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岩石材料的宏观力学特性与其内部细观结构演化有十分密切的关系,对典型难溶盐岩钙芒硝在盐溶液溶浸环境下力学特性弱化和细观结构演化进行研究,初步揭示其力学特性弱化的细观机制。研究发现:在盐溶液溶浸作用下,由于矿体胶结物中亲水性矿物吸水膨胀崩解、钙芒硝中硫酸盐的溶解、化学反应离子交换、氯离子侵蚀损伤等因素的作用,钙芒硝孔隙率随“溶液浓度”和时间的变化而非线性演化,从而导致力学特性严重弱化。在盐溶液中溶浸20 d,钙芒硝强度弱化系数低至0.1~0.2。由于钙芒硝矿体内泥质胶结成分的水理水化作用,泥质部分膨胀或崩解,钙芒硝矿体变形表现出应变软化与韧性破坏特征。细观结构演化结果表明,盐溶液溶浸作用下,难溶钙芒硝孔、裂隙演化缓慢,但在淡水溶液中孔隙演化速度是半饱和与饱和溶液中的数倍甚至数百倍。淡水中溶浸48 h后孔隙率高达16.62%,是原始状态孔隙率的9倍;半饱和盐溶液溶浸48 h后,孔隙率是原始状态的3倍,而饱和溶液溶浸48 h后,孔隙率增幅仅为2.8%。孔隙率变化主要是由于钙芒硝矿体中硫酸盐的溶解和结晶,胶结物成分(主要为伊利石、蒙脱石)的水理、膨胀,这也是钙芒硝力学特性弱化的根本原因。本研究对深入认识可溶岩(包括钙芒硝)物理力学特性弱化,并指导盐类矿床原位溶浸开采及层状盐岩溶腔油气储库建造等相关工程实践,具有重要理论意义与应用价值。
The macroscopic mechanical properties of rock materials are closely related to the evolution of their internal mesostructures. The study on the weakening of mechanical properties and the evolution of mesostructures of typical hard-dissolving salt rocks Glauberite in salt solution leaching reveals the weakening of the mechanical properties Meso-mechanism. The results show that under the salt solution leaching, due to the action of swelling and disintegration of hydrophilic minerals in the mineral cement, the dissolution of sulfate in glauberite, chemical reaction ion exchange, chloride ion erosion and other factors, The porosity changes non-linearly with the “solution concentration” and the time, resulting in a serious weakening of the mechanical properties. In salt solution dipping 20 d, Glauber’s salt weakening factor as low as 0.1 to 0.2. Due to the hydration and hydration of the mud cementation components in the glauberite ore body, the muddy part expands or disintegrates, and the deformation of the glauberite ore body shows the characteristics of strain softening and ductile failure. The results of meso-structure evolution show that under the salt solution infiltration, the sparsity of the poorly-dissolved glauberite is slow, but the pore evolution rate in freshwater solution is several times or even hundreds times higher than that in the half-saturated and saturated solution. After 48 h of immersion in freshwater, the porosity was as high as 16.62%, which was 9 times that of the original state. The porosity was 3 times that of the original state after the semi-saturated salt solution leached for 48 h, Porosity increases only 2.8%. The change of porosity is mainly attributed to the dissolution and crystallization of sulphate and the hydration and swelling of the cements (mainly illite and montmorillonite) in the glauberite orebodies, which is also the fundamental reason for the weakening of the mechanical properties of glauber’s salt. This study is of great theoretical and practical significance for further understanding of the weakening of the physical and mechanical properties of soluble rocks (including glauberite), guiding the in situ leaching of salt deposits and the construction of oil and gas reservoirs in layered salt caverns.