Frictional properties of granite gouges in direct shear test

• Main Author: Qin, Yuchen
• Other Authors: Wu Wei (CEE)
• Format: Final Year Project
• Language: English
• Published: 2017
• Subjects: DRNTU::Engineering::Engineering::Civil engineering::Geotechnical
• Online Access: http://hdl.handle.net/10356/72046
• Institution: Nanyang Technological University

The main objective of this project is to investigate the shear strength behaviour of crushed granite gouges in a direct shear test. Crushed Granite gouges are used to simulate the natural wear products often found in rock joints or fractures. Gouges were sheared at different normal stresses and different speeds to observe the effects they have on shear stress. Normal stresses of 1 MPa, 3 MPa, 5 MPa and shearing speed of 0.2 mm/min, 1 mm/min, 5 mm/min were used. Casting and shearing procedures follow the ISRM suggested method closely. Gouges were sieved after each test to determine the relative proportion of grain sizes after shearing. Four key findings were gathered for this project. Firstly, as shear displacement increases, shear stress also increases. However, no distinct peak in the shear stress versus shear displacement graph is observed for any of the shear tests done on gouges. This is different from typical graphs from the shearing of natural rock fractures. Secondly, shear stress versus shear displacement graphs from shearing of granite rock gouges closely resembles those of loose soil. Both show an increase in shear strength as shear displacement increases until a maximum stress is reached. Subsequently, the shear stress remains relatively constant after the maximum stress is reached. Thirdly, as the normal stress applied increases, the maximum shear stress also increases. Moreover, the increase is proportional i.e. 2 MPa increase in normal stress will cause a 1 MPa increase in maximum shear stress. Lastly, shearing speed does not have a noticeable effect on shear stress in gouges.