Performance of filter gabion with pipe as a simple countermeasure against slope failures due to torrential rainfalls

Abstract

Sediment disasters become more serious and most of the sediment disasters of the natural slopes are due to shallow surface failures. The surface layers normally consist of sand or sandy soils. In order to clarify the mechanism of the surface failures, we have conducted a series of model tests. It was found from the model tests as the rainwaters were accumulated at the toes of the slopes, they triggered slope failures. It is important to drain promptly the accumulated rainwaters from the surface layers in order to prevent the large surface failures. Filter gabions with pipes placed at the toes of the slopes were introduced. The objective of this paper is to evaluate the performance of the filter gabions with pipes to prevent surface failure. The investigations were conducted by using the saturated and unsaturated consolidation analysis method with an elastoplastic model considering two suction effects. At first, the consolidation analysis method was verified by simulating slope model experimental tests with and without filter gabions. The analyses of the slope models with filter gabions having drainage pipes installed were then performed. Four cases with different pipe lengths were analyzed. More reductions of pore water pressures (PWPs) were observed as the pipe lengths increased. In the case with the longest pipe installed, the failure prevention performance was the largest.