Analysis And Application On The Principle Of "Balance Force System" In Bolt Support

In order to solve the problem that the lack of a unified explanation to bolting support theory which has widely recognized,the principle of balance force system in bolt support was put forward,and theoretical analysis and industrial test research was carried out.The compressive stress on the surface of roadway which produced by bolt plate and the anchorage force in the anchored section was regarded as a pair of balanced forces in this paper.The bolt in the tunnel support was substituted by a group of equilibrant,so stress law of anchor bolt,in addition to the mechanical analysis of roadway surrounding rock anchored,was studied by the perspective of balanced force.On the basis of the Mohr-Coulomb criterion,the equivalent stress formula in the elastic region of the finite thickness cylinder under the equivalent confining pressure was derived.With the two different situations that the anchored zone in surrounding rock was located in the plastic zone or elastic zone,theoretical formula of the radial resistance which emerged in the anchorage zone rock against the periphery rock mass was calculated separately.In the different development range of surrounding rock loose circle,the action mechanism of bolt in rock mass which effected in the range of balance force system was studied.According to the design background of Xutuan coal mine 83return air blind incline shaft,and combined with the geological mechanics environment test and the laboratory experiments of designedlaneway section,the depth of plastic zone,the equivalent stress of the Mohr's Kulun criterion and the radial resistance in the anchorage zone to the external surrounding rock mass was computed.Finally,in the light of the roadway reinforcement bolt support scheme which was implemented on the spot,the comparative analysis was carried out by the monitoring results of the tunnel surface displacement on the design section,The deformation control of the anchor to rock mass in the anchorage zone was researched.The results shown that no matter where the anchored section of bolt locate,the radial resistance of rock mass to the periphery rock mass could always improved.but the equivalent stress in the elastic range of anchorage zone could reduced by the bolt in the "small loose circle".Therefore,combined arch action of bolt was appeared in "big loose circle".However,the anchor in "small loose circle" has the function of combined arch and "overhang".Monitoring datas analysis shown that the deformation velocity of surrounding rock was controled effectively by the bolt in the tunnel support.In short,several innovative theoratical reference and site construction experience to the similar tunnel was provided in this paper.