皖南红层软岩崩解特性试验分析

采用皖南地区3种红层软岩开展了室内“饱水-干燥” 循环(湿-干循环)条件下的崩解试验。研究了不同湿-干循环次数下岩石的崩解现象和特征;分析崩解物的颗粒粒径分布随湿-干循环次数的变化规律;对浸泡岩样的水溶液离子浓度进行测试,同时对经历不同湿-干循环次数的岩样开展扫描电镜(SEM)试验;探讨软岩的崩解机理,比较分析不同岩石崩解特性的差异。试验结果表明:3种岩样的耐崩解能力大小依次为岩屑砂岩、钙质细砂岩、砂质泥岩;随着湿-干循环次数增加,砂质泥岩和钙质细砂岩耐崩解指数逐渐下降,岩屑砂岩的耐崩解指数基本不变;浸泡水溶液中Na⁺、K⁺、Ca²⁺、Mg²⁺等离子浓度随着湿-干循环次数增大有不同程度的变化,水-岩化学作用的剧烈程度与崩解性之间存在一定的对应关系;湿-干循环对不崩解的砂岩的微观形貌影响不大,而易崩解的砂岩容易形成裂缝或者颗粒剥落。不同岩石崩解性的差别与所含矿物成分及含量密切相关,也与岩石结构特征有关,颗粒粒径小且填隙物胶结强度低的岩石更容易崩解。

Experimental Study on Slaking Characteristics of Red-bed Soft Rock in Southern Anhui Province

Laboratory slaking tests with three red-bed soft sandstones in southern Anhui Province were carried out under the condition of “saturation-drying” cycle (wet-dry cycle). The phenomenon and characteristics of rock disintegration under different wet-dry cycles were studied. The variation of particle size distribution with wet-dry cycles was analyzed. Ions concentrations in aqueous solution soaked rock samples were measured. At the same time, scanning electron microscopy (SEM) tests were carried out on samples experiencing different wet-dry cycles. The slaking mechanism of soft rock was discussed, and the differences of disintegration characteristics of three kinds of rocks were analyzed. The test results show that the disintegration resistance of the three rock samples is lithic sandstone, calcareous fine sandstone, sandy mudstone in turn. With the increase of wet-dry cycles, the disintegration index of sandy mudstone and fine calcareous sandstone gradually decreases, while the disintegration index of lithic sandstone basically remains unchanged. The concentration of Na⁺, K⁺, Ca²⁺ and Mg²⁺ in immersed solution varies with the increase of wet-dry cycles, and there was a certain corresponding relationship between the intensity of water-rock chemical interaction and disintegration. Wet-dry cycling has little influence on the micro-morphology of non-disintegrated sandstone, while the easily disintegrated sandstone is prone to fracture formation or particle spalling. The difference of disintegration of different rocks is closely related to the mineral composition, content and the structural characteristics of rocks. The rocks with small particle sizes and low cementing strength of interstitial materials are more likely to disintegrate.