基于湿度应力场理论的硬石膏岩膨胀试验研究

The swelling tests of anhydrite based on the humidity stress field theory

传统的湿度应力场理论处理硬石膏围岩膨胀问题时,未反映膨胀特性与湿度状态之间的时变关系。以该理论为基础,设计硬石膏岩膨胀试验:不同初始湿度下的膨胀,不同浸水时间的膨胀,以及膨胀后的抗拉强度测试。试验发现:随初始湿度的增加,硬石膏岩膨胀持续的时间增长,最大膨胀应变和应力增大,终止时的吸水率和结晶水率增加,而自由水率近于0;相同初始湿度下,随浸水时间增加,其吸水率先快速后缓慢增加,结晶水率逐渐增大到接近于吸水率,自由水率逐渐减小到接近于0;随吸水率的增加,其最大轴向膨胀应变、最大侧向膨胀应力和抗拉强度都呈增大趋势。根据试验结果,建立了湿度状态时变系列方程以及含时间效应的膨胀本构模型。

The traditional humidity stress field theory cannot perfectly describe the time-dependent relationship between the swelling state and humidity state when simulating the swelling process of anhydrite rock mass. Based on this theory, the swelling tests on anhydrite rock mass were designed to investigate the swelling with different initial humidities and soaking time. In addition, tensile strength tests were carried out after swelling. The testing results showed that with the increase of initial humidity, the duration time of swelling, the maximal axial swelling strain, and the maximal lateral swelling stress increased. The water absorption rate and crystallisation water rate of anhydrite increased at the end of the test, while the free water rate was close to zero. Under the same initial humidity, with the increase of soaking time, the water absorption rate exhibited a rapid increase first and then slowly grew. The crystallisation water rate gradually increased to the water absorption rate, while the free water rate decreased to close to zero. With the increase of water absorption rate, the maximum axial swelling strain, the maximum lateral swelling stress and the tensile strength increased. Therefore, this study proposed the time-dependent humidity state equations and the time-dependent swelling constitutive model according to the testing results.