Mechanical model analysis of lining frost-heave failure in cold region considering frost-jacking

Shallow groundwater or narrow-deep lined canals have suffered the vertical frost heave at the top of the canal in cold regions. The lining fracture and whole uplift frost damage are also prone to occur, leading to the low stability of the canal at low temperature. However, the existing engineering models of canal frost heave have focused only on the normal one of the canal slope. This study aims to consider the combined effect of vertical frost heave on the top of the canal and normal frost heave on the slope. A mechanical engineering model was established to consider the canal frost heave. Sensitive soil was selected to simulate the moisture-heat-mechanical coupling numerical models in the canal. The frost heave was then used under different dip angles of the slope, width-to-depth ratios, and groundwater levels. The maximum tensile stress was calculated to locate the different freezing depths and dip angles of the slope during frost-jacking. The specific mechanism of canal lining was then explored to clarify the distribution of vertical and normal frost heave during frost-jacking. The internal force of canal lining plate and frost-jacking strength of canal slope were evaluated to calculate the critical slope length, critical groundwater level, and dangerous location of frost-jacking failure. Finally, the engineering mechanics model was proposed to test the actual case. The experimental data was in agreement with the field observation. The results show that the freezing counterforce was failed to offset the upper tangential frost-jacking force, particularly for the lower lining with the short slope length. The lining was also suffered from the jacking disease as a whole. Otherwise, a frost-jacking force was formed inside the lining. The greater the freezing depth and the dip angles of the slope were, the larger the area of the lining bearing the upward tangential force was, and the greater the frost-jacking tensile stress was. The position of the maximum tensile stress caused by jacking was shifted to the lower part of the canal with the increase of freezing depth and inclination angle of the canal slope. The maximum tensile stress was negatively related to the groundwater level. The critical water level of the lining was the critical groundwater level of the original ground frost heave. At the same time, the frost heave of the original ground was a necessary and insufficient condition for the canal to produce the frost pull. The numerical fitting indicated that the minimum curvature radius of the frost depth line at the top of the canal increased with the increase of frost depth and dip angles of the slope. The depth of frost shared a linear relationship with the minimum curvature radius. The dip angles of the slope exhibited a greater impact on the fitting slope. The maximum error of tensile stress was verified by the numerical model to be 1.5%. The frost-jacking position error was within 16.01%. Therefore, the slope range of the freezing line radius function was 1.047 to 4.040 in the soil conditions of the Ningxia irrigation area. There were the overall uplift pattern of small canal and the cracking failure pattern of large canal linings. The damage mechanism was then clarified to prevent and control the anti-frost heave of canal lining. The finding can also provide a strong reference for engineering design and code revision.