STUDY OF THE SOIL-WATER CHARACTERISTIC CURVE (SWCC) FOR WETTING AT LOW MATRIC SUCTION VALUES FOR COMPACTED SHATTERED CLAY SHALE IN THE CISOMANG AREA

• Main Author: Putri Kabila, Merizka
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/84150
• Institution: Institut Teknologi Bandung

The Soil-Water Characteristic Curve (SWCC) is a graph that shows the relationship between the soil water content and variations in soil matric suction. SWCC plays an important role in the practical implementation of unsaturated soil mechanics in geotechnical engineering and is a preliminary step in understanding soil behavior. The Soil-Water Characteristic Curve is closely related to three domains of soil mechanics analysis: shear strength, volume change, and permeability function. These three aspects are essential components used in soil mechanics analysis. SWCC has two different initial soil conditions, namely drying SWCC and wetting SWCC. Soil or rock material that has potential to undergo volume changes due to variations in water content is also known as expansive soil. This type of soil can cause damage to structures built on it. Expansive soils are widespread in Indonesia, with one distribution area located along the Jakarta-Bandung toll road project passing through the Cisomang area. According to the regional geological map of the Cianjur Sheet, the rocks in the Cisomang area are clay shale. Cisomang clay shale is classified as expansive soil. Problems with the soil in this area are caused by the presence of clay shale formations and the occurrence of wetting. To understand the mechanisms of this issue, quantification in unsaturated-saturated soil mechanics is necessary. Changes in water content influenced by climatic factors can be observed from the Soil-Water Characteristic Curve (SWCC) data. The measurement of SWCC is conducted using the filter paper method, which requires different equilibration times for each type of soil due to the influence of soil permeability. ASTM D5298-16 recommends a minimum equilibration time of seven days. However, this recommendation may not be suitable for clay shale with specific soil moisture content, thus this research is needed to determine the appropriate equilibration time for compacted shattered clay shale. In laboratory testing, the equilibration times obtained for soil moisture contents of 15%, 20%, 25%, 28%, and 30% were 7, 14, 14, 21, and 21 days, respectively. The laboratory measurement results were then used as data to update the fitting curve using the Fredlund and Xing (1994) equation. The resulting drying SWC parameters are: (1) a = 20000; m = 3.7; n = 0.9 in gravimetric water content, (2) a = 20000; m = 3.6; n = 1 in volumetric water content, (3) a = 40000; n = 1.4; m = 4.1 in degree of saturation. Subsequently, a parametric study was conducted using SEEP/W to verify the laboratory test results and to obtain equilibration times for water contents of 15%, 20%, 25%, 28%, and 30%, which were 11, 13, 13, 15, and 17 days, respectively. The results obtained from the numerical modeling were close to the laboratory test data. .