建筑废弃物再生微粉改良土-膨润土竖向防污隔离墙研究

Subsurface contamination is a serious problem in China, and it needs effective ways to control and govern. Vertical cutoff wall is the most basic and effective way to control subsurface contamination. Soil-bentonite cutoff walls, which have characteristics of low hydraulic permeability, good chemistry compatibility and low cost, is a promising technique in containment and treatment of contaminated subsurface soil and water. However, soil-bentonite walls have low strength and large compressibility which restrict the large-scale application. Recycled powder from construction waste which is porous can be used to improve the performance of soil-bentonite cutoff walls. It has a great significance in utilization of construction waste resource and improvement subsurface environmental conditions. The project focuses on the key scientific problem ‘performance of soil-bentonite walls amended with recycled powder’. It studies the following issues with the methods of theoretical analysis, test, and numerical simulation: compressibility, hydraulic conductivity and contaminant transport characteristics of soil-bentonite amended with recycled powder; assessment of performance of soil-bentonite walls amended with recycled powder. The goal of the project is to reveal the improvement of soil-bentonite walls amended with recycled powder, and to provide theoretical basis and methods for cutoff wall design.

我国城市地下水土污染严重，亟需有效控制和治理。竖向防污隔离墙是最基本而有效的地下水土污染防治技术，其中，土-膨润土隔离墙渗透性低、化学相容性好、费用少，适合我国国情，应用前景良好。但土-膨润土隔离墙强度低，墙体压缩性大，制约了其大规模应用。本项目拟采用疏松多孔的建筑废弃物再生微粉改良土-膨润土竖向防污隔离墙性能，应用到我国数量庞大的地下水土污染防控工程中，对建筑废弃物资源化利用及地下环境改善都具有重大意义。本项目围绕关键科学问题再生微粉改良土-膨润土隔离墙的防污性能，拟采用多种研究手段相结合开展以下研究工作：不同再生微粉掺入量的砂土/粉土-膨润土的压缩性、渗透性和污染物运移特性，及再生微粉改良竖向隔离墙的防污性能评估，目标揭示再生微粉对土-膨润土隔离墙防污性能的改良效果，为竖向防污隔离墙优化设计提供理论依据和方法。

我国城市地下水土污染严重，亟需有效控制和治理。竖向防污隔离墙是最基本而有效的地下水土污染防治技术，其中，土-膨润土隔离墙渗透性低、化学相容性好、费用少，适合我国国情，应用前景良好。但土-膨润土隔离墙强度低，墙体压缩性大，制约了其大规模应用。本项目采用疏松多孔的建筑废弃物再生微粉改良土-膨润土竖向防污隔离墙性能，应用到我国数量庞大的地下水土污染防控工程中，对建筑废弃物资源化利用及地下环境改善都具有重大意义。项目围绕关键科学问题再生微粉改良土-膨润土隔离墙的防污性能，采用多种研究手段相结合开展了以下研究工作：（1）采用将废弃混凝土经过简单破碎并颗粒整形的方法制备得到再生微粉，测试其理化性质；（2）针对典型砂土-膨润土和粉土-膨润土，以不同再生微粉掺量配制满足塌落度要求的土-膨润土试样，进行固结渗透试验，研究再生微粉掺量对砂土-膨润土和粉土-膨润土压缩指数和渗透系数的影响规律，为隔离墙防污性能评估提供重要参数；（3）选择适合的再生微粉掺量，制备掺入再生微粉的砂土-膨润土和粉土-膨润土土柱试样，去离子水渗透试验测试土柱试样渗透系数，惰性离子（氯离子）扩散试验测试氯离子在土柱中的有效扩散系数和表观弯曲因子，惰性离子（氯离子）机械弥散试验测试氯离子在土柱中的机械弥散系数和纵向弥散度，重金属和有机污染物吸附试验测试土样的阻滞因子。试验得到的污染物运移参数是隔离墙防污性能评估的重要依据。（4）针对典型水力条件和隔离墙厚度工况，开展了再生微粉改良土-膨润土隔离墙的防污性能分析，提出达到隔离墙最优防污性能的再生微粉掺量，为改良土-膨润土隔离墙提供理论依据和方法。