Behavior and control of cable duct in proximity to ground excavation work

Large-scale open-cut ground excavation work was performed in the central part of the City of Hiroshima. This report summarizes the behavior and control results of an NTT cable duct located in close proximity to the work site. It was found that the work had large effects on the cable duct such as a cavity displacement of 3 to 7 mm, an inclination of 0.20 to 0.23 degree toward the excavation side, and occurrence of cracks of lining concrete. However, by comparing the measured values with the analysis values obtained by a preliminary study on the cable duct stress, the stress was estimated to be no higher than the allowable stress, and it was verified that no structural problems were caused. Also, the danger of damage to the cables caused by the peeling-off of concrete was eliminated by taking protective measures for the cables.