单向冻结条件下饱水砂卵石冻胀融沉特性试验研究

以北京典型饱水卵石7#地层为研究对象,利用恒温恒压冻胀融沉仪,研究不同干密度饱水砂卵石在开放系统和封闭系统条件下的冻胀率、融沉系数、冻胀力及水分迁移量。试验结果表明:①饱水砂卵石的冻胀率和融沉系数均小于1%,远小于黏土、粉土的冻胀率和融沉系数,且随干密度的增大而减小;②封闭系统砂卵石冻胀率(力)和融沉系数大于开放系统;③饱水砂卵石冻胀过程是排水过程,排水量占土颗粒质量比例不超过1%;④无论是开放系统还是封闭系统,砂卵石经冻胀融沉后,总有一定的变形残余量。研究成果为冻结法在北京深层地下空间应用提供理论依据和参考。

Experimental Study on Frost Heave and Thawing Settlement Characteristics of Sandy Gravel under Unidirectional Freezing

This paper investigated the frost heave ratio, thawing settlement coefficient, frost heave pressure, and water migration of typical saturated sandy gravel 7# in Beijing. A series of frost heave and thawing settlement tests were performed on sandy gravels with different dry densities under an open system and closed system by using constant temperature and pressure frost heave and thawing settlement instrument. The test results show that (1) Both the frost heave ratio and thawing settlement coefficient are less than 1%, which is significantly lower than the corresponding values for clay and silt. The frost heave ratio and thawing settlement coefficient both decreased with increasing dry density of sandy gravel; (2) The closed system of sandy gravel has higher values of frost heave ratio and thawing settlement coefficient compared with the open system; (3) The frost heave process of sandy gravel is a drainage process, in which the displacement of water is less than 1%; (4) After one freeze-thaw cycle, sandy gravel has residual deformations regardless of whether the system is closed or open. The results provide a theoretical basis and reference for the application of the freezing method for deep underground space in Beijing.