电化学作用对蒙脱石软岩颗粒物沉降与体积膨胀性影响的试验研究

EXPERIMENTAL STUDIES OF SUBSIDENCE AND EXPANDABILITY OF MONTMORILLONITIC SOFT ROCK PARTICLES UNDER ELECTROCHEMICAL TREATMENT

研制一种电化学作用改变蒙脱石软岩颗粒物膨胀性的试验装置,在该装置上对蒸馏水、NaCl溶液和NaCl电解液浓度及电位梯度等对蒙脱石软岩颗粒物在其中的沉降与沉降稳定后的体积膨胀性的影响进行试验研究。试验结果表明:直流电场的作用可以改变蒙脱石软岩颗粒物在蒸馏水电解液中的沉降速度,但不能改变其沉降稳定后的体积膨胀性。随NaCl溶液浓度的增大,软岩颗粒物在其中的沉降速度加快,并且沉降稳定后的岩样体积膨胀率随溶液浓度的增大呈负指数规律衰减。当岩样颗粒物在NaCl溶液中沉降稳定后,加电位梯度为0.5V/cm的电场,会使稳定后的岩样体积再次减小。在电场的持续作用下再次稳定后的岩样体积膨胀率仍随电解液浓度的增大呈负指数规律减小。电位梯度为0.5V/cm的电场能为加速黏土矿物颗粒物的沉降和抑制其沉降稳定后的体积膨胀性的电动现象提供足够的电势差。在电位梯度为0.5V/cm的电场作用后,再提高电位梯度,对改变岩样沉降稳定后的体积膨胀性没有明显影响。随着电解液浓度的增大,作用于岩样的电流强度增强,试验系统的温度升高。随着作用时间的延长,电解液浓度降低,电流强度呈负指数规律衰减,温度也随之降低。在直流电场作用过程中,电化学系统发生了电极和电解反应,蒙脱石软岩颗粒物的酸碱度发生了变化,在阳极区域的pH值降低,呈酸性;在阴极区域的pH值升高,呈碱性。

An experimental apparatus affecting the expandability of montmorillonitic soft rock particles under electrochemical treatment has been developed; experimental study of the subsidence and expandability of soft rock particles affected by distilled water, NaCl solutions, NaCl electrolyte concentrations and electric gradients is carried out. The experimental results are as follows： the treatment of direct current can change subsidence rate of soft rock particles in distilled water but its volume expandability is not affected when the subsidence is in stable state. With increasing in NaCl electrolyte concentrations, the subsidence rate of soft rock particles increased and then the swelling ratio declined of negative index while the subsidence was finished. On the basis of the stabilization and then addition of the electric gradient of 0.5 V/cm, sample volumes decrease, and the swelling ratio of soft rock particles has the same variation with above mentioned. It seems that the electric gradient of 0.5 V/cm can provide sufficient electromotive force for the subsidence and the expandability of soft rock particles. Increment of electric again gradient can not affect the volume expandability of samples in stable state after the electric gradient of 0.5 V/cm applied. With the increment of electrolyte concentrations, both electrical currents of soft rock particles and temperatures of the experimental system increased with the treatment time, both electrical currents and temperatures reduced because electrolyte concentrations weakened. During the electrochemical treatment, electrode reactions and electrolysis have been observed. It caused the variance of pH values of soft rock particles, pH value decreases in the anodic region which is acid while pH value increase in the cathodic region which is alkaline.