Resistivity Monitoring for Assessing Cement Grouting Effect

It would be important to investigate the actual grouting performance and to examine whether the original purpose of the grouting work would be achieved. Geophysical imaging technique has a high potential in the evaluation of the grouting effect as a non-destructive and cost-effective way. In order to study the applicability of resistivity monitoring technique to the assessment of cement grouting effect, we carried out DC resistivity monitoring before, during and after grouting work conducted for the reinforcement of weak ground. In accordance with the field monitoring, we also monitored the resistivity change of cement mortar specimens in a laboratory. The laboratory monitoring results clearly showed that electrical prospecting methods are good to locate the cement grouted zone. The field monitoring data were inverted by the four-dimensional (4-D) inversion algorithm and difference images were reconstructed. Owing to the 4-D inversion algorithm, we could more easily and clearly identify the decrease of resistivity in the region where the grout material was injected and infiltrated. Through the monitoring experiments at a field site as well as in a laboratory, we were able to know that DC resistivity monitoring technique is an effective way for evaluating the cement grouting performance.