【作者】 李洪峰；

【导师】 王立海； 单炜；

【作者基本信息】 东北林业大学 ， 林区交通工程， 2010， 博士

【摘要】 高等级公路加宽路基变形是影响加宽后公路的使用寿命、行车舒适的关键问题,而我国季节性冻土面积超过了全国面积的一半,开展季冻区高等级公路加宽对路基变形影响研究,对于在加宽工程中充分考虑季节性冻融的影响,有效控制新旧路基的整体稳定性和不均匀沉降,减少由此引起的上部路面结构层的开裂、破坏,降低管理、养护费用,保证加宽公路的质量,保持良好行车状况,具有特殊的理论与实践意义。本文结合同三公路方正至哈尔滨段公路加宽项目,通过室内试验、回归计算、理论分析、现场监测、数值模拟等方法,研究了不同条件下路基土的强度指标和抗剪强度变化规律、试验段加宽路基变形特性和不同工况加宽路基变形特性等。主要工作包括路基土工程性质试验研究、冻融循环后路基土强度指标变化规律及数学模型研究、现场监测数据分析、不同工况加宽路基变形数值分析,主要研究内容和成果如下：(1)通过室内土工试验结果分析,给出了加宽路基压实度标准建议值,总结了含水率、压实度变化对路基土强度指标影响规律,得出了在路基土中加入不同属性的土工格栅时强度指标和抗剪强度变化规律,得出了筋土界面剪应力、剪切位移、法向应力和含水率之间的相互影响规律,确定了进一步分析时有限元所需参数。(2)冻融循环三轴试验结果表明,随着冻融次数的增加,土的粘聚力逐渐减小,内摩擦角逐渐增大,但增大幅度较小,同一压实度下含水率高的土体粘聚力降低幅度较大。利用MATLAB数学分析软件对试验数据进行回归,建立了冻融路基土的粘聚力c、内摩擦角φ的回归方程,回归方程可进行冻融路基土强度指标预测。(3)对试验路段的观测断面进行了加宽路基的分层沉降、水平位移、孔隙水压力及土压力的试验监测,通过分析得出,加宽路基在分层填筑过程中分层沉降具有明显的加速过程,侧向变形、土压力和孔隙水压力不断增大,新路基填筑结束后,土压力稳定,土在固结过程中超孔隙水压力有明显的消散过程；在新填路基土作用下新旧路基出现差异沉降,随着填筑速率增大,沉降速率增大,侧向变形增长速度也较快,最大侧向位移深度在新填路基坡脚处比旧路基路肩处大；在土体固结沉降基本完成的时候,路基和地基处于较为稳定的状态,新旧路基沉降缓慢,差异沉降率基本稳定。(4)通过路基土室内试验确定有限元所需参数,利用有限元对现场施工进行仿真模拟,新路基路肩处、新旧路基结合处和旧路基路肩处不同深度的横向变形、竖向变形的有限元计算结果与实测值吻合较好,变形规律一致。(5)利用有限元进行了加宽方式、台阶开挖填筑、填土高度、填筑速率、使用土工格栅、冻融循环6种不同工况的数值仿真模拟,分析了公路加宽各工况对路基变形的影响,尤其对新旧路基结合处、新路基路肩、新路基坡脚、加宽后路基顶面、新路基坡脚外地基等典型位置的变形进行了对比研究,得出了不同工况对路基变形影响的规律。结合有限元计算结果分析,在季冻区高等级公路加宽工程中,为有效控制变形、避免施工塌方等,推荐采用高度100cm、宽度150cm路基开挖填筑方式：为减小加宽路基变形和差异沉降,推荐在新路基底部铺设2层土工格栅；为减小冻融对路基安全性的影响,建议控制含水率在最佳含水率附近,压实度采用本文给出的加宽路基压实度标准建议值。更多还原

【Abstract】 The key issue is the deformation of widening subgrade of high-grade way. It affects the life-span of the widened highway and driving comfort. As the area of seasonal frozen soil is more than half of the total land area in China, research on influence of widening in high-grade highway of seasonal frozen area on the deformation of subgrade makes a particular theoretical and practical significance on fully considering the influence of seasonal freezing-thawing in widening engineering, controlling the whole stability and asymmetrical settlement of new and old subgrade effectively, reducing the resulting cracking and damage of the layer on upper pavement,decreasing the management and maintenance costs, ensuring project quality and maintaining a good driving condition.The issue, the intensity indicators and variation laws of shear strength of subgrade soil under different conditions, deformation features of widening subgrade in test sections, deformation features of widening subgrade under different engineering conditions etc., had been studied with laboratory tests, regression calculations, theoretical analysis, on-site monitoring, numerical simulation methods etc., with expansion project of Tongsan highway from Fangzheng to Harbin in China.Its main duties include research on engineering properties of subgrade soil, variation laws of the intensity indicators of subgrade soil after freeze and thaw, study of Mathematical Model, data analysis of on-site monitoring, numerical analysis of deformation of widening subgrade under different conditions, the main research contents and results are as follows:(1) The results, the recommended value of compaction standard of widening subgrade and concluded that the law on the influence of the changing in moisture content, degree of compaction on the strength index of subgrade soil, strength index and the laws of shear strength of the subgrade soil with different properties of the geogrid and the interaction laws of shear stress, shear displacement, normal stress and the percentage of water content in the reinforcement-soil interface to determine the finite element parameters for the need of further analysis, had been achieved by the test analysis in the laboratory.(2) Triaxial test results of freeze-thaw cycles show that with the increase in the number of freezing and thawing, soil cohesion decreases and the internal friction angle increases, but it increases significantly smaller, under the same degree of compaction cohesion of the soil with high percentage of water content has a bigger drop. The regression equation of a cohesion c, friction angleφof subgrade soil in freezing and thawing had been build by the MATLAB mathematical analysis software to regress the test data, it can be used to predict strength index of subgrade soil in freezing and thawing. (3) The results, layer deposition is in a significant acceleration process in the stratified filling process of widening subgrade, the lateral deformation, pore pressure and earth pressure are also increasing. After the filling construction of new subgrade, earth pressure is stable, in the consolidation process of soil, water pressure of excess pore has a significant dissipation. Under the effect of the new fill subgrade soil, differential settlements between the old and the new subgrade occur, with the increasing of filling rate, the settlement rate increases, the growth rate of lateral deformation is faster, the depth of maximum lateral displacement in the toe of new fill subgrade is larger than it in the shoulder of old roadbed. When consolidation settlement of soil basically completes, the subgrade and foundation are in a relatively stable state, the settlement of the new and old roadbed is slow, differential settlement rate is basically stable, had been achieved by test monitoring on stratified settlement of widening subgrade, horizontal displacement, pore pressure and earth pressure of the observation section in the test section.(4) The finite element had been used to simulate the on-site construction by required parameters for finite element through the laboratory test of subgrade soil. The result, calculated results of the horizontal deformation and vertical deformation at different depths in the new roadbed shoulder, at the combination of the old and new subgrade and the old roadbed shoulder are consistent with the measured values and they reflect the same law, had been shown.(5) The finite element had been used to simulate numerical values in six kinds of different conditions, such as, the widening ways, excavation and filling of steps, filling height, filling rate, using geogrid, freezing and thawing. It had been analysed that the deformation features of widening subgrade is impacted by the different conditions, especially for comparative study of combination of new and old subgrade, the new subgrade shoulder, the toe of new subgrade, the top of the widened subgrade, foundation outside the toe of new subgrade and so on typical location. The deformation laws of widening subgrade had been found under different conditions and influential factors.In order to effectively controlling deformation and preventing landslides and facilitating the construction works considerations, according to the finite element analysis, the recommendations of height 100cm, width150cm excavation reclamation methods had been determined. In order to effectively reducing the vertical deformation and lateral deformation of roadbed, the way that Laying two layers of geogrid at the bottom of the foundation can be used to it. In order to reducing the influence of freezing and thawing on the security, the recommended value of compaction degree can be used to control moisture near best moisture. It had been provided by this article about compactness standard distributing with the subgrade height of widening subgrade.更多还原