基于PIV技术的高吸力下压实膨润土径向劈裂试验研究

Diametric Splitting Tests on Compacted Bentonite at Different High Suctions Based on PIV Technique

基于粒子图像测速(PIV)技术,采用饱和盐溶液蒸汽平衡法控制试样的吸力,对具有不同吸力的压实膨润土进行了一系列的径向劈裂试验.在径向压缩过程中用高速相机和Davis8.0采集软件拍摄图像,用PIVview2C软件得到试样径向压缩过程中裂隙开展情况和位移矢量场,同时结合其扫描电镜微观(SEM)试验进行了机理分析.试验结果表明:具有不同高吸力值试样的荷载-位移关系曲线均呈应变软化现象,并且上述现象随着吸力的增加越来越显著;峰值载荷随着吸力的增加而增加;当试样达到峰值载荷时未发现明显裂隙,试样发生压缩变形;而峰值过后可观测到明显裂隙,位移矢量场基本呈对称分布于劈裂面两侧;随后载荷迅速跌落,试样破环,破坏部分由于位移较大,矢量场显示为空白区.SEM微观试验结果表明随着吸力的增加集聚体间的吸附作用增加,从而导致劈裂强度随着吸力的增加而增加.

Based on the particle image velocimetry(PIV)technique,a series of radial splitting tests were carried out on the compacted bentonite specimens with different suction by saturated salt solution vapor balance method to control the suction of specimens.In the process of radial compression,images were taken by high-speed camera and Davis8.0 acquisition software,the cracks and displacement vector field were obtained by PIVview2 C software,and the mechanism was analyzed by combining with its scanning electron microscopic(SEM)test.The results show that the load-displacement relation curves of the specimens with different high suction values show strain-softening phenomenon,and the above phenomenon is more and more obvious with increasing suction.The peak load increases with increasing suction.When the load of the specimen reached the peak value,no apparent cracks were found and compression deformation occurred.After the peak value,apparent cracks appeared and the displacement vector fields distributed symmetrically on both sides of the splitting surface.Then the load drops rapidly and the specimen is destroyed,and the displacement vector field shows as a blank area due to the large displacement of the failure part.The results of SEM microcosmic test show that the adsorption between aggregates increases with increasing suction,which leads to the increase of splitting strength with increasing suction.