Experimental Study On Conditions Inducing Expanding And Self-healing Of Core Cracks In Earth Rock-fill Dam

The problem of the expansion and self-healing of core cracks in earth dam is a important and difficult problem in dam design. Investigating the problem is very useful to improve the designing theory of the earth rock-fill dam. Under the financial support of the Key Project of Chinese Ministry of Education under Grant No. 208114, this study focuses on the conditions inducing expanding and self-healing of the core cracks in the earth rock-fill dam by experimental studying. The mainly works and conclusions of the paper are as following:(1) The conditions of hydraulic fracturing include physical and mechanical .The former is the upstream of core existing cracks and the earth material's low permeability in core, which is usually to be possessed; The latter is forming the strong "water wedge" role after the reservoir water runs into the cracks. Due to the forming of the water wedge's role needs rapidly retaining water,and hydraulic fracturing usually easily happens in the first time of retaining water in the reservoir. if soil is saturated or the stable seepage has been formed, the possibility of hydraulic fracturing phenomenon is low.(2) Based on the test method and principle, we develop a set of experimental instruments which is suitable to study on the phenomenon of the core cracks's self-healing, at the same time we put forward the test method that display core cracks changes through the seepage flow.(3) Through the test datas and the phenomenon of 39 groups, from the core cracks'environment, we analyse the conditions which self-healing happens, called material condition and force condition. The material conditions are the core exists cracks, resists high strength flush and filter layer combined closely with thick soil granule; force condition needs higher water pressure to flush the core crack.(4) Through the test result and related theory, we can know the small sectional, the cracks which start on the upstream face but not throughout the core, near or equal to the moisture content of the optimal moisture content, suitable dry density of core materials, bigger proportion of materials particles, bigger dry density of inverted filler and the collocation of soil particles belong to limit state can improve the self-healing ability.(5) According to conditions of self-healing and analyze the influnced factors, we proclaim the mechanism of the self-healing from the external factor and internal factor. The mechanism mainly includes two sides, one is the soil grains'resedimentation can fill the crack, the other is the expansion of soil grain can cause the crack width reduced even closure.