The role of geophysics in the construction and stability assessment of tunnels

Geophysics play a vital role in the constructions of any major manmade structures in the world. One of those being the tunnels. In depth understanding of geophysical methods and a lot of information are needed in order to design a tunnel construction project. Comprehensive investigation on the ground condition has to be done before the field preparation study that will determine the stand-up time and the groundwater condition that may disrupt the tunnel construction. For tunnel stability assessment, an integration of geophysical methods is a must in order to obtain the most accurate results. Satellite imaging interpretation emphasizes on the structural tracing of negative lineament while field mapping emphasizes on location of underground seepage and major tectonic structures such as faults, joints and shear zones. Geoelectrical resistivity tomography survey is able to identify the differences in resistivity of Earth’s materials based on the water content inside of them. The best course of remediation could only be chosen once the output from all these studies are made available.

On The Supposed Onshore Extension Of The Penyu Basin, Peninsular Malaysia

The Penyu Basin is a Tertiary sedimentary basin located offshore Peninsular Malaysia. The basin is assumed to continue westwards beneath the Pahang River delta where as much as 115 m of Quaternary sediments overlie a bedrock of pre-Tertiary granites and metamorphic rocks. No Pliocene or older sediments beneath the delta have been reported. If the Quaternary sediments are considered as part of the Cenozoic Penyu Basin, the basin’s western limit may be delineated at the foothills of the coastal plain where those sediments onlap onto pre-Tertiary rocks. Therefore, any sedimentary rock of Tertiary age that may occur to the west of that limit most probably represents a separate basin.

Soil Moisture Retention Characteristics Of Saprock From The Weathering Profile Over A Biotite-Muscovite Granite In Peninsular Malaysia

The weathering profile at the slope cut near Km 16 of the Kuala Lumpur - Ipoh trunk road can be differentiated into an upper, 11.8 m thick pedological soil (zone I) and a lower, 31.9 m thick saprock (zone II) comprising silty sandy gravels that distinctly preserve the minerals, textures and structures of the original granite. In order to investigate the influence of particle size distributions on soil moisture retention characteristics, saprock samples were collected at depths of 26.53 m (Sample A), 31.29 m (Sample B) and 41.93 m (Sample C). Samples A and B, with porosities of 37%, comprise 33% gravel, 27% sand, 22% silt and 18% clay, and 31% gravel, 24% sand, 25% silt and 22% clay, respectively. Sample C with a porosity of 44% consists of 24% gravel, 28% sand, 38% silt and 10% clay. Tests with the pressure plate method show increasing suctions from 0 kPa through 0.98 kPa and 9.8 kPa to 33 kPa and 1,500 kPa to result in gravimetric soil moisture retentions of 31.9% through 28.6% and 23.3% to 16.9% and 6.8% in sample A, of 32.1% through 24.9% and 21.5% to 17.8% and 7.4% in sample B, and of 31.5% through 30.3% and 27.30% to 23.5% and 9.5% in sample C. Regression analyses of gravel, sand and clay contents plotted against moisture contents retained at high suctions (33 kPa and 1,500 kPa) yield negative trends with variable correlation coefficients (R2), though plots involving silt contents yield positive trends with large correlation coefficients (R2 >0.9966). It is concluded that adsorption of water on surfaces of silt sized particles (of mainly sericite derived from weathering of feldspars) that gives rise to the retention of soil moisture in saprock.

Lenggong Valley – Revisit Our National Treasure

Lenggong Valley was incepted as UNESCO World Heritage Site in 2012 for its marvellous cultural value. However, the status will be in peril if the valley is left neglected and nothing is done. The area is renowned for the discovery of prehistoric human settlement. Numerous studies and researches have been conducted at Lenggong Valley to increase the scientific knowledge of the surrounding areas for further conservation and development. Toba ash deposit from volcanic eruption in Sumatra, Indonesia and possible meteorite impact were also discovered within the valley. Geoelectrical resistivity survey have been conducted to determine the thickness of Toba ash. The results were correlated with borehole log from the Department of Mineral and Geoscience Malaysia (JMG), that shows the Toba ash layer is around 10 m in depth and presents low resistivity range of values (<100 Ωm). Water geochemical analysis at one of the known water spring shows the surface temperature is 27.6 °C, with a pH value of 7.47. Truth be told, Lenggong Valley has a diversity of archaeological sites and geosites that can be established as a geopark and a group of committee will be materializing it in year 2021 or 2022.

Geological sketches – out of time and fashion, but obsolete? An Essay

The sketching of geological features and objects played an important role in the development of the geosciences. Geological sketches may not be as commonly used for documentation purposes any longer, but may facilitate learning and understanding. By sketching geological features, the eye is trained to observe; this furthers understanding, and so improves study results.

Estimation of Dar-Zarrouk parameters and delineation of groundwater potential zones in Karlahi, part of Adamawa Massif, Northeastern Nigeria

Karlahi is largely underlain by granites and migmatites gneiss of the Adamawa Massif. The area lies west of Benue Trough and east of Cameroon volcanic line. The aim of this paper is to determine hydraulic properties of water bearing layer using parameters derived from Dar-Zarrouk equation and characterized them into groundwater potential zones. The resistivity values of the weathered and slightly weathered layers which make up the water bearing layers were added and an average was taken and used as the resistivity of the water bearing formation in computation of Dar-Zarrouk parameters in Karlahi area. The values of resistivity of water bearing formation ranged from 18 to 4963 Ωm with an average resistivity value of 549 Ωm and the thickness of the water bearing formation ranges from 21 to 32 m with an average thickness of 24.5 m. Conductivity values range from 0.000201 to 0.05509 (σ) while the longitudinal conductance range from 0.00483 to 1.2363 Ω-1, the transverse resistance ranges from 407 to 123504.3 Ωm2. The hydraulic conductivity and transmissivity values range from 0.14 to 25.87 m/day and 3.28 to 580.4 m2/day respectively. The longitudinal conductance values in Karlahi area revealed poor to good with an average longitudinal conductance value that is moderate. High transverse resistance values are located in the central and southern part of Karlahi area while low values are located in the eastern part. The spatial distribution map of transmissivity in the area revealed moderate to high transmissivity values in the north central part and a negligible to low transmissivity in southern part, extreme northeastern part. The groundwater potential map of Karlahi area shows negligible to weak potential groundwater zones in SW and SE, moderate potential in the central to northern part of Karlahi area.

Saturated hydraulic conductivity (Ks) of earth materials in a weathering profile over the Kuantan Basalt, Pahang, Malaysia

Three broad morphological zones can be differentiated at the weathering profile; the top, 3.80 m thick, pedological soil (zone I with sub-zones IA, IB and IC) comprising soft to stiff, brown clays and the bottom bedrock (zone III) being an outcrop of vesicular olivine basalt. The intermediate zone II (saprock) is 1.12 m thick and consists of brown, very stiff, sandy clayey silt with many lateritic concretions. Laboratory constant head permeability tests show the saturated hydraulic conductivity (Ks) to vary with depth; sub-zone IB having a conductivity of 0.007 cm/hr, and sub-zone IC (saprolite), and zone II (saprock), having conductivities of 0.147, and 0.447, cm/hr, respectively. The conductivity values show no correlation with physical properties of the earth materials, but increase with increasing sand, gravel, and silt, contents. The conductivity values also decrease with increasing clay and colloid contents. The low hydraulic conductivity of sub-zone IB will lead to surface runoff and ponding over natural ground surfaces during rainfall events, though over disturbed ground surfaces, infiltration is anticipated in view of exposed saprolite and saprock earth materials with relatively high conductivity

Metamorphic rocks of the Kuching Zone Sarawak: Comment on Najiatun Najla Mohamad et al. (2020) The geology and stratigraphic framework of the Kuching Zone Sarawak: Current understanding and unresolved issues

Metamorphic rocks of Sarawak have been dated and are not Upper Carboniferous or older rocks nor are they correlatives of the Pinoh Metamorphics of Kalimantan. Two newly-dated rocks are Triassic and are named the West Sarawak Metamorphics and a third sample is Cretaceous.

Ultrasonic Pulse Velocities And Dynamic Elastic Constants Of Sandstones From The Semanggol Formation, Beris Dam, Kedah Darul Aman

The main 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. Ultrasonic pulse measurements show velocities of compressional and shear waves through the sandstones to increase with decreasing grain size; the pebbly sandstone with velocities of 2.210, and 5.171, km/s, and the coarse grained sandstone with velocities of 2.477, and 5.612, km/s, respectively. The medium grained sandstones have compressional and shear wave velocities of 2.457, and 5.793, km/s and the fine grained sandstones, velocities of 2.572, and 5.867 km/s, respectively. Dynamic elastic constants computed from the ultrasonic velocities also increase in values with decreasing grain size; Poisson’s ratio varying from 0.36 to 0.39, the modulus of elasticity from 35.076 to 48.210 GPa, the bulk modulus from 52.260 to 67.362 GPa and the modulus of rigidity from 12.637 to 17.468 GPa. Increasing velocities and elastic constants with decreasing grain size are considered to result from a denser arrangement of constituent grains as shown by increasing dry unit weights. Comparison with the results of an unconfined compression test on a fine grained sandstone indicate that the ultrasonic elastic constants are good approximations of static elastic constants.

Reconnaissance Of Kenny Hill Formation Outcrops In The Rawang Area, Northern Selangor, Malaysia

New outcrops of Paleozoic meta-sediments northwest of Kuala Lumpur expose the deformational effects of the Late Paleozoic-Mesozoic collisions between various Gondwana-derived continental fragments as they amalgamated to form the core of SE Asia. Over a duration of 6 months, beginning in August 2020, we conducted field trips within northern Selangor to new laterally extensive outcrops for field observations, structural mapping and to measure and log the stratigraphic section. This paper focuses on Upper Paleozoic Kenny Hill Formation outcrops in northern Selangor. The most studied is the heavily weathered Jalan Rawang-Bestari Jaya (JRBJ) outcrop, which is characterised by a steeply dipping (southwest), upward-coarsening succession of sandstones and shales interpreted as a system of ephemeral fluvial channels possibly related to Gondwana glaciation. Concretions within bedding planes and fractures were possibly formed around organic material. Less than 4 km to the east, the Scientex development has excavated fresher outcrops of the same rocks dipping to the NE. Metamorphic lineation is not present in either outcrop location. In addition, a monocline is exposed at outcrop location number 3 nearby. Finally, at Bukit Botak, 14 km to the southwest, a system of westward verging thrust faults, back thrusts and normal faults can be viewed and an angular unconformity or decollement marks the contact between the Upper and Lower Paleozoic. These laterally extensive outcrops are rare and are quickly subject to intense tropical weathering, the encroachment of jungle vegetation and urban development. Historic mapping and prior stratigraphic, structural, and petrographic studies have been conducted in the area, but these relied on poor exposures. As suburban development escalates in the area, we hope that new outcrops, featuring multi-dimensional views of these formations, such as the four described in this paper, will complement the earlier work.