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Estimating Some Mechanical Properties Of Rock From In-situ Rebound Values
[A CASE STUDY OF OREKE OPEN PIT QUARRY]
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CHAPTER TWO
2.0 LITERATURE REVIEW
A literature review revealed that most of the empirical equations introduced for determination of the Uniaxial Compressive Strength (UCS) of rocks based on the Schmidt hammer rebound number (N) are not sufficiently reliable mostly due to the relatively low coefficient of correlations. This is attributed to the fact that in most cases one formula is used for all types of rocks, although the density of rocks is introduced to the formulae in some cases. On the other hand, if one specific relationship between N and UCS is introduced for one rock type, the equation will yield a much higher coefficient of correlation (Torabi et al., 2010).
2.1 CONCEPT OF SCHMIDT REBOUND HAMMER
A Schmidt hammer, also known as a Swiss hammer or a rebound hammer, is a device to measure the elastic properties or strength of concrete or rock, mainly surface hardness and penetration resistance. It was invented by Ernst Schmidt, a Swiss engineer. The Schmidt hammer is distributed by Proceq and TQC worldwide. ( Basu, 2004).
The hammer measures the rebound of a spring-loaded mass impacting against the surface of the sample. The test hammer will hit the concrete at a defined energy. Its rebound is dependent on the hardness of the concrete and is measured by the test equipment. By reference to the conversion chart, the rebound value can be used to determine to compressive strength. When conducting the test the hammer should be held at right angles to the surface which in turn should be flat and smooth. The rebound reading will be affected by the orientation of the hammer, when used in a vertical position (on the underside of a suspended slab for example) gravity will increase the rebound distance of the mass and vice versa for a test conducted on a floor slab. The Schmidt hammer is an arbitrary scale ranging from 10 to 100. According to Aydin (2009) Schmidt hammers are available from their original manufactures in several different energy ranges these include:
i. Type L – 0.735 Nm impact energy
ii. Type N – 2.207 Nm impact energy and
iii. Type M – 29.43 Nm impact energy
The test is also sensitive to other factors:
1. Local variation in the sample to minimize this it is recommended to take a selection of readings and take an average value.
2. Water content of the sample, a saturated material will give different results from a dry one.
Prior to testing, the Schmidt hammer should be calibrated using a calibration test anvil supplied by the manufacturer for that purpose. 12 readings should be taken, dropping the highest and lowest, and then take the average of the ten remaining. Using this method of testing is classed as indirect as it does not give a direct measurement of the strength of the material. It simply gives an indication based on surface properties. It is only suitable for making comparisons between samples.
The Schmidt hammer has been used in rock mechanics practice since the early 1960s as an index test for a quick rock strength and deformability characterization due to its rapidity and ease of application, simplicity, portability, low cost and non-destructiveness. Most researchers in this area have proposed various empirical equations for calculating Unixial Compressive Strength (UCS) from N. they have found that Schmidt hardness and the LCS are closely related (Torabi, 2005).
Kahraman, (2001) explained that the Schmidt hammer has been widely used for testing the quality of concrete and rocks. It has been increasingly used worldwide because of its simplicity, rapidity, non-destructiveness and portability. The Schmidt hammer is a light hand-held device which consists of a spring-loaded mass inside a piston that is released when the hammer is pressed orthogonally onto a surface. The rebound height of the mass (R) is recorded on a linear scale and gives an indication of the strength of the material being tested. Schmidt hammer models are designed with different levels of impact energy, but the types L and N are commonly adopted for rock property determinations. The type L has an impact energy of 0.735 Nm which is only one third that of the type N.
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ABSRACT - [ Total Page(s): 1 ]ABSTRACTThe 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 COMPRES ... Continue reading---
LIST OF TABLES - [ Total Page(s): 1 ]LIST OF TABLESTABLES 4.1: Determination of Bulk Density for Location 4.2: Density Test Result for Location 4.3: Density Test Result for Location 4.4: Field Rebound Values 4.5: Standard Procedure of Bulk Density Determination 4.6: Standard for Uniaxial Compressive Strength (UCS) ... Continue reading---
LIST OF FIGURES - [ Total Page(s): 1 ]LIST OF FIGURESFIGURES 1: Details of an L type Schmidt hammer 2: Conversion Graph ... Continue reading---
TABLE OF CONTENTS - [ Total Page(s): 1 ]TABLE OF CONTENTSTITLE PAGE CERTIFICATION DEDICATION ACKNOWLEDGEMENT TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES CHAPTER ONE 1.0 INTRODUCTION 1.1 AIM AND OBJECTIVES 1.2 STATEMENT OF THE PROBLEM 1.3 SCOPE OF THE PROJECT 1.4 JUSTIFICATION OF THE PROJECT 1.5 LOCATION OF THE STUDY AREA CHAPTER TWO 2.0 LITERATURE REVIEW 2.1 CONCEPT OF SCHMIDT REBOUND HAMMER 2.2 GEOLOGICAL FORMATION OF MARBLE 2.3 MECHANICAL PROPERTIES OF MARBLE ... Continue reading---
CHAPTER ONE - [ Total Page(s): 1 ]CHAPTER ONE 1.0 INTRODUCTIONRock 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 si ... Continue reading---
CHAPTER THREE - [ Total Page(s): 2 ]CHAPTER THREE3.0 RESEARCH METHODOLOGY (DESK WORK)The research methodology is the general research strategy that outlines. The way in which research is to be undertaken and among other things, identifies the methods to be used in it. These methods, described in the methodology, define the means or mode of data collection or sometimes, how a specific result is to be calculated. Methodology also is the systematic theoretical analysis of the methods applied to a field of study.Therefore, the N ... Continue reading---
CHAPTER FOUR - [ Total Page(s): 7 ]The result obtained for the uniaxial compressive strength range from lowest value to the highest value which is 1.15×1040mpa respectively. Base on the standard present by Deere and Miller (1966) and ASTM (2001). The mean value obtain which is6.22×1040mpa made the marble to be classified as a rock with very low strength. 4.3 DISCUSSION The average rebound value was used trace the UCS with the corresponding bulk density in figure (4.1.1). The result shows that the uniaxial comp ... Continue reading---
CHAPTER FIVE - [ Total Page(s): 1 ]CHAPTER FIVE5.0 CONCLUSION AND RECOMMENDATION5.1 CONCLUSIONThe need to test rock in order to determine their physical and mechanical properties cannot be overemphasized .However , laboratory testing procedures and equipment may be required to do this for engineering project .Hence, the Schmidt rebound hammer (RN) has being used by many researchers to measure the strength and other engineering properties of rocks. This usually enables a quick and easy means of measurement. Marble be ... Continue reading---
REFRENCES - [ Total Page(s): 1 ]REFERENCESAggestalis, G, Alivazators, (2000) Correlating Uniaxial Compressive Strength with Schmidt Hammer Rebound Number, Journal of Bulleting Engineering Geology, Vol. 5,4, ppg 3 – 11.ASTM, (2001) Standard Method for Determination of Rock Hardness of Rebound Hammer Method, ASTM Stand 04.09(D5873-00).ASTM. D-5873(2005) Standard Test Method for Determination of Rock Hardness by Rebound Value Method.Aufmuth, E.R. (2002). A Systematic Determination of Engineering Criteria for Rocks. Journal ... Continue reading---
