Studies On Shear Strength And Deformation Characteristics Of Rockfill During Weathering

The long-term evolution of rockfill deformation is one of the key issues that draw great attention of engineers and researchers. The long-term deformation of rockfill has relationship with not only loading, but also with environment factors, including wetting-drying cycle, cooling-heating cycle and so on. This thesis aims to investigate the mechanical characteristics of loaded rockfill during weathering. The development of a new test device, experimental observations, physical interpretations, constitutive model, and numerical implementation as well as practical application are presented. The main achievements obtained in the thesis are as follows.1. A new device called weathering test apparatus for rockfill is developed to investigate the deformation and shear strength characteristics of rockfill under the coupling action of drying-wetting cycle, cooling-heating cycle and vertical loading. The apparatus include vertical loading unit, horizontal shearing unit, drying-wetting cycle unit and cooling-heating cycle unit.2. A series of weathering tests including block weathering tests, drying-wetting cycle test, cooling-heating cycle tests and wetting-cooling- drying-heating cycles tests were performed by using argillaceous siltstone rockfill. By analyzing the block weathering phenomena and weathering velocity of argillaceous siltstone rockfill under various environmental factors, the weathering characteristics of particle breakage were investigated.3. Based on the weathering test results on argillaceous siltstone rockfill, the deformation characteristics and mechanism caused by various environmental factors were investigated. On the base of the wetting-cooling-drying-heating cycles tests results, the degrading deformation law was investigated and a nonlinear constitutive model and an elasto-plastic constitutive model were developed to calculate the degrading strain of rockfill.4. Based on the wetting-cooling-drying-heating cycles tests on argillaceous siltstone rockfill, direct shear, re-direct shear and triaxial tests were performed. The shear strength characteristics and mechanism in weathering test were investigated. It was found that the change of the shear strength primarily rest with the actions of rockfill compaction and particle degradation.5. The finite element formulations of the present models were derived and incorporated into the FEM codes. They were applied to the evaluation of practical engineering problems.