共查询到16条相似文献,搜索用时 578 毫秒
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冻结地层加固法是一种环境影响小、加固效果好的地层加固方法,人工冻结壁的形成是一个复杂的热-力耦合问题。依托实际盾构隧道始发施工中冻结加固工程,采用有限差分软件Flac3D建立数值模型分析了地铁隧道水平冻结施工中温度场随时间的发展和分布特征,同时采用准热-力耦合的方法,分析了冻结施工中地表冻胀隆起变形规律。分析结果表明:冻结壁模拟交圈时间和设计交圈时间基本一致;冻结壁交圈前,地表冻胀隆起位移速率快,冻结壁交圈之后,地表冻胀变形逐渐趋近稳定。计算结论可供设计和施工参考,提供了一种简便的人工冻结加固施工的数值模拟方法。 相似文献
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针对黏性土淋洗效率低下问题,提出了人工冻结法协同竖井淋洗原位修复污染土壤的方法.通过垂直布设冻结板,水平冻结土体的竖井淋洗模型试验,研究冻结过程中土中温度场、水分场分布及融解期的排水方式,探讨了人工冻结法协同竖井淋洗原位修复污染黏性土的可行性.研究表明:利用人工冻结法,使未冻土侧水分或淋洗液在"冻吸力"作用下向冻结锋面迁移,然后利用塑料排水板完成融化水(淋出液)与土壤分离的方案可行,能够解决抽液过程中抽液井和注液井之间土体容易形成渗流通道出现优先流,导致淋洗效率低下的问题.在分步冻结模式下,未冻土侧水分在"冻吸力"作用下向冻土侧迁移,冻结-吸水量为22.78 L,融化-排水量为24.60 L;经历一次冻融循环后,相同冻结模式下冻结-吸水量达到30.40 L,在负压抽吸模式下排水量达到44.21 L.该研究结果为今后原位修复污染黏性土提供了新的思路. 相似文献
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复杂环境下浅埋暗挖隧道穿越薄富含水层冻结温度场研究 总被引:1,自引:0,他引:1
提出了南京地铁2号线新街口-上海路隧道穿越薄富含水层冻结法止水加固方案,利用ADINA有限元软件对该浅埋暗挖隧道涌水段建立冻结温度场数值模型,分析了冻结管间距、冻结盐水温度、冻结管直径对冻结壁发展速率、冻结壁厚度、平均温度的影响,以此为基础对冻结参数开展优化设计,并获得成功应用。研究结果表明:利用人工冻结技术能够有效解决这一特殊岩土工程难题。为了在支护段获得有效地止水冻土帷幕,冻结管间距应小于等于1 m;冻结工程中采取-30℃的盐水温度既能满足需冷量,又能符合经济性要求;采取大直径的冻结管对增加冻土墙厚度与降低冻土壁平均温度的影响并不显著。 相似文献
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不同土质的冻结温度是人工冻结法冻结壁设计重要依据。为研究土质对人工冻土冻结温度的影响,选取不同地区人工冻结法施工典型土层开展冻结温度试验,提供了不同地区典型土层的冻结温度范围,并结合水泥土、含盐土冻结温度试验进行对比分析。结果表明:同一地区不同土层的冻结温度随其土颗粒粒径的增大而增大;随水泥掺入比及龄期的增加,水泥土的冻结温度降低;随含盐量的增加,NaCl含盐土冻结温度线性降低,含盐量对氯盐土比对硫酸盐土的冻结温度影响更显著。研究成果对不同土性的冻结壁设计具有指导意义。 相似文献
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本文阐述了人工地层冻结法的基本工艺和特点,根据国内外施工实例,给出了冻结法在基坑施工中应用的五种方式。 相似文献
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中国地层土冻结技术研究的回顾与展望 总被引:11,自引:9,他引:11
The method of artificial ground freezing will be used extensively with the increase of underground construction. Great attention has being paid to the research and its application. The developmentsof ground freezing research in China are reviewed here. The state-of-art and prospect of ground freezingresearch are analyzed. 相似文献
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The finite element method, formulated for non-linear heat conduction, allows the solution of practically any ground freezing problem. Stabilization of wet soils by artificial freezing and freezing under roads induced by cold winter conditions are considered in this paper. Special features of the program used include parabolic isoparametric elements, a new time stepping scheme and an improved procedure for the estimation of thermal properties. 相似文献
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地铁建设中时有穿越富含砾石的地层,需使用冻结法施工,而砾石地层的热物理性质是冻结法设计的重要依据。为研究人工冻结砾石土热物理特性,通过自制试验仪器,开展了砾石土冻结温度、导热系数和容积热容量测定方法及其特性研究,并与黏土、粉土等典型土层进行对比分析。结果表明:砾石土冻结温度曲线变化符合常规变化规律,且冻结温度为-0.21 ℃,高于黏土、粉土等;砾石土容积热容量与黏土、粉土等相近,随颗粒粒径增大,常温和冻结状态下土体容积热容量比值减小,其中砾石土的比值为1.19;砾石土导热系数较大,冻结状态下达3.89 W/(m·k),是常温状态下的1.65倍,符合颗粒粒径对导热系数的影响规律。砾石土导热系数可按各组成物质的导热系数及其相应的体积比推算。 相似文献
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Depending on artificial freezing method applied in subway tunnel construction, a series of stress-controlled cyclic triaxial tests were conducted on freezing–thawing mucky clay to investigate their resilient and plastic strain behavior. In terms of practical engineering, this study focuses on three significant influencing factors which are artificial freezing temperatures, dynamic stress amplitude and loading frequency. This study demonstrates how these influence factors effect on the resilient strain or dynamic elastic modulus and accumulated plastic strain which are crucial to better understanding the strain behavior of freezing–thawing soil. The results indicate that the value of freezing temperature has slight influence on dynamic elastic modulus, but the freeze–thaw action can truly decrease the dynamic elastic modulus of soil, and soil with higher freezing temperature possesses larger accumulated axial strain. Besides, the dynamic elastic modulus decreases remarkably with the increasing of the cyclic stress amplitude, while the accumulated plastic strain behaves adversely. In addition, loading frequency has the least effect compared with other two factors, but lower frequency can generate larger accumulated plastic strain. 相似文献
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The paper presents a short survey of large Soviet experience in the field of artificial freezing and cooling of soils. Some examples of artificial ground freezing used for the development of mineral deposits, in mining and coal industry, in subway construction are given.
A special field of the cold application in the construction is the cooling of soils which have already had the negative temperature. This engineering method is applied in permafrost regions for improving the strengthening properties of the weak soils used as the bases of structures.
In the USSR this method is used successfully for improving the bearing capacity of frozen soils and for the creation of frozen waterproof screens in hydrotechnical engineering as well. Some examples of the employment of this method are also given. 相似文献