EXPERIMENTAL STUDY ON TENSILE STRENGTH OF UNDISTUBED Q2 LOESS FROM YANAN SHANNXI, CHINA
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摘要: 对陕西延安新宝塔山隧道Q2原状黄土进行了不同加载速率的无侧限抗压与贯入抗拉试验, 研究了Q2原状黄土抗压与抗拉强度的影响因素。结果表明:加载速率对宝塔山Q2原状黄土抗压和抗拉强度影响较大, 抗压强度与抗拉强度随加载速率增大而增大; 高径比对抗拉强度也有较大影响, 试验时当高径比控制在1.0左右时, 高径比对宝塔山Q2原状黄土的抗拉强度影响相对较小, 因此采用轴向压裂法测量黄土的抗拉强度时, 高径比宜控制在1.0;在试验加载速率范围内, 加载速率对宝塔山Q2原状黄土的压拉比影响不大, 其压拉比在9.88~13.68范围内变化。Abstract: The unconfined compressive and penetration tensile tests were conducted with different loading rates on undisturbed Q2 loess from Baotashan Tunnel in Yan'an, Shanxi, and the impacts on the unconfined compressive strength and tensile strength were studied. It shows that the loading rates have a great impact on the compressive strength and tensile strength, which all increase with the increase of loading speed. The ratios of height to diameter have a great influence on the tensile strength of the Q2 loess, when the ratio of height to diameter of the samples is about 1.0, the impact on the tensile strength tends to be relatively small. Therefore, when the tensile strength of loess is to be measured by axial unconfined penetration test, the ratio of height to diameter of the samples should be 1.0. Within the scope of the test loading rates, the loading rates have little effect on the ratios of compressive strength to tensile ratio for the undisturbed Q2 loess in Baotashan tunnel, which vary between 9.88 and 13.68.
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图 3 拉应力-贯入深度曲线
Figure 3. Curves of tensile stress vs. penetration depth of loess samples
图 4 抗压/抗拉强度与加载速度关系
Figure 4. Relation curve of compressive and tensile strength with loading rates
图 6 不同高径比试验前与试验后试样
Figure 6. Samples before and after test with different height-diameter ratios
图 7 不同高径比下拉应力与贯入深度关系
Figure 7. Relationship of stress and penetration depth at different height-diameter ratio
图 9 不同高径比抗拉强度降低幅度值
Figure 9. Reduction of the tensile strength at different height-diameter ratios
图 10 1.25 mm/min时抗压与抗拉强度关系
Figure 10. Correlation of unconfined compressive strength with tensile strength at 1.25 mm/min
图 11 压拉比与加载速率的关系
Figure 11. Relation between ratio of compressive strength to tensile strength ration and loading rates
表 1 试验用Q2黄土的物性指标
Table 1. Physical parameters of Q2 loess
w/% ρ/(g·cm-3) ds wL/% wp/% e αv/MPa-1 19.64 2.01 2.638 29.2 13.25 0.597 0.09 注：w—含水量；ρ—湿密度；ds—比重；wL—液限；wp—塑限；e—孔隙比；αv—压缩系数 
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