Study On Horizontal Frost Heaving Force Of Overwintering Pit In Seasonal Frozen Soil Regions

In seasonal frozen soil area the overwintering foundation pit exchange heat with the outside world for two-way cooling, which is different from the conventional natural ground on energy exchange, and it result in that the horizontal frost heaving force mechanism and distribution law of the lateral wall in foundation pit is different. The paper first analyzes the influence factors of the horizontal frost heaving force in overwintering foundation pit, and by using the more extreme physical field coupling finite element analysis software COMSOL Multiphysics, the changing law of foundation pit horizontal frost heaving force is analyzed under different conditions, such as the different extreme negative temperature (-4℃,-6℃,-10℃,-15℃), the different heat transfer coefficient (1.8W/(m·K),2.0W/(m·K)>2.3W/(m-K)), the supporting stiffness (the supporting pile material is selected as C20, C30and C50respectively), foundation pit depth (6m,10m), the initial moisture content (15%,20%,30%), hydrating (open or closed); Finally, the corresponding engineering measures are put forward. Through the research of the content above, some innovative research conclusions are put forward as follow:1. When the extreme temperature is-4℃,-6℃,-10℃,-15℃, freezing depth of foundation pit were1.52m,2.04m,2.75m,3.85m respectively; Corresponding to the greatest frost heaving force are:235.4kPa,259.5kPa,287.1kPa,305.9kPa,they appear in the upper depth of foundation pit, and is almost the same with frozen depth; The lower the extreme temperature is, the greater the frozen depth and the horizontal frost heaving force is.2. The heat transfer coefficient of the side wall of foundation pit has significantly effect on frozen soil depth. When the heat transfer coefficient is1.8W/(m·K),2.0W/(m·K),2.3W/(m·K), the frozen depth is1.48m,2.04m,2.8m, the maximum horizontal frost heaving force is:259.5kPa,288.5kPa,296.8kParespectively. The greater the heat transfer coefficient is, the greater the frozen depth and the horizontal frost heaving force is.3. The initial moisture content has less effect on the frozen depth of the foundation pit, when the moisture content were15%,20%and30%, the frozen depth is2.34m,2.04m,1.95m respectively; the maximum horizontal frost heaving force is:238.4kPa,259.5kPa,280.8kPa; They appear in the upper depth of foundation pit, and is almost the same with frozen depth; The greater the moisture content is, the more shallow the frozen depth become and the greater the horizontal frost heaving force is.4. The supporting stifness will mainly have no effect on the frozen depth. Under three different supporting stiffness conditions of C20and C30, C50, the frozen depth is always on about2m at temperature of-6℃; In the initial state, the horizontal frost heaving force is large, which is76.9kPa,173.5kPa,189.2kPa; The maximum horizontal frost heaving force is259.5kPa,291.5kPa,303.5kPa, which is appeared in the upper depth of the foundation pit, and is almost the same with frozen depth. The larger the rigidity is, the greater the horizontal frost heaving force is.5. When the different excavation depth of foundation pit is6m and10m, the maximum horizontal frost heaving force are259.5kPa,287.8kPa, which is appeared in the upper depth of the foundation pit, and is almost the same with frozen depth.6. The conditions of closed or open have significantly effect on horizontal frost heaving force. When there is water supply, the horizontal frost heaving force become bigger. The maximum horizontal frost heaving force is259.5kPa,512.9kPa respectively.Finally, according to the various factors effects of the horizontal frost heaving force of the wintering foundation pit of, the measures are proposed to eliminate or weaken the horizontal frost heaving force, such as drainage, water proof, heat preservation and so on.