DDARF Analysis On Failure And Anchoring Mechanism Of Jointed Rock

Rochmass within easy access is the basis of real projects. It has a crucial property of being incised by faults and joints. The original forming process of earth crust was companied with internal stress, which gradually complicated while the earth crust evolves with geological conformation movements, leading to the generation of large amounts of faults, joints and fissures. These structural planes, to some extent, reduce the rockmass strength. As a result, rockmass quality is closely related to the distribution, physical and mechanical properties of structural planes. Specifically speaking, its occurrence, roughness, cutting density, malleability, fluctuation, cohesion and filling properties all should be taken into account when judging the strength grade and stability of project rockmass. The study on the crack initiation, propagation and cut-through of structural planes and its internal regularities contributes much to the rockmass characteristic research, the revelation of rockmass failure mechanism and the security insurance of real projects.In this paper, DDARF method is adopted to study the characteristics of fractured rockmass. It focuses on the failure process, the variation of stresses and the displacement of the key points of jointed rockmass under the stress by numerical simulation, theoretical analysis and experimental verification. The paper consists of the following contents:1) After understanding the basic theories of DDARF method, its full structure especially the model creation and calculation part are thoroughly familiarized with. Simple examples are excised as a start, while in this process experience is summarized and accumulated. Then the software of autocad, screen capture and Excel are adopted to facilitate the modeling, the calculation appearance recording and data processing respectively. These assistances largely improve the simulation efficiency, making it possible for the complex model calculation.2) With DDARF method, model tests conducted by Lei Zhang and Nuandong Wen are simulated. Through a comparison of bolts in different locations and their different anchoring effects, the best bolt arrangement was obtained. The simulation result coincides well with the model tests conducted by former researchers. The shearing test conducted by Weishen Zhu is also simulated. Furthermore, in this simulation other than the original test, tests on models with echelon joints under different axial loadings were also simulated. The strength parameters were obtained through fitting the simulation data. The crack propagation process, cut-through status and the ultimate failure are studied, after which the shearing strengths of models in different operating conditions are compared.3) Adopting DDARF method, the excavation of two slopes with multiple arrays of random joints and two arrays of joints respectively were simulated. Its joint propagation process was observed and displacements of key points monitored. The stability security coefficient was obtained via conducting overload test and relevant analysis of key displacements. Besides, the overload test was also conducted on an ideal slope with the same exterior but zero joints, the stability security coefficient obtained as a result. A thorough comparison of these three slopes underlines the weakening of joints on slope stability.