ISSN 1000-3665 CN 11-2202/P

    干湿循环作用下云母石英片岩波速劣化机制

    Mechanism of wave deterioration of mica quartz schist under dry-wet cycle

    • 摘要: 干湿循环作用是导致鄂西北片岩区滑坡、崩塌地质灾害多发的重要因素,而关于片岩在干湿循环作用下物理力学性能劣化机制研究不足。针对鄂西北广泛分布的云母石英片岩,通过声波测试技术探究其波速在干湿循环作用下的劣化规律,并结合其试样表观特征及电镜扫描结果,从宏、微观角度探究其劣化机制。结果表明:干湿循环作用下,云母石英片岩孔隙率总体呈逐渐增大的趋势,在前5次增加速率快,增加幅度为43.74%,随后增加速率逐渐变缓、幅度变小。云母石英片岩波速不断减小,呈现出前期下降快,后期逐渐趋于平缓的现象,沿径向与片理面大角度相交方向的波速劣化幅度最大,平行片理面方向的波速劣化幅度最小。干燥状态下波速各向异性指数大幅增加,增长幅度为15%;饱和状态下呈波动变化特征,各向异性略有增大,增幅为1.6%。损伤程度指数与片理面大角度相交方向的最大,为0.28%;平行片理方向的最小,为0.169%。云母石英片岩试样不断有红褐色物质析出,片理面逐渐显化、扩展开裂;微孔隙、微裂隙不断发育扩展,孔隙率逐渐增大,导致其波速下降;孔隙、裂隙分布不均导致波速各向异性明显。研究成果可为探究干湿循环作用下岩石损伤劣化机理提供依据。

       

      Abstract: Dry-wet cycle is a critical factor contributing to the frequent landslide and collapse geological disasters in the schist area of northwest Hubei; however, limited research has been conducted on the deterioration mechanism of physical and mechanical properties of schist under the dry-wet cycle. In this study, the degradation of mica quartz schist widely distributed in northwest Hubei Province was investigated by the acoustic wave testing under the action of dry and wet cycling. The deterioration mechanism of mica quartz schist was analyzed from both macro and micro perspectives, combined with the apparent characteristics of the samples and the scanning results of electron microscopy. The results show that the porosity of mica quartz schist increases gradually with repeated dry-wet cycles, particularly during the first five cycles, where porosity increased by 43.74%. Afterward, the rate of increase slowed considerably. The wave velocity of mica quartz schist decreases continuously, showing rapid decline in the early stage and gradual flattening in the later stage. The wave velocity deterioration is the largest along the direction of large angle intersection between the radial and schistosity plane, and the smallest along the direction of parallel schistosity plane. In the dry conditions, the anisotropy index of wave velocity increased significantly, by 15%, whereas under the saturated conditions, the anisotropy increased slightly, with an increase of 1.6%. The maximum damage degree index is 0.28% in the direction of large angle intersection of the schistosity plane. The parallel schistological direction is the smallest (0.169%). In the mica quartz schist sample, the reddish-brown material precipitates continuously, and the schistosity gradually develops and spreads, and cracks. Micropores and microcracks develop and expand continuously, and the porosity increases gradually, leading to the decrease of wave velocity. The uneven distribution of pores and fissures results in obvious wave velocity anisotropy. This study provides a basis for exploring the mechanism of rock damage and deterioration under dry-wet conditions.

       

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