Research on adaptability of using molded bagged concrete to ameliorate heave in trapezoidal concrete channel

Abstract: Concrete channel could heave and even fail in winter under the combined impact of frozen-thawing, temperature fluctuation and mechanical stresses. Understanding the mechanisms underlying the failure of lining structure of the concrete channel is hence important. Taking trapezoidal concrete channel as an example, a numerical model was developed in this paper based on heat-moisture-stress theory, capillary force and water flow in soil to calculate the impact of these factors on concrete channel. In the model, the temporal change in temperature on the channel surface was treated as the top boundary and the groundwater table as the bottom boundary where the temperature remains stable. The multifield coupling software COMSOL was used to simulate potential occurrence of heaves in soil induced by frost. We simulated a 67-day heaving process induced by frost in the foundation soil and obtained the final heave simultaneously by solving the partial differential equations in COMSOL. Based on the results, the finite element software ABAQUS was used to simulate the nonlinear mechanical behavior of the contacts between the concrete lining and the soil, as well as the contacts between the molded bag concrete and the soil using different contact models. The stress and displacement at different location on the contacts were calculated using the ABAQUS. The result showed that: 1) the frost-induced heave varied spatially in the channel. The worst occurred at the center of the channel bottom and on the 1/3 the slope length (measured from the slope tip), and the least was on the top of the channel. 2) If the failure criterion was defined as when the concrete lining reached its plastic stage, the maximum non-uniform heave calculated by the ABAQUS was 2.98 cm for the traditional concrete lining. 3) Compared with traditional concrete lining, the molded bag concrete substantially reduced the force between the lining and the soil. This changed the mechanical behavior of their contact, thereby effectively reducing the stress on the molded bag concrete lining. The maximum stress on the top surface of the molded bag concrete lining was only 1/250 that in the traditional concrete lining, effectively improving its adaptability to uneven frost heave in seasonal frozen soil. The simulation results are in good agreement with experimental data and have implications for designing trapezoidal channels in seasonal frozen regions.