Experimental Research On Influencing Factors Of Consolidation And Failure Of Clay Core In Earth-rock Fill Dam

The hydraulic fracture is one of the most concerned and disputed issues in earth-rock filled dams. The hydraulic fracture of earth-rock filled dam will usually cause catastrophic results. In this context, starting with the consolidation deformation of core wall in earth-rock filled dams, the influence factors of core wall deformation was studied. Based on the Darcy’s Law and the van Genuchten’s model, an experimental and numerical united determination method for predicting the relative hydraulic conductivity of unsaturated soils was put forward. A failure mechanism experiment of clay core with cracks was designed to simulate the hydraulic fracture of impervious bodies and it demonstrated the possibility of failure for clay core walls. The main achievements in this thesis are listed as follows:1. By the designed one-way consolidation test, the influence of load and drainage condition on consolidation deformation of saturated remolded soils was analyzed. As the load raised, the consolidation time increased and under the same load condition, the consolidation deformation of soil samples which cannot strain were smaller than that which can drain freely. The time for unsaturated soil mass reaching stable was longer than that for consolidation deformation reaching stable. The loss of pore water was influenced significantly by the environment temperature and insignificantly by the load.2. Based on the generalized Darcy’s Law and the van Genuchten’s model, and through simple evaporation experiment and numerical analysis, the relative hydraulic conductivity of unsaturated soils could be obtained. Compared the numerical results with the observed experimental data, this method was showed to have certain reliability. Experimental data and numerical simulation was combined in this method and it had certain innovation in the aspects of Finite Element Method back analysis of model parameters. The experiment apparatus in this method was simple and cheap, and it had promotion value in the scientific research and production.3. By the designed failure mechanism experiment of the clay core with cracks, the influence of different kinds of factors on clay core walls was explored. The experiment results shown that the size of initial cracks in the clay core had great effect on hydraulic fracture. The initial crack would be closed when its size was small while it may become the pathways for hydraulic impact when its size was big and then led to the failure because of the invalid of impervious bodies. The blinding had great significance on whether soil samples can happen hydraulic fracture. In most cases, under high hydraulic pressure, soil particles can be washed away through chinks in the blinding, which made cracks further expanded and led the soil samples to happen hydraulic fracture failure finally. However, in other cases, inverted filters at the outside of impervious bodies can play a good role in seepage. The void ratio can influence the hydraulic pressure value needed for the happen of failure.