Approach to Numerically Model Edz in Vcr Mining

APPROACH TO DEVELOP A NUMERICAL MODEL OF EXPLOSIVE DAMAGE ZONE IN VCR MINING

SUBMITTED BY

DIVYANSH KHARE

2013JE0416

6th SEMESTER Dept. of Mining Engineering (2015-2016)

PROJECT GUIDE

DR. V.M.S.R. MURTHY

PROFESSOR

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DEPARTMENT OF MINING ENGINEERING

INDIAN SCHOOL OF MINES, DHANBAD

April 4, 2016

DEPARTMENT OF MINING ENGINEERING[pic 2]

INDIAN SCHOOL OF MINES

DHANBAD – 826004 (JHARKHAND),INDIA

Date: April 4, 2016[pic 3]

Certificate

This is to certify that the project entitled “APPROACH TO DEVELOP A NUMERICAL MODEL OF EXPLOSIVE DAMAGE ZONE IN VCR MINING” of Mr. Divyansh Khare and Mr. Ketan Mishra  is a bonafide work carried out by him under my supervision and guidance. The results embedded in this work have neither been published before nor submitted to any other institution for the award of the degree or diploma to the best of my knowledge and belief.

(V.M.S.R. Murthy)

Professor and Supervisor

ACKNOWLEDGEMENT

“Gratitude is the expression of the heart.” Therefore I would like to take this opportunity to extend my sincere gratitude to my project mentor Dr. V.M.S.R Murthy for his valuable guidance, co-operation and supervision throughout the course of this project. His efforts in making me understand and apply the knowledge that he bestowed upon me through many interaction have been instrumental and crucial in the completion of this project.

I am also grateful to the Head, Department of Mining Engineering, Prof. Phalguni Sen, for approving the subject and providing all necessary facilities. I express my gratitude to the entire teaching faculty in department for giving suggestions whenever approached.

I am also thankful to project co-ordinator G. Budi for his suggestions and helping me in my project work.

I am especially thankful to library staff for extending their help in my project work.

Dated: 04/04/2016                                                                (Divyansh Khare)

                                                                                2013JE0416

CONTENTS

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CHAPTER 1        

INTRODUCTION

1.1 BACKGROUND

The mechanism of dynamic failure of rock mass is very complicated since discontinuities such as cleavage cracks and defects with different shapes and orientations are commonly encountered in rock mass and they have significant influence on the deformation and failure characteristics of rock.It is impractical to consider the effects of rock cracks and defects individually in studying underground seismic wave propagation. Therefore, a reliable equivalent continuum model for rock mass under dynamic loading, which takes into account the rock constitutive relation, strength and failure characteristics, as well as strain rate effect, will be extremely useful. It is clear that the commonly used elasto-plastic and perfectly brittle models are simplifications of the actual behavior of a material.

Damage models do not take into consideration the pressure sensitive strength criterion. A pressure sensitive strength criteria i.e. Mohr-Coulomb criterion has been suggested and used to model the plastic flow of brittle materials such as rock, concrete and soil. But this model does not consider the elastic degradation and the rate-dependent properties of rock mass. Although rock always exhibits anisotropy after macro cracks occur, isotropic damage model is proved as an effective method to estimate the gross damage of rock mass subjected to blast. Among the continuum damage models, the damage scalar is defined as functions of the damaged Poisson's ratio, or extensional strain, or volumetric tensile strain[1] In volumetric compressive state, with the exception of very highly confined triaxial states of compressive loading, the response of brittle materials is highly influenced by the magnitude of the maximum principal tensile strain. This implies damage (the material stiffness degrading or softening) to rock mass may occur either by tensile or compressive stress although it is in volumetric compressive state at the near field of detonation. The effective Young's modulus decreases with increasing initial damage parameter value, and an apparent work-softening process occurs before failure. The decrease of P-wave velocity and effective Young's modulus is also observed. Thus, properly considering rock damage characteristics in numerical simulation of wave propagation is very important since the dissipation of energy by damage and plastic flow will cause rapid attenuation of shock wave.