The Bukit Timah Granite (BTG) formation is widely distributed in the central and northern parts of Singapore Island. This paper presents the key mechanical and physical properties of Singapore BTG rocks and residual soils, based on the Factual Geotechnical Reports of Downtown Line stage II sites. The variations of parameters including the index properties, the hydraulics, the strength and stiffness, the compressibility for residual soils, the unconfined compressive strength, the point load strength index, the abrasivity, and slake durability index for rocks are derived from laboratory tests based on samples from different depths of different borelogs. Statistical information including the average mean values, the standard deviations and the coefficient of variations are provided for these parameters. It is hoped that these statistics will provide useful reference and insights for future projects involving in BTG Formation.
The Bukit Timah Granite (BTG) is an acidic igneous rock formed in the lower middle Triassic period. There is considerable hybridization of the rock within the formation and evidence of assimilation (Pitts, 1984). Therefore, there is also a great variation in the mechanical and physical properties of BTG rocks. Through field investigations and laboratory tests, Zhao et al (1994) investigated the influences of the weathering grade and the weathering processes on the mechanical and physical properties of the weathered granitic rocks. Rahardjo et al (2012) compiled the variation of index and engineering properties of BTG residual soils with depth. Based on a large database from the Factual Geotechnical Reports on over 200 boreholes of the Singapore Downtown Line stage II (DTL2), this study presents the key mechanical and physical properties of BTG rocks and residual soils.
In this unconfined compressive strength test, the test specimen, the loading rate as well as the testing environment are shown in Table 1.
As can be seen from Table 1, the specimens in the test are generally standard test specimens. For some of them, due to sampling or storage, the specimen is not standard in geometry, and its tested strength needs to be converted to the value under standard condition (H/D=2). The specific calculation is performed according to equations (1) and (2) (ASTM 1986).
