Unconfined compressive strength (UCS) and tensile strength are two important geomaterialparameters that are used for performance prediction and design criteria. Both UCS and tensilestrength are affected by moisture content and thus the characterization of their dependence onmoisture content is of paramount importance.The unified effective stress theory proposed by Lu and Likos based on the suction stressenables the characterization of soils under both saturated and unsaturated conditions with oneclosed-form equation. This theory was verified by triaxial and shear test results for relativelyhigh moisture contents and, therefore, low suction levels (typically more than -700 kPa).Using two types of soils, the current study presented in this paper provides experimentalverification of this effective stress theory via indirect tensile (IDT) and UCS tests, both of whichare widely used in pavement engineering. The verification is extended in this study to lowmoisture contents ranging from 2.56% to 18.9% and high matric suction levels ranging from 600kPa to 16,000 kPa, which are the typical ranges for the base, sub-base, and subgrade layers inpavements. A new method is proposed to predict a soil's UCS and tensile strength at specifiedmoisture contents by taking simple soil water characteristic curve (SWCC) measurements andconducting UCS and IDT tests at two unsaturated moisture contents, which is experimentallyvalidated in this paper. On the other side, the IDT strength and UCS at a few different moisturecontents can be used to obtain the parameters α and n of SWCCs to avoid time-consumingSWCC measurements.
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