Mechanism Study And Numerical Simulation Of Tensile Crack Propagation In High

Tensile crack is a common hidden trouble and one of the main causes of destruction of earth-rockfill dams, so it is a threat to the safety of dams and a key issue desiderated to be solved. Therefore, studying the tensile property and failure mechanism of compacted clay under triaxial tension condition has great significance to the safety evaluation of earth-rockfill dams. In this thesis, based on the previous research works, the stress-strain behavior and failure mechanism of compacted clay under triaxial tension condition were investigated, then a three-dimensional meshless numerical simulation method of tensile crack of compacted clay was proposed. The main achievements obtained in the thesis are as follows:1. A horizontal triaxial tension-compression apparatus for soil was developed. This apparatus adopts strain-controlling loading mode, and can be used to obtain the procedural stress-displacement curve up to tensile failure of compacted clay under triaxial condition due to its large axial rigidity. This apparatus also can be used to carry out conventional triaxial test, triaxial tensile test and triaxial compression-tension combining test.2. A series of triaxial tensile tests, conventional triaxial tests, and triaxial compression-tension combining tests on core clay materials of Nuozhadu and Shuangjiangkou high earth-rockfill dams were performed. The stress-strain behavior and tensile failure properties of compacted clay under triaxial tension and compression-tension combining condition were investigated. Based on the test results, a tension-compression uniform joint strength criterion of compacted clay was proposed, and Duncan-Chang's EB constitutive model was extended to describe the deformation properties of compacted clay under compression, reversed loading and tension conditions.3. The calculating formulas for three-dimensional point interpolation meshless method were derived comprehensively, then a coupling approach of radial point interpolation meshless method and finite element method was proposed. By combining Biot's consolidation theory and the proposed coupling approach, a three-dimensional effective stress-strain computing program system was developed.4. The smeared crack model based on meshless method was proposed. By smearing crack into nodal influence domain of meshless method and considering the anisotropy of compacted clay during tensile fracture process, the computing mode of smeared crack theory based on meshless method was established, and the three-dimensional brittle fracture and blunt crack band meshless model were derived.5. By embedding the above research achievements in existing FEM computing program system, a three-dimensional computing program system was developed, which can be used to stress-deformation and tensile crack analysis of earth-rockfill dams. The transverse tensile crack and hydraulic fracturing crack problems in Shuangjiangkou high earth-rockfill dam were simulated and analyzed under three-dimensional condition, then the transverse tensile crack and hydraulic fracturing crack was analyzed and evaluated.