The Tensile Mechanism Experimental Research Of Compacted Clay

The crack of soil is one of the most common latent troubles and failure modes in soil structures, so it is of theoretical and practical significance to investigate clay's tensile character. A series of high earth-rockfill dams are under planning and construction, which puts forward numerous technical problems, and the tensile character of clay core the according crack control measures are two most significant ones among others. A new set of displacement-controlled uniaxial tensile apparatus was developed and then the tensile fracture character of compacted clay was measured. The main achievements obtained in the thesis are as follows:(1)A new displacement-controlled uniaxial tensile apparatus was developed to investigate the fracture mechanism of clayey soil. The apparatus, with a better integrity, a higher stability and a stronger axial rigidity compared with the former ones, can measure full tensile softening process of clay sample.(2)Three kinds of clay core material of Nuozhadu high earth-rockfill dam, highly plastic clay, core mixed clay and core gravel mixed clay were selected in this study. A series of experiments on fracture toughness were completed and how clay's fracture toughness varied according to different initial crack length was tested. The results indicate that clay's fracture toughness depend on not only its state parameter but also the initial crack length. So there are limitations on introducing the linear elastic fracture mechanics to analyze clay's tensile character.(3)Based on clay's non-linear fracture mechanics, by choosing the three kinds of clay core material of Nuozhadu high earth-rockfill dam, a series of tensile fracture mechanism tests were performed. How clay's tensile characteristic parameters varied with the clay's component and state parameters was investigated. Some conclusions were drawn from the results: 1. Cyclic test does not influence clay's tensile character. 2. With clay's water content increased, its tensile strength and fracture energy raise and then fall after arriving the peak value, while the strain corresponding to the maximum and the ultimate strain increase continuously. 3. Dry density has a much more crucial influence on clay's tensile character. Clay's fracture toughness, the ultimate strain, tensile strength and the corresponding strain are all diminished when the dry density of clay decreases. 4. Among the three kinds of testing material, the highly plastic clay has the best tensile ability, core mixed clay performs a little worse, while core gravel mixed clay has the weakest tensile ability.