DETERMINATION OF DEFORMATION PROPERTIES FOR ANISOTROPIC ROCK MASSES BY IN-SITU TORSIONAL SHEAR TESTING

For determination of the in-situ deformation modulus of rock mass at Bakhtiari Dam site, located in south-west of Iran, plate jacking tests (PJT) and dilatometer tests (DLT) carried out during the geotechnical investigations. In this study, the results of PJTs and DLTs were compared. This comparison involves 89 vertical and horizontal PJTs and 83 DLTs carried out in 6 rock units of Sarvak formation. Although, both PJTs and DLTs in the Bakhtiari Dam site were performed in same geological and geotechnical conditions, but there are not sufficient side by side data to make a paired two samples correlation. Therefore, the mean of in-situ data was compared at each rock unit. Besides Mann–Whitney U tests were performed to compare in-situ test results. The comparison shows that the deformation modulus measured by both methods has no significant differences. However, in low quality rock masses the moduli measured by the use of DLTs were greater than the modulus measured by PJTs. Conversely, in high quality rock masses the results of PJTs were greater than DLT’s.

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Determination of Volumetric Joint Count Based on 3D Fracture Network and its Application in Engineering

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.580-583.907 ◽

2014 ◽

Vol 580-583 ◽

pp. 907-911

Author(s):

Jin Liang Wu ◽

Ji He

Keyword(s):

Indirect Method ◽

Fracture Network ◽

Rock Masses ◽

Fracture Spacing ◽

The Monte Carlo Method ◽

Discrete Fracture Networks ◽

Discrete Fracture ◽

Survey Line

Volumetric joint countis an important parameter to evaluate the development of fractures. It is a fundamental representative for the strength and permeability of rock masses. However, cannot be directly measured in field. In this study, an indirect method is applied for its estimation. The main procedures are as follows: firstly, the volumetric joint frequencyis assumed for th fracture set, and then a series of 3D stochastic discrete fracture networks (DFNs) are generated using the Monte Carlo method according to; secondly, a survey line is drawn perpendicular to the fracture set in the each fracture network generated, the fracture spacing is measured along the survey line, then the average fracture spacing and its variance coefficient are calculated from all the DFNs; thirdly, by repeating the above two steps for differentassumed, the relevant average fracture spacing and its variance coefficient are obtained, and two relation curves are built up between and the average fracture spacing (or its variance coefficient); fourth, the exactis estimated through this relation curve between and the average fracture spacing according to the exact fracture spacing measured in situ; finally,is calculated by summing the exactof all fracture sets up. In this study, this indirect method is applied in the rock masses of Xiaowan Hydropower Station. The result shows that the fracture spacing will reduce and its variation coefficient becomes stable asincreases.

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Numerical Modelling and Assessment of Excavation Damaged Zone around the Underground Excavations: A Case Study

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.324-325.77 ◽

2006 ◽

Vol 324-325 ◽

pp. 77-80 ◽

Cited By ~ 1

Author(s):

Deng Pan Qiao ◽

Zong Sheng Zhang ◽

Shu Hong Wang ◽

Ya Bin Zhang

Keyword(s):

Rock Mass ◽

Stress Field ◽

Numerical Modelling ◽

Underground Mining ◽

Rock Masses ◽

Stress Concentrations ◽

Anisotropic Rock ◽

Excavation Damaged Zone ◽

Damaged Zone

This paper presents a study on the quantification of the degree of damage from the microseismic event data, for assessment of excavation damaged zone of anisotropic rock in Jinchuan mine and presents numerical simulation and prediction on the deformation and failure of the rock masses surrounding laneway under rock mass properties and excavating conditions. Following an introduction to the engineering geology and mechanical properties of the rock mass in the Jinchuan mine areas, this paper reveals the features of the measured in situ stresses and puts emphasis on an analysis of the mechanism of underground opening and damage induced by the underground mining. Stress and AE redistribution induced by excavation of underground engineering results in the unloading zone in parts of surrounding rock masses. A micromechanics-based model has been proposed for brittle rock material undergoing irreversible changes of their microscopic structures due to microcrack growth. A systematical numerical modeling analysis method was completed. Based on numerical modelling, a series of predicting curves for rock mass response and deformation are obtained, which provides the basis of guiding the design and construction of anisotropic rock cave in Jinchuan mine. The use of the in situ stress field results in enhanced modeling of the stress concentrations and potential failures at the mines has also been reviewed. Knowledge of the prevailing rock stress field at the mines is a critical component for such modeling which has led to improved rock mechanics understanding and operations at Jinchuan mines.

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