Analysis Of Surroundings Stability Of Pre-support For Gob-side Entry Retaining

The structure type of roadside support is always the key who constrain gob-side entry retaining to make success,the structure of pre-support separating wall can be explained that cylinder and H-T bolt pillar were arranged along the inside and outside of separating wall to form pre-support contours aimed at the defects that separating wall can not take the initiative pressure and have no strength in the early time,it is the emphasis that convert roadside support from passive to active.With the method of mechanical analysis and numerical simulation,the function of pre-support to improve the stress state of roadway can be researched and explain the stability mechanisms of surroundings with the effect of pre-support,then present “high strength suitable stiffness ? coordination ? suitability”three-phased design principles about pre-support system and carried it out based on gob-side entry retaining technology of bag-casting concrete which treated H-T bolt pillar as pre-support.Research shows that the fracture location of surroundings is closely related to the effects of actions of pre-support and the fracture location has a decisive influence on support resistance of separating wall;so there is a special mechanical relationship between pre-support and roadside support,pre-support can make pressure to give full play to self-supporting capability of surroundings and reduce the support resistance of separating wall.Pre-support and roadway side support also exit mechanical relationships,pre-support as an advancing fulcrum make the supporting point of roadway transfer to depths and reduce the actual load of peripheral coal of gateway while also reduce the overburden payload of direct roof,thus reduce the load of top and side anchor which caused by the outer load.Test monitoring found it is necessary result that the variation trend of top anchor load is out of sync with mine pressure behavior of end roadway under pre-supporting effect and with the load increase of separating wall top anchor load will be decrease.With the front of the excavation face,the axial force of pre-support increases and the axial force near the goaf islager than the roadway,and more stress concentration of anchor column were caused in the process that separating wall replace anchor column become the bearing body with the improve of setting load of anchor column;Pre-support can provide support resistance for the first time after the seam excavation,not only effectively inhibit the initial deformation of the roadway, but also maintain and control the stability of roadway in the later stage with separating wall.