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Enhancing Block Rock Failure Understanding Through Geosma-3D Numerical Analysis
Wang, S.H. (Northeastern University) | Guo, M.D. (Northeastern University) | Yang, Y. (Northeastern University) | Wang, Y. (Northeastern University) | Zhang, Y.B. (Northeastern University) | Che, D.F. (Northeastern University)
ABSTRACT Numerical analysis provides a useful tool to enhance the understanding of block rock masses. The stability of rock blocks of tunnel or underground opening are commonly analyzed based on rigid body limit equilibrium theory only by considering gravity, while the secondary stress field after excavation of the block is usually not taken into account. Existence of structural planes affects dynamical properties greatly in rock tunnel structures. Especially in hard rock tunnel engineering, the stability of rock is controlled in a sense by the number of blocks, i.e. the size, orientation and locations of the discontinuities. Key-block failures occur where blocks of rock which are separated form the rest of the rock mass by discontinuities slide of fall into an excavation. According to the geometric stochastic block theory and reliability analysis, a new program GeoSMA-3D (Geotechnical Structure and Model Analysis-3D) for simulating tunnel structural planes in rock mass is put forward to develop based on geometric stochastic block theory and modern computer technique. The new model assumed that rock mass consists of blocks, thus formulating a combination of block model. This program adopts vector analysis, which can simulate all excavation planes especially in the tunnel and other underground structure. It can also create three-dimensional structural model and analyze mobility of key-block in the simulation plane by means of geometry and kinematics theory. The distribution of all key blocks and the quantitative data are analyzed by means of the newly developed program. The results show that parts of the blocks' crown zone are under compressive stress, which gradually increases as the underground opening in Shimian Tunnel, Liaoning, China. It can be concluded that the new program is an effective tool for modeling blocky rock masses. 1 INTRODUCTION In all civil or mining engineering projects, there is an in situ state of blocks in the ground before any excavation or construction is started. It is very important in the development of a numerical model for rock engineering analysis to reproduce this in situ state as closely as possible. The design is so far mostly empirical. It assumes that the block is rigid and is located in an otherwise fixed body of rock and bounded by a combination of flat discontinuities and excavation surfaces. In practice these conditions are most likely to be approximated when extensive discontinuities occur in hard rock. In common with most other solutions for three-dimensional blocks, possible block movements are assumed to be limited to translation only, and rotation is excluded. Existence of structural planes affects dynamical properties greatly in rock tunnel structures. It assumes that the block is rigid and is located in an otherwise fixed body of rock and bounded by a combination of flat discontinuities and excavation surfaces. In practice these conditions are most likely to be approximated when extensive discontinuities occur in hard rock. In common with most other solutions for three-dimensional blocks, possible block movements are assumed to be limited to translation only, and rotation is excluded.
- Overview > Innovation (0.34)
- Research Report > New Finding (0.34)
ABSTRACT The paper deals with geotechnical study and slope stability analyses of the final slope at Lanjiberna Limestone open cast mine. The Lanjiberna open cast mine is mainly characterized top soil, dolomite, dolomitic limestone and limestone. The bulk density and direct shear tests were conducted at Rock Mechanics Laboratory of CIMFR on the samples collected from the field. The geotechnical mapping was done on the exposed benches of the quarry as per the norms of International Society of Rock Mechanics (ISRM 1978). The kinematic analysis was done to determine the critical orientation of structural discontinuities. After identifying kinematically possible failure modes, detailed slope stability analysis was carried out by GALENA software based on limit equilibrium method. The present study reveals that the 96m high final slope could be designed with 58 degree overall slope angle. The sensitivity analysis shows that the influence of water is also alarming. It was recommended that the slope should be kept in drained geomining condition by providing suitable drainage and keeping drainage effectively maintained 1 INTRODUCTION The Lanjiberna Limestone open cast mine is located in the Orissa state of India. There are three nos. of quarries in this mine namely Q-1_3,Q-4_5 and Q-2_6 respectively. The study was conducted at quarry no. 2–6. Presently quarry no. 2 and 6 are named as two different quarries. The mine management is going to join and merge these two quarries and proposed to work as a single pit by removing the ramp centrally located and by shifting the road towards north. The purpose of study was to suggest optimum slope design of quarry2–6. Presently the pit is being mined with 45 degree overall slope angle. The present Limestone production is 1.70 million tonne from the captive mines, which had been planned to increase to 4.20 million tones per annum. With the proposed enhanced production of mines from 1.70 million tones to 4.20 million tones per year, the total deposit will last for more than 27 years. The rock discontinuities were mapped at the exposed benches of the pit as per the norms of International Society of Rock Mechanics (ISRM 1978). Geotechnical mapping was undertaken to determine the critical orientation of structural discontinuities. After identifying kinematically possible failure modes, detailed slope stability analysis is carried out by limit equilibrium method. Sensitivity analysis was done to determine the most effective remedial measure for any critical slope. 2 GEOLOGY The slopes of the quarry are mainly characterized by topsoil, dolomite, dolomitic limestone and limestone, which are well jointed. Geologically, Langiberna limestone area belongs to Birmitrapur stage of the gangpur series of Indian Dharwars. In Lanjiberna, there are two, almost parallel, bands of limestone running East West separated by a band of dolomitic limestone of about 200 to 300m width. 3 GEOHYDROLOGY The climate of the area is sub-tropical. The average annual is around 1200 mm. The area of the quarry area does not have top-aquifer, as the weathered mantle is not developed below soil profile.