Experimental study on splitting tensile failure characteristics of frozen soils under impact loads
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摘要: 冻土的动态拉伸强度和破坏特性在涉及冻土工程高效破碎和安全稳定性分析领域具有重要的参考价值。为研究负温和加载率对冻土动态拉伸性能的影响，利用铝质分离式Hopkinson压杆试验系统开展了冻土的动态巴西圆盘劈裂试验，结合高速摄像系统，分析了温度和加载率对冻土动态拉伸强度、能量耗散和破坏模式的影响，探讨了冻土巴西圆盘的劈裂破坏机理及动态拉伸强度的影响因素。结果表明：冲击荷载作用下，冻结黏土和冻结砂土巴西圆盘试样均遵循中心起裂的破坏模式，试件破坏为沿轴向相对完整的两半；随着冲击气压的增加，两种冻土的加载率均呈线性增大；两种冻土达到动态拉伸峰值应力所需的时间在92~242 μs范围内；两种冻土的动态拉伸强度均存在明显的温度效应和加载率效应，动态拉伸强度随温度的降低和加载率的增加而增大；不同负温条件下两种冻土的吸收能与动态拉伸强度均存在较好的线性关系；冲击气压的增加会导致冻土试样的破坏程度加剧，高剪切应力引起的三角破碎区面积逐渐增大。Abstract: The dynamic tensile strength and failure characteristics of frozen soils have important reference value in the field of efficient crushing and safety stability analysis of frozen soil projects. To study the effects of negative temperature and loading rate on the dynamic tensile properties of the frozen soils, the aluminum split Hopkinson pressure bar system is employed to conduct the dynamic Brazilian disc splitting test of frozen soil. In addition, by using the high-speed camera system, the influences of temperature and loading rate on the dynamic tensile strength, energy dissipation and failure mode of the frozen soils are analyzed. Finally, the splitting failure mechanism of the Brazilian disc and the influencing factors of dynamic tensile strength of the frozen soils are discussed. The results indicate that under the dynamic loads, the Brazilian disc specimens of frozen clay and frozen sand follow the central initiation failure mode, and the specimens are split into two relatively intact halves along the axial direction. With the increase of the impact pressure, the loading rate of two frozen soil types increases linearly, and the duration required for reaching the dynamic tensile peak stress for them is in the range of 92~242 μs. The dynamic tensile strength of the frozen soils shows the obvious temperature effects and loading rate effects, and its values increase with the decrease of the temperature and the increase of the loading rate. There is a good linear relationship between the absorbed energy and the dynamic tensile strength of the frozen soils under various negative temperature conditions. With the increase of the impact pressure, the damage degree of the frozen soil specimens is aggravated, and the triangular fracture zone area caused by high shear stress gradually increases.
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Keywords:
- frozen soil /
- dynamic tensile strength /
- negative temperature /
- loading rate /
- failure mode
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图 1 动态劈裂拉伸试验中加载率的确定方法
Figure 1. Determination method of loading rate in dynamic splitting tensile tests
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图 3 冻土加载率和冲击气压的关系
Figure 3. Relationship between loading rate of frozen soils and impact pressure
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图 4 冻土动态拉伸强度和加载率的关系
Figure 4. Relationship between dynamic tensile strength and loading rate of frozen soils
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图 5 冻土巴西圆盘劈裂破坏机理及动态拉伸强度的影响因素
Figure 5. Splitting failure mechanism of Brazilian disc and influencing factors of dynamic tensile strength of frozen soil
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图 6 冻土动态拉伸强度与吸收能关系
Figure 6. Relationship between dynamic tensile strength and absorption energy of frozen soils
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图 7 冻土试样动态劈裂拉伸破坏过程
Figure 7. Dynamic splitting tensile failure process of frozen soil specimens
表 1 黏土颗粒级配
Table 1 Grain-size distribution of clay
粒径/mm 0~0.075 0.075~0.45 0.45~1 1~1.6 1.6~2 百分比/% 51.33 19.72 12.02 11.48 5.45 
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表 2 砂土颗粒级配
Table 2 Grain-size distribution of sand
粒径/mm 0~0.075 0.075~0.45 0.45~1 1~1.6 1.6~2 百分比/% 0.8 32.29 49.54 13.23 4.14
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表 3 冻土试样劈裂破坏模式
Table 3 Splitting failure modes of frozen soil specimens
土质类型 温度/℃ 冲击气压/MPa 0.10 0.11 0.12 0.13 冻结黏土 -15 
冻结砂土 -10 
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