Laboratory Soil Test

At present, various means of geotechnical tests have seen development. The test equipments and methods for the physical and mechanical properties have been matured gradually. The triaxial testing (not only general triaxial testing, but also the true triaxial tests and the triaxial testing of stress paths, KO consolidation, unsaturated soil, etc) have become the major equipments of the mechanical properties testing. The model test, on the other hand, has been developed into various forms of model, like Static Model, Dynamic Model, and Percolation Model Centrifugal Model and so on. Of course, in order to develop soil mechanics faster, we must also develop experimental techniques to meet the demand of the new era.

Strain localization of gabbro was studied using Photo elastic Coating Method by Zheng J (1983). The study of composite materials conducted by Berthaud achieved good results. In the early 1950s, with the development of test apparatus, the general triaxial test apparatus provide a favourable environment tool. The forced state of general triaxial test apparatus is clearer than direct shear test. Because of the axi-symmetric stress state, the development and evolution of strain localization in many kinds of stressful conditions could be tested by this apparatus. In the part of triaxial testing, it generally needs to use the precise microscopic instruments, like the scanning electron microscope and the CT equipment to well observe the process of localized deformation.

Soil mechanics is one of the highly experimental subjects. It will not be developed without the experimental test. On the other hand, if there is no theory as the guide, the soil test will be meaningless. The two are complementary. Some test equipments and test methods were put forward under the guidance of the theory. The triaxial shear test, for example, was developed under the guidance of the Mohr-Coulomb strength theory; some theories are on the basis of the existing test equipments and methods. The Duncan-Chang hyperbolic model, for instance, was developed by means of stress strain curve by triaxial apparatus. The developing of geotechnical testing technology must be combined with the developing of the soil mechanics theories.