The strength of the warm frozen soil is the key to the design of buildings and structures in the permafrost region, laying the basis for the safe operation and stability evaluation in the later stage of building/structure projects. In this paper, the frozen red silty clay is collected from Wudaoliang section of Qinghai-Tibet Highway, and prepared into samples for direct shear experiments. During the experiments, the direct shear properties of the samples were observed under different densities, normal stresses, water contents, temperatures, etc. The results show that, with the growing density, the cohesion of the frozen silty clay continues to increase, while the internal friction angle decreases first and then increases; with the growth in water content, the cohesion and internal friction angle show the same trends, but the angle increment is small; with the increase in normal stress, the internal friction angle exhibits a declining trend; the shear strength of the frozen soil has a linear relationship with temperature. Through theoretical analysis, the author established an expression for the relationship between shear strength and temperature of warm frozen soil at 0~-2℃, and confirmed that the shear stress-strain relationship of the frozen silty clay belongs to the strain hardening type, which obeys the hyperbolic model proposed by Clough and Duncan. The research findings lay a solid basis for the building/structure design in permafrost regions.

The cutting mud refers to the wastewater produced in the fabrication of ceramsite aerated concrete (CAC) blocks. To reduce the production and environmental impacts of these wastes, this paper puts forward a reuse plan that partially replaces the fly ash in CAC fabrication with the cutting mud. The dried powders in the mud of different concentrations were selected to replace an equivalent amount or a fewer amount of fly ash. The difference between the amount of dried powder and that of the fly ash being replaced was defined as the conversion coefficients. Then, the CACs fabricated under the equivalent replacement and under the converted replacement were compared in fluidity, compressive strength and dry density. The comparison shows that the CAC prepared when the cutting mud concentration is below 22% and the conversion coefficient is between 0.75 and 0.85 satisfies the production and quality requirements. Therefore, the wastewater produced in CAC fabrication can be treated effectively by replacing the fly ash with cutting mud. The replacement can reduce the harm and quantity of hazardous wastes, making them more recyclable.

A self-made pressure control device was developed to study the migration characteristics of chloride in concrete under pressure. The effects of water pressure, pressurized time, strength grade, water-binder ratio, chloride diffusion coefficient, saturation degree and solution concentration on chloride migration are determined. Considering with pressure, the theoretical model of velocity varies with time and position is established. The formula of water permeation depth is obtained. On this basis, the chloride migration model under the coupling of pressure permeation and diffusion is established, and compared with the chloride concentration obtained from the experiment.