Study On Load Bearing Characteristics Of Single Energy Pile In Silty Soil

The energy consumption of building heating and cooling accounts for about 10% of total energy consumption,and most of the unrecoverable energy such as coal is used,which will cause damage to the environment.As a new energy saving technology,energy pile can effectively combine pile foundation and ground source heat pump,which can not only bear superstructure load but also provide heating or cooling for buildings.In practical work,the energy pile is often accompanied by periodic changes in temperature,and the pile will expand with temperature rise(cooling and contraction),and the superstructure load will be combined to produce thermodynamic response,thus affecting the safety of the structure.Therefore,it is of great significance for the extension and application of energy pile to make clear the bearing characteristics of energy pile under the action of temperature.In this paper,through model test,the energy pile load-bearing characteristics under the different temperature effect of model test,to study the cyclic temperature under the action of silt in the energy pile load-bearing characteristics change,analyzes the different cycle paths of energy pile load-bearing characteristics,preliminary studied the temperature under the action of friction pile side friction calculation formula of the main research work and achievements are as follows:(1)The model test of single load bearing characteristics of energy pile under the action of constant temperature was carried out.The test was divided into different pile temperature and various working conditions of different vertical loads for comparison and discussion,and the variation rules of stress,strain,lateral friction and resistance of displacement pile on top of pile under soil pressure on the side of pile were obtained.The test results show that the soil pressure on the pile side increases(decreases)with the increase(decrease)of temperature.The displacement uplift(settlement)of the pile top will be restrained after the external load is applied,and the unrecoverable settlement will be left after the natural recovery.The stress of the pile body changes regularly along the pile depth,and the constraint in the middle is the largest and the stress value is the largest.(2)Based on the model test results,the lateral friction resistance at different depths of the pile was calculated,and the influence factor was obtained by using the influence factor method to estimate the lateral friction resistance at different depths of the pile.Heating upλ=-1.535(Z/L<0.6)or 2.32(0.6<Z/L<1);cooling λ=-1.18(Z/L<0.6)or-2.09(0.6<Z/L<1).(3)The model test of the influence of cycle temperature on the bearing characteristics of energy pile was carried out,and the test results of different cycle paths and different vertical load conditions were compared and analyzed,and the change rules of pile top displacement and pile stress after multiple cycles of temperature were obtained.The test results show that the horizontal soil pressure on the pile side returns to the initial state after the circulation without external load.After the external load is applied,the horizontal earth pressure will accumulate with the increase of the number of cycles.The displacement of pile top rises(sinks)as the temperature rises(falls).After the external load is applied,the displacement of pile top reaches the maximum value,and a slow settlement will occur.With the increase of the number of cycles,the residual non-recoverable displacement value will be accumulated continuously.The thermal stress of pile can be basically restored to the initial state after cycling when there is no load,and the thermal stress value will be accumulated with the increase of the number of cycles after applying the external load.(4)The ultimate bearing capacity test of single energy pile with or without temperature cycle is carried out,and the effect of cycle temperature on the ultimate bearing capacity of single energy pile is analyzed.In dry silty soil,the bearing capacity of the pile at the initial stage after two rounds of temperature cycling is basically unchanged.With the increase of the vertical pressurized load value,the bearing capacity decreases compared with that without load,and the ultimate bearing capacity is 90% when there is no load.