Geotechnical Site Characterization on a Cliff for a Dam Construction

High Contact Resistance Survey

Background

There are many cracks, joints, fractures and karstic spaces on the measurement surface of Limestone.

Purpose

The main subject of this study is for searching karstic features and voids within the body of local limestone for dam construction. 

Process

The determination of resistivity was performed by geoelectric exploration method with total 28 electrodes at 6m electrode spacing by our client belirti. These 28 electrodes are mounted on the drilled holes on the cliff by using bentonite solutions. Automatic measurements were taken with dipole-dipole, Wenner and Shlumberger arrays, and the measure data sets are combined for joint inversion by EarthImager 2D

Results

The contact resistance on the study area was varying between 20kOhm to 240kOhm during the measurements. Such high contact resistances result in low current injection between 1mA to 44mA. In spite of  low current  injection, the measured voltage signal strength was good between 0,11mV to 3210m with high resolution SuperSting R8The joint inversion result shows about 8%RMS error and L2=0.95. The high resistive areas demonstrate possible void areas and low resistive areas shows fractured areas on the vertical profile in the limestone outcrop

Benefits

  • Ease of use: It’s convenient to use AGI tools on extreme topography.

  • Specially designed tools: These rugged instruments are useful for work in all kinds of terrain and topograpy

  • Joint Inversion: It’s convenient to improve inversion results for noisy data sets on such high contact resitance areas.

Products Used