RESEARCH OF WETTING SOIL WATER CHARACTERISTIC CURVE (SWCC) ON HIGH MATRIC SUCTION VALUE FOR CRUSHED COMPACTED CLAY SHALE IN THE CISOMANG REGION

• Main Author: Atika Hasya, Cut
• Format: Theses
• Language: Indonesia
• Subjects: Teknik sipil
• Online Access: https://digilib.itb.ac.id/gdl/view/68093
• Institution: Institut Teknologi Bandung

Clay shale is a problematic soil composed of various clay minerals and has large expansive properties, when there is a change in water content. This raises many geotechnical problems in the planning design. However, the properties of clay shale in an unsaturated condition can be predicted using a soil water characteristic curve (SWCC). SWCC has two different initial soil conditions, namely drying SWCC and wetting SWCC which will form hysteresis. Therefore, measurements of SWCC were carried out with dry soil initial conditions to obtain wetting SWCC with high matric suction, which means it has low water content (3%, 6%, and 9%). SWCC measurements were carried out using the filter paper method, which required different equilibration times for each soil type because it was influenced by soil permeability. ASTM D5298-16 has recommended a minimum equilibration time of seven days. However, this recommendation is not necessarily suitable for clay shale with a certain soil water content. Hence this research is needed to ensure an appropriate equilibration time for crushed compacted clay shale. In laboratory testing, the equilibration time for water content of 3%, 6% and 9% was 15, 15, and 21 days, respectively. Numerical modeling was carried out to verify the results on laboratory tests and obtain equilibration times for water content of 3%, 6%, and 9%, which were 12, 15, and 20 days, respectively. The results obtained from numerical modeling are close to laboratory test data. Wetting SWCC can be expressed in terms of gravimetric water content, volumetric water content, and degree of saturation. To obtain SWCC in volumetric water content and degree of saturation, it is necessary to calculate the total volume of soil by measuring soil development to obtain a swelling curve. These measurements obtained regression values for the void ratio (e) and w.Gs and formed wetting SWCC with high matric suction for low water content with fitting curve parameters for three parameters, SWCC in gravimetric water content parameters, it was obtained: a = 1000; m = 0.8; n = 0.7, SWCC in the volumetric content parameter, it was obtained: a = 1000; m = 0.7; n = 0.6 dan SWCC in the degree of saturation parameter, it was obtained: a = 100,000; m = 1.6; n = 2.00. The permeability function is obtained indirectly when the matric suction is 0.01 kPa to 629198.08 kPa, the permeability coefficient is 1.74E-19 m/sec with the fitting parameter value a = 25; b = 1.5 and c = 5.00.