Failure Criteria On High-Strength Concrete And Full Lightweight Shale Ceramsite Concrete Under True Triaxial Compression

In recent years, with the development of society and the needs of special structures,the development of concrete is put forward higher requirements.Lightweight,high-strength concrete has become one of the implementation of the outline of the 2020 Chinese technology development goals. All light shale ceramsite concrete and high strength concrete as a new type of concrete has been widely used.The most of the concrete work is under complex stress state, uniaxial mechanical properties of conventional design can not meet the actual needs of the use of engineering. The main contents of this thesis is three-axis mechanical properties of full lightweight shale ceramsite concrete and high-strength concrete.The experiments of strength rating of LC30, LC40, LC50 shale full light concrete and high-strength concrete C70, C80, C90, and they were mixed with steel fiber steel fiber reinforced concrete were carried out under true triaxial compressive state in proportional loading by the large-scale static and dynamic triaxial testing machine in Dalian University of Technology. The failure modes of samples were observed, and the column failure, layered failure, splitting failure and shear failure of four kinds of typical failure characteristics, while the full lightweight shale ceramsite concrete is still plastic extrusion flow failure characteristics, and the ultimate triaxial strength, plastic strains,peak strains, total strains and stress-strain curves were also recorded.The results show the strength and deformation of full lightweight shale ceramsite concrete and high-strength concrete under triaxial compression are much larger than that of uniaxial ones, full lightweight shale ceramsite concrete has a very apparent "Platform of Plastic Flow(PoPF)" on the stress-strain curve, full lightweight shale ceramsite concrete and high-strength concrete were tested four kinds of failure modes.so the stress and the strain corresponding to PoPF should be design strength and design strain during an engineering design for lightweight aggregate concrete. Also, the effects of intermediate principal stress on strength and deformation are analyzed under triaxial compression,the ultimate stresses were predicted by triaxial strength model, and the absolute values of relative errors are all less than 7%, which prove the test results are accurateand reliable. Finally, the failure criterio of stress and strain are established based on octahedral stress-strain space respectively for different levels of full light intensity Shale concrete and high-strength concrete, the relevances of full lightweight shale ceramsite concrete test points and curves are better to the former, and the tension-compression meridians intersects hydrostatic pressure axis in high-pressure stress area, and the failure surface is closed; the relevances of high-strength concrete test points and curves are better to the former, and the tension-compression meridians without intersects hydrostatic pressure axis in high-pressure stress area, and the failure surface is opened;To explore the concrete strength grade and type of different effect on the failure criteria.