Geol. Soc. Malaysia, Bulletin 44, July 2000; pp. 75-82
Geology Department, FSFG
Universiti Kebangsaan Malaysia
43600 Bangi, Selangor D.E.
Abstract: Seismic reflection and geoelectrical resistivity imaging techniques were employed to investigate the shallow features of buried karstic limestone of Kinta Valley limestone formation because the sinkholes and cavities are quite common in this formation. The techniques were conducted along three traverse lines to evaluate the subsurface ground conditions for construction work of the school teacher’s quarters blocks. The site is located at Pengkalan, Pegoh in Ipoh district of Perak. The limestone bedrock topography has complex phenomena and highly relief subsurface topography due to the presence of karstic features. These features rise considerable difficulties in both the design and construction of the foundations, such as: foundation stability, settlement, and subsidence during the construction in this site. These geotechnical problems arise whenever foundations are established on the surface of the limestone bedrock or within the overburden soils.
The common depth point (CDP) shallow seismic reflection sections of the traverse lines show clearly the displacement system within the bedrock and the poor reflection data. This displacement system is usually associated with sinkholes or slow subsidence in the site caused by chemical dissolution. The poor reflection data qualities in the CDP sections were interpreted as voids of cavity zone. The Two dimensional resistivity inverse models of the traverse lines are showing the low resistivity anomalies. These anomalies are interpreted to represent swallow holes and determine the location of cavities zone.
Interpretation based on the combination of seismic reflection and electrical resistivity imaging survey has been a successful and satisfactory way to identify the location of the surface depression and subsurface conditions.