LAUSR

The shear strength parameters of the soil is the key engineering property required for the design of geotechnical structures and stability analysis. The shear strength of an unsaturated soil is controlled by matric suction. This research examined the effect of matric suction on the shear strength behavior of sandy clay using a series of experimental tests in the laboratory. The contact filter paper method was used to measure matric suction and the SoilVision knowledge-based system was used to give an approximation of the entire soil water characteristic curve (SWCC). The shear strength of the unsaturated sandy clay was examined using a series of unconsolidated undrained (UU) triaxial tests to identify the relationship between shear strength, cohesion, internal friction angle, and matric suction. The result shows that the shear strength of the soil increases as matric suction increases. It was found that when the matric suction is smaller than air entry value (AEV), the shear strength of the soil increases as matric suction increases and the increment is linear because the soil is in saturated conditions. At a certain matric suction value (on soil samples occurred at 40-600 kPa matric suction values), there is a significant increase in the shear strength of soil associated with the inter-particle force produced due to negative pore water pressure. Furthermore, at a high matric suction, the relationship between shear strength and matric suction tend to be stable as in a low water content, the matric suction is not transmitted effectively to the contact point of soil particles.