General geology mapping and geophysical survey for slope mitigation at Peria Kuala Krai, Kelantan

Slope survey has given high attention and this problem can also be solved using geophysical methods. A site investigation survey is done using geo-electrical resistivity and seismic refraction methods. The study area for geological mapping is located in Kuala Krai, Kelantan. The area is bounded by lines of longitude 102° 12'47 .1" to 102o15 '37.5" E and latitude lines to 05°24'0" to 05°26'36 .0" N. A cut slope in longitude lines 102°15 '5.6" E and latitude 05° 25'58 .3 "N has been selected as a research area. The objectives of the research are to produce geological map of Peria, Kuala Krai, Kelantan, to analyze slope stability by using geo-electrical resistivity and seismic refraction method, to detect for slope potential to failure and recommend some structures for slope reinforcement. The geo-electrical resistivity method of this study is the characterization of multi-electrode according to Wenner method using 41 electrodes to a current into the surface. A total of 41 electrodes were used to inject the electrical current and measure potential difference that exists between the electrodes. TERRAMETER equipment ABEM SAS System 1000 and ES464 electrodes system is used. The survey conducted with spacing between electrodes is 5 meters. Therefore, the maximum depth of data up to 30 m enables to gain beneath the lithology. For seismic method the data for each profile 7 readings for range -5 to 115 meters is taken. This method can show the thickness of the top soil, residual soil, weathered rock profile to bedrock. Geo-electrical resistivity method and seismic methods are used to identify areas of potential slope failure. The both method is taken 3 profiles data profiling. Preliminary findings from the data obtained shows that there is the potential for failure. Geo-electrical resistivity survey generally shown that the top layer consists of residual soil and weathered granite has resistivity between 285 a.m to 3235 am while granite rock resistivity range is 4900 fl.m to 13 786 a.m. For water saturated zone has a range from 57.8 a.m to below 200 0.m. It proved by resistivity value which there is water saturated zone around the slope study area. For seismic refraction method, the results obtained shows 3 layers. The area near this slope is unstable for long term. This is due to the position of a cut slope in study area are not installed any wall or retaining wall, which occur very clearly erosion in slope selected for investigation by using both of geophysical methods.