New triaxial device for unsaturated soils with local measurements

A new triaxial device is proposed to perform a complete local monitoring of the state of an unsaturated soil sample during triaxial testing by the use of local measurement devices comprising the measurement of local displacements (Hall Effect transducers), water content (new resistivity probe) and suction (High capacity transducer). Two triaxial tests were carried out on loess specimens (from 3.3 m in depth) from Northern France with this device at low stresses in the range of in-situ stresses. This soil is characterized by its sensitivity to collapse and a metastable structure. The in-situ stress state was reproduced by mean of a K-0 stress path (keeping lateral strain to zero). Results showed good quality and provided some preliminary behavior characteristics of a natural unsaturated loess, a type of material rarely tested up to now in the literature. They also showed the device quality and reliability.