Experimental Studies of Suction-Monitored Direct Shear Apparatus on Perth Poorly Graded Sand

Perth, Western Australia is a semi arid climate area. A soil characteristic at a near surface layer is relatively dry due to the deep water table, low humidity and high rate of evaporation. Subsurface exploration carried out in this study indicated that most soils in Perth are classified as poorly graded sand and remain dry along the year. Therefore, most Perth soils are considered to be in an unsaturated condition. The aim of this study is to evaluate the unsaturated Perth soil properties. Conventional and modified direct shear apparatuses were utilized in the shear strength evaluation of the saturated and unsaturated Perth soils. Modification of the direct shear apparatus was conducted by attaching a low capacity tensiometer to the direct shear top cap to measure the matric suction of the soil samples. The results indicate that during shear, suction is relatively low for a range of saturation degree of 50 to 100% and well within the tensiometer capacity, indicating that the modified direct shear apparatus is suitable for measuring the unsaturated poorly graded Perth sand

Cavitation in high-capacity tensiometers:effect of water reservoir surface roughness

High-capacity tensiometers (HCTs) are sensors made to measure negative pore water pressure (suction) directly. In this paper, a new approach is proposed to expand the range and duration of suction measurements for a newly designed HCT. A new technique is employed to reduce significantly the roughness of the diaphragm’s surface on the water reservoir side in order to minimise the possibility of gas nuclei development and the subsequent early cavitation at the water–diaphragm interface. The procedures employed for the design, fabrication, saturation and calibration of the new tensiometers are explained in detail. Furthermore, the performance of the developed HCTs is examined based on a series of experiments carried out on a number of unsaturated clay specimens. An improvement in maximum sustainable suction in the range of 120–150% of their nominal capacity was obtained from different surface treatment methods. Moreover, the results show an improvement of up to 177% for the long-term stability of measurements, compared to the developed ordinary HCTs with untreated diaphragms

Studies of rainfall-induced landslides in Thailand and Singapore

Unsaturated Soils: Advances in Geo-Engineering - Proceedings of the 1st European Conference on Unsaturated Soils, E-UNSAT 2008901-90