounding rock strength decrease along with strain increase under static pressure and dynamic pressure. This is the mechanical mechanism of large deformation for this kind of roadway. If reasonable rock physical and mechanics parameters are selected, then more reasonable analytic solutions can be obtained in theory. By improving residual strength status of fracture zone, the fracture zone radius can be effectively controlled. It is the mechanical mechanism of the roadway surrounding rock stability control, which can provide effective gist for the roadway arrangement and supporting design construction under static pressure and dynamic pressure.(2)By conducting the tests of indoor rock physical and mechanical properties, the uniaxial compressive, tensile and shearing strengths of sand rock mass at Ⅱ82mining area crosscut in Luling Coalmine were obtained. The shearing strength curve of sand rock was gained by matching. By analyzing the mechanical properties of mined rock mass and optimizing the mechanical parameters of mined rock mass with roclab software, the reliable mechanical parameters of rock mass was offered for the further numerical modeling establishment. Based on the analysis of rock constituents experiment, it can be concluded that the swelling rock constituents are precious few contained in roadway surrounding rock. This is merely single stress dilatation deformation mechanical mechanism rather than materialization dilatation deformation mechanical mechanism. Thus, it belongs to deviatoric stress soft rock of ⅡD project.(3)On the basis of saint venant principle, linear simplification of stope floor abutment pressure was made. Partitioning function ξ was introduced to calculate the intensities of floor abutment pressure distributions at different zones in working face direction. Based on the above, the integral representations of floor stress componentsσx, σy and τxy were computed. Then, the distribution law of abutment pressure in floor direction was analyzed.(4)Provided that mining stress field involves rectangle trepanning in the middle of elastic sheet, stress field nearby stope can be computed based on stope surrounding rock stress calculation model of Westergaad stress function. By simplified formula from stress field nearby traditional stope, it can be obtained:①under plane stress, principal stress value on the edge of stopeσ1,σ2and σ3, boundary equation r as well as maximal destruction depth value of stope floor rock mass h. According to the above equations, the maximal destruction depth value of mining floor in8#Coal hm=22.03m was obtained.②under plane strain, principal stress value on the edge of stopeσ1, σ2and σ3, boundary equation r’as well as maximal destruction depth value of stope floor rock mass h. According to the above equations, the maximal destruction depth value of mining floor in8#Coal hm=20.83m was obtained.(5)The computational formula of floor destruction depth under the condition of "big and small plastic zone" was proposed where both plastic zone radius of dynamic pressure influenced floor roadway and plastic zone range of stope floor were considered. The theoretical burial depth of1182mining area crosscuts had the distance of38.66m from stope floor, which was in line with field reality.(6)By adopting strain softening model in discrete element software UDEC, the mechanical model of stope and dynamic pressure influenced floor roadway was made, distribution features of stope floor abutment pressure were analyzed and following variation laws were acquired. The first is the variation law of floor fracture zone distribution along with working face advancing distance L. The second is that of floor fracture development along with working face advancing distance L. Through comprehensive comparison of influence laws of dynamic pressure on floor roadway surrounding rock equivalent stress, displacement, destruction line and fracture development, the internal activity law of dynamic pressure influenced floor roadway surrounding rock was given. In summary, this kind of roadway is influenced by lead abutment pressure of working face floor as well as upper roof fracture and revolving in the back of working face. There is uneven deformation for roadway surrounding rock from different parts at different depths, which can easily cause structural instability of support or abutment structure. Furthermore,"weak structure" part then triggers overall structural instability and global deformation.(7)The distribution law of surrounding rock equivalent stress, displacement and plastic zone is in organic connection with that of anchor rod axial force and failure zone wholly. By analyzing mechanical state of mining rock mass, supporting efficiency under different supporting ways was explained. In the same way, supporting efficiency under different supporting ways can be used to analyze mechanical state of mining rock mass. The supporting abutment behaviors of floor roadway at different parts involved transfer in different mining stages in working face. However, the stress was increased and supporting abutment property was improved as a whole. The action mechanism of structural reinforcement anchor rope means: structural reinforcement was made aiming at the weak location of single anchor rod supporting abutment structure to increase the thickness of anchor rod compound arch from original supporting way, enhance self-abutment capacity of surrounding rockand substantially reinforce the abutment capacity and structural stability of anchor netsupporting abutment structure. The action mechanism of structural reinforcementanchor rope on U-steel frame supporting roadway means: structural reinforcementwas made aiming at the weak location of shack supporting passive abutment structureto sharply improve the abutment capacity and structural stability of U-steel framesupport sides. In this way, highly intensive surface-protected capacity of U-steelframe support was fully used and active abutment property of anchor rope was fullydisplayed so to sharply improve the abutment capacity and structural stability ofU-steel frame supporting abutment structure. Suppose that there is the same stress fordynamic pressure influenced floor roadway, the supporting effect of shack-ropecoupling supporting is better than twice supporting of high-strength anchor-net-rope.Thus, beneficial reference can be provided for choosing reasonable supporting waysunder the same condition.(8)On the basis of detailed investigation into Ⅱ82mining area crosscuts geology,mining conditions and reasons of roadway surrounding rock failure, two sets oftesting programs of roadway stability controlling technology were proposed incombination with theoretical analysis and numerical simulation:①S cheme of high-strength stability supporting at U-steel frame②S cheme of high-strength stability supporting at anchor net supporting sectionThe long-term mine pressure observation station was arranged for the testroadway to observe surface displacement. The monitoring results suggest that: underthe conditions of the similar geology, mining conditions, construction techniques andforces, the support effect of shack-rope coupling plus floor grouting is bettercompared with twice structural reinforcement of anchor-net-rope plus floor grouting,which can control the extremely uneven deformation of dynamic pressure influencedroadway surrounding rock to larger extent and reduce roadway surface displacementquantity by a large margin. In addition, the service length of developing systemroadway can be prolonged with bigger promotional value. |
PDF Full Text Request