Study On The Response Of PHC Geothermal Pile Structure

The energy pile is a new energy-saving and emission-reducing technology that embeds the heat exchange tube in the pile foundation,and satisfies the needs of the building’s winter heating and summer cooling,and at the same time bears the pile foundation of the upper building structure load.Compared with traditional ground source heat pumps,it has obvious technical and economic advantages.Prefabricated pipe piles are an important type of pile foundation in engineering and one of the pile foundation forms that energy piles can use.At present,there are relatively few studies on prefabricated energy pipe piles at home and abroad.In this paper,the thermomechanical response of prefabricated energy pipe piles is studied based on the results of Suzhou field test combined with finite element numerical simulation.In this paper,based on the thermal response test of the Suzhou energy pile site,the temperature and strain of the pile body were monitored in real time through the distributed optical fiber arranged on the pile side.Two tests were carried out on site.The first test was to test the preheated pipe pile with single U-type buried pipe and parallel double U-shaped buried pipe constant heat flow.The heating time was 74h,then compare the single U type and parallel double U buried.Pile body temperature and strain under tube type.The results show that the temperature and strain of the pile under the double U-tube test are significantly larger than that of the single U-type buried pipe.The second test was to test the temperature rise of the No.65 pile of the parallel double U-type buried pipe for 600 hours,and to monitor the temperature and strain changes of the energy pile and the adjacent pile body.The results show that the temperature of the adjacent pile is affected to varying degrees.The effect of warming piles,the maximum temperature change reached 6 ℃.Secondly,the thermo-mechanical three-dimensional numerical model of prefabricated energy pipe piles was established by COMSOL.The thermo-mechanical response process of the parallel double U-shaped buried pipes was simulated by field test conditions,and the numerical simulation and field test results were compared and analyzed.,verify the reliability of the built model.Then the model is used to simulate the influence of the two factors of pile end constraint and buried pipe.The results show that when the pile is in the state of warming or cooling,when the pile end is in a partially restrained state,the zero point of the pile body will move upwards with respect to the fully restrained state of the pile end,and the smaller the pile end is constrained,the displacement of the pile body will increase by zero.The bigger.When the pile end is in the completely restrained state,the displacement of the pile head under the condition of heating or cooling is greater than the displacement of the pile end when it is in the partially restrained state.In addition,the pile end constraint also has a large impact on the pile stress distribution.When the pile end is in the completely restrained state,the pile end produces a compressive stress of 780 kPa when the pile body heats up,and the pile end generates a tensile stress of 800 kPa when the pile body cools down.Different ways of burying have a great influence on the thermo-mechanical properties of energy piles.Through the simulation of different buried pipes,the temperature,strain,stress and displacement of the pile body are as follows:parallel double U-shaped buried pipe>W-shaped buried pipe>single U-shaped buried pipe.