경사고임대 지지체의 수동저항에 관한 연구

Abstract

Raker method is used when strut or ground anchor is difficult to apply, and when the depth of excavation is shallow. However, current design standards of the raker method lack criteria for evaluation of the earth pressure acting on the kicker block, so it is not always safe during construction. In other words, there is no proper applicable standard for evaluation of passive earth pressure. Therefore, geotechnical designers have a different view on the design of the raker system to evaluate the passive pressure of the Kicker block. For this reason, some raker system adopted in the filed becomes unstable due to large displacement which often causes catastrophic disaster.

Earth pressure theory is plastic equilibrium state theory. The active earth pressure is the earth pressure when the soil is in plastic state due to decrease of horizontal force of soil. On the other hand, the passive earth pressure is the earth pressure when the soil is in plastic state because of the increase horizontal force of soil. Passive displacement which induces the passive earth pressure is larger than the active displacement. Therefore, it is unreasonable to apply the calculated passive earth pressure fully on the kicker block regarding stability evaluation.

The results of the review on the current design standards show that 50% or 100% of the passive earth pressure has been applied to stability evaluation of the kicker block. In the relation between passive displacement and active displacement, it is reasonable to reduce the passive earth pressure on the kicker block to 1/2. In addition, if the soil has cohesion, applying c=0 to stability evaluation is a conservative assumption on active earth pressure for the safety aspect.