Improvement Of The New True Triaxial Apparatus And Mechanical Characteristic Analysis Of Saturated Sand

Soil true triaxial apparatus is an important special test equipment testing soil mechanics characteristics under complex stress conditions. Xi'an University of Technology has independently developed a new true triaxial apparatus with a special structure pressure chamber. Therefore, it has important theoretical significance to solve the existing problems, and apply to the experiment research of different soils under controlling conditions of experimental research.Firstly, according to the drainage controlling condition in the new true triaxial apparatus, sand specimen molding, hydraulic leak-proof bag of small and intermediate principal stress, and the effects of the sample size, this thesis improve the structure of the true triaxial specimen pressure chamber. Then, on the bases of the preparation methods of sand, two different size samples of saturated sand are tented in different stress paths through true triaxial apparatus.Such results are achieved:1) The problems of sealing leaks of saturated sample, drainage controlling difficultly, and sand sample molded difficultly are solved by improving the structure of the true triaxial specimen pressure chamber. Then the experiment of cubic saturated sand samples, in carried under the drainage conditions during consolidation and shear process by the improving true triaxial apparatus.2) The new true triaxial pressure chamber of the cubic (70mm×70mm×140mm) specimen are made of steel. The sample size and shape can be controlled effectively.3) The stress-strain relationship, shear volume change characteristics and strength characteristics are examined and analyzed by taking drainage shear tests of cubic specimens of satuated sand under different consolidation confining pressure, and different stress paths.4) The experiment results as follows:①The stress-strain curves change from hardening type to softening type with the intermediate principal stress ratio increasing under the same consolidation confining pressure.②The stress-strain curves transform from the softening type into hardening one with the consolidation confining pressure increasing under the same intermediate principal stress ratio. Under different consolidation confining pressure the strength curves on theπplane shape of failure surface are similar and close to Matsuoka-Nakai criterion. 5) Comparing the experiment results between the two kinds of size samples of saturated sand, it indicates that the stress-strain curves are basically semblable under different stress paths, the shape of strength curves on theπplane is also basically similar. However, the strength of the former is slightly higher than the latter.