【作者】 段钊；

【导师】 赵法锁；

【作者基本信息】 长安大学 ， 地质工程， 2013， 博士

【摘要】 作为陕西省新兴经济区和重点水利项目的核心地带，泾河下游南岸黄土塬区滑坡频繁发生，曾造成严重的人员伤亡和经济财产损失，极大地制约着当地的经济发展和重点水利工程建设。本文以黄土滑坡的触发机理为主旨，通过现场实地调查，对区内黄土滑坡的发育类型、形成条件、分布规律进行了总结、分析；通过室内试验及数值技术，对不同触发条件下黄土力学行为和斜坡变形破坏规律进行了较系统的研究；并通过定量分析，刻画了造就区内滑坡发育特征的特殊控滑机理；最后以上述宏微观分析为基础，对黄土滑坡的触发机理进行了系统、深入的探讨。主要获得以下结论：⑴研究区黄土滑坡可分为灌溉流滑型黄土滑坡、灌溉滑动型黄土滑坡、侧蚀滑动型黄土滑坡、侧蚀滑塌型黄土滑坡和开挖垮塌型黄土崩塌5个类型。其中灌溉触发型是研究区发生频次最高、致灾后果最为严重的滑坡类型；侧蚀滑塌型具有滑体厚、潜伏期长等特点，一但滑动，将堵塞河道，严重影响沿线水利项目的正常运营。⑵研究区黄土滑坡在时间上具有数量逐年增长、春季高发的分布特征，在空间上具有群集性和分异性的分布特征。此外，灌溉触发型黄土滑坡还表现出多期性的时空特征。⑶常规三轴剪切试验（CTC）结果表明：研究区Q2黄土试样表现为应变软化特征；随着试样含水量的增高，其抗剪强度会显著降低；试样在高偏应力水平下易因体缩效应产生较高的孔隙水压力；通过对p′-q′平面中稳态线和破坏面的拟合，确定了液化可能发生的潜在不稳定区。⑷常剪应力三轴排水剪切试验（CSD）结果表明：该应力路径下土体的破坏机制为孔压激增造成的不完全排水剪切破坏；可按照应力应变特征将其破坏过程分为增压蠕动和液化剧动两个阶段；当孔压水平接近0.70时试样易发生液化。⑸减围压三轴剪切试验（RTC）结果表明：该应力路径下土体的破坏机制为围压降低造成偏应力持续增大土体发生压制破坏；该应力路径下试样同样表现为应变软化特征，但其抗剪强度远低于CTC试验结果，说明应力路径对土体的本构关系影响显著；在不排水条件下围压水平接近0.55时试样易发生破坏。⑹三轴固结不排水蠕变试验结果表明：偏应力越大、加载级数越多、含水量越高、试样蠕变变形越明显；试样在低应力水平下呈线性蠕变特性，随着应力的增大非线性蠕变特性逐渐显著；自建经验模型的适用性是一种具有公式简单、参数易获取优势的较为理想的蠕变经验模型；5元件广义Kelvin模型能够准确表现黄土衰减蠕变中线性粘弹性特点。⑺FLAC3D数值模拟试验结果表明：①灌溉触发型黄土滑坡是一种滑体薄、剪出口近水平的牵引式滑坡。水位持续上升致使斜坡坡脚饱和黄土层增厚，坡脚土体抗剪强度不断降低，是该类滑坡发生的根本原因；②侧蚀触发型黄土滑坡是一种厚度大，后缘滑面陡直，前缘深层剪出的牵引式滑坡。河流侧蚀不断改变斜坡形态，致使斜坡坡脚应力集中且缺乏侧向支撑，是该类滑坡发生的根本原因；③自定义蠕变模型较M-C模型促滑效应显著，体现在蠕变时间越长、水位越高、侧蚀越深斜坡的变形破坏特征越显著。⑻研究区黄土滑坡具有个性与共性共存的发育特征，受控滑因素影响显著，主要表现在滑动距离受液化程度控制、滑坡类型受地貌分异控制、群集发育受成生关系控制3个方面。⑼结合力学试验和数值分析结果较为深入地探讨了黄土滑坡的触发机理并提出了灌溉触发黄土滑坡的静态液化失稳机制、侧蚀触发黄土滑坡的蠕滑拉裂失稳机制以及基于蠕变的强度损伤促滑机制。更多还原

【Abstract】 Positioned in Shaanxi’s emerging economic zone and the heart of key water conservancyprojects, loess landslide at downstream of the Jing River in the south bank occurs frequently,leaving severe property loss and casualty and restriction of the local economic developmentand the key water conservancy projects construction. Under on-site inspection, the textsummaries and analyzes the development type, formation condition and distribution law ofloess landslide in this area. Loess mechanical behavior and slope deformation-failure lawunder different trigger condition were systematically studied in laboratory test, as well asnumerical analysis. In addition, by quantitative analysis, the specific landslide controlmechanism with landslide development features was described. On the basis ofmicro-and-macro analyses stated above, the text discussed the trigger mechanism of loesslandslide systematically and profoundly. Finally we arrive at the following review.⑴In this area, the loess landslide can be divided into5types, namely irrigation flowslidetype，irrigation slide type, lateral erosion slide type, lateral erosion slump type and excavationsubslide type. Irrigation trigger type is the most modal and destructive one. Lateral erosionslide type, with the characteristics of thick sliding mass and long latency, once slides, willblock the river channel and greatly affect the running of the line side water conservancyprojects.⑵Loess landslide in this area shows the temporal characteristics of a growing numberand high risk in spring, the spatial characteristics of clustering and variation. Plus, irrigationtrigger type also shows the spatial and temporal characteristic of multiphase.⑶CTC (Conventional Triaxial Compression Test) suggests that in research area, Q2loesssample is characterized by strain softening. With the rising of moisture content, shear strengthof the sample obviously reduces. Under high deviatoric stress, sample tends to shrink volumeand produce high pore water pressure. By fitting steady state line and locus line of peak inplane p′-q′, the latent instability area with the possibility of liquefaction was determined. ⑷CSD (Triaxial Drained Test at Constant Shear Stress) suggests that under this stresspath, incomplete drained shear failure caused by pore pressure booming is the main loesssample failure mechanism. According to the stress-strain behavior, the failure process can bedivided into boost creep and liquefaction paroxysm. When pore pressure gets to0.70, it tendsto liquefy.⑸RTC (Reduced Triaxial Compression Test) suggests that under this stress path, loessfailure mechanism works when the rising deviatoric stress resulting from the decrease ofconfining pressure damages the loess under stress. Under this stress path, sample also showsthe strain softening characteristic, but shear-resistant strength is much lower than the CTCresult, explaining that stress path greatly affects the soil’s constitutive relation. Underundrained shear, sample tends to be destroyed when confining pressure is close to0.55.⑹Consolidated undrained triaxial creep test suggests that with larger deviatoric stress,more load steps, higher water content, there will be more evident creep deformation. Underthe low stress, sample is characterized by linear creep. With the increase of stress, non-linearcreep characteristic becomes obvious. Self-built empirical modeling is one kind of idealempirical creep model with simple formula and easy access to parameter. Generalized Kelvinmodel with5elements can precisely describe the linear viscoelasticity during the decayingand creep process of loess.⑺What the text has got from FLAC3D numerical simulation experiment are as follows.Firstly, irrigation trigger type is retrogressive landslide with thin sliding mass andsubhorizontal shear opening. The basic reason for landsliding if this kind is that constantrising water level results in saturated slope toe and thicker loess layer and therefore soil shearstrength is gradually weakened. Secondly, lateral erosion trigger type is retrogressivelandslide with great thickness, straight sliding mass in posterior line and deep formation shearin the anterior line. The basic reason for landsliding if this kind is that lateral erosionconstantly changes the slope deformation, leaving the slope toe with concentrated stress andno lateral bracing. Thirdly, user-defined creep model owns better effect in promoting landslidedevelopment, compared with M-C (Mohr-Coulomb). With more creep time， higher water level and deeper lateral erosion, deformation failure characteristic will be more evident in theslope.⑻Landslides in the research area is characterized by the coexistence of individuality andgenerality and largely affected by landslide control element. Their main manifestations are asfollows. It gets controlled by liquefaction degree in sliding distance, controlled bygeomorphic element in sliding types and by interaction among landslides groups.⑼The text profoundly discussed the trigger mechanism of loess landslide and providedstatic liquefaction instability mechanism for irrigation trigger type of landslide, creep crackinstability mechanism for lateral erosion trigger type and strength damage slide promotionmechanism based on creep.更多还原