Determination of failure mechanism of very soft clay behind L-pile wall with physical model tests

Abstract

This paper presents physical model tests to verify the failure mechanism of soil behind the gap of contiguous L-pile retaining wall used to support the excavation in soft clay. The ratio of pile gap to pile width (Sg /B) of 0.1, 0.3, 0.5, 0.7, 1.2, 1.6, 2.0, and 3.0 was used. The undisturbed soft clay samples were obtained from an open cut in Samutprakarn province. The physical model tests were conducted in the vanity of the soil sampling area to avoid the effect of sample disturbance. The pressures were applied to the physical model using screw jack until the failure of soil between the L-piles was observed. The digital photos of soil movement were recorded during the test to monitor the failure mechanism. The test results show that the normalized failure pressures reduce as the gap width ratio (Sg /B) increases. The failure pressure of L-pile is lower than that of circular pile proposed by Winit [9] due to soil arching size. The failure arches are clearly observed in the model with Sg /B of 0.1–1.2, but not with Sg /B of 1.6–3.0.