Application of 2-D Resistivity Imaging and Seismic Refraction Methods for Engineering Geological Studies

Loading...
Thumbnail Image
Date
2011-06
Authors
Ismail, Nur Azwin
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Detailed knowledge of subsurface and structural geologY is essential for engineers before commencement of any construction projects. The effectiveness of 2-D resistivity imaging and seismic refraction in determining the amount of overburden, bedrock mapping, characterizing subsurface and investigation on karstic features were tested at five different locations in Malaysia. Interpretation of results obtained is supported by borehole records. Generally, Damansara is underlain by non rippable granite bedrock encountered at depth 10-30 m with velocity and RQD of >3000 ms-1 and 37-85% respectively. First and second layers are generally rippable with velocity 400-600 rns-1 and 1600-2000 rns-1 respectively which predominantly consists of gravelly soil and weathered layer. For Chendering, results indicate that the whole area are fractured metasediment shale bedrock with resistivity value, velocity and RQD of >5000 Om, 2155-3165 rns·1 and <8 % respectively, covered with <5 rn thick colluviurns with resistivity value of 1500-3000 (lm. Saturated zones with resistivity value <100 Om were found. Velocity of frrst layer is 340-740 rns·• while second layer have velocity 943-2040 rns·1 predominantly consist of gravelly soil and very poor shale or hard gravelly silt and silty gravel. These two layers are formed overburden with SPT -N value of 40-50 which is generally rippable while third layer is non rippable. As for Gopeng, the rock head of limestone bedrock encounter at depth 8-12 m with resistivity value of 70 Om. competent limestone bedrock with RQD of 40-50% and weak/fractured limestone with resistivity value xxiv > 100 Om and 20-100 Om respectively are also obtained. In correlation with borehole records, alluviums with thickness 6-10 m were identified. Other karstic features such as pinnacle and cavity with resistivity, value 20-50 Om are also detected. Lenggong results indicate that the study area generally made up with weathered granite grade IV and V, having resistivity value of 800-3000 Om. Granite bedrock is encounter at depth 8-47 m with resistivity value >3000 Om and velocity of>2000 ms-1 • First and second layer is rippable with velocity 312-583 ms-1 and 814-8550 ms-1 respectively while third layer is non rippable. Granite boulders with resistivity value 1500-3000 Om and saturated zones with resistivity value 0-100 Om are also identified. The results are correlated well with borehole records provided. For Limbang, it consists of highly fractured or weathered sandstone/mudstone with resistivity value > 300 Om. The saturated zones with resistivity value <1 0 Om were identified. Slightly weathered sandstone/mudstone bedrock is encountered at depth 15-30 m with velocity and resistivity value of >3000 ms-1 and 800-3000 Om which generally non · rippable. First and second layer with velocity 270-630 ms-1 and 790-2500 ms-1 are generally rippable which predominantly consist of gravelly soil and highly weathered and fresh sandstone/mudstone. Saturated zone with resistivity value <1 0 Om is also detected. XXV
Description
Keywords
APPLICATION OF 2-D RESISTIVITY IMAGING AND SEISMIC REFRACTION METHODS
Citation