多年冻土区公路路基病害分析与处治对策研究

发布时间：2018-02-23 04:06

本文关键词： 多年冻土融化夹层年平均地温融沉变形路基高度冻融循环回弹模量含水率片块石路基　出处：《长安大学》2014年硕士论文　论文类型：学位论文

【摘要】：青藏公路穿越550多公里生态环境恶劣、地质条件复杂的高原多年冻土地区，公路沿线发育着融沉、波浪、纵向裂缝等特有的病害，严重影响着公路的安全、舒适运营。本文针对上述病害，以多年冻土区路基病害调查、数值模拟和理论分析、室内试验和野外试验为主要研究手段，对路基病害进行了深入的研究，并提出了相应的处治对策。主要开展了以下几个方面的研究：（1）利用历次青藏公路病害调查资料，对多年冻土地区公路路基病害进行统计分析。结果表明：冻土路基下融化夹层厚度随多年冻土年平均地温的升高而增大，融化夹层厚度随年平均地温的变化率随地温的升高而加快，融化夹层厚度与路基高度的关系呈凹形抛物线；沉陷、波浪病害随年平均地温的升高呈先增大后减少的趋势，路肩和边坡部位填料经历冻融循环作用后压实度损失严重，路基填土内部含水率增大，总体上沉陷、波浪病害随路基下伏多年冻土含冰量的增加而增大；纵向裂缝随路基下伏多年冻土含冰量的增加而增大；翻浆主要出现在深季节多年冻土区，在高温多年冻土区也偶有发现。（2）应用热力耦合模型对多年冻土区路基温度场、变形场开展数值模拟研究，得到如下结论：多年冻土区路基变形在相同路基高度时，随年平均地温的升高而增大，在相同年平均地温时，随路基高度的升高而减小；路基产生变形的主要原因是路基下伏多年冻土升温导致的退化；对比0℃、-1.5℃等温线位置与形态，发现不管对于哪种地温类型的多年冻土，，通过提高路基高度来维护路基下伏多年冻土长期稳定性效果不明显；当路基高度为4m时，冻融循环作用造成路基填土的变形达到1.5cm左右，路基填料部分土体经冻融循环作用后强度衰减不容忽视。（3）针对高原多年冻土地区路基填料常见的冻融酥松现象，开展不同粉黏粒含量、不同含水率填料的冻融循环试验，研究冻融循环作用和含水率对路基土回弹模量的影响。试验结果表明：粉黏粒掺量大于15%时，回弹模量衰减规律基本类似，高含水率时，一、二次冻融循环作用后回弹模量衰减剧烈，而后衰减趋势变缓，直至稳定，低含水率试件衰减的较为均匀；12%粉黏粒掺量试件在含水率高时，衰减规律类似掺量大于15%的低含水率试件，12%粉黏粒掺量低含水率试件和9%粉黏粒掺量试件在经历多次冻融循环作用后，衰减已不明显；经历同等次数冻融循环作用后，20%、15%和12%粉黏粒掺量试件回弹模量随含水率的增大而减小，9%粉黏粒掺量试件回弹模量变化相对不是很明显；粉黏粒含量、含水率和冻融循环作用三种因素对粗粒土回弹模量的影响均不可忽视。（4）对片块石路基实体工程试验结果进行分析，发现片块石路基能够有效消除路基下伏的融化夹层，在同一深度处片块石路基地温明显低于普通路基，很好地保护了下伏多年冻土，同时，通过对5年的地温观测数据分析，片块石路基下冻土相比普通路基推迟融化近一个月，提前回冻一个月，片块石路基下多年冻土融化速率和升温速率明显比普通路基慢，片块石路基有效抵御了黑色路面吸热作用和全球气候变暖对路基下多年冻土扰动的影响。（5）通过对前面的分析，提出合理选择路基填料和采用片块石路基进行处治的对策。为减少路基填土经冻融循环作用产生的变形，提出路基填料粉黏粒含量应在15%以内的建议，同时必须做好路基排水工作，对于高温、高含冰量和地质条件复杂的地区，应把粉黏粒含量标准提高至12%以下；为减少因多年冻土地温升高造成的融沉变形，提出片块石路基的处治对策，保护路基下伏多年冻土，并经过青藏公路近11年的运营，证实了片块石路基的优良效果。
[Abstract]:The Qinghai - Tibet Highway crosses over 550 km of ecological environment and complex geological conditions , and is characterized by thaw settlement , wave , longitudinal crack and so on , which seriously affects the safety and comfort operation of the highway . In this paper , the main research methods of subgrade disease investigation , numerical simulation and theoretical analysis , indoor test and field test are carried out in permafrost regions . ( 1 ) Based on the investigation data of the disease of Qinghai - Tibet highway , the results show that the thickness of the thaw interlayer increases with the increase of the annual average ground temperature , and the thickness of the thaw interlayer increases with the increase of the ground temperature . ( 2 ) The thermal coupling model is applied to simulate the temperature field and deformation field of roadbed in permafrost regions . ( 3 ) The effects of freeze - thaw cycle and moisture content on the rebound modulus of subgrade soil were studied . The results showed that the decay law of elastic modulus after repeated freeze - thaw cycles was similar to that of 15 % . ( 4 ) According to the analysis of the test results of the block stone roadbed entity engineering , it is found that the block stone roadbed can effectively eliminate the thaw interlayer under the roadbed , the temperature of the block stone road base at the same depth is obviously lower than that of the ordinary roadbed , the lower volt permafrost is well protected , and meanwhile , the permafrost thawing rate and the temperature rise rate of the block stone roadbed are obviously slower than that of the common roadbed by the ground temperature observation data analysis of five years , and the block stone roadbed effectively resists the influence of the heat absorption of the black pavement and the influence of the global warming on the disturbance of permafrost under the roadbed . ( 5 ) In order to reduce the deformation caused by freeze - thaw cycling , it is suggested that the clay content of subgrade filler should be within 15 % . In order to reduce the thaw settlement caused by high temperature , high ice content and complex geological conditions , it is necessary to raise the clay content standard to less than 12 % . In order to reduce the thaw settlement caused by the temperature rise of permafrost , this paper puts forward the treatment strategy of block stone roadbed , protects the permafrost under the roadbed , and passes the operation of Qinghai - Tibet Highway for nearly 11 years .

【学位授予单位】：长安大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U416.1

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