黄土高填方路堤沉降规律及预测研究

发布时间：2019-06-19 08:38

【摘要】：在我国经济高速发展的今天,高等级公路里程和密度都得到了很大的提高。对于地形复杂的山区筑路,高填方路堤这种结构形式是极其常见的。在黄土分布比较广的地区,为了提高路堤填筑的经济性,常常以黄土为主要填料。因此,在了解黄土填料物理力学特性的基础上,对黄土高填方路堤的沉降规律及预测进行研究尤为必要。本文以太原市太行路工程阎家峰路段的高填方路堤为研究对象,首先对高填方路堤工后沉降进行了历时一年的沉降监测;与此同时,对现场取得的不同深度的压实土样进行室内土工试验。以室外沉降监测数据和室内土工试验数据为基础数据,对黄土高填方路堤的沉降规律及预测进行研究。主要研究内容和结论叙述如下:1.黄土的物理力学特性。对取得的不同深度处的压实土样进行土工试验,研究了黄土的粒径级配,液塑限,最大干密度对应的最优含水量,以及压缩特性。试验结果表明:(1)填方体孔隙比随着填方深度近似呈1/4正弦波周期性变化,重锤补夯界面处孔隙比最小。(2)高填方路堤经分层碾压及重锤补夯后压缩性明显降低,均变为中低压缩性土。(3)黄土具有压硬特性,即随着应力水平的提升,侧限压缩模量会变大。2.黄土高填方路堤沉降监测结果。在黄土高填方路堤纵向上选取五个断面进行沉降监测,监测结果表明:(1)根据沉降孔中沉降磁环的埋设位置,将高填方路堤大致分为四层土,其中第二层土和第三层土的沉降变化速率较快,压缩量较大;第一层和第四层土的沉降变化速率较稳定,压缩量较小。(2)高填方路堤在沉降前期大约8个月之内沉降速率较快,随后沉降速率变缓,最终沉降趋于稳定。(3)高填方路堤沉降值受填方高度,地形影响比较大,如果填方高度越低,地基在地形上对路堤的约束越强,那么路堤的沉降值也越小;原地基沉降约占路堤总沉降的10%,高填方路堤堤身沉降值s与填方高度h之间的线性拟合关系式为:s=1.109h-3.3889。3.黄土高填方路堤沉降预测。如果把高填方路堤沉降值随着时间的变化规律看作一个系统,由于高填方路堤沉降监测得到的原始数据较少,也就是说,这个沉降系统是一个小样本,贫信息的灰色系统,那么用灰色系统理论来研究这个灰色的系统将更为有效。本预测根据邓聚茏教授于1982年提出的均值GM(1,1)模型,利用三次样条插值函数生成该模型所需要的灰序列,通过模型运算,得到了高填方路堤K4+050断面中点处沉降前期和后期的沉降~时间响应式分别为:(?)~(0)(t)=7.980)0.216(-1)和(?)~(0)(t)=26.760)0.009(-1),其中t=2,3,...,n。两个时期原始序列和预测序列的灰色接近关联度01分别为0.65和0.998,平均绝对百分误差MAPE分别为7.65和0.61,即沉降后期的01要高于沉降前期,MAPE要低于沉降前期,用灰色系统理论对高填方路堤后期沉降进行灰色建模,预测结果精确性将更高。4.关于黄土高填方路堤沉降的有限元补充分析。根据实际工程简化出有限元分析模型,通过ANSYS有限元分析软件,得到高填方路堤等效应力云图和水平、竖向位移云图,通过有限元分析结果可以发现:(1)路堤填料经过分层碾压及重锤补夯综合处理后,高填方路堤在自重应力作用下路面沉降较小。(2)高填方路堤坡脚处水平位移偏大,施工时得加强对该区域土体的压实处理。
[Abstract]:Today, the high-grade highway mileage and density have been greatly improved in the high-speed development of our country. The structural form of high-filled embankment is very common for road-building in mountainous areas with complex terrain. In the area with a wide distribution of loess, in order to improve the economy of the filling of the embankment, the loess is often used as the main filler. Therefore, on the basis of understanding the physical and mechanical properties of the loess, it is especially necessary to study the settlement rule and the prediction of the high-fill embankment of the loess. In this paper, based on the high-fill embankment of Yan 'a peak section of Taiyuan Taihang Road Project, the settlement monitoring of the high-fill embankment is carried out for a period of one year. At the same time, the indoor geotechnical test is carried out on the compacted soil samples at different depths. Based on the outdoor settlement monitoring data and the indoor geotechnical test data, the settlement rule and the prediction of the high-fill embankment of the loess are studied. The main research contents and conclusions are as follows:1. Physical and mechanical properties of loess. The compaction soil samples at different depths are subjected to soil test, and the optimal water content and the compression property of the loess are studied. The results of the test show that (1) The void ratio of the fill body is approximately 1/4 sine wave periodic variation with the filling depth, and the aperture ratio at the interface of the heavy hammer is the smallest. (2) The compressibility of the high-filled embankment is obviously reduced after the layered rolling and the weight-filling and the compaction of the heavy hammer are obviously reduced, and the high-fill embankment becomes the low-compressibility soil. (3) The loess has the pressure-hard property, that is, with the increase of the stress level, the compression modulus of the lateral limit increases. The results of the settlement monitoring of the high-fill embankment of loess. In the longitudinal direction of the loess high-fill embankment, five sections are selected for settlement monitoring, and the monitoring results show that: (1) According to the buried position of the settlement magnetic ring in the settlement hole, the high-fill embankment is roughly divided into four layers of soil, wherein the settlement change rate of the second layer soil and the third layer soil is faster, The compression amount is large, the settlement change rate of the first layer and the fourth layer soil is relatively stable, and the compression amount is small. (2) The settlement rate of the high-filled embankment is faster in the first 8 months before the settlement, and then the settlement rate is slow, and the final settlement is stable. (3) The settlement value of the high-fill embankment is affected by the filling height and the terrain, and if the height of the fill is lower, the stronger the foundation's constraint on the embankment on the terrain, the smaller the settlement value of the embankment, and the settlement of the original foundation accounts for 10% of the total settlement of the embankment, The linear fitting relation between the settlement value s and the filling height h of the high-fill embankment is: s = 1.109h-3.3889.3. Settlement prediction of high-fill embankment in loess. if that settlement value of the high fill embankment is view as a system with time, the raw data obtained due to the high fill embankment settlement monitoring is less, that is, the settlement system is a small sample, the poor information gray system, Then the grey system theory is used to study the grey system to be more efficient. According to the mean GM (1,1) model proposed by Prof. Deng Juli in 1982, the three-spline interpolation function is used to generate the grey sequence required by the model, and the settlement-time-response formula at the middle point of the K4 + 050 section of the high-fill embankment is obtained by means of the model operation: (? ) ~ (0) (t) = 7.980) 0.216 (-1) and (? ) ~ (0) (t) = 26.760) 0.009 (-1), where t = 2,3,... and the average absolute percent error MAPE is 7.65 and 0.61 respectively, i.e.,01 in the late settling period is higher than the pre-settling period, and the MAPE is lower than the settling period, The grey system theory is used to model the post-settlement of the high-fill embankment, and the accuracy of the prediction results will be higher. Finite element supplementary analysis on the settlement of high-fill embankment in loess. according to the practical engineering, the finite element analysis model is simplified, the effect force cloud image and the horizontal and vertical displacement cloud image of the high-fill embankment are obtained through the ANSYS finite element analysis software, The settlement of the high-fill embankment under the self-weight stress is small. (2) The horizontal displacement at the toe of the embankment of the high fill road is too large, and the compaction of the soil in the area shall be strengthened during construction.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：U416.12

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