| Bolt anchoring can effectively improve the stability of jointed rock masses,whic h is a common reinforcement method of engineering rock mass.It is of great significa nce to study the bolted rock joints and then use them to guide the reinforcement of en gineering rock masses.At present,there have been a lot of researches on bolted rock j oints,but they mainly focus on the situation of the same lithology on both sides of the rock joints.There are few mentions of the research on the bolted heterogeneous rock j oints with different lithologies on both sides of the rock joints.In fact,the bolted heter ogeneous rock joints exists widely in nature.When the bolts are used to reinforce the bolted heterogeneous rock joints,they will pass through different rock formations.Du e to the asymmetry of the rock strength on both sides of the rock joints,the shear insta bility mechanism will be changed.Therefore,it is of important scientific significance and engineering value to carry out research on the shear failure law of bolted heteroge neous rock joints.In view of this,combined with theoretical analysis,numerical simul ation and laboratory tests,the shear test of the bolted heterogeneous rock joints was ca rried out.The main research contents and conclusions are as follows:(1)Sensitivity analysis of factors influencing the shear strength of bolted heterogeneous rock joints.Three influencing factors of normal stress,structural surface roughness and anchoring angle are selected,and orthogonal tests are carried out under different strength ratios of upper and lower wall rocks λ,and the sensitivity of each factor to shear strength is analyzed.The results of the study show that for bolted heterogeneous rock joints,the anchoring angle is the most sensitive to shear strength,the roughness of the rock joints is second,and the normal stress is the smallest.(2)Research on shear failure characteristics of bolted heterogeneous rock joints.Based on laboratory tests and numerical simulations,the changes in shear strength and the number of cracks with λ under the three anchoring angles are analyzed,that is,for the bolted heterogeneous rock joints,when the anchor strength is greater than the strength of the upper and lower wall rocks,and the strength of the bottom wall rocks When fixed,with the increase of λ,the shear strength first increases non-linearly and then tends to be gentle,and the number of cracks first decreases non-linearly and then tends to be gentle;in the two cases of λ≤1 and λ>1,the three anchoring angles resist the curve of the average shear strength and the number of cracks with λ presents a bilinear form,and the change rate of the curve in the first stage is greater than that in the second stage;for bolted heterogeneous rock joints,when the anchor strength is greater than the upper and lower wall rock,the failure mode of the sample shows that the side with the lower wall rock strength has a greater degree of failure.(3)Research on the precursory information of shear failure of bolted heterogeneous rock joints.Combined with laboratory tests and numerical simulations,the energy,ringing count,source distribution and number of cracks in the shearing process are analyzed.The results show that the evolution process curve of acoustic emission energy,ringing count and number of cracks will go through three stages.In the second stage,the number of cracks increases drastically,which can be used as precursor information for sample failure,and corresponding early warning measures can be taken. |
