【作者】 唐东旗；

【导师】 彭建兵；

【作者基本信息】 长安大学 ， 地质工程， 2013， 博士

【摘要】 黄土高原地区是人类重要的活动场所，近年来，黄土地区的经济得到了巨大发展，但由于黄土地区独特的地貌形态为当地经济发展和居民生活带来了很大局限，这也使得黄土地区的切破、削坡现象较为多见。这种对坡体的改造作用引发了很多严重的地质灾害，为当地居民的生产和生活带来了巨大威胁。2011年9月发生于西安灞桥白鹿塬北缘的滑坡造成了32人死亡严重地质灾害，多家依靠塬边取土生产的工厂被关停，引起了国内外的广泛关注。在此背景下，对由于人类工程活动所引起的黄土滑坡进行了大量的野外调查、地形测绘和资料分析，选取了以坡脚开挖所引起的黄土滑坡作为研究对象。从边坡开挖所引起的黄土滑坡的基本特征出发，对影响坡体开挖所造成边坡失稳的特征进行了分析。根据调查结果对由开挖活动引起的黄土滑坡进行了滑动模式的划分，在此基础上对坡脚开挖的黄土滑坡机理进行了研究。通过本文的研究，主要取得以下几点成果：（1）通过野外现场调查和文献资料分析，认为坡体开挖形成卸荷节理，节理走向与边坡走向近似一致，黄土大量发育的节理对坡体的稳定性起一定的控制作用；滑坡后缘裂缝呈弧形和“双耳”状展布；开挖边坡的高度不同，则坡体的运动速度不同，产生危害较为严重的边坡高度多为70m以上；工程开挖类型的滑坡在空间分布表现为：高度的集中性和条带性分布。（2）根据开挖速度的快慢和影响因素对由坡脚开挖所引起的黄土滑坡划分为：快速开挖－拉剪滑移模式黄土滑坡、开挖与降雨耦合模式的黄土滑坡和开挖与冻融耦合模式的黄土滑坡。并对每种类型滑坡发生机制和滑坡特征进行了分析。（3）对原状饱和黄土和非饱和黄土开展了三轴剪切RTC应力路径试验。试验结果表明RTC试验呈剪缩性的应变硬化特征。在非饱和黄土RTC应力路径下造成土体的破坏剪应力较小，土体更易破坏。在饱和黄土试验中，由于在土体变形破坏的过程中不排水条件，产生了超孔隙水压力，加速土体的破坏变形。（4）对不同条件下坡脚开挖所引起的坡体稳定性变化进行数值计算。计算结果表明：在边坡坡角一定的情况下，坡高控制了坡体的稳定性；其稳定性随放坡角度的增加逐渐降低，这种变化在开挖进尺较小时影响并不明显；地层结构对坡脚开挖的影响表现为：结构越复杂，则坡体越稳定；开挖进尺对坡体稳定性的影响表现为：随着开挖进尺增加，坡体的安全系数逐渐减小，在坡体开挖进尺过程中安全性存在拐点。（5）根据坡体破坏的表现形式分为：应力控制型、坡角控制型、地层结构控制型、开挖进尺控制型。根据坡体的受方式不同分为：拉裂破坏区、压剪滑移破坏区、减压剪切破坏区。（6）在坡脚开挖所引起坡体的应力分布特征、坡体变形的物理力学性质变化的基础上，解释了坡体开挖造成裂隙产生、裂缝扩展变形直至失稳的力学机制，认为坡脚开挖是造成坡体失稳变形的决定因素。更多还原

【Abstract】 The Loess Plateau is an important arena for human activities. Loess region’s economyhas been a huge development in recent years. But its unique topography makes a lot oflimitations for local economic development and human living, which makes the cutting slopephenomenon to be more common. This kind of behavior caused a lot of serious geologicaldisasters, which brought a great threat to production and living of local residents. Northernmargin slope of Bailu tableland of Xi’an city produced landslide and killed32people inSeptember2011, causing widespread concern at home and abroad and many factories wereshut down. In this background, the loess landslide caused by human engineering activitiesmake a large number of field surveys, topographic mapping and data analysis, and select theloess landslide caused by the slope toe excavation as the main object of study. The basiccharacteristics of the slope toe excavation loess landslide make the statistical analyses of theinfluence factor of slope toe excavation. On this basis of sliding mode of slope toe excavationclassified, the slope toe excavation induced mechanism of loess landslide is studied.Some main innovative ideas are got as follows in this paper:(1) Through wild field investigation and documentation analysis, that the slopeexcavation formed unloading joints, joints direction approximate unanimously with the slopetoward, To some extent, joints control the slope stability. Landslide edge cracks were "U"shape and "double ears"-shaped distribution. Different slope heights, there is a differentmoving speeds. The slope height70m above is more serious harm. Excavation types oflandslides distributed as follows: high degree concentration and bands distribution.(2) According to the excavation speed and the influence factors of slope toe excavationof loess landslides, which are divided into: quickly unload model of loess landslide,excavation and rainfall coupled model of loess landslide and excavation and freeze-thawcoupled model of loess landslides. The typical cases were analyzed by each type landslidemechanism and the landslide characteristic. And to every type of landslide mechanisms andcharacteristics were analyzed.(3) The triaxial shear RTC stress path tests carried out on undisturbed saturated loess and unsaturated loess. The test results show that the RTC test was contraction under shear andstrain hardening characteristics. Under the RTC stress path test results show that the soil shearstress is lower and easier to destroy. Undrained soil deformation process of destruction, thefailure process is so quick that the excess pores. Excess pore water pressure accelerateddestruction of deformation of the soil.(4) Under different slope toe excavation condition makes the numerical calculation ofslope stability. The results show that the slope angle of certain cases, the slope height controlsthe stability of the slope. Its stability gradually decreases with excavation angle increasing,this change of the slope toe excavation distance is lesser which effect is not obvious.Stratigraphic structure’s influence on the slope toe excavation is: the more complex structure,the smaller impact of excavation. Excavation distance of the slope influence is: with theincrease of excavation distance, the safety factor of a slope gradually reduced, and there is aturning point in the process of excavation.(5) According to the slope failure modes are divided into: stress control type, slope anglecontrol type, control type stratigraphic structure, excavation footage control type. Accordingto the slope failure modes are divided into: stress control type, slope angle control type,control type stratigraphic structure, excavation footage control type. According to differentstress is divided into: tensile failure zone, compression and shear slip zone, reduced and shearfailure zone.(6) Based on the stress distribution characteristics and physical and mechanicalproperties changes of slope deformation and slope structural stress analysis caused by slopetoe excavation, which explains the slope excavation resulting in cracks generated andexpansion and deformation until failure mechanics. Considered slope toe excavation is adecisive factor cause the slope instability.更多还原