scholarly journals Previous classification of rock mass surrounding underground excavations and rock support design using block models

2021 ◽  
Vol 74 (4) ◽  
pp. 511-519
Author(s):  
Iure Borges de Moura Aquino ◽  
Rodolfo Renó ◽  
Roberto Mentzingen Rolo ◽  
André Cezar Zingano ◽  
Hernani Mota de Lima
2006 ◽  
Vol 34 ◽  
pp. 29-38
Author(s):  
Subas Chandra Sunuwar

The principal objective of rock support is to assist the rock mass to support itself. One common example is where the rock support system (e.g. rock bolts and shotcrete) actually becomes integrated with the rock mass. Rock support strengthens the rock mass surrounding an excavation by creating a reinforced zone, which maintains the integrity of the excavated surface, possesses sufficient flexibility to allow for the redistribution of stresses around the excavation, and has enough stiffness to minimise the dilation (opening) of discontinuities. Rock mass classification systems are used worldwide as a basis for tunnel support design. The Q and Rock Mass Rating systems have been extensively applied in rock support design on most of the hydropower projects in Nepal. Generic design guidelines based on rock mass classification systems cannot provide suitable rock support for every site. Therefore some modifications are necessary to suite the site-specific ground conditions including local rock mass and geological hazards. There are relatively few tunnels excavated in the tectonically active Nepal Himalaya. Large diameter tunnels in Nepal are commonly lined with concrete whereas recently smaller-diameter tunnels are either shotcrete-lined or left unsupported. "Leaky" lining has been used in most of the projects to avoid the heavy reinforcement needed to withstand the occasional very high external water pressures.


Author(s):  
Shyam Sundar Khadka ◽  
Ramesh Kumar Maskey

 This study focuses on the design and stability analysis of underground structures in the Lesser Himalayan Region of Nepal. The rock support design for such opening depends upon the rock mass strength. In this study a proposed Kathmandu University Geo-Lab tunnel and cavern, which passes through weak rock mass conditions, was used as a case study. Existing empirical and analytical methods for the stability of the proposed tunnel and cavern are used for the estimation of support pressure and design support. A detailed numerical study was carried out in 2D finite element analysis to design the tunnel in such region. The results of analysis showed that the support pressure and deformation can be predicted very well from the numerical analysis.Kathmandu University Journal of Science, Engineering and TechnologyVol. 13, No. 1, 2017, page: 1-19


2014 ◽  
Vol 51 (5) ◽  
pp. 520-539 ◽  
Author(s):  
Shili Qiu ◽  
Xiating Feng ◽  
Chuanqing Zhang ◽  
Tianbing Xiang

For rock support in burst-prone ground, the wall-rock velocity adjacent to the surface of underground openings is a vital support design parameter, and depends on the seismic source mechanism inducing rockburst damage. In this study, to estimate the wall-rock velocity evoked only by rock slab buckling (an important rockburst source mechanism), a comprehensive velocity assessment method is proposed, using an excellent slab column buckling model with a small eccentricity, which relies on a novel compressive or tensile buckling failure criterion of rock slab. The true-triaxial loading–unloading tests and rockburst case analyses reveal that rock mass slabbing induced by high rock stress has major impacts on the evolution and formation of buckling rockburst in deep tunnels. Using a method based on the energy balance principle, the slabbing thickness of intact rock mass is also calculated by an analytical method, which indicates that the slabbing thickness parameter has a nonlinear relation to the following six parameters: uniaxial tensile strength (UTS), uniaxial compressive strength (UCS), normal stress (σn), length of joint (L), friction angle ([Formula: see text]), and joint roughness coefficient (JRC). These proposed models and methods have been quite successfully applied to rockburst and slabbing cases occurring in deep tunnels. These applications show that slab flexure is an important source mechanism invoking high wall-rock velocities and leading to severe rockburst damages in the area surrounding deep tunnels.


1979 ◽  
Vol 27 (2) ◽  
pp. 409-442 ◽  
Author(s):  
B. SJOGREN ◽  
A. OFSTHUS ◽  
J. SANDBERG
Keyword(s):  

2014 ◽  
Vol 72 (1) ◽  
Author(s):  
Seyed Vahid Alavi Nezhad Khalil Abad ◽  
Edy Tonnizam Mohamad ◽  
Ibrahim Komoo ◽  
Roohollah Kalatehjari

This paper presents an assessment of weathering effect to the rock mass structure by studying the joint characteristics of tropically weathered granite. Joint survey was performed by scanline method and the results were analyzed statistically by stereographic projection plots. The overall trend of mean joint spacing followed a sharp decrement from fresh to moderately weathered zone and then a slight increment to highly and completely weathered zones, whereas the overall trend of mean joint trace length showed a gradual decrement over progress of weathering. In addition, the degree of joints inclination and weathering zones revealed an increasing trend in the percentage of horizontal joints from fresh to completely weathered rocks, while no specific relation was found between the numbers of major joint set and different weathering zones. The results of this study may contribute to understanding the behavior and better classification of weathered granitic rock mass as a heterogeneous mass in engineering works.


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