Research On Seismic Dynamic Disaster Of Roadway And Rock Mass Structure And Degradation Of Seismim Performance Of Ground Buildings In Coal Mining Areas

A large number of coal mining areas of the formation of different forms, sizes, criss-cross and three-dimensional distribution are formed due to continuous mining of coal resources in an efficient exploitation, all kinds of infrastructure just as a growing number of buildings, bridges, transmission towers and tunnels are inevitable to be built on the coal mining areas with the rapid development of construction and increasingly tense of land resources. But the problem is debatable that whether buildings can be built in the coal mining areas decided by the goaf\s stability, and the collapse phenomenon of building damage and surface subsidence caused by rock movement and deformation of coal mining areas is unusually severe. It is inevitable to face damaging effects of the dynamic loads and various disturbances in the process of coal mining, but the influence and damage of coal underground structure caused by various dynamic disasters such as earthquakes had been little considered the design of mine construction. In China more than 80% of mining areas are in strong earthquake area, but there are no specially detailed calculation methods and seismic design codes or standards of coal underground structure. The problems just as stability of coal mining areas under earthquake, interaction between roadway structure and the surrounding medium or between dynamic response of building and coal mining areas are important issues for seismic safety research of coal mining areas can not be avoided.Based on the elastic-plastic mechanics, structural dynamics, earthquake engineering and mining subsidence study, the method of field research, experimental research, theoretical analysis and numerical simulation is carried out to do research work revolves the problems just as seismic dynamic disaster of underground structures and degradation of seismic performance of ground buildings in coal mining areas. The following research work and some useful research results are got mainly from this paper just as follows:(1) Through the establishment of elastoplastic mechanical model of movement and deformation of rock overlying the coal mined areas, mechanics criterion of movement deformation and breaking of coal mining overburden can be got. Exploring the region of stress distribution evolution and variable displacement of goaf rock under the influence of coal mining. The protection principle of pressure relief of fractured rock is just as follows elastic energy in rock mass will be released in time during the process of coal mining. So elastic energy of disasters in rock mass can be released in time to avoid the mine dynamic disasters occur, and it can reduce the mine pressure of rock mass to protect the structure of rock roadway.(2) Through establishing the mechanics model of seismic dynamic response of coal column, the internal force response and stress field evolution regularity of coal column under earthquake load were discussed mainly, and the earthquake damage rule of coal column is as follows that the elastic zone, plastic zone and fracture zone form inside the coal column within under the weight of overlying strata, the evolution and development of the plastic zone towards to the internal of coal column continuously. Then the rupture zone increases gradually and core elastic region decreases, leads to internal friction of rock failure surface and internal cohesion of coal column decreases, reduces the binding effect of coal rock and coal column appear stripped off, and the whole phenomenon of instability and destruction of coal column come true finally. The initial damage in different parts of the mine roadway has much greater impact and difference to its instability and failure modes, the roof and department of coal mine roadway structure belongs to the locations of high stress concentration and easy to damage, and they need to be pay attention to take reasonable precautions.(3) The earthquake dynamic response differences of different areas (just as roof, floor and department) in the same section of roadway mine location are studied to explore seismic dynamic damage characteristics and influencing factors of mine underground tunnel structure of different cross-sectional shape, then the seismic response characteristics and failure modes of mine roadway can be got as follows:The seismic performance of shallow coal mine roadway is poor relatively and geostress has a greater impact to the seismic performance of deep coal mine roadway so the safety and stable performance of deep coal mine roadway is not easy to ensure. The seismic performance of circular roadway is the best one relatively, horseshoe-shaped roadway is followed and the seismic performance of rectangular tunnels is the weakest one relatively. Low-frequency earthquake has greater impact on seismic dynamic response of coal mine tunnels, with the frequency of seismic loads increases, displacement response of roof and department of coal mine tunnel showing a trend as increase firstly, then decrease and gentle change finally. Dynamic response of near-surface shallow coal mine tunnel exacerbate due to the amplification of seismic waves in the surface. When the buried depth of coal mine tunnel deeper, seismic dynamic response of the mine tunnel structure can be reduced due to strong binding effect of rock medium.(4) Through discussing the stress field distribution of damage regional of rock considering rock damage due to the strength reducing and the stiffness degradation of rock and making comparative analysis of the impact of seismic force catastrophic of underground coal mine roadway structure caused by damage effects, studies have shown that additional load of coal mine roadway structure and vibration of coal (rock) layer appear at the same time caused by seismic waves, and seismic waves reduce the carrying capacity of coal (rock) layer of coal mine roadway structure seriously. High stress concentration areas always appear the top side of the roof and department of coal mine roadway structure under earthquake, plastic failure region of rock of coal mine roadway structure considering rock damage due to the strength reducing and the stiffness degradation of rock lower than the rock not considering rock damage due to the strength reducing and the stiffness degradation significantly. The forced vibration form of coal mine tunnel and surrounding rock caused by earthquake close to the basic form of seismic waves vibrating. The main role of the surrounding rock media is to spread effect, energy absorption and migration effect. The response of acceleration, peak displacement and internal force of different parts of the same section of mine roadway structure decrease considering damage effects can slow and coordinate rock’s deformation, the energy dissipation capacity of fractured rock mass increase and it reducing the propagation of seismic energy and deformation of rock effectively. Destroy power of seismic shear waves is mainly reflected the level of shear of coal mine tunnel structure and seismic longitudinal wave’s destroy power is mainly reflected the level of tension and compression of coal mine tunnel structure, seismic longitudinal wave can also increase the load of roadway structure to some extent. Summarizes the principle of controlling seismic response of coal mining rock considering damage due to the property of pressure relief and energy dissipation and vibration absorption of coal mining fissures rock media.(5) Through discussing the nature of the stress wave change when the seismic waves acting on rock and making an analysis of seismic wave propagation attenuation characteristics between the goaf surrounding rocks and filling materials with different dielectric medium filling effect, point seismic dynamic stability conditions of the filling goaf. The study found that compression failure, tensile failure and resonance sabotage are mainly manifestations of the dynamic failure of rock (coal pillar) caused by seismic wave. When the intensity of the rock in coal mining areas meet the conditions σb+kσα> σ’ after filling the mining areas and it can keep the seismic stability of goaf. Seismic dynamic response of the surface can be mitigated due to goaf’s presence, however coal mining areas may become hidden danger to exacerbate the large collapse of dynamic instability of surface under severe earthquakes. The damage of the surface on coal mining areas is relatively smaller caused by earthquake, the strength of filling material and mining fractured rock reduce, their stiffness deteriorate and damping and energy dissipation capacity increase. So disaster energy of seismic waves absorb efficiently. The venues of goaf group are much more dangerous than the one of single goaf. Vibration form of acceleration response of goaf are similar as the original source incentives and there is a lag in the time and has been extended in the vibration form.(6) The study found the system of disaster evolution of mining areas is related to solid, liquid, gas and other complex coupled multiphase systems. The deterioration of seismic performance of buildings in mining areas caused by four areas just as environmental and load factors, materials, components and structures. Coupling effect between harsh natural environment and complex mechanical environment is the driving force, destruction of materials is the root cause, destruction of components is macro performance and structural performance deterioration is the direct cause of the deterioration of the seismic performance of buildings in mining areas. Repeated high-intensity mining stress is the cause of produce disasters for the buildings in the mining areas under the influence of repeat mining.(7) Through exploring disaster evolutionary mechanism of damaged buildings caused by coal mining and earthquake, point out the process of deterioration of seismic performance of building caused by coal mining under earthquake. Using damage mechanics and energy theory to explore formative mechanism of the building caused by mining damage and earthquake, the study found that coal mining of underground change the seismic wave field of coal mined areas, the damage of the building caused by coal mining damage mainly in the lower floors. Plastic hinges of the building structure in mining area can be formed at the weak layer under the earthquake, reducing the seismic performance of the structure. Seismic performance evaluation method of the building damaged by coal mining is proposed based on the theory of energy dissipation, explores the process of energy dissipation evolution of the building damaged by coal mining under earthquake. Make a description that the coal mining damage exacerbated the breakage of the buildings caused by earthquake loads. Propose the protection strategy of filling underground mining and resistance to mining subsidence and isolation of building, and it can control the movement and deformation of rock in mining area and it can also achieve resistance to mining subsidence and isolation of building.