Experimental Study On The Mechanical Behavior Of Dam Concrete Under Triaxial Stress States

Concrete is a widely used building materials because of its outstanding advantages, such as its local high-availability and excellent durability. When used in ordinary civil engineering, its strength can be made good use of because concrete is mostly under simple stress state in these circumstances. However, for mass concrete hydraulic structures, like gravity dams and ocean platforms, concrete usually works under complex stress state which is very different from concrete under uniaxial stress state. Up to now, researchers home and abroad have performed substantial investigations on mechanical properties of concrete under multiaxial stress state. Nevertheless, less research is devoted to dam concrete, especially when concrete is subjected to triaxial tension or tension-compression-compression. With Xiluodu Dam project as support background, the study here focuses on the strength and deformation of wet-screened two graded concrete under triaxial stress state. The major contributions are summarized as follows:(1) A new test method of double steel plate-plastic brush hybrid connection has been developed to impose tension stress on the specimens’surface. The test results indicate that the new method can improve the test precision by a uniform stress transmission and vanish of end restriction conditions of the specimens.(2) Experiments have been conducted on wet-screened two-graded aggregate dam concrete under compression-compression-compression、tension-compression-compression、 tension-tension-tension stress states.25test procedures according to various stress ratios were performed with one geometrical size100mm×100mm×100mm. The strength of concrete under traixal stress state has been increased several times compared to concrete under uniaxial stress state. While for concrete under tension-compression-compression, the strength has been reduced due to the presence of tension stress. Furthermore, the strength for concrete under triaxial tension, little change has been found.(3) A failure criterion for wet-screened two-graded aggregate dam concrete in the octahedron stress space has been proposed using Ottosen and five-parameter failure criterion expression, which can be used as theoretical reference for dam concrete design. With some parameters adjusted in the failure criterion presented, stress-strain curves could be predicted where the nonlinear orthotropic material constitutive model is used.