Large-scale low-friction geotechnical true tri-axial apparatus and its application

Firstly, an introduction is made to the large-scale geotechnical true tri-axial apparatus developed by Changjiang River Scientific Research Institute. The functions of this apparatus can be described as follows: (1) The true tri-axial tests on coarse grained soil can be carried out steadily. (2) The maximum value of σ₃ is able to achieve 3.0 MPa, while that of σ₁ is able to achieve 15.0 MPa. (3) The specimen size is 300 mm (length)×300 mm (width)×600 mm (height). (4) The loading process can be set arbitrarily, both the stress control and the strain control are available, and loading in three directions is independently, which makes it possible to simulate complex stress paths. (5) The whole process stress-strain curves of coarsely grained soil can be obtained. Through an engineering case, the researches on the mechanical characteristics of coarse grained soil under complex stress conditions are conducted using this apparatus, and the stress-strain rules are obtained at different stress levels. The strength parameters of the specimen in different loading paths are achieved, and a preliminary analysis for the applicability of strength criterion is made. The successful development of the large-scale low-friction true tri-axial apparatus provides a new technical method in studying the strength and deformation of coarse grained soil under high stress levels and complex stress paths.