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【目的】三峡库区秭归盆地侏罗系地层广泛分布软硬相间夹层，该地层的软弱夹层是区内水库滑坡发育的关键控制因素。长期降雨和库水位变动引起的干湿循环过程对软硬相间地层尤其是软弱夹层产生劣化，但目前尚缺乏关于干湿循环下该软弱夹层岩土性质劣化规律的研究。为了系统地研究长江水干湿循环作用下该软弱夹层的抗剪强度参数劣化规律及其概率特性变化规律，【方法】共开展了120组长江水不同干湿循环周期下三峡库区侏罗系软弱夹层重塑样的直剪试验，研究三峡库区侏罗系软弱夹层的剪切力学特性和干湿循环下的抗剪强度参数损伤规律，实现了基于Copula函数的干湿循环下软弱夹层抗剪强度参数的概率特性表征。【结果】结果显示：软弱夹层脆性指数随循环次数的增加而降低，黏聚力随着干湿循环次数的增加而衰减，最后趋于稳定，内摩擦角维持在37°～47°之间。【结论】剪切过程中呈现典型的应变软化特征；相同法向应力下峰值剪应力和残余剪应力均随着干湿循环次数的增加而减小，法向应力越大，软弱夹层的剪切模量越大、峰值强度与残余强度就越大；峰值黏聚力的衰减符合指数函数变化，残余黏聚力的衰减符合线性函数；黏聚力变异系数随着循环周期逐渐增大，参数离散性逐渐增强；此外干燥状态下的变异系数高于饱和状态，说明干燥下的离散程度更强。研究揭示了干湿循环下软弱夹层的剪切强度劣化机理，有望为三峡库区滑坡地质灾害演化及防控研究提供理论依据和数据参考。
Abstract：[Objective]Jurassic strata are widely distributed in the Zigui Basin in the Three Gorges Reservoir area. The weak interlayers in the Jurassic strata are the key control factors controlling the development of reservoir landslides. The wetting-drying cycle process caused by long-term rainfall and reservoir water level changes degrades the Jurassic strata especially the weak interlayers. However, there is still a lack of research on the deterioration law of the geotechnical properties of the weak interlayers under wetting-drying cycles. In this study, the degradation of shear strength parameters and the variation of their probabilistic characteristics of the weak interlayer under the action of wetting-drying cycles by the Yangtze River water were systematically studied.[Methods]A total of 120 direct shear tests were carried out on the remodeled samples of Jurassic weak interlayers in the Three Gorges Reservoir area under different wetting-drying cycles of Yangtze River water. The shear strength properties of the Jurassic weak interlayers and the damage law of shear strength parameters under wetting-drying cycles were studied, and the probabilistic characterization of shear strength parameters of weak interlayers under wetting-drying cycles was realized based on the Copula theory.[Results]The result show that the brittleness index of the weak interlayer decreases with the increase of the number of cycles, the cohesion decreases with the increase of the number of wetting-drying cycles and finally tends to be stable, and the internal friction angle varies between 37° and 47°.[Conclusion]The weak interlayers show typical strain softening characteristic in the shear process. Under the same normal stress, both the peak shear stress and the residual shear stress decrease with the increase of the number of wetting-drying cycles. The larger the normal stress is, the larger the shear modulus and peak and residual strength of the weak interlayer are. The attenuation of peak cohesion conforms to exponential function, and the attenuation of residual cohesion conforms to linear function. The variation coefficient of cohesion increases with the increase of the cycle period, and the dispersion of the parameters increases gradually. In addition, the coefficient of variation under dry condition is higher than that under saturated condition, indicating that the degree of dispersion under dry condition is stronger. This study reveals the deterioration mechanism of shear strength of weak interlayers under wetting-drying cycles, which is expected to provide theoretical basis and data reference for the evolution and control of landslide geological disasters in the Three Gorges Reservoir area.
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基本信息:
DOI：10.13928/j.cnki.wrahe.2023.11.017
中图分类号:TV223.2
引用信息:
[1]柯琪睿,李长冬,姚文敏,等.干湿循环下侏罗系软弱夹层剪切特性与抗剪强度参数概率表征[J].水利水电技术(中英文),2023,54(11):192-204.DOI:10.13928/j.cnki.wrahe.2023.11.017.
基金信息:
国家自然科学基金项目(42107181);国家自然科学基金重大项目(42090054); 中国博士后科学基金资助项目(2021M702932)
2023-01-30
2023
2023-10-16
2023
1
2023-11-20
2023-11-20