Structural improvement of the construction joint of the cut and cover tunnels

Abstract

Yamatogawa route of Hanshin expressway is an urban tunnel route consisted of cut and cover tunnels. After the recovery of the underground water, many water leakages have been seen at many structural joint of the tunnel. Thermal expansion of the structural joint, resulted by the seasonal thermal fluctuations and direct solar radiation, is considered as the cause of the water leakages. Water leakages will be resulted in bad influences on the durability of the tunnel and also safe driving of cars running through this tunnel. Therefore, installation of adequate structural joint to accommodate thermal expansion at the joint is necessary to prevent water leakage. In order to study the amount of thermal expansion at the structural joint, field measurement of temperature, structural expansion of the joint, and dependency on the over burden depth and the interval of structural joints were investigated. As the result of the investigation, the average 6 mm seasonal expansion was observed at the structural joint with standard interval length of structural joint. Under the from 1 m to 4 m overburden depth, average 5 mm seasonal expansion was also observed. It was based on the special quality of the used material of waterproofing system and the structure by keeping these in mind, and the leaking cause was presumed. The outline which considered new waterproof structure will be reported without changing the present specification substantially.