Analysis On Coupling Model Of Permafrost Slope Supported By Frame Structure With Anchors

Figuring out the freezing and thawing process of frozen soil slope is the key to the prevention and control of frozen soil slope failure. The freezing and thawing process of frozen soil slope is a comprehensive problem considering the interactions of temperature, moisture and stress. In order to prevent the slope failure effectively,we need to take full account of the heat-moisture-stress coupling effects, and then support for permafrost slope.In order to study the working mechanism of frame supporting structure with anchors in permafrost region, the calculation model of frozen soil slope with frame anchors is established, which has considered heat-moisture-stress coupling,supporting structure and soil coupling and the coordinate effect among frame anchors and soil. Regarding the frozen soil as plane elastic body, ice latent heat in the soil is considered by using apparent heat capacity method, the variation of parameters over time is considered by using ice impedance factor, and the basic equations of moisture, temperature and stress of the frozen soil are given. Regarding the anchors as bar element, the frame as beam element, the coupling of frame anchors and soil mass is considered by using combined type, the equilibrium equation of the coordinate effect among frame, anchors and soil is derived, and the multi field coupling model of the soil slope is established.The analytical solutions are obtained by using the finite element method, based on the platform of MATLAB software, the program is written and verified with the existing experimental research. Through analysis of examples, the distribution law of temperature, moisture and stress of slope and freeze-thaw reaction of the supporting structure is given, and it is shown that:(1) The top of the slope is greatly influenced by temperature, the moisture content of the active layer is close to saturation when thawing, and the supersaturated "bubble" appears at the bottom;(2)The maximum value of shear stress during freezing is two times of that of thawing,the distribution of which is even and the slope is stable. The shear stress mutation occurred in the active layer and stable permafrost layer interface during thawing when the slope is unstable, and the interface is the potential slip surface;(3) In a freeze-thaw cycle, the horizontal displacement increases first and then decreases and it increases with the increase of slope height, the relationship of the horizontal displacement under three conditions is that freezing > melting > initial;(4) In aperiod, the anchor force first increases and then decreases, and it increases with slope height increases, axial force increment is the largest at the front of the bolt of each layer and decreases gradually along the bolt length direction, the internal force increment of column is larger and gradually decreases along the downward slope, the anchor force and column internal force decreases significantly when thawing. The analysis results show that: when frozen soil slope is supported by frame and anchor,the supporting structure should be designed and calculated according to frost condition.