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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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A method used Schmidt hammer to determine the uniaxial compressive strength of rock is to calibrate between Schmidt hammer rebound and uniaxial compressive strength test of laboratory and is the results are an empirical equation.
PROCEDURE
1. Specimen shall be tested at a moisture content close to field condition as possible.
2. L/D ratio, preferable be 2 to 3 if L/D L2, then correction shall be applied.
3. Dia of the test specimen shall be measure to the nearest 0.1mm by averaging two diameters increased at right angle to each other at about the upper height, the mid height and the lower height of the specimen.
4. Specimen should be prepared in such a manner that the cylindrical surface shall be smooth and free from abrupt and irregularities.
5. Clean the surface of the two bearing discs and the test specimen. Place the specimen on the lower disc.
6. Carefully align the axial of specimen with the centre of thrust of the spherical seat.
7. Apply load continuously at a constant stress rate within the limit of 0.5mpals to 1.0mpals.
8. Record the maximum load on the specimen of failure in N within 1% accuracy.
CALCULATIONS
The UCS of the specimen is calculated by dividing the maximum load carried by the specimen during the test by the average cross sectional area.
3.5 ESTIMATING OF DENSITY
The density test of the marble indicate the limit weight of the marble, which is necessary for the Architect or Engineer who is designing the structure to support the marble.
The standard specifications prescribe minimum densities, the minimum densities are used to classify stones, for example, there are three classes of marble with each class having a different density as well as different strength requirements.
Generally, a higher density marble is probably hardness porous and stronger, but this is not always the case, and note that there is no density for shade specified in ASTM 62% although it could be determined, if desired, using the procedure of ASTM 1997.
Density is important in the context of cosmogenic – nuclide measurements because the costric ray flux is attenuated according to mass depth below the surface, i.e it’s necessary to thick of depth of over burden or sample thickness in g/cm3, a unit of mass per square area, rather simply in length.
In order to estimate the density, Katz, et al., (2000) derived an equation which is stated below.
D (Inkg/m3) = - 287441308 x 1n (HR)
Where D is the density
HR is the average rebound hammer value
3.6 ESTIMATING OF YOUNG’S MODULUS
Young’s modulus determination unconfined compressive strength (UCS) testing is carried out using a Schmidt Rebound Hammer with measurement and applied stress with reporting of the stress/strain plot.
At present, there are many methods for measurement young’s modulus of rock.
In these study, different cylindrical sample sizes were used in the experiments, the relationship between sample size and compressive strength was investigated for the sample kind of stud formation, the load cell, strain ranges and LVDT are connected to the sample and data logger named text box 1001. Stress – strain relationship of rock is highly variable under uniaxial compressive tests and they don’t exhibit excellent elastic in the experiments.
In this work, tangent and secant elasticity modulus is used and defined as;
Secant elasticity modulus is measured as the slope of the line from the origin to 50% of ultimate strength
Tangent modulus is measured at 50% of ultimate strength at the slope of a line tangent to the stress – strain curve, ED/DE. It’s most suitable for the incesutuff sample which don’t exhibit excellent elasticity.
Thereafter, Katz, et al, (2000) derived and equation for estimating Young’s modulus, which is stated below.
In E = 81.967 + 3.091 x In (HR)
Where E is the Young’s modulus
HR is the average rebound hammer value.
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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 TWO - [ Total Page(s): 3 ]CHAPTER TWO2.0 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 ... 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---
