Effect of water content on the mechanical properties of artificially frozen red clay
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摘要:
在冻结法施工中, 冻土的强度及变形特性对冻结壁的稳定性至关重要。为了研究不同含水率对冻结作用下土的强度和蠕变的影响, 以江西红黏土为研究对象, 通过冻结三轴试验, 在-10℃下研究含水率对冻结红黏土强度及蠕变特征的影响。试验结果表明: 16%~32%含水率范围内, 冻结红黏土的抗压强度随含水率的增加先增大后减小; 16%~28%含水率范围内, 随着含水率增大, 其黏聚力逐渐增大, 内摩擦角逐渐减小; 围压为0.2 MPa与0.5 MPa下的蠕变曲线都显示含水率较低时只会出现衰减蠕变阶段和稳定蠕变阶段, 含水率较高时会出现加速蠕变阶段。含水率对红黏土的力学性质影响较大, 研究成果可为江西地区红黏土地层地铁隧道建设人工冻结法施工提供参考。
Abstract:In the construction of artificial freezing methods, the strength and deformation characteristics of frozen soil are crucial to the stability of frozen walls. To investigate the effect of different water contents on the strength and creep of the soil under freezing action after specimen preparation, the specimen was kept in an incubator for 24 hours, and the influence of moisture content on the strength and creep characteristics of Jiangxi red clay was studied by freezing triaxial tests at -10℃. The results show that the compressive strength of frozen red clay first increases and then decreases with increasing water content in the range of 16%-32%. In the range of 16%-28% water content, the cohesion increases and the internal friction angle decreases with increasing water content.The creep curves under confining pressures of 0.2 MPa and 0.5 MPa show that the red clay with a low water content only has a decay creep stage and stable creep.The results can be used as a reference for the artificial freezing method in the construction of subway tunnels in the red clay stratum in Jiangxi Province.
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Key words:
- freezing method /
- red clay /
- moisture content /
- triaxial test /
- mechanical characteristics
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图 2 试样恒温专用环境箱
Figure 2. Special environment chamber for control soil sample temperature
图 5 0.2 MPa围压下不同含水率冻结红黏土的偏应力-轴向应变曲线
Figure 5. Variation of deviator stress of frozen red clay and axial strain with different water contents under a confining pressure of 0.2 MPa
图 6 0.5 MPa围压下不同含水率冻结红黏土的偏应力-轴向应变曲线
Figure 6. Variation of deviator stress of frozen red clay and axial strain with different water contents under a confining pressure of 0.5 MPa
图 7 1.0 MPa围压下不同含水率冻结红黏土的偏应力-轴向应变曲线
Figure 7. Variation of deviator stress of frozen red clay and axial strain with different water contents under a confining pressure of 1.0 MPa
图 8 不同围压下冻结红黏土剪切强度与含水率的关系曲线
Figure 8. Relationship curves of frozen red clay between shear strength and the water content under different confining pressures
图 9 不同含水率下冻结红黏土的摩尔强度包络线
Figure 9. Shear strength envalopes of frozen red clay with different water contents
图 11 0.2 MPa围压下不同含水率冻结红黏土的蠕变曲线
Figure 11. Creep curves with different water contents of frozen red clay under a confining pressure of 0.2 MPa
图 12 0.5 MPa围压下不同含水率冻结红黏土的蠕变曲线
Figure 12. Creep curves with different water contents of frozen red clay under a confining pressure of 0.5 MPa
表 1 试验红黏土物理参数
Table 1. Physical parameters of the red clay
液限wL/% 塑限wP/% 最大干密度ρd/(g·cm-3) 天然含水率ω/% 最优含水率ω/% 相对密度Gs 45.5 18.2 1.693 22.3 19.7 2.72 
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表 2 试验方案
Table 2. Testing program
编号 含水率/% 围压/MPa 试验温度/℃ 干密度/(g·cm-3) 试验内容 A-16 16 0.2 三轴剪切、三轴蠕变 A-18 18 三轴剪切、三轴蠕变 A-20 20 三轴剪切、三轴蠕变 A-22 22 三轴剪切、三轴蠕变 A-24 24 三轴剪切、三轴蠕变 A-28 28 三轴剪切 A-32 32 三轴剪切 B-16 16 0.5 -10 1.693 三轴剪切、三轴蠕变 B-18 18 三轴剪切、三轴蠕变 B-20 20 三轴剪切、三轴蠕变 B-22 22 三轴剪切、三轴蠕变 B-24 24 三轴剪切、三轴蠕变 B-28 28 三轴剪切 B-32 32 三轴剪切 C-16 16 1.0 三轴剪切 C-18 18 三轴剪切 C-20 20 三轴剪切 C-22 22 三轴剪切 C-24 24 三轴剪切 C-28 28 三轴剪切 C-32 32 三轴剪切 注：每组试验都设置至少一组对照组
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