Study On Bearing Characteristics And Settlement Calculation Method Of Energy Pile Group Considering Temperature Effect

Shallow geothermal energy as a common clean energy source is abundant and widely distributed in our country.Energy piles can effectively extract shallow geothermal energy,which can be used as heat source for heating and cooling buildings.As a combination of traditional buried tube heat exchanger and pile foundation,energy pile technology has the advantages of less investment in the early stage and high heat transfer efficiency.Energy pile has been popularized and applied to a certain extent since its birth.Compared with the application status of energy pile,there are still some deficiencies in its theoretical analysis,which restricts the development of energy pile.In the actual working process,the energy pile will provide load-bearing and heat transfer functions.While bearing the upper load,it is necessary to consider the influence of temperature load caused by temperature change.Energy piles generally appear in the form of group piles.In the calculation of energy pile group,it is necessary to consider not only the influence of upper load and pile-pile interaction,but also the influence of temperature stress caused by heat transfer of energy pile.This paper will carry out the research on the change of temperature field of adjacent ordinary piles caused by heat exchange of energy piles,based on which the settlement calculation method of energy pile group will be established.The bearing characteristics of energy pile group were analyzed based on numerical simulation.The research results of this paper are as follows:(1)The numerical model of single energy pile was established by numerical simulation software,reasonable assumptions were made according to the simulation results,and the analytical solution of soil temperature field around energy pile was obtained by using solid cylinder heat source model.The temperature effect of energy pile on adjacent common pile and the temperature effect of energy pile on soil in the same position are analyzed.The results show that the influence of energy pile on the temperature of adjacent ordinary pile is not much different from that of soil in the same position.The temperature field model of adjacent common piles is obtained by considering the temperature variation of adjacent common piles affected by energy piles as that of soil in the same position.(2)Exponential function is selected as the load transfer model of energy pile side,and hyperbolic function model is selected as the load transfer model of pile end.The load transfer model of single energy pile was obtained by considering the influence of temperature change at the pile-soil interface.The load-settlement curve of energy single pile is obtained by using the calculation method of pile foundation settlement,and the rationality of the method is verified.Based on the traditional equal-pier replacement method,the modified equal-pier replacement method which can estimate the average settlement of energy group piles is obtained by reasonably improving the response parameters.The influence of pile-pile interaction and heat exchange of energy piles on the temperature stress of adjacent piles is considered.Modify the parameters in the load transfer model.Combined with the deformation coordination method,the settlement calculation method is obtained when there is only one energy pile in the energy group.(3)The numerical models of single energy pile,double energy pile,four energy pile and nine energy pile are established respectively.Analyze the temperature field changes of energy pile group in different positions and in different quantities.The settlement and bearing characteristics of energy group piles under different working conditions are studied.