Study On The Influence Of Seasonal Frost Heaving Of Steel Sheet Pile Supporting Structure

As a kind of increasingly popular support pile,steel sheet pile is widely used in foundation pit engineering because of its advantages of convenient construction,repeated use and good water retaining performance.Steel is an excellent heat-conducting material with a thermal conductivity of 45W/m·K,which is about 35 times that of concrete.Under cold conditions,due to the existence of steel sheet piles,the external negative temperature can pass through the steel sheet pile after excavation.Conducted into the sidewall of the foundation pit and the soil below the foundation pit.The low temperature causes the water in the soil to freeze and has a seasonal frost heaving effect.Seasonal frost heave caused by temperature changes can have a combined effect of internal support axial forces,horizontal displacement of the containment structure,and the environment surrounding the foundation pit.This paper is based on the underground comprehensive pipe gallery project outside the Shiyuanhui Park in Yanqing District,Beijing.The minimum temperature in the Yanqing area can reach-18°C in winter.The support system of the underground integrated pipe gallery project outside the World Garden Park is steel plate pile,based on engineering geological survey,theoretical analysis,numerical simulation,field test and engineering test,conduct research on seasonal frost heaving of overwinter foundation pit of underground pipe gallery project,and provide reference for construction and monitoring of similar foundation pit engineering.The main contents and conclusions of this paper are as follows:(1)The mechanism of frost heaving theory and seasonal frost heaving were summarized,mainly for migration and ice formation;introduces the three-field coupling theory of heat-water-force and the pile-soi-water thermodynamic model based on coupling theory..(2)The impact of seasonal frost heaving on the underground integrated pipe corridor project were summarized and analyzed.The minimum temperature in winter in Yanqing is-18°C,the average temperature in winter is about-13°C,and the freezing depth of the site is generally 0.5m~1.0m.During the wintering period,the cumulative variation of surface settlement of soil around the foundation pit is about 15 mm,and the average cumulative variation of surface settlement is 5mm;the average variation of horizontal displacement of steel sheet pile top is about 1cm,and the average variation of horizontal displacement of pile top is average.In the range of 5mm~7mm;the average cumulative variation of the axial force of the steel support is about 70 kN.(3)The ABAQUS finite element software was used to simulate the data.The data of the supporting structure and the displacement of the supporting structure were found to be changed before and after the frost heaving.The change trend was the same as the monitoring data response,which verified the feasibility of the model.Sexuality,and the data change rate is large at 0~-10 °C,and the data change rate is small at-10°C~-20°C.