酸化环境下红层软岩力学性能劣化机理研究

The problem of rock mechanics properties degradation in acidic environment is one of the important issues for the evaluation and estimation of rock engineering service life. Currently, the systematic research limitations of macro and micro properties changes for the rock mass under the acidification of the environment. The project researches the red bed soft rock mechanical strength weakening in acidic environment caused by the environmental pollution. As the breakthrough point of the alkaline red bed rock and soil strongly corrosion by acidic water, uses the petrology, analytical chemistry, environmental science, rock mass mechanics and chemical dynamics subject research methods, with the macro-micro detection technology to carry out indoor experimental research, analyze and quantify the macroscopic physical and mechanical properties, alienation degree of microstructure of red bed mudstone by acid corrosion process. On this basis, to identify the most significant micro-structural parameters control the change of the mechanical strength indicator. From the micro and the macro, reveals the micro control mechanism of the macroscopic mechanical properties deterioration in the erosion process. And according to its chemical behavior characteristics in the acid erosion process, from the perspective of chemical erosion added to explain the degradation mechanism of the macroscopic mechanical properties, and establish the chemical prediction model of red bed soft rock in the acid environment to quantitative understanding the dissolution in red bed soft rock by acid. This study in order to further predict and evaluate the soft rock materials in erosion environment provide theoretical basis for the engineering properties and durability.

岩土体长期在化学介质作用下，其性能将逐渐劣化，直至最终达到破坏，是一个不可逆的过程。环境污染不断加剧，化学介质对岩土体性能的影响日益突出。本课题选取公路、铁路等建设工程常见的红层软岩为研究对象，针对环境污染导致的酸化环境下红层软岩力学性能的劣化问题，以酸性环境水对粘土矿物含量较高的红层软岩的强烈溶蚀作用为切入点，综合采用地球化学、岩土力学等多学科研究方法，借助宏细观检测技术，开展模拟溶蚀试验，分析酸化环境下红层软岩宏观物理力学性能及其微观结构劣化程度；在此基础上，找出显著影响力学性能变化的微结构参数，从微观到宏观，揭示其宏观力学性能劣化的微观机理；研究酸对红层软岩溶蚀作用过程的化学行为特征，揭示其宏观力学性能劣化的化学机理。本项目的研究成果可为评价酸化环境下红层岩土体的长期稳定性、长期强度，提供理论依据。

本课题针对酸性介质作用下四川盆地地区白垩系灌口组红层软岩力学性能的变化特性开展研究。分析了红层软岩受酸侵蚀后其物理、化学效应，探讨了其变化规律，获得了以下认识：. 1. 对不同酸性介质下红层泥岩模拟侵蚀试验前后微观结构和矿物溶蚀情况进行分析，得到酸性介质对红层软岩微观结构的破坏和对粘土矿物、造岩矿物以及钙质胶结物的溶蚀情况。. 2. 对在不同酸度酸性介质中浸泡的红层软岩浸泡液进行离子检测，得到析出离子的浓度变化规律和酸性介质对不同造岩矿物、粘土矿物的水-岩反应规律，分析了红层软岩受不同酸性介质侵蚀的微细观机理。. 3. 随着浸泡液酸度的增加，岩体波速下降明显，其机理为溶液中的H+与钙质胶结物、粘土矿物等矿物质发生了水-岩化学作用，主要过程为逐步溶解钙质胶结物和粘土矿物，使岩体孔隙率增大，溶液侵入岩体空隙和不连续面中，进一步扩大水-岩作用效应，破坏岩体本身结构，减弱岩体刚度，从而使岩体波速降低。随着酸液侵入岩体深度和分布范围的不同，也会使波速产生一定的降低，在沉积较差、不连续面赋存的红层软岩中尤为明显。. 4. 对酸性介质对红层泥岩力学性能劣化影响机理进行分析。试验表明随着酸度的增加，酸性介质对力学性能劣化越明显，这主要是物理和化学的耦合作用。分析表明，粘土矿物的溶蚀与力学性能劣化联系紧密。