Experimental Research On Regular Patterns Of Water Migration And Mechanism Of The Formation Of Ice Films Between Different Mediums In Freezing Silty Clay

With the increasing construction in frozen soil regions, pile foundation engineering hasbeen widely used. The problem of thermal disturbance produced by pile foundationconstruction has attracted wide attention from scholars. Bearing capacity and deformation ofpile foundation during the refreezing process will directly affect the safety and stability of thefollow-up engineering; refreezing time which is required to achieve the frozen strength of pilewill affect the undertaking of the design, construction and follow-up work of pile; there is asignificant rheological property in ice film at the interface between pile and soil during therefreezing process, which will effect the stability of long-term bearing capacity of pilefoundation. Therefore, it is of great significance to study the water migration rule of soilaround pile during the refreezing process and the formation mechanism of ice film formed atthe pile-soil interface.On the background of on-site tests of bored pile foundation in silty clay permafrostfoundation in Chuma River in DK1047section of Qinghai-Tibet railway line, thermaldisturbance produced by construction of bored pile in frozen soil region, distribution oftemperature of the pile foundation during the refreezing process are studied, leading to theimportance and feasibility of the study of water migration and ice film phenomenon duringthe refreezing process of pile body.Water migration during the refreezing process of pile body is different from that undergeneral situation, pile body material is connect to the soil during the refreezing process, withthe formation of ice film at the interface of two different material. A one-dimensional freezingmodel is used to study on the water migration of freezing silty clay with the presence of a pilebody.By using testing instruments like low-temperature freezing-thawing cycle test boxXT5405, temperature sensor, FLUKE tester, and self-developed devices, all of whichcomposed of a set of indoor water migration testing device. Under unidirectional freezingmode, freezing of silty clay samples is studied from top to bottom; temperature during thefreezing process is controlled by adjusting the temperature of top and bottom plate of the testbox. Silty clay is used as soil samples in the tests, samples with different initial water contentand dry density are prepared, temperature difference between hot and cold plate is controlled,and water migration is studied when different materials are attached to the top of soil sampleunder certain freezing time, the materials include aluminum plate, concrete plate, organicglass plate, wood and so on. Data like temperature change of the sample over time, watercontent distribution at the end of freezing, change of frost heaving amount, quality andthickness of ice film are measured during the freezing process, and the phenomenon on the surface of sample is observed after freezing. The following results are obtained underdifferent conditions: water migration change of freezing silty clay over time and depth, theinfluence of different factors on water migration rule, physical characteristics of ice film atinterface between different materials and ice film, distribution of frost heaving amount duringthe freezing process of soil and the influence of different factors on frost heaving amount,associated phenomena on the surface of soil during the freezing process.Coupled analysis of water and heat of tested samples is undertaken based on finitevolume method, corresponding empirical formula and parameters are selected, and calculationresults of coupled water and heat are obtained. The numerical calculation results arecompared with the measured ones, and there is a good consistency between them. Theinfluence of dry density, initial water content, temperature difference, and freezing time oncalculation results is analyzed, as well as their influence on the changing rules of watermigration.Based on different research methods and comparative study of operating results underdifferent conditions, some useful conclusions and valuable data are obtained. All of whichprovide will beneficial references for the study of water migration phenomenon in the processof freezing, formation mechanism of ice film at pile-soil interface, and for the further analysison long-term bearing capacity in frozen soil regions.