Study On Load Transfer Characteristics Of Anchor Based On Interface Shear Between Frozen Soil And Cement Mortar

With the strengthening of national economic construction in cold regions,a large number of slopes have been encountered in engineering construction in permafrost regions.As an important means of slope support,anchor is also widely used in frozen soil slope.The physical and mechanical properties of soil in cold regions will change with the change of climate and other factors,which has a significant influence on the pull-out performance and safe use of anchors in the permafrost.At present,under the condition of temperature and moisture content changing,the bearing capacity and deformation response of anchor rod has not yet had a complete research,this paper according to the change of the soil temperature and moisture content designed an indoor experiment,and confirming the change law of mechanics parameters in the contact surface between anchor and frozen soil.On this basis,the nonlinear differential equation of load transfer in anchor’s anchorage section was deduced,the mechanical model of anchor transfer was established,then the bearing capacity and deformation response of anchor under different temperature and water content were analyzed.The influence of temperature field of anchor-frozen soil system in different periods was calculated by ABAQUS finite element software.First of all,in view of the problem of the mechanical parameters change law in the contact surface between anchor and frozen soil,the shear test of the interface was designed.By setting the initial water content of different gradient and freezing temperature on the samples,the change law of mechanical parameters in the contact surface between cement mortar and frozen soil with the initial water content and temperature of the soil was obtained.The results show that with the decrease of temperature,the cohesion of the interface gradually increases to a certain value and then remains stable,and the internal friction angle increases with the decrease of temperature,and the cohesion and internal friction angle of the contact interface first increase and then decrease with the increase of water content,and there was a critical water content,in which the interface shear strength reached the maximum.Under a small load,the stress-displacement relationship is close to a straight line.With the increase of shear stress,the stress-displacement relationship develops into a curve,and the velocity decreases continuously.When the shear stress increases to a certain value,the shear displacement increases sharply.Secondly,assuming that the shear stress and shear displacement of the anchor are hyperbolic nonlinear,the nonlinear differential equation of load transfer in the anchorage section of the anchor that considering temperature and water content was derived,and the differential equation was solved by finite difference method.Based on answers to analysis the stress distribution characteristics,the results show that the uplift bearing capacity of the anchor rod increasing with the temperature’ decrease,and anchor anchors’ axial force and shear stress distribution will also be influenced by temperature,the lower the temperature was,the shear stress more concentrated in the anchor’s tensioning ending,and the faster the anchor’s axial force damping.With the increase of moisture content,the pattern of manifestation of the uplift bearing capacity of the anchor is increasing fist and then reduce.Finally,the transient temperature field considering phase change latent heat is established by ABAQUS numerical simulation software,and the obtained temperature field is input into the bearing capacity analysis model as a field variable to establish the sequential thermal mechanical coupling model of the anchor soil system,and the stress deformation and bearing capacity of the anchor soil system in four periods of freezing period,melting period,maximum temperature and minimum temperature are analyzed respectively,The results show that the shear strain and displacement of the soil around the anchor are affected by the temperature,and the lower the temperature is,the smaller the deformation is.In the melting period,the soil has the widest range of displacement,which is due to the largest thickness of the melting layer in the melting period.In the early stage of drawing,the thawed soil deforms first,and in the later stage,the deformation is caused by the upward movement of the frozen soil in the lower part.The ultimate bearing capacity of the anchor in the lowest temperature period and freezing period is much higher than that in the highest temperature period and melting period;The axial force distribution of the anchor shows strong nonlinearity.Finally,the transient temperature field that considering the latent heat of phase change was established by ABAQUS numerical simulation software,and the sequential thermodynamic coupling model of the anchor-frozen soil system was established,which was consistent with the results verified by theoretical method.Finally,the deformation under stress and bearing capacity of the anchor-frozen soil system in the four periods of freezing period,thawing period,the highest temperature and the lowest temperature were respectively analyzed.The results show that the shear strain and displacement of the soil around the anchor under the drawing load were affected by the temperature,and the lower the temperature,the smaller the deformation.The soil in thawing period has the widest range of displacement,because the thickness of thawing layer in thawing period is the largest.The thawing soil deforms first in the early stage of drawing,and the deformation is caused by the upward movement of the lower permafrost in the late stage of drawing.The ultimate bearing capacity of the anchor in the minimum temperature period and freezing period is much higher than that in the maximum temperature period and thawing period.The ultimate bearing capacity of the anchor in the lowest temperature period is the highest,and which is the lowest in thawing period.