Abstract
The empirical and numerical design approaches are considered very important in the viable and efficient design of support systems, stability analysis for tunnel, and underground excavations. In the present research work, the rock mass rating (RMR) and tunneling quality index (Q-system) were used as empirical methods for characterization of rock mass based on real-time geological and site geotechnical data and physical and strength properties of rock samples collected from the alignment of tunnel. The rock mass along the tunnel axis was classified into three geotechnical units (GU-1, GU-2, and GU-3). The support systems for each geotechnical unit were designed. The 2D elastoplastic finite-element method (FEM) was used for the analysis of rock mass behavior, in situ and redistribution stresses, plastic thickness around the tunnel, and performance of the design supports for the selection of optimum support system among RMR and Q supports for each geotechnical unit of tunnel. Based on results, Q support systems were found more effective for GU-1 and GU-2 as compared to RMR support systems and RMR support systems for GU-3 as compared to Q support systems.
Highlights
Modeling of rock mass is a very difficult job due to the presence of discontinuities, anisotropic, heterogeneous, and nonelastic nature of rock mass, using empirical and numerical methods [1, 2]. e complex nature and different formation make the rock masses a difficult material for empirical and numerical modeling.During initial stages of excavation projects, the detailed data are not available about strength properties, deformation modulus, in situ stresses, and hydrological of rock masses [3]
finite-element method (FEM)-based software Phase2 was used for the analysis of the design support system for the tunnel. e input parameters like physical and mechanical properties of rock mass, stresses, deformation modulus of rock mass, and support systems recommended by rock mass rating (RMR) and Q-system as given in Table 2 were used in Phase2 software
The empirical and numerical methods were used to evaluate rock mass quality and estimate the support element required for headrace tunnel and stability analysis of tunnel before and after support system installation for selection of optimum support systems. e stability analysis of models developed for each geotechnical unit in Phase2, was carried out after installment of Q and RMR support systems
Summary
Modeling of rock mass is a very difficult job due to the presence of discontinuities, anisotropic, heterogeneous, and nonelastic nature of rock mass, using empirical and numerical methods [1, 2]. e complex nature and different formation make the rock masses a difficult material for empirical and numerical modeling.During initial stages of excavation projects, the detailed data are not available about strength properties, deformation modulus, in situ stresses, and hydrological of rock masses [3]. E complex nature and different formation make the rock masses a difficult material for empirical and numerical modeling. To handle the nonavailability of the detailed project data, the empirical methods like rock mass classification systems are considered to be used for solving engineering problems [4]. E empirical methods used defined input parameters in designing of any underground structures, recommendation of support systems, and determination of input parameters for numerical modeling [5]. The empirical methods do not evaluate the performance of support systems, stress redistribution, and deformation around the tunnel [6]. Erefore, it is very important to consider these parameters in designing of optimum underground structure and support systems. Numerical modeling is gaining more attention in the field of civil and rock engineering for prediction of rock mass response to various excavation activities [7]. e numerical methods are convenient, less costly, and less timeconsuming for the analysis of redistribution stresses and their effects on the behavior of rock mass and designing of Advances in Civil Engineering Borehole GGW-1
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