Study On The Improvement Of Frost Heaving Characteristics Of Channel Base By Replacement Technology

In recent years,a large number of water delivery channels have been constructed in Xinjiang area of China.However,due to the seasonal permafrost,the channels are seriously damaged,which seriously affects the production and living of the people who live downstream.Because of the lower altitude in Xinjiang area,the ground temperature is higher.By using the "thermal semiconductor" effect of the gravel,the higher temperature of the inside of the channel bottom can be utilized to improve the temperature of the channel lateral base,and therefore reduce the frost depth of the channel lateral base.This article carry out unidirectional freezing tests of soil material and gravel materials,in which the changes of temperature and moisture fields under the different groundwater levels(realized by different replenishment conditions)are measured,and accordingly the effect of gravel particle size on the ascension of temperature in the channel lateral base is analyzed.In addition,the channel finite element model is built based on hydrothermal coupling theory,by which the reference value of the gravel heat exchange technology to the practical engineering application is analyzed.The main results of this paper are presented as follows:(1)Unidirectional freezing tests of channel base soil sample is carried out,and the changes of soil temperature field and moisture field with respect to different water replenishment conditions are obtained.Under the water replenishment condition,the frost depth of soil obviously increases,and the top temperature obviously decreases.The soil moisture migration is affected by the frozen front,the moisture migration is obvious before the frozen front arrived,but the unfrozen water content almost remains unchanged after the frozen front passed.(2)The unidirectional freezing tests of gravel samples with different particle sizes under different water replenishment conditions are completed,and the effects of particle sizes and water replenishment conditions on the temperature field changes and cooling rates in the gravel samples are compared,the temperatures in these samples increases first and then decreases with the increase of particle size.For different water replenishment conditions,the temperatures in the top region of a gravel sample are nearly invariant,which implies that the temperature in the top region of the gravel sample is not sensitive to the change of the water replenishment condition.(3)The finite element model of channel with gravel groove is established by using hydrothermal coupling theory.The results show that the freezing depth of the channel improves more obviously with the increase of the temperature gradient under the same partical size,and the freezing depth decreases obviously with the increase of the particle size under the same temperature gradient.