石灰和粉煤灰对石油污染土的斥水性影响及固化土的水稳定性研究

Oil contamination transformed the surface nature of soil particle and reduced its strength and anti-deformation. The water repellency and the structural stability of solidified soil in moisture environment need to be studied before it used for engineering.. Lime and fly ash are selected as solidified materials. Tests of batch adsorption and column leaching are carried out firstly to measure the oil adsorptivity and its stability of different combination of soil, lime and fly ash. Tests of water drop penetration time and molarity of ethanol droplet are used secondly to build the quantitative relationship between water repellency with solidified material, oil content and water content, respectively. The correlation between water repellency and adsorption intensity is set up by combining above two results. Then, simulating the moisture environment of absorption-liberation, wetting-drying and soaked, indicators of water repellence, unconfined compressive strength, cohesion and internal friction angle are measured and the effect of moisture variation on soil strength and water repellency is analyzed. Finally, tests of infrared absorption spectrum, X-ray photoelectron spectroscopy, CT and SEM are conducted to obtain the new resultant and micro-structure distribution. It hopes to evaluate the interaction mechanism among petroleum, lime and fly ash, and construct the theory on the structural stability of solidified soil in moisture environment.. Results can enrich the chemistry theory in geotechnical engineering field, and guide the development of solidified technology on oil contaminated soil.

油膜包裹改变土颗粒表面的润湿性，降低土的强度和抗变形能力。以石灰和粉煤灰固化石油污染土，研究固化材料对斥水性的影响及水环境变化条件下固化污染土的结构稳定性，是工程利用前需探索的科学问题。. 开展批处理吸附试验和柱浸出试验，测试不同配比粘性土、石灰、粉煤灰的石油吸附量及其吸附的稳定性；实施石油污染土和固化污染土的水滴穿透试验和酒精入渗试验，量化固化材料配比、含油率、含水率与斥水性间的关系，建立斥水性与石油吸附性的相关性，实现以斥水性指标间接表征石油吸附的稳定性；模拟吸湿-放湿循环、干湿循环及浸水饱和三种水环境变化，分析固化污染土斥水性的变化规律和强度特征；并利用红外吸收光谱、光电子能谱、CT和SEM扫描，确定新相物质及土微结构形貌，查明石油、石灰和粉煤灰间的相互作用，构建无机材料固化石油污染土的水稳定机制。. 研究成果可丰富岩土工程化学理论，指导开发固化石油污染土新技术。

油井、石油储罐和设施的泄漏导致大面积的土体被污染，被土体吸附石油易于引发二次污染。石油污染集中于0~40 cm，通过对其改性固化后用于填筑路堤或地基等，是石油污染土的一种有效处理措施。以石灰和粉煤灰固化石油污染土，研究固化材料对斥水性的影响及水环境变化条件下固化污染土的结构稳定性，是工程利用前需探索的科学问题。①吸附稳定性研究表明：石灰和粉煤灰对石油的吸附解吸均符合lagergren二级动力学非线性方程，其加入可改善对石油的吸附稳定速率及吸附量，吸附平衡时间由400 min缩短至60 min，吸附率提高39%。吸附与环境温度呈反相关，石灰粉煤灰的加入可缓解温度敏感性。即时及过时淋滤条件下，石油污染物在土中最大迁移深度为6和4cm，石灰和粉煤灰固化可有效控制石油迁移。②斥水性研究表明：石灰粉煤灰固化可提高石油污染土斥水性，轻度污染下，增大密度可抵抗湿度的润滑软化；中度污染，油水间存在相互竞争作用，协同增加固化材料掺量和密度较单一改变利于斥水性稳定。③水环境对斥水性及强度影响研究表明：石灰粉煤灰固化石油污染盐渍土具有良好的力学性能。28 d 12%石灰+22%粉煤灰固化污染土较石油污染土的抗压强度值提高423.2~719.3%；黏聚力增长156.4~188.5%，内摩擦角增长23.7~30.3%，符合相关规范中用于不同部位路堤、路基填料的设计要求。干湿、吸湿-放湿及冻融循环条件下，强度轻微波动后趋于稳定，斥水性维持较好。水循环后固化土中石油在横向由内向外迁移，纵向由上向下迁移。④相互作用研究表明：污染较轻时，过多无粘性粉煤灰产生滑珠作用；污染较重时，粉煤灰吸附大量石油后致使其参与火山灰反应掺量较小。过多的二灰易引起土体胀松和石油离解，减弱固化材料间的联结和土颗粒的支撑作用。随污染加剧，石油逐渐体现润滑和疏水特性，限制二灰接触反应和土颗粒持水性能。水分为参与二灰间火山灰反应的必要条件，较小污染和湿度有助于固化污染土形成水硬性整体构架，过量水分则产生稀释润滑等不利影响。研究成果可指导开发固化石油污染土新技术。