Full-scale test of Direct-buried Cable in Sand under Repetitive Loading

Abstract

Direct-buried cable construction can minimize cumbersome processes, thereby decreasing construction time and cost. However, there is no regulation on burial depth that consider the long-term performance of backfilling soil for direct-buried cables. This study examines the mechanical response of direct-buried cables subjected to repetitive loads. This experimental study uses a full-scale chamber to replicate field construction. The stress on the cable, vertical displacement on the surface, and shear wave velocity between loading plate and cable are continuously monitored during 10,000 repetitive loading cycles. A miniature electrical cone is used to indirectly quantify the initial relative compaction. Repetitive loading densifies the soil around the cable, increasing stress on the cable and accumulating vertical strain. The trends are more pronounced with lower initial relative compaction. The shear wave velocity increases during repetitive loading, suggesting a change in the earth pressure coefficient. Applied stress – vertical strain allows the estimation of resilient modulus. These observations will provide a better understanding of the mechanical response of backfilling soil. Additionally, the uniaxial compression test of the underground power cable made for direct burial is conducted to measure the displacement of the cable insulator under the field condition obtained from the full-scale test. Then mechanical stability of the cable is investigated based on the axial displacement of the cable insulator.