寒区道路盐渍化路基盐份迁移过程及变形机理研究

The salty soil area in China is about 0.2 million square kilometres, which is ranked as 4th in the world. Salt expansion and frost heave have been leading to a series of technical problems on infrastructure construction such as highway and railway in cold regions. Therefore, it is very urgent and important to prevent salt expansion and frost heave from destroying road. In this project, the driving mechanism on salt transportation in soil and salt expansion mechanism will be clarified through indoor and outdoor freezing-thawing tests. And analytical theory of salt transportation in soil will also be proposed..Some triaxial tests of mechanical properties of salty soil will be carried out to discuss the influence of salt on frozen soil strength and establish strength criterion and constitution of salty soil. Some creep tests of frozen soil with different temperatures, moisture contents, and salt contents will also be performed to determine long-term strengths and stress-strain relationships..Some methods on keeping salt from intruding into embankment will be developed, whose validity will be checked by in-situ contrast tests..A mathematical and mechanical model of heat, moisture, salty and mechanical interaction in salty frozen embankment will be deduced, and its corresponding numerical analytical method will also be developed. All of these will be verified and modified by in-situ tests. Then, according to this model, long-term thermal and mechanical stabilities of embankment in cold salty regions will be predicted and evaluated. At the same time, reliability of control measures on salty embankment will be analyzed. And some new embankment structures and measures on guaranteeing the stability of salty embankment in cold regions will be eventually proposed.

我国盐渍土面积约20万平方公里，居世界第4位。盐胀和冻胀给寒区公路、铁路等基础设施的建设带来一系列的技术难题，如何防止盐胀和冻胀对道路的破坏便成了亟待解决的问题。本项目拟通过室内外试验，揭示在冻融循环作用下，土壤中盐分迁移的驱动机制及盐胀机理，给出寒区土壤中盐分迁移分析的计算理论。对含盐冻土的力学特性进行三轴试验研究，探讨盐分对冻土强度的影响规律，建立含盐冻土强度准则和本构模型。对不同温度、含水量及含盐量冻土进行蠕变试验，确定其长期强度和应力应变关系。研发寒区阻隔盐分侵入路基及防治盐胀的方法措施，并通过野外对比试验对其有效性进行验证。建立含盐冻土路基的热-水-盐-力相互作用的数学力学模型，提出其数值分析方法，采用野外试验结果进行检验和修正，然后对高寒盐渍土区路基的长期热力稳定性进行预测和评价，分析盐渍土路基防治措施的可靠性，最终确定能够确保寒区盐渍土路基稳定性的路基结构及方法措施。

我国盐渍土面积约有20多万平方公里，居世界第4位，其中严重的区域是新疆塔里木盆地、青海柴达木盆地、青海湖边缘和阿拉善荒漠等寒冷冻土地区，故其盐渍土又可称为含盐冻土。含盐冻土地基在岩土工程中是特殊地基，它兼有盐渍土和冻土二者之间的特殊性和复杂性，使得公路、铁路等出现一系列路基病害问题。我们在本项目的资助下，对冻结盐渍土的物理力学特性进行了深入的研究，取得了如下成果：.通过盐渍土在封闭和开放系统下的单向冻结和冻融循环试验，建立了盐渍土冻结温度与盐分性质和土体结构的关系，结合“水分活度准则”，从分子角度阐述了水、盐结晶过程，确定和提出了盐分迁移机理和计算理论。建立了冰压力与盐分浓度、融化活化能、液体压力的关系和盐结晶压力与盐分浓度的关系，得出盐渍土的变形是各组分的热膨胀系数及其差异性、冰-水相变、盐分相变共同作用的结果。.基于室内外试验，从微观角度定量阐释了含盐量对冻结盐渍土强度的影响，提出了盐分影响下的冻结盐渍土屈服准则，探讨了含盐量及相关参数对偏平面形状函数的影响，建立了冻结盐渍砂土双屈服面旋转硬化模型，修正了冻结盐渍砂土的有效应力。.分别对寒区盐渍化普通路基和防盐措施路基进行室内模型试验，发现路基变形是冻胀、融沉和盐胀、溶沉共同作用的结果，提出了“透水土工布-块石隔断层-防水土工布”的阻隔盐分侵入路基及防治盐胀的措施，并在北麓河修建该措施的路基和对比路基，考证了防盐措施的有效性。.建立了含盐冻土的热-水-盐-力耦合数学力学模型，给出其数值分析方法，结合室内和野外研究结果，对模型进行了检验和修正。利用层次分析法，评价了寒区盐渍化路基的稳定性，认为寒区防盐措施路基处于较稳定的状态。.本项目申请专利5项。发表论文56篇，其中SCI论文40 篇，EI论文9篇; 已录用待发表论文3篇，其中SCI论文2篇，EI论文1篇。2014年获“何梁何利基金科学与技术进步奖”1项。2017年获国家科技进步奖“创新团队奖”（排名2）。招聘中科院“百人计划”1名，培养研究生19名。