Vertical Electrical Sounding for Geotechnical Site Characterization

Background

The site borehole information demonstrates that the sediments are sitting on the top of Ignimbrite and there is also fractured Ignimbrite weathered with the content of clay is located at the bottom. 

Purpose

The study was made to determine the sedimentary thicknesses as well as to obtain the contact between high resistivity values associated to Ignimbrite and low-resistivity values associated with Ignimbrite fractured and weathered with the content of clays. 

Process

The determination of resistivity was performed by Schlumberger vertical electrical sounding method with 4 electrode manual cables. The twenty-one manual measurements performed starting from AB/2=1m and extending up to AB/2=120m. SuperSting™ WiFi R8/IP/SP/Wi-Fi, manual cables (VES), using Schlumberger array. The data Processing with EarthImager™ 1D software.

Results

Five layers were interpreted in this study. The sedimentary thickness up to Ignimbrite layer has been interpreted of approximately 6 meters. The high resistivity values found in the fourth layer with 300 Ohm-m have been associated with the Ignimbrite and the low-resistivity values in the fifth layer associated with Ignimbrite fractured and weathered with the content of clays. This contact has been estimated approximately at 28 meters depth. Ancient boreholes made in the area of study corroborate the interpreted lithology. 

Products Used

• SuperSting™ R8
• Long Manual Cable set
• EarthImager™ 1D software