Experimental Study On The Mechanical Characteristics Of Horizontal Bearing Capacity Of Frozen Soil Pile Foundation

The permafrost in China is widely distributed and rich in resources.In recent years,the economic development of the permafrost regions has been highly valued by the state.The construction of a large number of transport infrastructures in permafrost regions has promoted the extensive use of pile foundations.In recent years,the Climate warming has resulted in the rising temperature of the permafrost and even the melting of the surface of the permafrost,which will seriously affect the interaction between the pile and soil.In permafrost regions,the structures are often subjected to horizontal loads such as strong winds,earthquakes,water shocks,and mechanical braking.Compared with vertical loads,pile foundations under horizontal loads are more complex.Based on the above reasons,the experimental study on the horizontal bearing capacity of permafrost pile foundation under different temperatures,frozen soil and soil melting environment is carried out.The main conclusions are as follows:(1)Under the same load,the tensile and compressive strains of the pile are distributed symmetrically,and the tensile strain is slightly larger than the compressive strain.the distribution of the bending moment of pile and the tensile and compressive strain along the pile foundation first increase and then decrease.There are two maximum displacements,and the maximum positive displacement is significantly greater than the maximum reverse displacement.Under the same frozen soil environment,with the increase of horizontal load,the bending moment,displacement and tensile and compressive strain of the pile in the same buried depth are increasing gradually,and the increasing trend is becoming more and more obvious.In addition,the depth of the maximum buried,the reverse bend point and the displacement zero point gradually increase.In the range of thawing soil,the bending moment,the displacement,and the tension and pressure strain of the pile become larger when the temperature rises from-5? to-2?,but when the temperature continues to rise to 2?degrees centigrade,the bending moment and the tensile and compressive strain of the pile decrease significantly,and the displacement of the pile body increases significantly.With the increase of temperature,the maximum of pile bending moment,reverse pile body displacement and tensile and compressive strain of pile body are all increased,and the buried depth of the displacement zero point and the counter bend point also are increased.(2)Under the same load,pile top displacement and pile head angle of-5?frozen soil,-2?frozen soil and 2?thaw soil increased in sequence,but the numerical difference between thawing soil and frozen soil is quite different.After the entire loading process is completed,the time consuming of-5?frozen soil,-2?frozen soil and 2?thaw soil were gradually reduced,but eventually the pile top displacement and pile head angle increased.Compared with frozen soil,thawing soil can reach a larger displacement in a relatively short period of time,which shows that the horizontal stiffness of the soil is decreased significantly.In the same buried depth,the moment,the displacement and the tension and compression strain of piles all increase with the extension of loading time,and this trend gradually decreases and eventually becomes stable.With the prolongation of loading time,displacement zero point of pile body and the buried depth of Counter bend point of displacement,bending moment,tension and compressive strain of pile body all increase gradually.(3)At the initial stage of constant load,the growth rate of maximum bending moment and maximum reverse displacement of pile body of-5?frozen soil,-2?frozen soil and 2?thaw soil increase in turn,at the same time,the pile bending moment and the pile body displacement in the permafrost environment are increasing in turn,and the difference between the soil and the frozen soil increases gradually.This indicates that the upper layer thawing intensifies the rheological process of the lower permafrost.Under the same load,the growth rate of pile top displacement and pile head angle of-5?frozen soil,-2?frozen soil and 2?thaw soil increase in turn,the time consumed by the displacement of the pile top and the corner of the pile head tends to increase gradually.after stability,the displacement of the pile top and the angle of the pile head are also increased gradually.The rheological process of pile foundation under the condition of melting soil is more intense.This is mainly because the length of pile head is lengthened by the condition of thawing,which makes the deformation of the lower pile foundation bigger.By the pile-soil interaction,it is known that the permafrost surrounding the pile is more loaded from the pile body.The increase of load will aggravate the rheological process of frozen soil,which has a negative effect on the bearing capacity of frozen soil pile foundation.(4)Pile foundation through three stages of deformation under horizontal load,elastic deformation stage,plastic deformation stage,-5?,-2?;frozen permafrost,2 levels of critical load and temperature of thawing the horizontal ultimate bearing capacity and horizontal bearing capacity characteristic value and the corresponding horizontal displacement of pile top are:1000N/0.43 mm,900N/0.73 mm,700N/1.03;1400N/3.25,1300N/5.35,1100N/11.07;800N/0.32 mm,720N/0.52 mm,490N/0.71mm;...