Abdul Ghani Rafek

The distribution of rare earth elements in tropical granitic soil: a case study from Malaysia

A total of 93 samples of rock, altered soil representing various weathering grades from an ideal granite weathering profile exposed at a road cut along the Kuala Lumpur-Karak highway, Peninsular Malaysia, were studied. The fresh, unaltered parent rock is petrographically distinguished into two types: (1) coarse grained porphyritic biotite-muscovite granite, and (2) medium grained biotite-muscovite granite. The rock has undergone some degree of brittle deformation. A weathering index map based on the procedures suggested by Ibrahim Komoo et al. Warta Geologi17(3), 105–109 (1991) shows the spatial distribution of unaltered to slightly altered rocks (index 2–4), weathered rocks (5–8) and residual soil (9 and 10) for the profile under study. For each sample, 11 major elements were determined using X-ray fluorescence technique (XRF) and nine rare earth elements, La, Ce, Nd, Sm, Eu, Tb, Dy, Yb and Lu, by the instrumental neutron activation analysis (INAA). All REEs decrease with increasing weathering grade, suggesting a depletion of the REEs due to weathering. The depletion rate is variable, the fastest being Sm and La. A Masuda-Coryell diagram for the three groups of samples, that is (1) fresh to slightly weathered rocks, (2) moderately to highly weathered rocks, and (3) residual soils, shows three curves with a similar pattern of negative Eu anomalies. The concentration of elements is in the order 1>2>3, suggesting strongly that the REEs diminish gradually in the course of the weathering. A rock-soil interface has been recognised to exist at weathering index 4. It is believed that at this interface, most REEs leave their primary carriers which undergo rapid breakdown, most probably plagioclase, biotite and hornblende and possibly ilmenite and apatite, into weathering solution, together with Fe2+, Ca2+, K+, Mn2+ and Mg2+. Anomalously low concentration of REEs in index 4 material supports this idea. The leached-out REEs are temporarily incorporated into newly formed secondary minerals (secondary carriers) before gradually leaving the system from index 6 onwards.

A Low Cost Alternative Approach to Geological Discontinuity Roughness Quantification

The surface roughness of geological discontinuities can be considered a key parameter in the evaluation of the stability of structures constructed within rock masses. Several different methodologies can be applied to determine this parameter and they vary in their complexity. The aim of this study is to correlate the peak friction angle (ϕp) of discontinuity planes of fresh bedrock with the Joint Roughness Coefficient, JRC. A simple low cost approach is presented based on the determination of JRC and the application of derived polynomial equations to determine the peak friction angle, ϕp from the surface roughness from geological discontinuities for the major lithologies found in Peninsula Malaysia. Eight thousand six hundred and seven tilt tests were conducted to obtain the correlations between peak friction angles with JRC of granite, schist, limestone, quartzite and sandstone. The respective polynomial equations are as follows: for granite ϕp= −0.071 JRC2 + 3.56 JRC + 35.6° for schist ϕp = −0.022 JRC2 + 3.21 JRC + 28.1° for limestone ϕp= −0.0635 JRC2 + 3.95 JRC + 25.2° for quartzite ϕp = −0.083 JRC2 + 4.17 JRC + 27.6° for sandstone ϕp = 0.0424 JRC2 + 1.13 JRC + 29.2° For all the derived polynomials, the coefficient of determination, R2 was greater than 0.9. The JRC can be determined as part of an engineering geological investigation and the respective polynomial applied to determine the peak friction angle, ϕp for the specific lithology.

The geomechanical strength of carbonate rock in Kinta valley, Ipoh, Perak Malaysia

The stability of both cut rocks and underground openings were influenced by the geomechanical strength of rock materials, while the strength characteristics are influenced by both material characteristics and the condition of weathering. This paper present a systematic approach to quantify the rock material strength characteristics for material failure and material & discontinuities failure by using uniaxial compressive strength, point load strength index and Brazilian tensile strength for carbonate rocks. Statistical analysis of the results at 95 percent confidence level showed that the mean value of compressive strength, point load strength index and Brazilian tensile strength for with material failure and material & discontinuities failure were 76.8 ± 4.5 and 41.2 ± 4.1 MPa with standard deviation of 15.2 and 6.5 MPa, respectively. The point load strength index for material failure and material & discontinuities failure were 3.1 ± 0.2 MPa and 1.8 ± 0.3 MPa with standard deviation of 0.9 and 0.6 MPa, respectively. The Brazilian tensile strength with material failure and material & discontinuities failure were 7.1 ± 0.3 MPa and 4.1 ± 0.3 MPa with standard deviation of 1.4 and 0.6 MPa, respectively. The results of this research revealed that the geomechanical strengths of rock material of carbonate rocks for material & discontinuities failure deteriorates approximately ½ from material failure.

Fractures of Gunung Ledang Granite: Insight to Post-Cretaceous Structural Event

Based on the deformations in the Cretaceous rocks and also the results of the radiometric dating of the fault zones [Zaiton Harun, Late Mesozoic—Early Tertiary faults of Peninsular Malaysia, 9], it is proven that tectonics of onshore Peninsular Malaysia was still active during post-Cretaceous. These deformations may contribute to the basin formation/inversion during Tertiary period in Sundaland. The study area is Cretaceous granite, Gunung Ledang, which is situated in North Johor. The objective of this study is to determine the major fracture sets at regional scales and outcrop scales and reconstruct the structural events. In this study, the focus is on the negative lineaments of Gunung Ledang at a regional scale and the fractures of the Puteri Waterfall at outcrop scale. During site visit, the details of the fracture, e.g., infilling and sense of motions, are recorded. From the observations and analysis, there are 3 negative lineament sets at regional scale: N-S, NE-SW, and ESE-WNW; four fractures sets found at the outcrop scale: N-S, NE-SW, E-W, and NW-SE. The outcrop-scale fractures are all steeply dipping to almost vertically dipping. The crosscutting relationships show that the chronology of the fractures is N-S, NE-SW/E-W, and NW-SE, from oldest to youngest. NE-SW fracture displaces a N-S mega-crystal quartz dyke in left-lateral motion, which deduces a ~ N-S compression. Another possible Riedel system (right-lateral strike-slip) formed on the same NE-SW fractures, which deduce a ~ E-W compression. The chronology of these two events is hard to define because of lack of clear field evidences.

Development of empirical correlation of peak friction angle with surface roughness of discontinuities using tilt test

The significant influence of surface roughness of discontinuity surfaces is a quantity that is fundamental to the understanding of shear strength of geological discontinuities. This is due to reason that the shear strength of geological discontinuities greatly influenced the mechanical behavior of a rock mass especially in stability evaluation of tunnel, foundation, and natural slopes. In evaluating the stability of these structures, the study of peak friction angle (Φpeak) of rough discontinuity surfaces has become more prominent seeing that the shear strength is a pivotal factor causing failures. The measurement of peak friction angle however, requires an extensive series of laboratory tests which are both time and cost demanding. With that in mind, this publication presents an approach in the form of an experimentally determined polynomial equation to estimate peak friction angle of limestone discontinuity surfaces by measuring the Joint Roughness Coefficient (JRC) values from tilt tests, and applying ...

In situ determination of layer thickness and elastic moduli of asphalt pavement systems by Spectral Analysis of Surface Waves (SASW) method

Spectral Analysis of Surface Waves (SASW) is a non-destructive method for determining the stiffness profile of pavement sites. The method consists of generation, measurement, and processing of dispersive elastic waves in layered systems. The test is performed on the pavement surface at low strain level, where the elastic properties are considered independent of strain amplitude. During an SASW test, an impact source was used to generate energy at various frequencies. Two vertical acceleration transducers are set up to detect the energy transmitted through the testing media. By recording signals in digitised form using a data acquisition system and processing them, surface wave velocities can be determined by constructing a dispersion curve. Through forward modeling, the shear wave velocities can be obtained, which can be related to the variation of stiffness with depth. This paper presents the results of two case studies for near-surface profiling of two different asphalt pavement sites.

Results of Geoelectrical Soundings for Mapping of a Marine Clay Along the Tangkak-Pagoh Highway Johor, Malaysia

Geoelectrical resistivity soundings conducted along the north-south expressway in the Tangkak-Pagoh area during its construction enabled the mapping of a marine clay which was present in alluvium. The apparent resistivity curves of the marine clay area, were characterised by low apparent resistivity values falling to almost zero, and a characteristic shape which was different from areas of weathered metasediments and weathered granite adjacent to this area. Apparent resistivities for both metasediments and granite were intermediate to high, with a distinct upward convex curve for metasediments and a flat upward convex curve for granite. Quantitative interpretation was able to distinguish between an upper and a lower clay horizon, which have differentconsistency and fine sand content. The thickness of the upper clay horizon, which varies between 8.0 m to 9.0 m according to borehole data showed good agreement with that obtained by resistivity soundings. The base of the lower clay horizon remained undetected by the resistivity soundings because of its very low specific resistivity. Using the thickness of weathered layers as observed along the road cuttings as a guide, good agreement between field data and calculated values was obtained in determining the specific resistivities and individual layer thicknesses for the granite and metasediment weathering profiles.