黄土地区非对称加筋路堤作用机理及变形特性研究

发布时间：2018-07-07 09:21

本文选题：现场试验 + 数值模拟　；参考：《华中科技大学》2014年博士论文

【摘要】：目前,我国尚无黄土地区公路建设规范,对黄土地区公路路堤变形特性缺乏系统的研究。受路堤填料性质、环境因素和重载车辆荷载的影响,黄土地区公路路堤尤其是非对称路堤,经常出现过大沉降、不均匀沉降、边坡失稳和支挡结构破坏等病害,严重影响了公路的长期运营性能。研究重载交通条件下路基不均匀沉降的成因,分析行车动荷载作用下路基的力学响应,进一步摸清黄土路堤动力变形特性,对治理公路病害、延长公路使用寿命、减少后期养护费用具有重要的理论与工程实际意义。本文通过开展现场试验和数值模拟分析,对黄土地区非对称加筋路堤作用机理、变形特性、稳定性和动力响应特性进行了系统的研究。 (1)采用颗粒流软件PFC2D建立格栅加筋拉拔数值模型,对拉拔过程中筋土界面的宏观力学行为和细观组构参量的演化规律进行了分析,模拟结果表明：剪切带内砂土的组构各向异性直接影响了砂土的抗剪强度；强力链组构各向异性主方向与主应力方向相一致,在荷载传递过程中起主导作用,而弱力链组构各向异性主方向与主应力方向相垂直。 (2)针对黄土地区非对称路堤长期监测资料空白的现状,在山平高速公路试验段开展现场监测工作,对黄土非对称加筋路堤地基沉降、侧向位移、基底压力和格栅变形进行了研究。试验结果表明：采用格栅加筋能有效减小非对称路堤侧向变形；路堤填筑过程中,相同竖向位置处第一层格栅应变最大,第二层格栅次之,第三层格栅最小 (3)通过建立二维有限元数值模型,对采用格栅加筋和加EPS (Expandable Polystyrene Sheet)板工况下黄土非对称加筋路堤在填筑期和运营期的变形特性进行了对比分析,对交通荷载大小、格栅刚度和加筋间距等重要设计参数进行了参数分析。数值模拟结果表明：交通荷载作用下,采用格栅加筋可以很好地控制非对称黄土路堤的沉降和侧向变形；交通荷载越大,加筋效果越显著；增加格栅刚度和减小格栅间距对于控制坡脚侧向位移的约束效果较好,而对于减小路堤顶面沉降效果不明显。 (4)通过建立数值模型,对比分析了加格栅和加EPS板工况下黄土非对称加筋路堤的稳定性,研究了填土参数、加筋参数、路堤高差和交通荷载大小对路堤边坡稳定性的影响。数值模拟结果表明：采用格栅加筋路堤的边坡安全系数始终大于加EPS板工况,格栅加筋路堤破坏时所出现的塑性贯通区面积比加EPS板时大,格栅加筋路堤的稳定性好于加EPS板工况。 (5)考虑山西省运煤车辆行车荷载的影响,将交通荷载视为半正弦波循环荷载,通过数值模拟研究了黄土地区非对称加筋路堤的动力特性,对交通荷载振幅、频率、行车间隔和路堤两侧高差等重要参数进行了参数分析。数值模拟结果表明：交通荷载振幅和频率对路堤变形影响较大,而行车间隔和路堤两侧高差的影响较小；交通荷载作用下,采用格栅加筋的黄土非对称路堤变形控制效果好于加EPS板。本文研究成果对于将格栅加筋应用于黄土地区非对称公路路堤变形控制具有重要的参考价值,对于提高黄土地区公路路堤设计水平,延长路堤使用寿命,减少路堤养护费用具有重要的理论意义和实际意义。
[Abstract]:At present , there is no systematic study on the road embankment deformation characteristics in loess area , which has seriously affected the long - term operation performance of the highway . The paper studies the mechanism , deformation characteristics , stability and dynamic response characteristics of asymmetric stiffened embankment in loess area .

( 1 ) Using the particle flow software PFC2D , a numerical model of grid reinforcement drawing is established , and the macro - mechanical behavior and the evolution law of the meso - structure parameters are analyzed . The simulation results show that the texture anisotropy of the sand in the shear zone directly affects the shear strength of the sand .
The main direction of the strong chain fabric anisotropy is consistent with the main stress direction , and plays a leading role in the process of load transfer , while the main direction of the weak force chain fabric anisotropy is perpendicular to the main stress direction .

( 2 ) On the basis of the present situation of long - term monitoring data of asymmetric embankment in loess area , on - site monitoring work is carried out in the test section of Shanping Expressway , and the foundation settlement , lateral displacement , foundation pressure and grid deformation of asymmetric reinforced embankment of loess are studied . The results show that the lateral deformation of asymmetric embankment can be effectively reduced by using grid reinforcement .
In the process of embankment filling , the first grid strain at the same vertical position is the largest , the second grid is the next , and the third grid is the smallest .

( 3 ) By establishing a two - dimensional finite element numerical model , the deformation characteristics of the loess asymmetric reinforced embankment under the condition of grid reinforcement and EPS are compared and analyzed , and the parameters of the important design parameters such as traffic load size , grid rigidity and reinforcement spacing are analyzed . The numerical simulation results show that under the action of traffic load , the settlement and lateral deformation of the asymmetric loess embankment can be well controlled by using the grid reinforcement .
The greater the traffic load , the more significant the reinforcement effect .
The effect of increasing the grid stiffness and reducing the grid spacing on the lateral displacement of the control groove is better , and the settlement effect of the embankment top surface is not obvious .

( 4 ) By establishing a numerical model , the influence of filling parameters , reinforcement parameters , height difference of embankment and traffic load on the stability of embankment slope is studied .

( 5 ) Considering the influence of traffic load of coal - carrying vehicles in Shanxi Province , the traffic load is considered as a half - wave - wave cyclic load , and the dynamic characteristics of asymmetric stiffened embankment in loess area are studied by numerical simulation . The numerical simulation results show that the amplitude and frequency of traffic load have great influence on embankment deformation , and the influence of traffic load amplitude and frequency on embankment deformation is relatively small ;
Under the action of traffic load , the deformation control effect of loess asymmetric embankment with grid reinforcement is better than that of EPS board .

The research results are of great reference value to the application of grid reinforcement in the deformation control of asymmetric highway embankment in loess area . It is of great theoretical and practical significance to improve the design level of highway embankment in loess area , extend the service life of embankment and reduce the maintenance cost of embankment .
【学位授予单位】：华中科技大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：U416.12

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