흡입응력 개념을 적용한 불포화 모래사면의 안정 해석

Abstract

In this study, a stability analysis of unsaturated sand slope existing water table is conducted considering suction stress concept. It is assumed that slope is composed of sand with the range of relative densities 40%, 60%, and 75%, respectively. The analysis considers the ground water level located at depth of 5m below the ground surface, and variation of suction stress, moisture content and matric suction above the water table under steady infiltration rate conditions. To analyze the stability of unsaturated sand slope, the Soil Water Characteristics Curve (SWCC) of the sand with the range of relative densities 40%, 60%, and 75% were measured using the automated SWCC apparatus. Based on the SWCC, the Suction Stress Characteristics Curve (SSCC) and the Hydraulic Conductivity Function (HCF) were estimated by van Genuchten (1980)'s SWCC fitting parameters both drying and wetting processes. The stability analysis of unsaturated sand slopes was carried out under no infiltration and steady infiltration rate conditions using these experimental results.

As the results of stability analysis, under no infiltration condition, the factor of safety is increased at the zone between 0 to 0.4m above the water table due to effect of suction stress. However, under infiltration rate conditions, the factor of safety is increased at the all depths in slope due to effect of suction stress. Of course, as infiltration rate approaches the value of the saturated hydraulic conductivity, the stability of sand slopes are decreased due to decreasing suction stress. However, slopes are maintained in a more stable states under steady infiltration rate conditions than no infiltration condition. It is confirmed that the unsaturated sand is reached to pendular state at the relatively small matric suction range, and suction stress does not occurred at all depths in slope under no infiltration.