In order to screen the good proportions of concrete under freeze-thaw environment, cement heat of hydration tests and uniaxial compression tests of concrete after freeze-thaw are carried out under different conditions to investigate the effects of admixture and water-cement ratio on the structural properties of concrete, to determine the good proportions of concrete in cold areas, and to establish the stress-strain prediction curve of the whole process after freeze-thaw. The results show that: (1) The total heat of hydration decreases with increasing mineral admixture content. However, a small dosage of silica fume can enhance early-age heat release. The reactivity of the materials at early ages follows the order: cement > silica fume > fly ash; (2) A small amount of fly ash and silica fume admixture into concrete can play the microaggregate and volcanic ash effect, improve the concrete compactness, and strengthen the structural frost resistance and mechanical properties; (3) Low admixture (0~10%) silica fume incorporation is beneficial to structural frost resistance, fly ash (0~20%) incorporation leads to first increase and then decrease in structural frost resistance, so there is an optimum value of fly ash incorporation, water-cement ratio leads to significant decrease in structural frost resistance, 15% fly ash—10% silica fume—0.36 water-cement ratio is an excellent concrete ratio applicable to cold regions; (4) The prediction curve of compressive stress-strain of concrete after freeze-thaw is proposed, which can be applied to the nonlinear analysis of concrete in cold regions.

The clay shock method is gradually introduced as auxiliary construction in the shield tunnel that crosses the existing structures. The rheological properties of the clay shock slurry have an important influence on the backfilling injection construction of mid-shield. The hydration mechanism and rheological properties of the slurry are investigated based on the analysis of the material composition of the clay shock slurry. The RVDV-1T rotational viscometer with stepless speed regulation was used to carry out the rheological test. The applicability of the commonly used shear-thinning rheological model to characterize the rheological properties of the clay shock slurries was studied. The effects of stirring time, stirring rate, hydration time, and water-powder ratio on the rheological properties of the clay shock slurries were analyzed. The permeability and diffusion of the clay slurry in the stratum were investigated based on the actual project. The research results are as follows. (1) The Bingham model is more suitable for characterizing the rheological properties of the clay shock slurries. (2) The apparent viscosity and yield stress of clay shock slurry initially increase and then decrease with increasing stirring time and stirring rate. They also increase with increasing hydration time and decrease with increasing water-powder ratio of component A. (3) The soil in the infiltration zone is affected by the injection of the clay slurry, resulting in cohesive effect and an increase in strength. (4) The penetration diffusion distance of the slurry in the sand and round gravel strata is between 5 and 10 cm. The apparent viscosity and the yield stress of the slurry have a strong negative correlation with the diffusion distance. The permeability coefficient and the porosity of the stratum correlate positively with the diffusion distance. The research results provide reference for the engineering application of the clay shock method.