Warta Geologi, Vol. 45, No. 4, December 2019, pp. 393–399
Point load strength of clastic sedimentary rocks from the
Semanggol Formation, Beris Dam, Kedah Darul Aman
J. K. Raj
Engineering Geology Consultant,
No.83, Jalan Burhanuddin Helmi 2, Taman Tun Dr. Ismail,
60000 Kuala Lumpur, Malaysia
Email address: jkr.ttdi.tmc@gmail.com
Abstract:
The Beris Dam is founded on a sequence of thick bedded conglomerates and pebbly
to fine grained sandstones with minor mudstone mapped as the Semanggol
Formation of Triassic age. The conglomerates have an average dry unit weight of
23.85 kN/m3, and apparent porosity of 9.8%, whilst the pebbly
sandstones have corresponding values of 25.35 kN/m3, and 3.9%,
respectively. Coarse, and medium, grained sandstones have similar apparent
porosities of 3.8%, but dry unit weights of 25.33, and 25.36, kN/m3.
Fine grained sandstones, which are laminated, have an average dry unit weight
of 25.81 kN/m3, and apparent porosity of 2.2%. Diametral tests on
air dried core specimens (of 51.6 mm diameter) show them to fail in typical
tensile splitting mode, except where inherent fracture or bedding planes are
present. The fine grained sandstones split along laminae and yield a point load
strength index [Is(50)] of 2.44 MPa, whilst the relatively porous
conglomerates yield an index of 5.16 MPa. Diametral tests on pebbly sandstones
yield a strength index [Is(50)] of 6.89 MPa, while those on coarse
and medium grained sandstones yield indices of 8.64, and 8.83, MPa,
respectively. Decreasing strength indices with increasing particle size are
considered to result from the greater surface area of the coarser grains that
allows preferential extension of failure crack traces along grain boundaries. It
is concluded that the point load strength of clastic rocks from the Semanggol
Formation is influenced by their texture as well as inherent discontinuity
planes present.
Keywords:
Point load strength, Semanggol Formation, clastic rocks
ISSN
0126–5539; e-ISSN 2682-7549
DOI :
https://doi.org/10.7186/wg454201902
