Geoelectrical response of cavities in limestones: an experimental field study from Kurnool District, Andhra Pradesh, India

Abstract

Geoelectrical field studies on cavernous Precambrian limestones of the Cuddapah Basin were conducted on an experimental basis in parts of Kurnool district, Andhra Pradesh, India. The objective was to study the effectiveness of the technique in delineating potential ground-water zones in them. The studies were confined to two sites viz., a bore hole tapping a cavity in Koilkuntla limestones at Illurukothapeta near the township of Banganapalli and over dry and water-filled parts of the Bilum caves in Narji limestones near the village of Kolimiguntla. These represent small- and large-dimension cavities, respectively. The field studies at these sites comprised a number of radial Schlumberger resistivity soundings, Wenner and Lee resistivity profiling, Lee resistivity soundings, buried current source dipole-dipole resistivity mapping, mise-à-la masse potential measurements and self-potential measurements. It was possible to delineate the orientation and lateral extent of the cavity encountered at 13 m depth in the borehole and the western extension of the water filled part of Bilam cave occurring at 35 m depth. Results of radial soundings in demarcating the shallow cavity encountered in borehole and mise-à-la-masse potential measurements for demarcating the extension of the water filled Bilam cave were found significant and useful. Self-potential measurements revealed the direction of ground water flow near the borehole.