含方解石脉石炭系灰岩单轴压缩的变形破裂特点

MECHANICAL BEHAVIOR OF CARBONIFEROUS LIMESTONE CONTAINING CALCITE VEINS UNDER UNIAXIAL COMPRESSION CONDITIONS

沉积岩形成后由于构造运动和热液运移而导致节理裂隙中晶体生长形成岩脉充填,方解石脉充填节理裂隙后与母岩形成整体,公路隧道及边坡工程中会经常遇到岩体中充填有大量的方解石脉。方解石脉与围岩之间的边界由于形成地质结构,所以对于岩体在应力作用下的力学响应具有重要作用,另外方解石脉的充填厚度也会显著影响到岩体的整体力学行为。本次研究从贵州省惠水至兴仁高速公路工程野外露头采集了含有不同厚度方解石脉的石炭纪石灰岩,考虑到不同厚度方解石脉充填以及区域长期降雨过程中水对岩石力学行为影响这两个重要因素,首先对天然以及饱和后的岩石切片开展了矿物组构的统计分析,然后在实验室制备了标准圆柱形岩石试样并开展了天然以及饱和后的单轴压缩力学实验。通过单轴压缩实验获得了试验过程的全应力-应变曲线,针对破裂后试样采用工业CT扫描及三维重构获得了岩石试样中的裂缝形态特点。经过对饱和以及天然状态下含不同厚度方解石岩脉灰岩的力学行为和裂缝分布的分析发现,由于方解石岩脉厚度和含水饱和度的增加,其单轴受压状态下整体塑性显著增加且强度明显降低,岩石饱和后矿物组构的变化以及方解石脉厚度的增加对其力学行为以及破裂模式有明显影响。另外随着方解石脉厚度变化而导致的力学行为变化表明,方解石岩脉充填在岩石中不仅形成地质结构面而影响其力学行为,另外由于与母岩形成整体抵抗变形而导致其力学行为产生显著变化。

The natural fractures generated by geological movement can form the lattice structure pattern in the sedimentary rocks.Crystal growth of carbonate mineral in these pre-existing fractures result in the calcite sealing in the limestone.In this study,mineralogical composition was analyzed and the concerns include hard minerals and water sensitive minerals.Water saturation can affect the minerals content and lead to water sensitive damage.Uniaxial compression experiment was carried out on the cylinder-shaped samples of the Carboniferous limestone containing calcite veins.Complete stress-strain relationship of the compression experiment combined with CT scanning results reflect two aspects for the role of calcite vein in the mechanical behavior of limestone under compression conditions.One aspect is the structural effect played by the interface between calcite vein and host rock,and another aspect is the joining of the thick calcite vein together with the host rock to resist compression.Significant brittleness of the limestone containing thin calcite veins is illuminated through the experimental results.More plasticity and lower strength are shown with thickness increase of the calcite vein in the limestone.