Stuady On The Law Of Anchor Invalidation And Stress Variable Under Different Lateral Pressure Coefficients

Along with the upper part coal resources dried up, underground mining depth increasing, followed by complex geologic environment such as the high crustal stress, high karst water pressure, the high earth temperature and mining disturbance, which has taken much challenge to existing anchoring technique.Therefore, to study the breakage law of the anchorage which is suffering from complex stress condition located at surrounding rock in deep mining has much significance in increasing the strength of support system.Based on the study of the deep rock mass deformation characters and engineering mechanics characteristics, the deformation characteristics of surrounding rock has been obtained. To master the change rules of geostress, the characteristics of deep rock mass have been analyzed. And on this foundation have summarized the anchor net failure mode, familiar with the anchorage failure mode and influencing factors.According to the study and discussion, adopting the method of indoor experiment and theoretical analysis, the deep anchor invalidation and stress variable rule of the deep complicated stress condition has been studied.The following conclusion has been got.(1) The anchor damage is mainly dominated by interfacial debond of anchor-anchoring layer interface in surrounding rock anchorage failure form.,and anchor damage often occurs mainly in the anchor and anchor joint surface and the inside.(2) There are some different changing trends between combined anchorage and integralanchorage in anchor load curve after the peak period. Specific performance of their difference:Composite anchor after peak load has fallen sharply and then tends to a stable value of the smaller while integral anchoring would keep the maximum load and a small fluctuation after reaching the maximum.lt has shown that this kind of difference depends on whether rock on interface constrain has been released.According to the mechanics analysis of the interface debonding, prove the relationship of the changes on the anchoring force and surrounding rock stress has been proved, the mechanics mechanism of its effects on the anchoring force are obtained on the foundation.(3) When the surrounding rock stress are in a state of uniformity and stability, if the anchorings layer elastic deformation occurs, the radial stress interface friction force produced by lateral load can help to increase anchorage force. While if the stress is in a state of instability, the phenomenon of stress concentration will occur, it is easier to generate local failure caused by anchor solid, which will affect the ultimately anchoring effect.It is shown that it is help to avoid the anchor solid failure by reasonablely selecting anchorage form according to the stress condition of surrounding rock and support requirements.(4) The changing process of anchorage interface can be divided into elasticity, plasticity and debonding deformation stages according to the interface mechanics analysis. And a conclusion has been made that it is the plastic deformation of the anchoring force that can provide the anchorage force effectively according on the study of mechanical performance of all anchorage interface.(5) The equilibrium equations have been established by anchorage infinitesimal element. The coulommb yield conditions and non-associated flow rule has been applied to calculate the anchoring interface shear stress and axial force distribution model.