先注浆再冻结对粉细砂力学性质影响的低温三轴试验（英文）

Influence of freezing after grouting on mechanical properties of fine sand based on low-temperature triaxial test

人工地层冻结法中主要存在局部强度不足以及冻胀融沉2个弊端,而预注浆法可以提高粉细砂地层的整体强度及控制冻结后的地层冻胀量,被认为是对人工地层冻结法的有效补充。鉴于预注浆可以有效改善土体的强度及抗渗性,进行了一系列低温三轴剪切试验,研究了单纯冻结与先注浆再冻结2种试验方案对粉细砂抗剪强度的影响。在分析先注浆再冻结提高粉细砂强度效果的基础上,重点分析冷却温度、水灰比、含水量、养护时间以及侧压等对抗剪强度指标及应力-应变曲线峰值处割线模量的影响。研究结果表明:粉细砂抗剪强度随冷却温度的降低而增大,与水灰比、含水量、养护时间呈正比关系;割线模量也随冷却温度的降低而升高,与水灰比、含水量呈正比关系;此外,先注浆再冻结粉细砂土样的黏聚力与温度呈良好的线性关系,与水灰比、含水量呈良好的指数函数关系;内摩擦角与温度、含水量呈良好的幂函数关系,与水灰比呈良好的指数函数关系。该研究结果可为先注浆再冻结粉细砂的力学强度指标分析提供参考,也可为先注浆再冻结工法的水灰比、养护时间选择提供指导。

Partial deteriorated strength of frozen soil as well as frost heave and thaw subsidence were two main disadvantages of the artificial ground freezing method.The pregrouting method was regarded as a good supplement to the artificial ground freezing method to enhance the overall strength of fine sand ground and control the frost heave amount of ground after freezing.In view of pregrouting can effectively improve the strength and anti-permeability of soil,a series of indoor low-temperature triaxial shear tests were carried out and the effects of two experimental schemes,namely,freezing and freezing after grouting,on shear strength of fine sand were analyzed.Based on the analysis of fine sand strength improved by freezing after grouting,effects of cooling temperature,water-cement ratio,water content,curing time and lateral pressure on the strength and secant modulus at the peak of stress-strain curve were emphatically analyzed.The results show that the shear strength of sample increases with the decrease of cooling temperature and is proportional to water content,water-cement ratio as well as curing time,respectively.The grouted frozen samples always present higher secant modulus as expected with the decrease of cooling temperature and are proportional to water content,water-cement ratio and curing time.Besides,the cohesion c of fine sand reinforced by grouting and freezing shows a linear relationship with cooling temperature and an approximate exponential relationship with water-cement ratio and water content.Power function relationships are found among internal friction angleφ,cooling temperature and water content.There exists an exponential relationship between internal friction angleφ and water-cement ratio.This research provide references for the mechanical strength indices of fine sand reinforced by grouting and freezing,and guidance for the selection of watercement ratio and curing time for artificial ground freezing projects.