Preliminary slope stability investigation using 2-dimensional geophysical electrical resistivity survey

A geophysical resistivity method was utilized in investigating the subsurface profile for slope stability study at Precinct 9, Putrajaya, Malaysia. Rainfall is a crucial factor that can trigger slope failure. The resistivity distribution of the study area was measured via ABEM SAS 4000 Terrameter. 2-D electrical-imaging resistivity data of the subsurface profile for each survey line were computed through inverse modelling, aided by borehole sampling data. From the inversion, the resistivity models show a variation of 0 to 100000 Om for the 6 survey lines. The low resistivity value ranging from 10 to 300 Om indicates the high water content zone whereas the higher resistivity value ranging from 300 Om to 100000 Om indicates dry zone. Based on the lithology profile from borehole sampling, the bedrock layer is encountered at approximately 10.5 m from the surface with the condition of fresh to highly weathered. The rock quality designation (RQD) shows the value of 0 to 100% that indicates the presence of rock fractures which cause seepage flow. Hence, the zone of high water content indicate by low resistivity value has risk of slope failure that requires remedial measures. To enhance the quality of subsurface characterization, additional tool such as seismic refraction survey should be employed to produce a more comprehensive and reliable results.