| With the adjustment of China’s energy structure and the development of coal mining technologies,huge economic benefits had been brought by new production processes and technologies,and made a lot of new challenges for mine fire prevention as well.However, serious damage happened in perpetual sealing walls while they were compressed and attacked when massive roof caving;besides, which has been causing frequent accidents of coal spontaneous combustion,crossheading are large in number, so is the workload of sealing wall and were severely damaged after compression,lead to widespread leakage underground mine,which would do greater impact on regular production. As to the workload of traditional sealing walls is too big and la waste of time. But the fracture of sealing walls would produce new air-leakage lanes and then it may cause spontaneous combustion of float coal. Scholars at home and abroad had launched a lot of theoretical and experimental studies on filling material for closed wall in recent years, and put forward a series of material filling sealed of high-strength, low-cost,and highly elastic. However, the construction conditions underground mine is complicated changeable,to estimate the effect of building an airtight wall is rather difficult, closed wall stability, reliability is difficult to guarantee, closed wall stress or after the devastating impact is difficult to determine,these problems can be solved or not is closely related to the prevention effectiveness of fire underground mine.Based on the researches of sealing walls home and abroad, we conclude the application situation and materials research of sealing walls. Mechanism, Damage index and stability judgement index are also discussed here. With coal ash as basic material,sodium silicate and lime combination as the curing agent,we found the optimize formula of high volume of coal ash combined with engineering indicators underground mine by orthogonal test of three factors and four standards. we conclude stress strain curve features and mechanical characteristic parameters as well as failure characteristics on optimize formula through uniaxial and triaxial test.Combined with the oretical mechanics based on shear strength, maximum shear stress, the maximum bending moment theory and derive a theoretical relationship between the closed wall,derivate the thickness formula of the closed wall.Combined with mechanism of perpetual sealing walls,we found the mechanical models of the sealing wall. In accordance with perpetual sealing walls mechanism and failure theory, we built the mechanics and mathematical models of sealing walls and determined the relevant boundary conditions.8617 Face of mine for Yungang return airway geological conditions,got the corresponding numerical simulation of different conditions combined with theoretical thickness formula.FLAC 3D was adopted to simulate the stress field, displacement field and failure field of sealing walls under different working conditions. By analysis on the numerical simulation results, we calculated the reasonable thickness of the wall.Contact with the failure mechanism and influencing factors on sealing wall in crossheading,based on the failure mechanism and influence factors of sealing walls in crossheading,focused on the current situation in sealing walls construction in 8617 working face in Yungang coal mine, introduct the import technology to FLAC 3D based on ANSYS modeling software,we got the corresponding numerical simulation of different conditions combined with theoretical thickness formula,establish a liaison Lane closed wall three-dimensional numerical model and establish the corresponding boundary conditions with ANSYS software. Based on the analysis of stress field, displacement field and failure field of sealing walls, we determined the reasonable thickness and reasonable position of closed wall from a theoretical point of view.This paper get the optimal ratio of fly ash solidified material parameters and mechanical properties based on the experimental study,establish mechanics model and numerical models and boundary conditions of sealing walls according to the theoretical analysis, Determine the key parameters of permanent closed wall in mined-out area and crossheading.which will provide more efficient method to determine wall thickness and is very significant to control air leakage and coal spontaneous combustion in goaf and working face as well as to the closed wall construction in the similar mine. |
