高庙子膨润土的胀缩变形特性及其影响因素研究

以高庙子钠基膨润土为对象,研究了干密度、竖向压力、浸泡液体、吸湿方式对其膨胀变形的影响,探讨了浸泡液体变化引起的渗析变形以及加卸载循环中的变形规律。试验表明膨润土的水–力–化学耦合作用非常复杂:干密度、竖向压力、浸泡溶液及其浓度均对膨润土的膨胀变形有显著影响;无荷状态下,饱和蒸气吸湿与浸水饱和两种方法得到的膨胀变形存在巨大差异;先在氯化钠溶液、再在蒸馏水中浸泡的试样的膨胀变形小于直接在蒸馏水中浸泡的试样的膨胀变形。浸泡液体由氯化钠溶液调整为蒸馏水,试样膨胀;而由蒸馏水换为氯化钠溶液,试样则压缩。在高浓度盐溶液中浸泡的初始干密度低的试样,浸泡液体调整为蒸馏水后,初始可产生压缩变形。加卸载循环中的规律比较独特,既表现出塑性压缩变形,亦存在塑性膨胀变形,用巴塞罗那膨胀土模型对其进行了解释。

Swelling-shrinkage behaviour of Gaomiaozi bentonite

An experimental study was carried out on compacted samples of Gaomiaozi sodium bentonite.Complex coupled hydro-mechanical-chemical behaviour of bentonite was observed.The influence of dry density,vertical stress and soaking liquid on swelling of beutouite was studied,and the swelling deformation was obviously effected by all these factors.There was large difference of swelling deformation obtained under zero stress between the conditions of soaking with water and exposuring to saturated vapor.An investigation of the osmotic deformation induced by changing soaking liquid was also attempted.The samples dilated when the soaking liquid changed from the sodium chloride solution to the distilled water,while they shrunk when the soaking liquid changed from the distilled water to the sodium chloride solution.However,an initial collapse,after changing the soaking liquid to the distilled water,was observed for a sample with the low dry density and ever soaked in high salinity solution.The swelling deformation obtained for the samples soaked directly in the distilled water was larger than that immersed first in the sodium chloride solution and then in the distilled water.After swelling deformation or osmotic deformation reached the equilibrium,the samples were subjected to cyclic stress,and both plastic compression and plastic expansion were induced.This phenomenon would be explained with Barcelona Expansive Model.