随着在软土地区高速公路大规模兴建，路基稳定性问题频繁出现，稳定性评价的正确与否对工程的设计及施工影响重大。黄陵至延安高速公路是国家规划建设的国家级主干线路包（头）～北（海）公路的重要路段，该项目的建设实施，对改善公路路网布局，特别对加快陕北能源开发，促进区域经济发展起着十分重要的作用。该路段路基土以黄土为主，其中特殊性岩土路基比较发育，以软土及湿陷性黄土为主。本文围绕黄延高速公路路基的具体情况，重点对公路路基的沉降变形进行了分析和评价，探讨了软弱路基的处理方案。通过研究，本文主要得出如下认识： (1)分析了研究区地质、工程地质背景：黄延高速公路穿越黄土塬峁梁丘陵地貌。地质构造简单，地层平缓。全线仅发现四条小断层，未发现有明显影响线路稳定的地质构造，构造运动平稳。地表水系不甚发育，地下水以基岩裂隙水为主。拟建路线选线合理，沿线工程地质条件良好，适宜建路。 (2)分析与研究了沿线的路基组成，根据各种特殊性岩土的分布及其特点，对路基进行了稳定、次稳定、不稳定三种类型的划分。 (3)通过对路基某一断面用FLAC3D进行计算，实例计算表明：路基的中、下部土体有向内挤压的趋势，路基中心因为两端对称没有侧向位移，从路堤中心向路堤两端方向，侧向位移逐渐增大，在路堤肩点以下侧向位移最大；随着荷载的增加路基沉降量随之增大，但增加量呈现衰减的趋势，路基中心沉降量最大，路肩较小。 (4)用双曲线法和三点法对路基三个断面进行沉降预测，依据软土的工程地质特征，结果表明双曲线法更适合黄延高速公路软土路基的沉降预测。 (5)在阐述路基沉降机理的基础上，分析了传统的路基沉降计算方法e～p曲线法与e～lgp曲线法对路基总沉降量的计算带来了一定的偏差。依据软土的工程地质特征，二者比较结果表明：e～lgp曲线法较为适合该研究区软土路基沉降计算。 (6)利用毕肖普法、普遍条分法与总应力法对典型路堤的稳定性进行了计算与分析，结果表明：黄延公路软土路基稳定系数偏低，需要对软土路基进行处理。 (7)本文在探讨湿陷性黄土及软土各种处理措施的适用条件和优缺点的基础上，针对研究区湿陷性黄土及软土的特点和实际情况，通过研究论证后认为：强夯法和灰土挤密桩法适合该地区路段湿陷性黄土的处理，换填法和粉喷桩适合沿线软土的处理，并分别对这四种地基处理方案进行了探讨，以期为该公路工程的实施提供一定的参考。

With the large-scale construction of expressway in soft soil area, the problem of roadbed stability appears frequently.The preciseness of stability evaluation has great influence on the design and construction of project.Huangling to Yanan expressway is the important line in the national main highway—Baotou to Beihai, which is planned and constructed by government. The construction of this project is very important to improve the national layout of the road network.It especially makes a crucial role in the energy exploitation in northern of Shanxi and the economic development of the area.The adverse roadbed soil includes mainly collapsible loess and soft soil. Basing on the specific circumstance of roadbed of HuangYan expressway, this paper emphasis analyzes and calculates the settlement and distortion of the roadbed, discuss the schemes about treatment of roadbed of HuangYan expressway.This paper has launched research and following conclusions are gotten: (1)Analyses the geological and engineering geological background of research region: HuangYan expressway crosses-over loess plateau hilly ground geomorphy.The geological structure is simple and structure motion is slack. It is found only four small faults along the whole line.A distinct impact on the line stable geological formation is undiscovered. Geological tectonic movement smoothes.The hydrografical system of ground surface is underdevelopment and underground water includes mainly bedrock frature water. The quasi-road selects proper line and the engineering geological condition along the road is good.So,it is suitable to be constructed. (2)Analyses and studies the composition of roaded along the road.According to all kinds of distribution and characteristic of peculiarity soil,three road types are divided—stability roadbed,second stability roadbed,and instability roadbed. (3)Calculating a section of the roadbed with FLAC3D,the exact calculation indicates that the middle and lower roadbed soil have trend of extruding to inner.The middle roadbed has no lateral displacement because of bilateral symmetry.Lateral displacement augments gradually from middle roadbed to bilateral roadbed and the maximal lateral displacement is at the lower of roadbed shoulder.The roadbed settlement augments gradually with entrying into power but the numerical number is become to weakening trend.The maximal settlement is at middle roadbed and the minimum is at roadbed shoulders. (4)Settlement of roadbed is predicted by hyperbolic method and three-point method. According to engineering geological characteristic of soft soil, the results indicate that hyperbolic method is better fit for the soft soil settlement prediction on HuangYan expressway. (5)By explaining the settlement mechanism of the roadbed, the paper analyses deviation of traditional calculation method about settlement of roadbed including e～lgp curve method and e～p curve method. Compare result indicate that e～lgp curve method is more suitable to the settlement calculation of roadbed in research area according to engineering geological characteristic of soft soil. (6)The stability of roadbed is calculated by bishop method, strip method and total stress analysis method; the result indicates that the stability coefficient of roadbed is low and treatment is needed. (7) Based on appliance condition and merits and faults of all kinds treatment methods to the collapsible loess and soft soil, against characteristics of the collapsible loess and soft soil, the conclusion is arrived.Compacted method and lime-soil compaction pile are fit for the collapsible loess treatment; reversing fill and dust jet pile are fit for soft soil. Four programs are designed individually to give suggestion for engineering.