ESTIMATING SOME MECHANICAL PROPERTIES OF ROCK FROM IN-SITU REBOUND VALUES (A CASE STUDY OF OREKE OPEN PIT QUARRY)

ABSTRACT

The research deals with estimating some mechanical properties of rock from in-situ rebound value in Oreke open pit quarry ,N-Type  Schmidt rebound hammer data were collected from Oreke open pit .the data were collected with the view to ascertain the suitability of Schmidt hammer for quick ,cheap and less cumber some estimation of the uniaxial compressive strength of marble .The data collection was strictly carried out by ASTM and suggested equation by different authors.Uniaxial compressive strength,density, young modulus were determined using value conversion graph.uniaxial compressive strength for location 1 was 70MPa which mean the rock is medium in classification and location 2 and 3 was 55MPa this implies that is medium in term of strength , type is competent metamorphic  rock.

TABLE OF CONTENTS

TITLE PAGE                                                                                                                 i

CERTIFICATION   ii

DEDICATION   iii

ACKNOWLEDGEMENT  iv

TABLE OF CONTENTS  vi

LIST OF TABLES  viii

LIST OF FIGURES  ix

CHAPTER ONE   1

1.0           INTRODUCTION   1

1.1           AIM AND OBJECTIVES. 2

1.2           STATEMENT OF THE PROBLEM    2

1.3           SCOPE OF THE PROJECT  3

1.4           JUSTIFICATION OF THE PROJECT  3

1.5           LOCATION OF THE STUDY AREA   3

CHAPTER TWO   4

2.0           LITERATURE REVIEW    4

2.1           CONCEPT OF SCHMIDT REBOUND HAMMER   4

2.2           GEOLOGICAL FORMATION OF MARBLE   8

2.3           MECHANICAL PROPERTIES OF MARBLE   11

CHAPTER THREE   14

3.0           RESEARCH METHODOLOGY (DESK WORK) 14

3.1           DETERMINATION OF BULK DENSITY   14

3.2           PROCEDURE FOR COLLECTING REBOUND HAMMER VALUE   15

3.3           CONVERTED FROM N – L TYPE DATA   16

3.4           ESTIMATING UNIAXIAL COMPRESSIVE STRENGTH OF MARBLE (UCS) 16

3.5           ESTIMATING OF DENSITY   18

3.6           ESTIMATING OF YOUNG’S MODULUS  19

CHAPTER FOUR   21

4.0           RESULT AND DISCUSSION   21

4.1           RESULTS  21

4.1.1       DETERMINATION OF BULK DENSITY   21

4.1.2       PROCESSING PROCEDURE   24

4.1.3       CONVERTED FROM N-TYPE TO L-TYPE DATA   25

4.1.4       ESTIMATION UNIAXIAL COMPRESSIVE STRENGTH   26

4.1.5       ESTIMATED DENSITY   28

4.2           ESTIMATED YOUNGʹS MODULUS  29

4.3           DISCUSSION   31

CHAPTER FIVE   32

5.0           CONCLUSION AND RECOMMENDATION   32

5.1         CONCLUSION   32

5.2         RECOMMENDATION   32

              REFERENCES  33

LIST OF TABLES

TABLES                                       TITLE                                                           PAGE

 4.1:             Determination of Bulk Density for Location 1; 22

4.2:              Density Test Result for Location 2  22

 4.3:             Density Test Result for Location 3  23

 4.4:             Field Rebound Values  24

 4.5:             Standard Procedure of Bulk Density Determination  30

 4.6:             Standard for Uniaxial Compressive Strength (UCS) 31

LIST OF FIGURES

FIGURES                                     TITLE                                                       PAGES

1:                           Details of an L type Schmidt hammer 7

2:                           Conversion Graph  27

CHAPTER ONE

1.0       INTRODUCTION

Rock mechanics engineers design structures built in rock for various purposes, and therefore need to determine the properties and behavior of the rock. The UCS of rocks is one of the important input parameters used in rock engineering projects such as design of underground spaces, rock blasting, drilling, slope stability analysis, excavations and many other civil and mining operations. ISRM (1981) testing of this mechanical property in the laboratory is a simple procedure in theory but in practice, it is among the most expensive and time-consuming tests. This calls for transportation of the rock to the laboratory, sample preparation and testing based on the international standards. In order to carry out these standard tests, special samples, such as cylindrical core or cubical samples, need to be prepared. Preparing core samples is difficult, expensive and time-consuming. Moreover, the preparation of regular-shaped samples from weak or fractured rock masses is also difficult.  Under these circumstances, the application of other simple and low-cost methods to carry out the above tasks with acceptable reliability and accuracy will be important. Therefore, indirect tests are often used to estimate the UCS, such as Schmidt hammer, point load index and sound velocity. Indirect tests are simpler, require less preparation and can be adapted more easily to field testing (Feneret al. 2005).

The Schmidt hammer rebound hardness test is a simple and non-destructive test originally developed in 1948 for a quick measurement of USC and later was extended to estimate the hardness and strength of rock. The mechanism of operation is simple: a hammer released by a spring, indirectly impacts against the rock surface through a plunger and the rebound distance of the hammer is then red directly from the numerical scale or electronic display ranging from 10 to 100. In other words, the rebound distance of the hammer mass that strikes the rock through the plunger and under the force of a spring, indicates the rebound hardness. Obviously, the harder the surface, the higher the rebound distances. (Torabiet al. 2010; Schmidt, 1951).