季节性冻土区桩锚支护结构水平冻胀演化规律研究

Study on Evolution of Horizontal Frost Heave of Pile-anchor Retaining Structure

近年来,季节性冻土区越冬基坑工程因水平冻胀引起的事故频发,但相关水平冻胀机理的研究成果较少。开展了北京市昌平区的越冬基坑现场监测,分析桩锚支护结构在不同补水和刚度条件下的地温变化、土体水分迁移、支护结构受力状态及支护结构水平位移的演化规律。研究结果表明:温度梯度引起土壤土水势变化,导致土体内部水分的竖向和侧向迁移,从而引起水平冻胀作用,诱发基坑支护桩的水平位移,增大支护结构中的锚杆拉力。此外,开放补水条件显著增强了水平冻胀作用,导致更大的冻胀力和冻胀变形,而刚度较大的支护结构对基坑的约束作用更强,能有效限制基坑水平冻胀变形。研究成果可为寒区工程支挡结构的设计和施工提供借鉴。

Despite frequent accidents in recent years caused by horizontal frost heave in overwintering foundation pit projects in seasonally frozen soil areas,there are few research results on the mechanism of horizontal frost heave.In this paper,based on the field monitoring of an overwintering foundation pit project of pile-anchor supporting structure in Changping District of Beijing,the evolution of frost heave characteristics such as temperature,moisture migration,stress state of supporting structure and horizontal displacement of supporting structure was analyzed.Studies have shown that the temperature gradient causes the change of soil water potential,leading to the vertical and lateral migration of water in the soil,which causes horizontal frost heave,induces horizontal displacement of supporting piles,and increases the anchor rod tension.In addition,water supplement significantly enhances the horizontal frost heave effect,resulting in greater frost heave force and deformation,while the stiffer supporting structure has a stronger restraint on the foundation pit and can effectively reduce the horizontal frost heave deformation.The research results can provide support for the design and construction of supporting structures in cold areas.