Frost Heave of Irrigation Canals in Seasonal Frozen Regions

Jian Xu,Yugui Yang,Qinze Wang,Songhe Wang,Jiulong Ding,Yanfeng Li

doi:10.1155/2019/2367635

Abstract

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.

Highlights

Water resource shortage is a great constraint for the development of economy and society in China, especially for the backbone of the country, viz., agriculture [1]
Even more severe is the threatening frost damage of lining structure under seasonal frost actions [4], as presented in Figure 1. e embedded depth of foundation was generally set below the frozen depth to address this issue, and the work quantity devoted may occupy about one-third of the overall. is may be valid in constructing small-scale water conservancy projects; this kind of antifrost measure is impossible for a large irrigation area by increasing the burial depth in view of the large expense. us, a rational estimation of frost heave in irrigation canals is required to provide guidance for formulating more economic antifrost countermeasures [5]
Two physical processes are included such as water migration and ice segregation [6, 7]. For the former, the ice and water pressure and ice segregating temperature were combined by both capillary model and generalized Clausius– Clapeyron equation, and the changes in ice content, permeability, and deformation were incorporated in constructing frost heave theory [8, 9]. e ice content was indirectly obtained by the variation of unfrozen water content with temperature that can be determined by nuclear magnetic resonance (NMR), differential scanning clorimetry (DSC), and time-domain reflectometry (TDR) and can be empirically derived from simple functions [10]

Summary

Introduction

Water resource shortage is a great constraint for the development of economy and society in China, especially for the backbone of the country, viz., agriculture [1]. Two physical processes are included such as water migration and ice segregation [6, 7] For the former, the ice and water pressure and ice segregating temperature were combined by both capillary model and generalized Clausius– Clapeyron equation, and the changes in ice content, permeability, and deformation were incorporated in constructing frost heave theory [8, 9]. To reveal the mechanism of frost heave in canal lining, this paper carries out a model test on a large U-shaped irrigation canal with concrete lining structure. e coupled heat and water migration and frost heave-induced deformation and force in the normal direction are investigated based on the monitored data. en, based on the assumption of frost heave in soil originated from the phase transition of both migrated and original water into ice and in situ water into ice, a practical frost heave model is constructed with a simple equation for coupled heat and water migration. e model is numerically implemented in the COMSOL platform, and the rational thickness of the insulation board is discussed based on the partial insulation method

Model Test on Frost Heave of a U-Shaped Irrigation Canal in Loess Stratum

Findings

Governing Equations