【作者】 庞旭卿；

【导师】 倪万魁；

【作者基本信息】 长安大学 ， 地质工程， 2007， 硕士

【摘要】 本文以路基黄土为研究对象,以直剪试验、三轴试验、载荷试验和电镜扫描试验为主要手段,对压实前后路基黄土的微观结构、抗剪强度、地基承载力等特性进行了系统的试验研究和深入的理论分析,对预防和治理黄土路基的地质灾害有着重要的实际意义。本文的研究工作和主要成果如下:首先,对压实前后的土样做了颗粒分析和电镜扫描观察,对比分析了压实前后黄土的粒度组成、孔隙特征和微结构类型的变化,得知压实后黄土中集粒、块粒表面胶结物剥落,颗粒变细,大孔隙减少,原始颗粒骨架破坏,微结构类型由絮凝状微胶结结构和支架大孔微胶结结构变为镶嵌结构和叠置结构。其次,对路基黄土进行了直剪、无侧限抗压强度与三轴压缩、单轴高压固结等试验。分析了原状黄土与压实黄土强度参数(c、φ)的影响因素及变化规律,建立了用含水量表示的抗剪强度公式;利用软化系数表现了水对路基黄土无侧限抗压强度的影响;研究了路基黄土三轴试验条件下的应力一应变特征、应力路径及剪切破坏型式,探讨了路基黄土Et-μt模型。最后,对原状黄土与强夯、振动碾压、冲击碾压不同处治方案下的压实黄土地基承载力采用了载荷试验、动力触探、标准贯入、静力触探等手段进行检测。通过回归分析得出了一般新黄土的容许承载力与物理指标之间的相关关系,编制了一般新黄土地基承载力表,该成果为《公路桥涵地基与基础设计规范》的修订提供了可靠的依据,具有很高的实用价值。通过对载荷试验与单轴高压固结试验条件下路基黄土的应力—应变曲线与时间—沉降曲线特征分析,探讨了路基土体的强度变形特征。通过对各处治方案下路基黄土的压实度、抗剪强度与地基极限承载力比较分析,提出了黄土路基有效的施工处治方案。通过对地基承载力不同的检测手段对比分析,指出了合理有效的检测方法。更多还原

【Abstract】 Focus on the subgrade loess, by main means of direct shear test, triaxial test, load test and Scanning electric microscope (SEM) test, this paper carries systemic trial research and thorough theories analysis on its characteristics including microstructure, shear strength, ground bearing capacity and so on of the intact loess and the compacted loess. It is of great significance in preventing and dealing with the geological disasters of the loess subgrade. The studies and main fruits as follows:Firstly, changes of the particulate components, pore characteristic and microstructure of the intact loess and the compacted loess are contrasted by the way of grain-analysis and SEM. From the analysis and observation, it could be seen that the surface cementation of conglomeration peels, grain becomes thinner; the original grain framework of the loess is destroyed, the flocculate cline-cementation structure and plank-macrospore cline-cementation structure turns to be embedded structure and pile-up structure.Secondly, a series of subgrade loess tests were carried out under direct shear, unconfined compressive strength test, triaxial test and monopodium compression test. The change rules and the influence factor of parameter of shear strength are analyzed. Then the formulae of the shear strength are established with water contend. The effect to unconfined compressive strength of subgrade loess by water was manifested utilizing softening coefficient. And then the character of stress strain, stress path, shear failture model on the triaxialtest are studied. E_t -μ_t model of subgrade loess is discussed.Finally, the load test, power touch scout, standard enter, static touch scout and other detection methods are adopted for studying compacted loess ground bearing capacity in different deal schemes including strong tamper, vibration grinding press, striking grinding press and the intact loess. The correlativity between allowable bearing capacity and physics Index of neo loess is elicited through regression analysis, and the table of allowable bearing capacity of the neo loess is worked out The fruits provide reliable basis for edition of "Specifications for Design of Ground Base and Foundation of Highway Bridges and Culverts". The character of stress deformation is discussed through analyzing traits of load deformation curve and time-settlement curve on load test and monopodium compression test. Based comparison analysis of the degree of compaction , shear strength, ultimate bearing capacity of various processing schemes, the effective processing schemes of construction are put forward. On contrast analysis of various detection methods of ground bearing capacity, the reasonable and effective detection methods of ground bearing capacity are brought forward.更多还原