Mechanical model and validation of frost heave damage of precast concrete slab lining trapezoidal canal in open system

Abstract: The precast concrete slab lining trapezoidal canal is widely applied in cold regions of northern China, but the calculation method of frost heaving force distribution and the mechanics model of frost heaving damage under high groundwater level conditions have not yet been set up. Due to similar weather condition and soil texture in the specific region, the strength capacity of groundwater supply on each point of the concrete lining slab becomes the decisive factor of the strength of frost heaving on each point. Through Winkler assumption for mechanic characteristics of soil, the strength of frost heaving on each point of the concrete lining slab is only related to the capacity of water supply on the corresponding point; according to the functional relations between frost heaving force, frost heaving strength and groundwater depth, the article proposed a method to calculate the frost heaving force distribution on the concrete lining slab. By applying the idea to a type of precast concrete slab lining trapezoidal channel whose precast concrete slab size was moderate, a mechanics model of frost heaving damage in open system was established. The article divided precast concrete slab lining canal into 2 types. One had large precast concrete slabs, and as caulking material was cement mortar with weak bond strength, the integrality of the type was worse; the other had moderate precast concrete slab size and caulking material was usually flexible material with strong bond strength such as polyurethane, plastic waterproof ointment, so the integrality of the type was excellent and it was the main research object of this article. With the preceding model the distribution of axial-tension, shear force and moment in the canal slope lining plate can be calculated, respectively. Combining mechanical analysis with engineering practices, the manifestations and the reasons of frost heaving damage of precast concrete slab lining trapezoidal channel were classified as axial-crack, shear failure and bending rupture of joints between precast concrete slabs. According to different forms and reasons of frost heaving damage, the controlled sections for checking the possibility of frost heaving damage were confirmed, and the corresponding judge rules were proposed. The method to check normal displacement caused by frost heaving on joints between precast concrete slabs was put forward based on the unit-load method. The calculation method and the mechanics model discussed in the article were based on different groundwater supply intensity of different point on canal lining, so it had great commonality, and it could calculate the distribution of frost heaving force on concrete lining canal with different types of cross-section. Finally, an engineering example was carried out, and the results showed that the model was reasonable and reliable and can serve as reference and theoretical basis for engineering designs.