Experimental Study On The Influence Of The Breakage Of Overlying Key Strata On The Variation Of Pressure In Goaf

A series of mining damage and environmental problems caused by coal mining are related to the movement of overlying strata.However,pressure in goaf will constantly change with the movement of overlying strata.Therefore,this paper will study on the relationship between goaf pressure changes and the fracture in overlying key strata based on key strata theory.So as to achieve the goal of mastering the internal movement law of overlying strata.Theoretical analysis,physical simulation,numerical simulation and field observations are used in this thesis.Firstly,through the physical simulation to investigate the impact of the fracture in overlying key strata on pressure changes in goaf.And influence factors on goaf pressure is analyzed by using numerical simulation.After that,a goaf pressure monitoring system and technological method are developed independently,and field experiments are carried out,obtaining qualitatively a normal effect of the fracture in overlying key strata on goaf pressure variations.Physical simulation shows that a ladder-like pressure increase is found in goaf with the fracture of overlying key strata after coal mining.During the initial mining period,the pressure of the measuring point is in a ladder-like growth until it is finally stable,and the goaf pressure is far less than in-situ stress.During the normal mining period,the goaf pressure increases step by step when the key strata which are just above measuring points are broken,after which goaf pressure is back to in-situ stable stress with different slope curves.Numerical simulation indicates that under the condition of no key strata,the goaf pressure will increase from zero to the final stable value in a linear-increasing way.When measuring points are arranged during initial mining period,a ladder-like pressure increase is always found in goaf with the fracture of overlying key strata,and the final value of pressure will be less than in-situ stress.When measuring points are arranged during normal mining period,goaf pressure will be influenced by key stratum horizons,key stratum thickness and mining height.Based on research results above and complex goaf conditions,a goaf pressure monitoring system and technological method are developed independently,and site measures are carried out in Zibo Wangzhuang Coal Mine,which verifies the accuracy of monitoring system and basic rules of goaf pressure changes.