硬石膏膨胀特性及其湿度应力场膨胀本构模型

The swelling properties of anhydrite and its himidity-stress-field swelling constitutive model

硬石膏岩遇水表现出很强的膨胀特性,且由于地下水分布的动态不均匀性,导致围岩不均匀膨胀。以梁忠高速公路礼让隧道中硬石膏岩为研究对象,采用土工固结试验仪,设置不同初始浸泡水量,对硬石膏进行侧限膨胀试验,研究其吸水率、膨胀应变及应力变化规律。结果表明:硬石膏吸水率呈先快后慢型增长,快速增长过程中硬石膏吸收的水主要转化为结晶水,慢速增长阶段,硬石膏内部自由水逐渐增多;硬石膏膨胀应变及膨胀应力随浸泡水量增加而增大,当浸泡水量为硬石膏完全石膏化理论耗水量的1/4时,达到二者增长率明显减小的转折点;硬石膏吸水率具有时间效应,且吸水率与时间呈负指数关系,基于此,结合湿度应力场理论,得到了硬石膏湿度应力场膨胀时变本构。

The anhydrite rock swells obviously when it＇s exposed to water, and the non-uniform dynamic distribution of groundwater leads to uneven expansion of surrounding rock. We take the anhydrite rock in Lirang tunnel, Liangzhong highway, as the research object,and set different initial water amount to carry out the anhydrite confined swelling experiment with using the consolidometer, which aims at figuring out the change rules of water absorption, swelling strain and confined swelling stress of the anhydrite rock. The results show that the water absorption rate of anhydrite increases rapidly at first and then slowly. The water absorbed by anhydrite in the process of rapid growth is mainly converted to crystal water, and in the slowly growth process, the free water inside the anhydrite gradually increases. The swelling strain and swelling stress of anhydrite increase with the increase of soaking water. When the soaking water volume is one-fourth of the theoretical water consumption of complete gypsification, it reaches the turning point where the growth rates of swelling strain and stress significantly decrease. The water absorption of anhydrite rock has a time effect, and there is a negative exponent relation between water absorption and time. Based on it, combined with the humidity stress field theory, the anhydrite time- dependent constitutive is obtained.