【作者】 朱宝龙；

【导师】 胡厚田；

【作者基本信息】 西南交通大学 ， 岩土工程， 2005， 博士

【摘要】 近年来,在我国山区铁路、公路建设中,常遇到一种分布在斜坡上的软弱土,它与海相、湖相等沉积的软土的物理力学指标类似,但在形成原因、分布范围、物质组成及其它特性上又有所区别,为此称其为“类软土”,它是指炭质页岩、炭质灰岩、炭质泥岩等一套含炭的黑色软质岩及其风化产物,在特殊的工程地质条件和气象、水文地质条件下形成的饱水层,受长期浸泡软化或间有微生物作用而形成的坡残积、坡崩积和坡洪积“软土”。 本文以北京—珠海高速公路粤境南段K108类软土滑坡为例,通过现场试验、室内试验、现场监测、理论研究及数值模拟等方法,对类软土的工程特性进行了较为系统地研究,并对与类软土滑坡相适应的新的支挡结构——钢管压力注浆型抗滑挡墙从设计计算理论、施工工艺等方面进行了研究,取得了以下主要结论和成果: (1) 系统地总结了类软土滑坡典型的工程特性。对K108类软土滑坡的地层岩性、构造特征、水文地质特征及滑坡产生原因、过程进行了分析。 (2) 通过室内试验,研究了类软土的物理力学性质,给出了各项指标的典型值;得出了确定类软土的指标界限值,其天然含水量、孔隙比、压缩系数、天然快剪强度等指标与一般沉积软土类似,仅含水量略小于液限:研究得出类软土具有弱—中的膨胀性;同时,研究了类软土的触变性,得出其触变试验曲线。 (3) 通过对多个类软土试样进行详细的扫描电镜(SEM)观察,得出类软土具有以下四种主要的微观结构:絮凝结构、定向排列(层流)结构、紊流结构及复合式结构。 (4) 通过室内单轴剪切蠕变试验,研究了类软土的蠕变特性。得出类软土在不同正应力条件下不同含水量的剪应力—应变—时间关系,应用Burgers体模型方程对蠕变试验结果进行拟合,得出了不同正应力下的流变力学参数;同时,得出类软土原样与重塑样在三种不同含水量条件下的类软土的长期强度。 (5) 应用化学热力学理论,对类软土的成因及成土化作用进行了分析。讨论了类软土中黏土矿物的形成与演化;提出了类软土的成因模式。 (6) 对K108类软土边坡稳定性进行了有限元分析。首先,介绍了有限元强度折减法技术的原理,定义了边坡的破坏标准及土体的本构关系、屈服准则;其次,应用有限元强度折减技术对K108类软土路堑边坡进行了模更多还原

【Abstract】 Recent years have seen one sort of slopes consisting of special soft soil during montanic railway and highway construction in China. This special soft soil is significantly different from sedimentary soft soil in its formation, distribution, physical components, but remains similar properties of mechanics. Therefore it is called "similar soft soil". Similar soft soil means the special eluvial-declivous, colluvial-declivous and diluvial-declivous soft soil which comes from the series of carbonaceous soft rock such as carbonaceous shale, carbonaceous limestone, carbonaceous mudstone and its weathering products under specific conditions determined by engineering geology, meteorology, hydrogeology, long-term saturation and microbial reactions etc.Taking the case of similar soft clay landslide located in south K108 of Guangdong segment of Beijing-Zhuhai highway, engineering characteristic of similar soft soil is systematically investigated by field monitoring, indoor test, theoretical calculation and numerical simulation. Some work is also done for the designingtheory and constructing technics of new pattern retaining structure------steel-tubebored grouting anti-sliding retaining wall. Main results and conclusions achieved are presented as follows.1. Important engineering characteristics of similar soft soil landslide are systematically summarized. Analysis is given to the strata lithology, geologic structure, hydrogeologic properties, the cause and process of the K108 landslide.2. Physical and mechanics properties of similar soft soil are studied by indoor test. The parameters of physics and mechanics and their range are obtained, among which natural water content, void ratio, coefficient of compressibility and natural shear strength are almost the same as those of the sedimentary soft soil, just water content a little less than liquid limit. The thixotropy and dilatability of similar soft soil are studied and the thixotropy-testing curve is drawn.3. By SEM observation of the dominant mineral component, lamellar kaolinite, and landslide thrust, the micro-structure of similar soft soil are categorized into four types: flocculent structure, turbulence structure, direction-array structure and complex structure.4. Creep properties are studied on basis of simple-shear creep test. The curves of shear stress-strain-time are drawn with different water content. The creep behavior of similar soft soil is described based on the Burgers visco-elastic model. The shear rheological parameters and long-term strength of natural and recomposed samples ofsimilar soft soil are obtained. It’s shown that the long-term strength drops rapidly with water content increasing.5. The chemical thermodynamics theory applies to analyze the cause of formation and soil-forming action of similar soft soil. Formation and evolvement of clay minerals in similar soft soil are discussed. Soil-forming mode of similar soft soil is that mother rock goes through the procedure of weathering, grain-grouping and soil-forming.6. The strength reduction technique of FEM applies to the stability of K108 similar soft soil landslide. A brief introduction of this technique is given and slope failure, constitutive model and yield criterion of soil are defined. The numerical simulation of K108 similar soft soil roadcut slope is conducted, which proves to be consistent with limit equilibrium analysis. Also the stability of K108 similar soft soil landslide is analyzed by soft soil creep model. The factor of safety drops 20% due to creep properties. In addition, the process of excavation is simulated which keeps consistent with creep situations in practice.7. Theoretical investigation of the new pattern of retaining structure, steel-tube bored grouting anti-sliding retaining wall, is conducted. Its properties and advantages are introduced and the designing methods are proposed. From the perspective of single pile, FEM applies to steel-tube bored grouting micropiles based on Winkler foundation model. Also the stability of slope reinforced by steel-tube bored grouting micropiles is analyzed and the design method is presented. The equivalent bending-resistant stiffness method is taken to explore the situation of decomposition of mechanics between micropiles row. Internal forces of the retaining structure are passed on to micropiles row through cross-section area or lateral bending-resistant stiffness. FEM is used to simulate the soil arching effect between micropiles. The influence of different micropiles array on soil arching and load assignment between micropiles row is studied.The steel-tube bored grouting anti-sliding retaining wall composed of one or several rows of steel-tube bored grouting micropiles is considered as underground continuous wall. Internal forces of retaining wall are calculated by foundation counterforce method ("m" method). The design method, strength check and calculation of overturn and sliding instability of retaining wall are presented.8. Taking the example of K108 similar soft clay landslide in Beijing-Zhuhai highway, the whole technics of construction of steel-tube bored grouting anti-sliding retaining wall is proposed by the way of flow chart.9. The effect of steel-tube bored grouting anti-sliding retaining wall applied to reinforce similar soil slopes is checked by means of field excavation, indoor test, dynamic probe, permeability test, PS wave test and pressuremeter test. The K108更多还原