Experimental Research On The Frost Heave Mechanism Of Seasonal Frozen Soil And Upward Freezing Pulling Test Of Near Water Foundation

In the north and western alpine areas of China, there lies a vast expanse of tundra which has a great influence on the production and economic activities, and also the utilization and protection of the environment. Because of the reiterative melting of the soil in the seasonal tundra region, the engineering establishment of the superstructure has been devastatingly threatened. According to the investigation into the gardening construction and slipway pile foundation on the lakeshore in the cold north of China, the frost heaving phenomena has occurred frequently at the rate of more than 90%. 1.5% of the total investment of the slipway construction has been put into use for handling frost damage caused by frost heaving each year. In Changchun city of China, the annual outlay for slipway in the parks has reached nearly ten thousand yuan,,which not only economically burdens the city's development and construction, but also to an extend baffles the harmonious unity between the human landscape and natural environment. The project aims to settle the problem of frost heaving of the buildings,lakeshore sideway pile foundation and kiosk pile foundation.This article starts with a research on the composition of the soil and its structural characteristics, and then sums up the influence of these characteristics on the soil's physical mechanics and physical chemistry characteristics on the basis of analyzing the substantial components and structure of the frozen earth .This article also makes a deep analysis of the mechanism of the frozen earth and draws the conclusion that freezing and expanding of the soil are effected by many factors:the inner factors (its category and characteristics,the water contained before freezing,the water level under the ground,etc) and many other factors(like the weight it burdens).Then the article puts forward the observation method of frost heaving displacement test. According to the purpose of the experiment, it figures out the equipments needed at the place where the test is carried out, and it at the same time pointes out the techniques relatively applied in the experiment and its detailed process.A great deal of raw data were collected from an in-situ test of three experimental observation periods in two typical frost-heaving observation station—Southlake Park and Changchun Park in Changchun city.A curve graph about each period's frost-heaving displacement of the slipway piling was drawn after collating the data.On this basis,by relating it to the curve graph about the change of the temperature,an analysis was made about the characteristics of the frost-heaving displacement of the slipway piling in Eastlake Park and Changchun Park.Corresponding measures are put forward through the analysis of the frost -heaving mechanism of the slipway pile foundation---add something between the piling and earth to cut off the transmission of the tangential frost-heaving force to pile foundation and thereby eliminate the source of frost-heaving force.Thus based on this thought,rigid sleeve and soft sleeve are adopted against frost heaving.I.Rigid-sleeve project:After accurately work out the frost depth of the earth where the pile foundation lies,add a protective sleeve to the outside surface of the compresol pile and elastic-plastic material to the inside surface(hydrophobic material,like modified asphalt waterproof sheets).When the earth around frosts,the upward tangential frost-heaving force will directly work on the rigid sleeve and then the rigid sleeve glides along the pile.But once the direct transmission of the tangential frost-heaving force to pile foundation is cut off,frost-heaving displacement will not occur.II.Flexible-sleeve project: After accurately work out the frost depth of the earth where the pile foundation lies, add a synthetic polymer waterproof sheet to the outside surface of the compresol pile so that the tangential frost-heaving force of the earth will directly work on the soft sleeve.Synthetic polymer waterproof sheet has very good extensibility which minimizes the possibility of displacement and cut off the direct effect of the tangential frost-heaving forceIn order to validate the applicability of these two measures,a test-bed was set up when the observation station was firstly founded.The result was satisfactory according to the experimental study through three observation periods of data collection, collation and analysis.This article does a contrast and analysis with one of the period's data to validate the effectiveness of these two measures.The data at the same time tests the rationality of some other frost-heaving measures and is of great significance for putting forward better and more completed measures for the basic buildings against frost-heaving and for their constructing and maintenance on the seasonal tundra region.