寒旱区土体盐渍化HTSM多场耦合地质环境系统灾变演化机理与工程效应研究

The farming-pastoral zone belong to semiarid area in the west of Jilin province, annual evaporation capacity is 2.6 times of precipitation, the temperature is minus 30℃ in winter and 35℃ in summer, the special climatic conditions formed the special features of the soils near the surface with the characteristics of seasonal frozen soils, salinized soils and dispersive soils at the same area, which gives rise to the main environmental geological problems are as follows: wetland shrinkage→ dry up; grassland degeneration→ salinization→ desertification, pasture reduced; road frost heave and frothing, slope failure of embankment, the life-span shortened for concrete structure, ecological environment seriously deteriorated..In order to slow down grassland degeneration, a large scale diversion project has been built up, under the effect of temperature and humidity a kernel series change of time dependent salinization can be occurred, three key scientific problems is presented as follows: ① Time dependency and distribution law of the salinization structural parameters; ② Evolution mechanism of geological environmental system by mainly microstructure and coupled of Hydro-Thermal-Salt-Micro structure four phases for the salinization; ③ Mechanism of mutual feedback effect between large scale diversion project and salinization soils reclamation in vulnerable environment. This research project will comprehensively apply the interdisciplinary including Engineering Geology, Micro Structural Soil Mechanics, Soil Chemistry，Unsaturated soil mechanics and many other theories, to set up multi phases coupling model take into account of the large scale diversion project, to explore the evolution mechanism of salinization environment system in cold and semiarid area, to provide an example of sustained development for salinization reclamation in cold and semiarid area. .

吉林省西部属半干旱温带，年蒸发量2.6倍于降雨量，气温从冬季-30℃至夏季的35℃，这一特殊的气候条件使得该地区近地表的土体兼具季冻土、盐渍土与分散土三种特殊土的特性，导致主要环境地质问题为：湿地减少→干涸；草地退化→盐渍化→荒漠化，牧场缩减；道路冻胀翻浆、堤坝边坡失稳，砼构筑物寿命缩短，生态环境严重恶化。.为了减缓草原土地退化、启动了大型引水工程，在温度场、湿度场周期作用下会引起以盐渍化时效性为核心的系列变化。提炼出三个关键科学问题：①盐渍化结构性参数的时效性与分布规律；②以结构变化为核心的水－热－盐－结构四场耦合土体盐渍化环境系统演化机理；③脆弱环境盐渍土复垦与大型引水工程互馈效应机理。本项目拟综合运用工程地质学、微观土力学、土化学、非饱和土力学、模型试验等多学科交叉方法，建立考虑大型引水工程的多场耦合模型，探索寒旱区土体盐碱化环境系统演化机理，为寒旱区盐渍土复垦与可持续发展提供示范。

项目以3个灌区为引水工程加上长春、农安为辅助地点共5个点为研究地点，如图1所示。五年来，我们以每年10-15次的频率到现场观测、取样、调查，对五个研究区的引水工程包括试验段、试验田等现场水渠引发的工程问题进行了筛查，取得了千余条数据，每年在室内进行了几百组的土体物理力学性质的常规测试、土化学、水化学、SEM、CT、压汞等项试验，在室内进行了大型物理模拟试验，与吉林省水利勘察院合作，在现场进行了不同护坡材料的边坡稳定性示范试验，得到了大量的观测数据，采用线性和非线性理论，建立了水、热、盐、结构四场耦合模型，并通过力学的计算，建立了五场耦合模型，通过与吉林省水利勘察设计院的合作，在大型的试验边坡分析监测基础上，对所建立水、热、盐、结构五场耦合模型进行了验证与改进，综合研究灌区的研究成果，进一步完善与重大引水工程安全相关盐渍化评价综合分类系统，编制报告，出版专著，最后提交结题报告。不同覆盖层条件下土体盐渍化参数时效性与分布规律研究，长期监测分散性盐渍土体在温度、干湿、时间的叠加条件下土的工程地质性质变化规律，明确进行分散土的定义、建立水热盐的迁移耦合模型，为制定分散土的规定。寒旱条件下盐渍化过程的物质迁移与结构变化及不良工程效应模型试验，研制仪器在室内物理模拟自然条件叠加人类活动情况下土体中的物质迁移与转化规律。水-热-盐-结构多场耦合条件下土体苏打盐渍化环境系统演化机理研究，从物质组成和微观结构特征上进行分散土物质迁移的机理及成因机制研究。脆弱环境盐渍土化与大型引水工程互馈效应综合地质模型研究。互馈效应综合地质模型验证与盐渍化防控对策。