摘要
原状滑带土具有较强的水敏性,揭示饱水软化下滑带土强度特性演化及弱化机制是评价拟建高速公路沿线顺层边坡稳定性的重要前提。针对四川盆地马边河流域某典型顺层边坡,取原状滑带土开展室内直剪试验、固结不排水三轴试验和环剪试验等研究强度弱化规律;同步结合电镜扫描、核磁共振微细观探测技术,揭示其强度弱化机制;最后,探讨考虑饱水软化作用下顺层边坡稳定性的快速评价法。结果表明:饱水软化下原状滑带土的抗剪强度弱化显著,且显著弱化时域为前1h,该时域中滑带土含水率增幅79.6%,黏聚力下降45.0%,内摩擦角下降36.2%,有效黏聚力下降46.6%,有效内摩擦角下降21.5%;滑带土中粗颗粒咬合阻碍剪切面的形成,而饱水软化后咬合摩擦转变为滑动摩擦,应变软化特征明显;滑带土的强度弱化源于其内部结构的剪切破坏,黏土矿物吸水膨胀,颗粒间胶结破坏,小孔隙体积增大,结构趋于疏松,导致强度弱化明显;基于室内直剪试验和极限平衡法,提出了能够用于快速评价顺层边坡稳定系数的定量关系式。
The undisturbed slip zone soil has strong water sensitivity,and hence understanding of the strength behavior and weakening mechanism of slip zone with water-saturated softening shall be essential to evaluating the stability of bedding slope along a proposed expressway.The direct shear tests,the consolidated undrained triaxial tests and the ring shear tests were carried out to study the strength weakening laws of the undisturbed specimens taken from the slip zone of a typical bedding slope in Mabian River of Sichuan Basin.Meanwhile,with the aids of scanning electron microscope(SEM)and nuclear magnetic resonance(NMR),the strength weakening mechanism of the slip zone soil was analyzed.Finally,the rapid evaluation method of the bedding slope stability considering the saturated softening was explored.The results show that the shear strength weakening of undisturbed slip zone soil with saturated softening is prominent,and the first hour was identified as the time domain of sharp weakening.In this time domain,the water content of slip zone soil increased by 79.6%,the cohesion decreased by 45.0%,the internal friction angle decreased by 36.2%,the effective cohesion decreased by 46.6%,and the effective internal friction angle decreased by 21.5%,respectively.The occlusion of coarse particles in slip zone soil hinders the formation of the shear plane,and after the saturated softening,the occlusal friction changes into sliding friction,leading to the occurrence of the obvious strain softening.The reduction of shear strength of slip zone soil is attributed to the shear failure of its internal structure.During saturated softening,clay minerals swell due to water absorption and the cementation among solid particles is destroyed.Based on NMR,it is revealed that the volume of small pores in specimens increases under the submerging conditions and the structure tends to be loose,resulting in the evident strength weakening of the undisturbed specimens.Furthermore,a quantitative relation is proposed to rapidly assess the stability of bedding slope based on the direct shear test and the limit equilibrium method.
作者
邬凯
周立荣
张乐
向波
赵海松
张俊云
左涛
Wu Kai;Zhou Lirong;Zhang Le;Xiang Bo;Zhao Haisong;Zhang Junyun;Zuo Tao(Sichuan Highway Planning Survey Design and Research Institute Ltd,Chengdu,Sichuan,610041,China;Southwest Jiaotong University,Chengdu,Sichuan,610031,China)
出处
《土木工程学报》
EI
CSCD
北大核心
2023年第S01期24-34,共11页
China Civil Engineering Journal
基金
国家自然科学基金项目(41877269)
四川省交通运输科技项目(2021-A-02)
四川省科技计划重点项目(2021YFS0321)
关键词
顺层边坡
原状滑带土
饱水软化
强度特性
稳定性评价
bedding slope
undisturbed slip zone soil
saturated softening
strength behavior
stability evaluation
