Study On The Supporting Effect Of Prestressing Anchor Rod In The Roadway Of Coal Mine

Anchor rod supporting is one of the most common supporting methods. Prestressedanchor can make roof form composite within the prescribed key layer, prevent theabscission layer of roof in anchorage zone, and have the effect to stabilize surroundingrock at the top of the roadway. The prestress of which can influence the effect of thesupporting largely. When the rod prestress is too high, it could make anchor rod’s failurewith uprooting from anchorage of rock, and while the rod prestress is too low, it couldn’tcontrol delamination phenomenon of stratum in the anchoring zone effectively. Therefore,it has great theoretical and practical significance to study the reasonable prestress of rodsupporting and its supporting effect in roadway.Firstly, this paper introduces several kinds of common supporting theory respectively,and studies the deformation mechanism of surrounding rock, the effect of prestress anchorrod supporting mechanism and its strengthening mechanism to surrounding rock, it isconcluded that the applying of prestress is helpful to improve the weak carrying capacityand the concentrated stress field in the shallow surrounding rock after excavation ofroadway, and it also has a better improvement effect for the bearing capacity ofsurrounding rock in deep surrounding rock. Then with the increase of prestress, the moreapparently of the improvement effect, which can reflect the decrease of the two-sidehorizontal displacement and vertical displacement of roof in the roadway.Secondly, analyze the mechanical characteristics and influence factors of prestressanchor rod, it is considered that the numerical value of the rod prestress is related to theconditions of mining geology, the conditions of roof separation, the key stratum’s loading.It needs to apply high prestress if the bearing capacity of surrounding rock is lower, theloading of strata is higher and the roof separation is easy to occur. Whereas a low prestress.The rod’s length, diameter, arrangement, spacing and the way of anchoring can also affectthe value of prestress and then influence the supporting effect. Then deduce the formulas for the experience of minimum anchor rod’s prestress onunit area in theory. And different types of surrounding rock of roadway supporting modelsare established using numerical simulation software of ANSYS, supporting effect ofapplying different prestress in different case are analyzed, thus that the reasonable prestressrange of anchor rod supporting is concluded.Finally, the worksite application results show that the rod support parameters isreasonable; the derived formula can be used to determine the reasonable bolting prestressof I~IV class surrounding rock. When the anchor rods in I and II surrounding rock areapplied with the prestress between the given value, the supporting effect is goodWhile the anchor rods in the III and IV surrounding rock are applied with prestressbetween the given, the supporting effect meet the requirements, and roof don’t haveabscission layer and displacement, roadway surrounding rock deformation obtains goodcontrol, the stability is very high, and the cost is reasonable. So the conclusion which isobtained by simulation has real reliable guidance significance in the mine bracingengineering or other similar geological conditions mining area.