季冻区在建高铁路基越冬秸秆覆盖效果分析 Alternative Title Effects of Straw Mulch on Subgrade under Construction in Seasonally Frozen Soil Area 李振萍 Subtype 硕士 Thesis Advisor 慕青松 2016-05-29 Degree Grantor 兰州大学 Place of Conferral 兰州 Degree Name 硕士 Keyword 深季节冻土区 高铁路基 防冻害 秸秆覆盖 数值计算 Abstract 修筑在深季节冻土区的高铁路基，如果按设计完成施工，则可以保证最大冻深在防冻层内，不会进入下部高含水量、高冻胀率的原始地层。但在实际工程施工过程中，由于种种原因，经常会遇到冻结前只完成填筑部分路基的情况。此时，如果在无保护措施的情况下越冬，则路基下高含水量、高冻胀率的原始地层将进入冻结状态，可能导致已填筑部分路基填料层发生不均匀变形、压实度降低等问题，影响工程质量。为避免最大冻深达到路基之下，根据当地资源条件，采用秸秆材料覆盖路基，是一种经济有效的防冻害工程措施。本文通过利用商用软件分析秸秆覆盖下路基的热状况，提供秸秆覆盖措施的工程设计参数。 利用所选计算模型及相应参数，对秸秆覆盖下路基的热状况进行了模拟。结果显示在无覆盖的情况下，对填筑至设计高度2/3以下的路基，最大冻深均有可能进入下部高含水量、高冻胀率的原始地层，从而引起工程问题。在填土高度一定时，计算小麦和水稻两种秸秆同一覆盖厚度下温度场的变化，结果表明小麦秸秆的保温效果比水稻的更好；对不同覆盖厚度下计算，结果表明最大冻结线随着覆盖厚度的增加而上移，存在最小临界覆盖厚度；对同一厚度不同含水量和压实密度的秸秆覆盖下计算表明，含水量和压实密度的变化对覆盖效果的影响很大；对填筑至不同高度的路基，以最大冻深不进入路基填料之下为判据，分别计算地表为平均温度、最低温度和极端最低温度对应的最小覆盖厚度。这一结果对实际工程设计有一定参考价值。 Other Abstract The subgrade preparation for high speed railway construction in deep seasonally frozen soil area, if under given design, the maximum frost-free depth can be ensured by not reaching the water- rich and frost-susceptible natural soil situated below. However, due to various reasons, the subgrade construction may not be completed before winter comes. In the case without any preventive measures, the said frost-susceptible soil will be in frozen status that may cause those completed subgrade portion in deformation or lowered compact level and finally affects the quality of construction work. To prevent the soil beneath the subgrade from frozen, considering local available resources, paving corn stover onto subgrade is an economical and practical measures. This article is to provide engineering parameters on stover coverage, by studying the thermal state of the subgrade and use of commercial software. Using the selected model and the corresponding parameters, the thermal conditions of the stover covered subgrade are calculated. It found that, for the subgrade filled with less than 2/3 of design thickness in absence of straw mulch, the maximum frozen depth are likely to enter the natural soil with lower high water content, high rate of frost heave. When the roadbed filling height is a constant value, to calculate the embankment temperature field with two different straws (wheat and rice) covering, the results shows that the heat preservation effect of wheat straw is better than rice. To calculation the embankment temperature field with different straw thickness, the results shows that the ground frost level could move up with the increase of covering thickness, there is a minimum covering thickness existed. In a case of different water content and compaction density of straw, but the same covering thickness, It Shows that, the change of moisture content and compaction density have great influence on the cover effect. The next step is to calculate the temperature conditions in the case of the subgrade filled with different filler thickness taking maximum frozen depth not entering the bottom of the subgrade as the criterion, it offers the minimum thickness of straw mulch corresponding to different filler thickness under average temperature, minimum temperature and extreme minimum temperature respectively. This result has a certain reference value to the practical engineering design. URL 查看原文 Language 中文 Document Type 学位论文 Identifier https://ir.lzu.edu.cn/handle/262010/226231 Collection 土木工程与力学学院 Recommended CitationGB/T 7714 李振萍. 季冻区在建高铁路基越冬秸秆覆盖效果分析[D]. 兰州. 兰州大学,2016.
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