Sandstone Rippability Assessment Based on Specific Energy Relationship with Tensile Strength and Surface Hardness

Abstract

Rock with moderate strengths (20 to 70 MPa) effectively excavated by ripping method which is considered as shallow excavation or surface striping method. Disputed between client and contractor often occur due to the lack of proper assessment to determine the rippabality of hard material. Practically, rippability of in situ rock is assessed based on field ripping test that being conducted using actual ripper dozer which is time-consuming and expensive. Therefore the assessment of rippability of rock based on specific laboratory tests able to resolve the conflict that occurs on ripping method. The correlation between specific energy with surface hardness and tensile strength is chose as the material properties to assess in order to determine the rippability of rock in this study. Few samples of Sandstone undergone several laboratory tests such as laboratory ripping test, Brazilian's test and Schmitt hammer test in order to obtain the required parameters in this study. The average tensile strength (?T) obtained was 4.62MPa with a range of value from 3.19 to 7.50 MPa whilst the average rebound number (R) obtained for Sandstone was 26.6 with a range between 19.0 and 34.0. The specific energy (SE) obtained indicates an average value of 3.95 MJ/m3 with a range value between 1.73MJ/m3 and 6.45 MJ/m3 . The correlation of R and ?T with SE shows a relatively good relationship. Parameters of R and ?T are acceptable and reliable for assessing rippability of Sandstone based on the value of regression coefficient (R2) which is consistence above 0.8 for both correlation between SE, R and ?T.