Specialized triaxial equipment and laboratory procedures

The material properties as well as stress-strain behaviour of engineering materials including soil and rock are very useful for the design of various engineering structures on the surface and underground. For geological materials such as soil and rocks, there is a high demand for laboratory testing techniques. In order to provide meaningful data from laboratory testing, the apparatus must be truly capable of simulating existing insitu field conditions, including the stress-strain behaviour and permeability characteristics. For this purpose, various types of triaxial apparatus have been developed during the past 5–5 decades ( Handin, 1953 ; Anderson & Simons, 1960 ; Hoek & Franklin, 1968 ; Hambly & Reik, 1969 ; Dusseault, 1981 ; Smart, 1995 ; Indraratna & Haque, 1999). Triaxial apparatus may be classified depending on the (a) capacity of the triaxial cell (i.e. high-pressure, or low-pressure), (b) loading system (i.e. plain strain, quasi-static stress, polyaxial stress) and (c) use of single-phase flow or multiphase flows ( Table 2.1 and Fig. 2.1 ).