ABSTRACT
In many geotechnical problems, one of the most common shear strength testing equipment is the direct shear apparatus to study shear strength behaviour of soils. This paper represents features of a new unsaturated direct shear apparatus designed and built in Tarbiat Modares University. The new apparatus enables using axis translation technique to control or measure soil matrix suction. This apparatus includes an air pressure chamber equipped with a shearing box inside. A particular pressure panel has been designed for the control and application of apparatus devices. The apparatus is also equipped with separate horizontal and vertical loading components. Horizontal loading device includes a hi-precision electro servo motor system, while vertical loading device is equipped with a pneumatic jack. A data acquisition system was designed to measure and acquire the variation of test data. Six conventional direct shear tests were then carried out on compacted unsaturated kaolin-sand mixtures. These tests were conducted in constant water content condition in different net normal stresses. The axis translation technique was used to measure or control soil matrix suction.
