True Triaxial Apparatus With Rigid-Flexible-Flexible Boundary and Remolded Loess Testing

Abstract

Abstract Several kinds of true triaxial apparatuses have been devised and applied to obtaining the strength and deformability behavior of soils under different stress paths. However, for these true triaxial apparatuses with flexible loading boundaries boundary interference is still not solved. This paper presents a new type of true triaxial apparatus, with rigid-flexible-flexible boundaries, which addresses the boundary interference using four division strip-platens. This apparatus applies three principal stresses on a 70-mm cuboidal specimen from two rigid platens along the vertical direction and four hydraulic rubber bags around four side faces of the cuboidal specimen. The rigid platens and hydraulic rubber bags were assembled in a true triaxial chamber and driven by three servo-hydraulic cylinders. Four division strip-platens are installed along the lateral edges of the confining side wall of the chamber to separate adjacent rubber hydraulic bags and can adjust themselves to accommodate dimensional changes in the deforming specimen. Therefore, this apparatus does not only allow independent control of stresses applied in three dimensions to a cuboidal specimen but also resolve the boundary interferences. The effectiveness of this apparatus was confirmed by tests on remolded loess under five stress paths with the intermediate principal stress parameter b = 0, 0.25, 0.5, 0.75, and 1. The test results show that the stress–strain relationship, volume strain, and failure strength of remolded loess depend on the stress path.