DRAINED SHEAR STRENGTH OF COMPACTED KHON KAEN LOESS
Keywords:Unsaturated Soil, Compacted Soil, Khon Kaen Loess, Consolidated Drained Triaxial Test, Soil Water Characteristic Curve
The objective of this study was to determine the relationship between drained shear strength
and matric suction of compacted Khon Kaen loess. Khon Kaen loess in this study was compacted at 95% by
modified method. This soil sample was investigated a soil water characteristic curve (SWCC) from the
pressure plate test. Moreover the relationship between drained shear strength and matric suction was
determined from the consolidated drained triaxial test (CD Test) under saturated and unsaturated condition.
Three saturated specimens were tested to determine an effective friction angle (φ´) and an effective cohesion
(c´). Another three unsaturated specimens were tested with various matric suction of 30, 180 and 280 kPa,
respectively. The net confining pressures of these specimens were constant at 100 kPa. To determined
drained shear strength at unsaturated condition, an effective friction angle (φ´) was assumed to be constant
with a matric suction value. The SWCC of compacted Khon Kaen loess showed a bimodal curve. The first
air-entry value and the first residual volumetric moisture content was 4 kPa and 20%, respectively. The
results of saturated consolidated drained triaxial test (CD Test) presented that an effective friction angle (φ´)
and an effective cohesion (c´) was 31 degree and 54 kPa, respectively. Moreover the unsaturated triaxial test
showed a linear relationship between drained shear strength and matric suction with the φb angle of 28 degree.