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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。
The artificial ground freezing method mainly has two shortcomings of insufficient local strength and frost heaving and thawing, while the pre-grouting method can improve the overall strength of fine silt formations and control the amount of frost heaving after the freezing. It is considered that the artificial ground freezing Law effectively supplement. In view of pre-grouting can effectively improve the strength and impermeability of soil, a series of low-temperature triaxial shear tests were carried out, and the effects of simple freezing and first grouting re-freezing on the shear strength of fine sand were studied . Based on the analysis of the effect of grouting and re-freezing to improve the strength of silty sand, the key points of shear strength and stress-strain curve, such as cooling temperature, water-cement ratio, water content, curing time and lateral pressure, The impact of volume. The results show that the shear strength of fine sand increases with the decrease of cooling temperature and is directly proportional to the water-cement ratio, water content and curing time. The secant modulus also increases with decreasing cooling temperature, And the water content is proportional to the ratio; In addition, the first grouting re-freezing fine sand sample cohesion and temperature showed a good linear relationship with the water-cement ratio, water content showed a good exponential function; internal friction angle and Temperature, water content showed a good power function, and water-cement ratio was a good exponential function. The results of this study can provide a reference for the analysis of mechanical strength index of grout re-freezing fine sand, and also provide guidance for the selection of water-cement ratio and curing time of first grouting and re-freezing method.