Geoelectrical Survey for Engineering Investigation

Abstract

Water seepage erosion has been and remains one of the major engineering problems. However, most engineers will much depend on borehole data and soil test for designing and problem detection. By considering of the cost and destructive method, selection of geoelectrical prospecting would be appropriate. Therefore, two electrical geophysical surveys were carried out in Sekolah Menengah Kebangsaan Dato' Haji Mohd Nor, Gelugor, Pulau Pinang to map the presence of the unknown underground water sources (saturated zones) and its movement. With the total of seven resistivity lines parallel to each other and self potential (SP) with 5 m × 5 m gridding survey were successfully done. The resistivity result from line 1 (R1) to line 6 (R6) shows the subsurface consist of saturated zones with range between 3 m up to 10 m depth, before it reaches the R7 which is believed as the accumulation zone. Meanwhile, as for SP result it shows the water flow from higher value (north-east) towards the lower value which is mostly at the south area. In conclusion, geoelectrical survey could assist in detecting and solving engineering problems as it proven by the result from each method.

Correlation of Self Potential and Ground Magnetic Survey Techniques to Investigate Fluid Seepage in Archaeological site, Sungai Batu, Lembah Bujang, Kedah, Malaysia

“…For both SP and Magnetic surveys were interpreted, the half width rules was used with the distance along the x-axis and SP data and magnetic residual data on the y-axis using excel graph to determined the aquifer depth as shown in Figure 2-5 and the result of half width rules which was obtained from the graph was also shown in Table 1; the mean value, standard deviation, Pearson's correlation coefficient, Testing the significance of r (2-tailed) and Correlation significant at 0.8 which is a strong correlation is shown in Table 2 obtained from Equation (1 & 2). Self-Potential: A total of 84 points were carried out, the field data obtained was interpreted using surfer 8 software, the survey coordinates and SP measurement were input into the software and the results were displayed in contoured map which obtained from non-polarizing coppercopper sulfate electrodes are very related to seepage flow patterns and the anomalies were positive and negative in this study which ranges from -30mV to +35mV as shown in Figure 6, inflow fluid produces negative potentials, the fluid outflow results produces positive potentials, which is in agreement with Mizunaga et al (2006), Leonard et al (2011), Teh-Saufia et al (2013.…”

“…A resultant magnetic field is created which encompasses the earth and can be represented as a vector quantity having a unique magnitude and direction at every point on the earth's surface. The earth's magnetic field is not completely stable says by Teh-Saufia et al (2013). Both naturally-occurring and man-made magnetic materials can locally modify the earth's magnetic field as reported by EPA (2016).…”

“…Magnetic method is a passive geophysical technique which measures the strength of the total magnetic field at any given point on the earth; magnetic survey is used in environmental investigations to detect magnetic anomalies variations in the expected field which can be attributed to the presence of buried steel or iron objects as stated by Teh-Saufia et al (2013), Rao & Murthy (1978), Nordiana et al (2014). Magnetic surveys are always used to detect induced magnetism in iron and steel objects such as underground storage tanks (USTs), buried drums, and ferrous landfill refuse, performed as part of environmental investigations; these materials are unique for their ferromagnetic ability to be magnetized said by Nettleton (1973), Nordiana et al (2013).…”