MAGNETICS, 2-D RESISTIVITY AND GEOTECHNICAL STUDIES FOR SHALLOW SUBSURFACE SOIL CHARACTERIZATION IN LEMBAH BUJANG, KEDAH

Abstract

Magnetic and 2-D resistivity surveys were conducted on the same line for soil characterizations. 2-D resistivity survey employed Pole-dipole array with 1 m electrode spacing while magnetic survey employed 2 m station spacing. Soil drilling was performed using hand auger at the 21st m on the line with 0.2 m sampling interval. All data were processed and overlaid for integration and validation. The magnetic results showed the distribution of magnetic residual as -4.55 to 1.61 nT, with the magnetic low (-4.55 to -0.058 nT) was identified at distances 10 to 26 m, 36 to 44 m, 74 to 82 m, 88 to105 m, 120 m and 150 m. Three zones were identified based on the 2-D resistivity results; low (16.9-35.2 Ω-m), moderate (73.3-152 Ω-m) and high (317-1373 Ω-m). The low resistivity values might be due to clay with high water content, and the low magnetic susceptibility distributions were due to soil of sedimentary origin. The samples obtained were sticky with variable sizes, greyish to brownish/reddish in color, and some of the samples exhibited the presence of shiny and black spots. The characteristics of the samples suggested that the soil was a product of completely weathered rock, classified as Grade V with high water contents and weak.