Study On Coal Pillar Failure Mechanism And Stability Of Strip Wongawilli Mining Technology

The problems of mining under structures,railways and water bodies are more and more serious in China's coalmines.In order to achieve the maximum recovery of coal resources,coal mining under structures,railways and water bodies were studied.Strip Wongawilli mining technology is a high-efficiency mining method that combine strip pillar mining layout and Wongawilli mining technology.Moreover,it can both reduces mining damages,protect surface structures and carry on continuous production,increase mining efficiency and recovery ratio.The surface subsidence reduction of Strip Wongawilli mining through overlying strata control,and the stability of coal pillar is the key to control overburden strata.Based on the Wangtai and Zhaowu coal mines,theoretical analysis,similar and numerical simulation were combined to study the failure mechanism and stability of coal pillar.This paper mainly includes the following aspects:(1)Based on the position relationship of Strip Wongawilli mining irregular pillar,strip coal pillar,mining room and branch entry.Five kinds of entry layout were put forward,and main equipments and parameters of the mining were introduced.(2)The deformation and damage evolution of coal pillar were studied by Similar and numerical simulation.The stress field,displacement field and plastic zones in surrounding rocks were also analyzed,and the results provide reference basis for the control of surrounding rock and roof management of Strip Wongawilli mining.(3)The overburden strata movement structure model of Strip Wongawilli mining was set up,and the stress state of coal pillar was analysed to build a systematic model in Strip Wongawilli mining.The coal pillar load theory was put forward,and the reasonable mining width and coal pillar width were given.(4)The instability mechanism of the Strip Wongawilli mining residual coal pillars was uncovered by the integrate analysis of gradually damage theory and catastrophe theory.Meanwhile,the criterion and cusp catastrophic mode of pillar instability were also established.Based on the dates of simulation experiment and engineering,it was concluded that the instability mechanism of the Strip Wongawilli mining room pillar,irregular pillar and strip coal pillar.And it also showed that the relevant pillars would be instable with one of the coal pillars instability.Then,the whole pillar system was invalidated and the “Domino effect” was occurred which caused the aggravated overburden failure and the extensive surface subsidence.(5)The technology system of coal pillar stability control was proposed based on the structure characteristics of overburden strata,the stress distribution and the instability mechanism of Strip Wongawilli mining,which was included the layout of roadway,the reasonable size of mining,the strength of coal pillar,the management of the roof and the advancing speed of the working face.Then the safety and high efficiency mining can be achieved by the Strip Wongawilli mining.