电化学作用下泥岩物性变化的微结构响应与能量转化机理研究

Previous laboratory and field studies have shown that applying a low voltage or a low potential gradient to electrodes inserted in rock and soil mass, and the matrix structure, mechanical strength and engineering characteristics of rock and soil mass were improved. So, reveal the change rule and interaction relations of physical properties of rock and soil mass under electrochemical is a fundamental key problem for electrochemistry treatment methods applied to engineering practices. Based on the contrastive experimental of mechanical properties, swell-shrink characteristic and disintegration of mudstone with electrochemical modification or not, combined with measured results of electricity, mineralogy and microstructure characteristic of mudstone quantitatively and qualitatively, the change rule and interaction relation of physical properties of mudstone under electrochemical was studied. Based on the quantum-mechanical theories, the molecular dynamics model of crystal structure of mudstone mineral were established, combined with the qualitative analysis of current transmission mechanism and electrokinetic effect, included electro-osmosis, electrophoresis and ion migrated of mudstone mass and it’s particles under electrochemical, and microstructure response mechanism of mudstone physical properties change were revealed. The difference of fracture characteristics and energy accumulation and dissipation of mudstone with electrochemical modification or not under different strain rate levels in range of static loading rate was analysis comparatively, and energy-transfer mechanism of mudstone physical properties change were revealed by back analysis. Based on the electrochemical modified test of large-scale mudstone samples, the influence of electrochemical parameters, such as electric potential gradient, action time, electrode type and layout on modified effect of mudstone was studied quantitatively and qualitatively, quantitative relationship between macro physical properties improved effect of mudstone and electrochemical parameters were established.

实验室和现场试验表明对岩土体施加低压直流电场可以改变岩土体的基质结构改良其力学和工程特性，揭示电化学作用下岩土体物性变化规律及其相互作用机理是电化学处置方法应用于工程实践的关键基础问题。基于电化学作用前后泥岩力学特性、胀缩性、崩解性等物性的对比试验，结合其电学、矿物学参数及微结构的定性定量测定结果，研究电化学作用下泥岩物性变化规律及其间的相互关系；基于量子力学原理建立泥岩矿物晶层结构的分子动力学模型，结合电化学作用下泥岩块体及颗粒物的电流传递机理，电泳、电渗及电迁移等动电效应的定性分析，揭示泥岩物性变化的微结构响应机理；对比分析静态加载速率范围内不同等级应变率下改性前后泥岩压裂破坏和能量耗散特征差异，反演分析阐明泥岩物性变化的能量转化机理；基于大尺度泥岩样品的电化学改性试验，定量研究电位梯度、作用时间、电极种类、布置方式等对改性效果的影响规律，建立电化学参量与宏观改性效果间的量化关系。

泥岩所导致的工程问题是在水化或风化作用下，岩体质量持续恶化的结果，泥岩支护加固方法大多聚焦在已破碎或软化崩解的泥岩的加固上，只是从力的平衡角度进行加固，通过改变泥岩的外在因素实现泥岩工程的稳定性控制，存在着较多的局限性和时效性。本项目基于煤系软岩的电化学改性试验，对比分析了电化学作用前后软岩的零电荷点与电荷密度、ζ电位与等电点、矿物成分含量与晶体结构、孔裂隙结构与强度特征以及电阻率等的变化规律，阐明了电化学改性煤系软岩力学特征强化、水化特征弱化的内在机理。系统研究了电极材质、电解液种类浓度、加电时机以及电位梯度等参数对煤系软岩电化学改性效果的影响规律，发明了软岩电化学改性的渗滤式试验装置与方法，巧妙的避免和减弱了电化学作用过程中水电解产生的极端pH环境对岩样和电极的腐蚀作用，揭示了电化学作用下软岩力学强度、吸水性、胀缩性、电阻率、矿物组成成分及其含量等物性间的联动机制。基于蒙特卡洛及分子动力学方法，构建了高岭石超晶胞模型，系统研究了高岭石的吸水特征，阐明了温度及压力对水分子在高岭石颗粒表面的吸附量、吸附位、吸附热、吸附能以及高岭石体积膨胀性等的影响规律，揭示了高岭石吸水的分子机制；并利用相关Perl程序得到了不同电场条件下高岭石表面水分子的吸附形态和极化构象、扩散系数、相互作用能以及氢键的演化规律，揭示了电化学改性煤系软岩的分子机理。基于煤岩电渗物性与双电层原理，发明了一种电化学提高煤层气采收率的方法，研制了煤岩电动-压动三轴渗流试验装置，并进行了煤样在不同电位梯度条件下的饱水单相渗流与气-水两相渗流试验，发现施加电场后煤中残余水饱和度降低，两相流区间、气-水相对渗透率与气体有效渗透率均增大，研究成果为减小煤层气储层含水饱和度并延长钻井产气周期提供了解决思路。