Rebound Hammer Report
1.0 OBJECTIVE
This experiment deals with determination of rock strength when a certain load implied on the rocks. Students should be able conducted the experiment, understanding the theory and recognize the rock strength on different types of rocks in Malaysia.
2.0 LEARNING OUTCOMES a) To determine a rock strength on different types of rock formation in Malaysia. b) To evaluate the physical properties of rocks for civil engineering application. c) To understand the theory rock test.
3.0 THEORY
Rebound hammer test is undertaken using Schmidt’s hammer L-type (N-type for concrete material). Test procedure is simple and equipment is portable and easy to operate. Test can be undertaken on site and the number of test is unlimited. Test can be carried out on the surface of irregular block or, on core samples does not involve destruction of sample (minimize sample usage). Index value obtained is rebound number (R), which is an indicator on the degree of hardness of rock surface being tested. Rebound hammer test is frequently used in estimating the compressive strength of joint surface in rock. The value of R can be used to estimate the compressive strength of rock using the following equation (Franklin, 1989):
Log10 JCS = 0.00088(γ)(R) + 1.01
Where, JCS (MPa) is the compressive strength of rock surface; γ is unit weight of rock (kN/m3). The term JCS means joint compressive strength, which implies the surface strength of joints (fracture planes) in rock. This means that rebound hammer test can also be used to estimate the surface strength of joint in addition to rock block sample. For fresh rock (weathering grade I), JCS is approximately equals to the UCS of the rock material. In other words when rock is not weathered, its surface compressive strength is approximately equals to the strength of its material composition (usually measured by UCT). 4.0 EQUIPMENT AND MATERIALS 1. Rebound Hammer (L-type) 2. Steel Base 3. Calibration Anvil
This experiment deals with determination of rock strength when a certain load implied on the rocks. Students should be able conducted the experiment, understanding the theory and recognize the rock strength on different types of rocks in Malaysia.
2.0 LEARNING OUTCOMES a) To determine a rock strength on different types of rock formation in Malaysia. b) To evaluate the physical properties of rocks for civil engineering application. c) To understand the theory rock test.
3.0 THEORY
Rebound hammer test is undertaken using Schmidt’s hammer L-type (N-type for concrete material). Test procedure is simple and equipment is portable and easy to operate. Test can be undertaken on site and the number of test is unlimited. Test can be carried out on the surface of irregular block or, on core samples does not involve destruction of sample (minimize sample usage). Index value obtained is rebound number (R), which is an indicator on the degree of hardness of rock surface being tested. Rebound hammer test is frequently used in estimating the compressive strength of joint surface in rock. The value of R can be used to estimate the compressive strength of rock using the following equation (Franklin, 1989):
Log10 JCS = 0.00088(γ)(R) + 1.01
Where, JCS (MPa) is the compressive strength of rock surface; γ is unit weight of rock (kN/m3). The term JCS means joint compressive strength, which implies the surface strength of joints (fracture planes) in rock. This means that rebound hammer test can also be used to estimate the surface strength of joint in addition to rock block sample. For fresh rock (weathering grade I), JCS is approximately equals to the UCS of the rock material. In other words when rock is not weathered, its surface compressive strength is approximately equals to the strength of its material composition (usually measured by UCT). 4.0 EQUIPMENT AND MATERIALS 1. Rebound Hammer (L-type) 2. Steel Base 3. Calibration Anvil