| With the rapid development of economy,our country began to constantly strengthen and improve the construction of infrastructure,since the qinghai-tibet railway construction,pile gene,its unique advantages is widely used in permafrost region,considering the pile foundation in the process of using force is very complex,except under vertical load and is subject to train braking,earthquake,strong winds and flood,such as the horizontal load,and at present most of the research is only limited to the effect of vertical or horizontal load separately on frozen soil pile foundation’s bearing capacity,load distribution and the influence of the relative displacement of piles and soil,the frozen soil pile foundation bearing capacity under combination load characteristics research is less,Therefore,this paper studies the vertical bearing capacity characteristics of frozen soil pile under different load conditions and different temperatures under horizontal loads,and simulates the stress distribution of soil around the pile through ABAQUS software.The main conclusions are as follows:(1)Horizontal load will increase the vertical settlement of pile foundation.The settlement mainly occurs when the vertical load is large.The greater the horizontal load,the greater the settlement will be generated by the same vertical load,and the application of horizontal force will reduce the bearing capacity of pile foundation.Pile under horizontal load will produce lateral displacement,vertical load will be back in the position of pile top lateral displacement curve of the inflection point,pressure side by elastic deformation of soil into the plastic deformation phase the horizontal load,along with the vertical load increases,the same horizontal load caused by the decrease of lateral displacement of the pile top,lateral displacement of the pile body of zero position becomes shallow,the smaller the influence of the horizontal load on the pile deflection,the vertical load action in advance can restrain the flexural deformation of the pile body.(2)Applying the horizontal load in advance will make the resistance of the upper soil change,the average freezing strength of the pile side decreases,the position where the maximum freezing strength occurs moves down,the axial force of the pile generated by the same vertical load increases,and the load transferred to the soil at the pile bottom increases.After vertical load is applied,the position of the maximum bending moment and the position of the zero point of pile bending moment both move up,and the maximum bending moment decreases.The vertical load has a significant inhibitory effect on the bending moment of pile.(3)The vertical settlement of pile foundation increased under the preacting horizontal load in three temperature environments,and the effect of horizontal force on the vertical settlement of pile foundation in frozen soil environment was smaller than that of thawing soil at 2℃.The same horizontal load for-10℃,frozen-6℃,2℃ melting permafrost soil lateral displacement of pile head,in turn,increases,applying vertical load of three temperature displacement of pile top and pile lateral inhibition effect is different,of which 2℃ inhibition effect is most obvious in the cases of melting soil,pile up the sharpest of lateral displacement of the zero position,horizontal load of pile lateral disturbance radius reduced the most.(4)applying horizontal load in advance of 2℃ melting soil of pile side to freeze the intensity and the influence of axial stress of pile,pile side biggest frozen strength compared to reduce most permafrost environment,the most obvious effect on the increase of axial force of horizontal loading,and 6 ℃ frozen soil pile lateral strength of frozen in less than 2 ℃decreased amplitude,axial stress of pile increases slightly,when the temperature drops to-10℃ when,before and after applying horizontal load of pile freeze strength decrease is not obvious,horizontal load effect on axial force of pile body is not big.(5)When vertical load is applied in advance,the pile bending moment caused by the same horizontal load in the three temperature environments decreases to varying degrees,and the bending moment at-10℃ decreases the most.The main reason is that the reverse bending moment generated by the pile side freezing force at-10℃ is relatively large,which offsets part of the bending moment.Under permafrost and thaw soil conditions,the flexural stiffness of pile foundation can be improved by applying vertical load in advance,and the lower the soil temperature is,the greater the decreasing range of the flexural moment value of pile is.(6)The horizontal load will lead to the increase of the soil pressure in front of the pile,and the effect mainly occurs at the top of the soil.When the load increases to a certain value,the soil at the upper part of the compression side is the first to reach the yielding state and plastic fracture occurs,and the horizontal bearing capacity of the pile foundation decreases rapidly.After the vertical load is applied,the soil damage at the pile tip first appears on the contact surface between the pile bottom and the permafrost.With the increase of the load,the soil damage area gradually expands to the surrounding. |
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