水-盐效应对饱和黄土力学特性和结构性的影响及机理研究

Often the mineralization degree of loess is high in irrigated areas, and the pore-water salt effect prevails in the saturated loess, which is the potential cause of loess slope instability in the irrigated area. Yet, there is insufficient research on this subject. In the above context, this project plans to use intact loess samples from Heifangtai in Gansu Province, with the aim to investigate the pore-water salt effect on soil behavior and fabrics of saturated loess. By performing lab tests at both macro and micro scales along with theoretical analysis, the mechanics of pore-water salt effect is explored. The main research subjects of this project are: (1) perform permeability test and K0 consolidation triaxial test, study the pore-water salt effect on the characteristics of saturated loess behavior; (2) perform SEM test and self-consolidation test, study the pore-water salt effect on the characteristics of loess fabric; (3) propose a concept namely the “state of fabric”, build the macro and microstructure model that links the soil properties at different scales, find out the mechanics of pore-water salt effect in the saturated loess. The outcomes of this research can provide technical support on the study of loess fabric, in the meanwhile, it also facilitates the understanding of loess properties in circumstance of irrigation and lixiviation. This research has both theoretical and practical significance.

灌区黄土的矿化度高，水-盐效应在饱和黄土中普遍存在，是导致灌区黄土边坡失稳的潜在原因。然而，人们对于其影响灌区黄土边坡稳定性的主要方式和作用机理仍然缺乏认识。为此，本项目拟以甘肃省永靖县黑方台为主要研究区域，采用细-微观试验和理论研究相结合的方法，系统研究水-盐效应对饱和黄土力学特性和结构性的影响，揭示水-盐效应的机理。拟开展的研究包括：（1）开展渗透试验和K0固结三轴试验，研究水-盐效应对饱和黄土力学特性的控制机制；（2）开展扫描电镜试验和自沉降试验，分别从定量和定性的角度研究水-盐效应对饱和黄土结构性的控制机制；（3）提出结构状态参数概念，构建细-微观结构模型，系统分析细-微观参数的相关性，研究饱和黄土中水-盐效应的机理。本项目的研究成果可为进一步研究黄土的结构性提供技术支撑，也可为分析和完善灌溉、淋滤等环境中发生黄土滑坡的力学机制提供理论依据，具有重要的科学研究意义和实际应用价值。

灌区黄土的矿化度高，水-盐效应在饱和黄土中普遍存在，对其机理缺乏认识导致灌区黄土斜坡滑移的孕灾背景仍然不清。本项目以延安某治沟造地工程为研究区，采用细-微观试验方法系统研究了饱和黄土中离子浓度对其原位应力状态、剪切强度、破坏模式和结构性的影响，阐明了饱和黄土中的水-盐效应机理。首先，对研究区的黄土取样分析，明确黄土中主要的离子类型；其次，采用同类型离子配置不同浓度的盐溶液对黄土试样进行淋滤和饱和，开展了变水头渗透试验、K0固结静三轴和动三轴试验研究，揭示了水-盐作用下饱和黄土独特的强度衰减和变形劣化规律；在此基础上，借助成熟的微观成像技术（如扫描电镜、核磁共振等）对黄土的微结构特征进行了分析，从颗粒接触、孔隙分布特征等角度揭示了黄土中水-盐效应的微观机理；最后，基于研究区的实际情况，补充开展了黄土单轴压缩冻融循环试验和波速试验，重点研究了盐分-冻融耦合作用下黄土的强度变化规律，以波速试验为手段首次建立了盐分-冻融-波速的经验关系，并对黄土的饱和度以及强度进行了预测，且取得了满意的预测效果，这部分成果是本项目在实践中的重要出口。总之，本项研究不仅有科学研究意义，还具有重要的实际应用价值和应用前景。