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The excessive fluorine content in ash-sluicing water has become one of the main environmental pollution problems in the thermal power generation industry. This study selected 5 representative soil types and used fluoride ions (F-) as the pollution control factor. The experimental results showed that the isotherms of the F- solutions prepared by deionized water (adsorbed by Jianbi clay and Fengrun sandy soil) and ash-sluicing water all conformed to the Langmuir isothermal adsorption equation. In terms of the F- solution prepared with ash-sluicing water, the adsorption isotherm of Tianshengqiao red clay conformed to the Langmuir isothermal adsorption equation; the adsorption isotherms of Beijing silty soil and Fen River loess conformed to the Henry isothermal adsorption equation. In terms of the maximum adsorption capacity, Tianshengqiao red clay > Jianbi clay > Beijing silty soil ? Fen River loess > Fengrun sandy soil. Through the experiments, we also found that the adsorption capacity decreased with increasing pH, and the pH buffering effects of the 5 soils, from high to low, were Tianshengqiao red clay > Jianbi clay > Beijing silty soil > Fen River loess > Fengrun sandy soil.

Gradation has an important influence on the mechanical properties of earth and stone materials after compaction, and a reasonable gradation is the key to ensure compaction quality. In this paper, a set of earth and stone materials gradation detection system based on digital image processing was proposed, which was suitable for detection in the construction sites. The system obtained images which were taken from multiple directions of materials transport vehicle, used the thresholding method to segment the images, detected particle contours through edge detection algorithm of Canny to realize the image recognition of particle size, and drew the gradation curve of earth and rock materials finally. It was verified by selecting limestone aggregates of different gradations, and the results showed high accuracy. The system can realize on-site detection of the earthwork gradation rapidly and accurately at a dam construction site.

A GCTS medium-sized triaxial apparatus is used to conduct a single-line method wetting test on three kinds of rockfill materials of different mother rocks such as mixture of sandstone and slate, and dolomite and granite, and the test stress conditions is the combination of spherical stress p and deviatoric stress q. The test results show that (1) for wetting shear strain, the effects of spherical stress p and deviatoric stress q are equivalent, and wetting shear strain and deviatoric stress q show the power function relationship preferably. (2) For wetting volumetric strain, the effect of deviatoric stress q can be neglected because it is extremely insignificant, and spherical stress p is the main influencing factor and shows the power function relationship preferably. (3) The wetting strains decrease significantly with the increase in initial water content and sample density generally, but the excessively high dry density will increase the wetting deformation. Also, the wetting strains will decrease with the increase in the saturated uniaxial compressive strength and average softening coefficient of the mother rock. Based on the test results, a wetting strain model is proposed for rockfill materials. The verification results indicate that the model satisfactorily reflects the development law of wetting deformation.

The in-situ material engineering parameters of Changheba dam, the highest ECRD built on thick overburden in China, is studied through FE analysis. The nonlinear model proposed by Duncan is selected to simulate the stress-strain relationship of soil and rockfill materials. The dependence of the permeability coefficient of clayey material on the void ratio is considered. FE analysis based on laboratory tested parameters is performed. Meanwhile, parameters back analysis is conducted based on monitored deformation and pore pressure at the end of construction. The analyzed results show that the in-situ parameters of some dam material are quite different from in-lab tested parameters. The in-situ modulus and friction angle of blast rockfill material is smaller than in-lab tested values. The difference might be caused by scaling effect of particle size and depends on scaling ratio between in-lab samples and in-situ material. The overburden might have a higher in-situ modulus than laboratory tested samples, which might due to the in-situ long-term stress history and scaling effect. Both high pore pressure and small settlement is observed in the core wall. It is shown by back analysis results that the gravelly clay core may have lower in-situ permeability and relatively higher stiffness. The stress path in in-situ gravelly clay core is different from which in in-lab triaxial test might be an important cause.

Numerous methods for identifying dispersive clays have been proposed: the pinhole test, the double hydrometer test, the crumb test, the sodium adsorption ratio test, the percentage of the exchangeable sodium cation test, and a number of different auxiliary tests. However, the results of these methods have been in some cases inconsistent. Therefore, in this study, identification tests and conventional laboratory index tests for 34 cohesive soil samples collected from 10 domestic and foreign engineering projects completed by the China Institute of Water Resources and Hydropower Research over the last 20 years were analyzed and compared. The results showed that the dispersive grade of clay was not directly related to the gradation, specific gravity, liquid limit, or plasticity index but was closely related to the soil pH value. Moreover, the pinhole test was not suitable for identifying the dispersion of soil with a low clay content or high expansion.