Influence Of Different Form Joints On Rock Characteristics And Its Engineering Application

As the construction of key projects in rocky areas increases, the study of rock properties has became a focus of research. In the long forming process of rock mass, complicated geologic process and tectonic forces would result in all kinds of discontinuity surface in rock mass Therefore, the properties’of rock mass are determined by both rock and structural surface. And in the construction of underground projects, the main reason of aggravating rock mass destruction is the fragile structural surface. Instability and destruction of the rock mass in the large number of projects are derived from the structural surface, ultimately causing the destruction of the geotechnical engineering. Thus, in order to understand the strength, deformation and movement of the rock mass, we should put emphasis on the structural surface of the rock mass and study the crack initiation, expansion and through process of these rock joints and fractures in the construction, which has a great significance for properties study, failure mechanism of rock mass and the stability analyzing of geotechnical engineering.In this paper, DDARF is adopted to study the characteristics of fractured rock mass which focuses on the failure process, the variation of stresses and the displacement of the key points of jointed rock mass under the stress by numerical simulation, theoretical analysis and experimental verification. The paper consists of the following contents:1) Study and trial for DDARF. Learning the principle of DDARF thoroughly, grasping the automatically generated method of joint network and the triangle block unit, and the analytical method of the block boundary cracking.2) Calculating the biaxial compression test of a group of en echelon fissures specimen with the method of DDARF. Obtaining the consistency of the results compared with the same physical experiment of predecessors and verifying the effectiveness of the new approach; calculating the extension status of cracks, the stress strain change, peak intensity and the law of crack stress under different coefficient of horizontal pressure, and drawing envelope diagram with this set of data, obtaining the values of c and φ, and analyzing the stability of surrounding rock.3) Simulating and analyzing the stability of surrounding rock mass with one group joint sets in cavern excavation with DDARF. Analyzing rupture process and the critical point displacement of the surrounding rock, the angles adopted here of the joint set were30°,45°and60°, and the comparative analysis of these3conditions led to the conclusion that the angle of the joint set, to some extent, played a leading role in the failure of rock mass; when the angle was45°, the contrastive analysis of three side pressure coefficients of geostatic stress (K) at1.5,1.2,0.5led to the conclusion that when K>1and K<1, its influences on the stability of the adjacent beds’vault and side wall were different.4) Simulating and analyzing the stability of surrounding rock mass with two groups joint sets in cavern excavation with DDARF. The angles of the joint sets were firstly changed, with three groups conditions of3O°nd-30°,45°nd-45°nd60°nd-60°. The stability of surrounding rock mass was the worst when the joint angle was60°nd-60°. Then the comparative analysis of three lateral stress coefficients with1.5,1.2and0.5were obtained, with the result that when the lateral stress coefficient was1.5the stability of surrounding rock mass was worst.