石膏矿岩水致老化效应试验

为研究石膏岩的水致老化效应，在室内模拟石膏矿采空区的水环境条件，包括不同空气湿度环境和饱和地下水环境。将石膏岩岩样置于其中，定期取出测定其力学性质指标，得到石膏岩老化的宏观力学表现，并结合核磁共振技术测定试验过程中石膏岩岩样内部的孔隙结构变化，分析石膏岩的水致老化机制。研究结果表明，水对石膏岩的老化效应具有显著的影响。老化程度随时间递增，石膏岩的单轴抗压强度、巴西抗拉强度和弹性模量与置于水环境中的时间基本呈负指数关系，泊松比则无明显变化规律；石膏岩老化程度和老化速率与水的状态密切相关。相对湿度越高，石膏岩的老化越显著，老化速率也更快，尤其是被液态水浸泡时，石膏岩的老化最显著，老化速率最快。水对石膏岩的老化过程是水的物理作用与化学作用的耦合，而化学作用是水致石膏岩老化的根本原因。石膏岩与水接触时，石膏的溶解、重结晶作用的不断进行改变着石膏岩的矿物组成结构，使其结构由紧密变得松散，孔隙率增大，力学性质不断弱化。该试验研究结果可为石膏矿开采的设计及采后空区的长期稳定性评估提供参考。

Experiments on ageing effect of gypsum rock induced by water

To investigate the water-induced ageing effect on gypsum rock, different water environment conditions were simulated in the laboratory, including different air humidity conditions and saturated groundwater conditions which may exist in the gypsum mines. Mechanical parameters of gypsum rock specimens were obtained under the pre-set conditions for different times. Meanwhile, the variation of pore structure in gypsum rock specimens was measured by nuclear magnetic resonance equipment. Then, the water-induced ageing mechanism of the gypsum rock was revealed. The results showed that the effect of water on the ageing of gypsum rock was obvious. Firstly, the ageing extent of gypsum rock increased with time, whereas mechanical parameters including uniaxial compressive strength, Brazilian tensile strength and elastic modulus decreased with time in a negative exponential relation. However, the Poisson’s ratio of gypsum rock had no clear relation with time. Secondly, the ageing extent and ageing rate of gypsum rock were closely related to the state of water. The higher the relative humidity was, the more pronounced the ageing extent was and the faster the ageing rate was. In particular, the ageing extent of gypsum rock was the most significant and its ageing rate was also the fastest when fully submerged in water. Generally, the water-induced ageing mechanism of gypsum rock was caused by the coupling of physical and chemical effects of water, and the chemical effect was the primary cause for the ageing effect. When the gypsum rock was exposed to water, the continuous dissolution and recrystallisation of the gypsum rock changed the mineral composition of the gypsum rock. As a result, the rock structure became loose, the porosity increased, and mechanical properties gradually weakened. The research results provide references for designing the gypsum mining and the evaluation of the long-term stability of gypsum goaf.