Geotechnical description of sandy sediments of the surf zone using electrical resistivity measurements

Abstract

The geotechnical description of sandy sediments of the surf zone was done in two ways: directly, through standard geotechnical testing proposed by ASTM (American Society for Testing and Materials) and indirectly, through electrical resistivity measurements. The geotechnical property chosen for the description of the sediment was porosity, due to its influence in a wide range of soil properties. The indirect estimate of porosity through resistivity measurements was based on Archie’s equation. However, the difficulty in generalizing this equation is the empirical determination of the cementation exponent (m). For this reason, the values proposed by other authors were tested. A comparison of the porosity values obtained by the two methods (directly and indirectly using different values for cementation exponent) showed that it is not advisable to use cementation exponent (m) from other authors indiscriminately. Moreover, the application of the porosity values obtained by the ASTM tests allowed calculating a more suitable cementation exponent value for sandy sediments of the surf zone (between 1.48 and 1.79). Besides porosity, other geotechnical parameters, such as void ratio (e) and total density (pt), were also differentiated by measuring the electrical resistivity of selected samples allowing to describe the geotechnical state of the sediment with higher confidence.