Experimental Study On Internal Force And Deformation Of Slope Frame-anchor Support Structure In Freezingthawing Loess Area

In the existing slope engineering application,due to the advantages of reasonable stress,high economic benefit and convenient construction of the slope frame anchor supporting structure.In recent years,it has been well developed and applied.It is a new type of flexible support structure,but the existing theoretical research on slope frame anchor support in the freeze-thaw environment lags behind the actual project,resulting in safety accidents after the slope is unstable And personal safety.At the same time,the theoretical design calculation does not consider the influence of the soil body on the internal force and displacement of the support system after freeze-thaw damage.Therefore,this paper analyzes and researches the problems mentioned above through indoor tests,SEM scanning,theoretical calculations,and field tests.The main achievements are summarized as follows:(1)Through the indoor freeze-thaw test and the triaxial shear test(UU),the variation law of the shear strength index of the frozen-thawed undisturbed loess under different water content,different temperature gradients and different freeze-thaw cycles was studied.The effects of temperature gradient and water content on the strength of freeze-thaw loess are analyzed.At the same time,the most unfavorable moisture content value and the most unfavorable freeze-thaw temperature gradient value are obtained.(2)Define the damage variables of cohesion,porosity and elastic modulus of freeze-thaw loess under the most unfavorable moisture content and the most unfavorable freeze-thaw temperature gradient through a combination of laboratory test and micro test.The damage evolution equation is obtained by fitting the three damage variables,and the comparative analysis is carried out.It is more appropriate to select the damage variable defined by porosity.On the premise of Winkler's internal force calculation model,an internal force calculation method considering the damage of freeze-thaw loess was established.It is consistent with the field test results of slope under natural freezing and thawing environment.The combination of damage internal force calculation method and field test can further demonstrate the rationality,reliability and correctness of the consideration of soil freezing and thawing damage variables in the internal force calculation of slope frame anchor support structure.(3)By formulating the slope test plan under natural freeze-thaw conditions,the relationship between the axial force and the length and time of the anchor rod and the axial force of the concrete frame beam stress steel bar with time and length are obtained.The bending moment of the beam and the distribution of the stressed steel bars were studied,and the actual internal force and deformation changes of the slope frame anchor supporting structure under natural freezing and thawing conditions were analyzed.The internal force calculation results of the anchors are compared with each other,and the reasons for the difference between the two methods are analyzed,which further explains the feasibility and correctness of the damage calculation method,thus guiding the engineering practice.