Study On Wetting Deformation Characteristics Of Low Permeability Gravel Soil Core Wall Material

Earth-rock dam with core wall is a very common dam type in earth-rock dams.Gravel soil is characterized by high strength,low permeability and low compressibility.More and more earth-rock dams with high core wall use gravel soil as core wall material.Whether gravel soil exists wetting or not and how the wetting deformation is related to the space-time evolution law of deformation of high core earth-rock dam.According to the current literature,compared with rockfill,there are few wetting research results of gravel soil core wall material.The test of coarse gravel soil particles should use large-size samples.At the same time,the poor permeability of gravel soil and the difficulty of saturated consolidation and drainage of the samples are the technical bottlenecks for the wetting test of gravel soil core wall materials.Therefore,it is urgent to find a new test technology to explore the wetting deformation characteristics of gravel soil and reveal the influencing factors of the wetting deformation of gravel soil,so as to provide technical support for accurately simulating the deformation of high core earth-rock dam.In this paper,the accelerated drainage patented technology of sand core of Yangtze River Academy of Sciences and the pore-forming sample preparation device are used to realize the rapid wetting test of gravel soil core material under a certain stress state by vacuum pumping saturation method.For 200 m high core earth-rock dam,two groups of complete single-wire large triaxial wetting tests were carried out for gravel soil at Lianghekou under the initial moisture content of 7% and 10%.The sample size was Φ300 mm× 610 mm.Four stress levels of 0.2,0.4,0.6 and 0.8 and a total of 16 wetting tests were carried out under four confining pressures of 0.2MPa,0.4MPa,0.6MPa and0.8MPa for each group.The effects of initial moisture content,confining pressure and stress level on the wetting deformation of gravel soil are studied,the variation law of sample saturation is explored,and the difference of wetting deformation law between gravel soil core material and rockfill material is analyzed.The test results show that the sand core accelerated drainage technology can realize rapid saturation of the sample under pressure without affecting the stress-strainrelationship of the sample.The core material of gravel soil has wetting phenomenon,and the wetting deformation is larger than that of rockfill.Humidification deformation is related to initial moisture content and stress state.The larger the initial moisture content is,the smaller the wetting deformation is.The larger the stress level is,the larger the wetting deformation is.The larger the confining pressure,the smaller the wetting deformation.In the deformation calculation of high core earth-rock dam,the wetting deformation of gravel soil core material should be considered during water storage,and sand core accelerated drainage technology is a new method to realize the wetting deformation research of gravel soil.