精确制备不同含水率岩石试样的化学热力学方法

Chemo-thermodynamical method for precisely preparing rock sample with different water contents

在岩石力学试验研究中,常常需要精确制备不同含水率的岩石试验样品,而目前的方法尚难以保证所需的精度。为此,提出一种精确制备不同含水率岩石试样的方法,其基本原理是将欲制备的岩石试件烘干或饱水后放置于恒湿环境中,烘干样或饱和样会逐步吸湿或去湿而增加或减小重量,其含水率逐步增加或减小,直至稳定,最终得到稳定、均匀、含水率各异的试验样品,而其中的关键是如何获得一个稳定的恒湿环境。基于化学热力学中单组分的气-液平衡理论,提出了一种稳定恒湿环境的获取方法,其基本原理为:由于岩石中组分水的化学势与恒湿环境中的水气的组分水的化学势在起始阶段不相等,因此,二者中的水气压力也不同,必然有组分水的迁移;当岩石中的水气压力大于恒湿环境中的水气压力时,水便从岩石中迁移至恒湿环境中,使岩石失水,而当岩石中的水气压力小于恒湿环境中的水气压力时,水自恒湿环境中迁移至岩石中,使其含水率增加,直至二者中的水气压力平衡,即可得到某一特定含水率的岩石样品。这样制备的岩石样品满足化学热力学平衡的要求,其含水率内外一致,上下相同,是含水率均匀分布的合格样品。该方法还能制备其他方法无法实现的含水率相差甚微的岩石试件,也可直接应用于精确制备不同含水率的土样。

Rock samples with different water contents need prepare precisely in many rock mechanical tests;but current methods are not able to meet the accuracy.This paper proposes a method to precisely prepare rock samples with different water contents.Its principle is that dried or saturated rock samples,kept in the environment with a constant humidity,and they will absorb moisture to increase weight or lose moisture to decrease weight until a constant water content for rock samples is obtained.The key point in this procedure is to create an environment with a constant humidity.For this purpose,a method is proposed based on the vapor-liquid equilibrium theory.At the beginning stage,chemical potential of water component in rock samples does not equal to that of water component of vapor in humidistat environment,which leads to different vapor pressures,transformation of water components and variation of water content in rock samples.When vapor pressures reach an equilibrium state,a precise constant water content homogeneously distributed in whole rock sample is obtained.This method is capable to obtain the water contents of rock samples with very slight differences which can not be obtained by the current methods,and also to precisely prepare the soil samples with different water contents.