| With the rapid development of China's economy, the demand of mineral resources is increasing. The open-pit mine is bound to be transferred to the development trend of underground mining, and more roadways will be excavated and used. Underground tunnel construction should not only ensure the exploitation of mineral resources in the normal work, but also ensure the safety of construction and protection of mineral resources reasonable use.How to reduce the damage of surrounding rock caused by blasting excavation,to control the damage range of surrounding rock in the production and design requirements, has become an important issue in the current and future period of time. Therefore, it is very important to carry out the research on joint damage of surrounding rock under blasting load.In order to study the damage of joint tunnel under dynamic load.This paper is based on the geological data of a mine as a prototype. On the basis of theoretical analysis, the experiment and numerical simulation of blasting load on the surrounding rock damage of jointed roadway are carried out with the experimental study of the application model, field test analysis and numerical simulation. The main conclusions of this paper are as follows:(1) Two experimental models of complete rock mass and jointed rockmass were separately cast. Experimental study on cyclic excavation of jointed rock mass is carried out. The first stage was artificial excavation, in the second stage, blasting excavation was done with the 50 g blasting charge, and in the third, stage blasting excavation was done with the 50 g blasting charge. The paper analyzed the blasting damage range and damage degree of similar model roadway surrounding rock, and the relationship between the blasting damage and the anchorage range of the anchor bolt. The effect of blasting load on the surrounding rock of roadway is directional, and the crack generated by blasting is mainly based on the radial crack. After excavation, the jointed roadway did not collapse, and the bolt played a very good supporting role.(2)The finite difference program FLAC3 D was used to simulate the propagation of detonation waves in the joint and the whole roadway.Detonation waves have a certain degree of attenuation in the process of propagation. The existence of the joint increases the amplitude of the detonation wave. Compared with the intact rock mass, the detonation waves decay more quickly in the jointed rock mass.(3)Based on the finite difference program FLAC3 D, the damage range of the joint plus anchor and complete anchor roadway in the process of cyclic excavation was simulated under the action of blasting load. In intact rock mass, the maximum damage ranges of the tunnel vault, caused by cyclic excavation are respectively 30 cm, and in jointed rock mass, that are respectively 40 cm.(4)After the tunnel excavation, the maximum displacement of the roof,the two side and the bottom plate of the roadway and the joint roadway are basically the same, and the maximum displacement is gradually increased to a certain value.After the circular excavation, the maximum deformations of the tunnel vault, two sides and bottom plate in intact rock mass are 9.2 mm, and that in the jointed rock mass are 17.35 mm.Displacement of the jointed rock mass is 1.87 times than that of the intact rock mass. The numerical simulation results of blasting damage of surrounding rock in jointed roadway and complete roadway were compared. It is found that the damage area of the roof in the jointed roadway is obviously more than that of the bolt, and the results are basically in agreement with the experimental results. It is recommended to increase the length of the bolt in the jointed roadway to expand the scope of support to ensure the stability of the roadway. |
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