Soil frost heave acts as a driver of the emerged fracture in the concrete lining of irrigation canals and subsequent water leakage in seasonal frozen ground. A model test was carried out on the frost heave of a U-shaped canal with concrete lining. The heat and water migration during freezing, and frost heave-induced deformation, and force in normal direction were live monitored by high-precision transducers. The results prove that the freezing front descends downward over time at a specified thermal boundary, with considerable migration of water within the scope of 0–40 cm. The maximum deformation occurred at the bottom of the lining and decreased upward with the rate of frost heave lowering over time while the normal force showing little change in the monitoring points, implying that stress concentration does not show up during freezing. Besides, the layered settlement observation reveals that frost heave dominates the total deformation while creep, the universal source of deformation, accounts for a negligible proportion. A practical model was proposed based on a simple theoretical model for heat-water coupled transfer in a partially saturated medium and was numerically implemented in COMSOL. The computed results were compared with the monitored data including frozen depth, water content, normal displacement, and frost heave force. Finally, the rational thickness of the insulation board was determined based on the partial insulation method.
Wetting-induced collapse of coarse saline soil foundations is a frequently encountered problem in the inland basin of Northwest China, but this particular behavior and relevant treatment have not been given adequate attention. Specimens treated by silicate cement were used in wetting collapse testing at conventional foundation loads, with five cement contents and four curing durations considered. The results indicate that in the case of no curing, the collapsible deformation during wetting declines at higher cement contents, and a stepwise development of deformation was noticed over the wetting duration. Specimens treated by cement after curing exhibit a decrease in the compressive deformation during wetting, and part of them show volume expansion instead. The complex hydrolysis and hydration reaction of cement in the process of curing primarily accounts for this. Moreover, the collapsibility coefficient varies within a narrow range in the noncuring case, proving the limited influence of cement inclusion; however, a gentle range, from 2.0 to 4.0 %, can be found after curing, beyond which it slightly varies. An elastoplastic model was established, incorporating a variable boundary seepage equation, and was then used for modeling a field immersion test. The rationality of the model was verified by comparing the measured and simulated results, including the degree of saturation and vertical displacement. The optimal depth and width for cement treatment was discussed in view of the practical engineering.
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