三峡库区滑坡地带岩石特性的研究

针对三峡库区组成滑坡岩层的主要岩石——泥质岩、灰岩、砂岩,通过显微镜观察、X射线分析显微镜的定量分析及室内岩石力学强度试验,对各岩石的特性进行了分析。显微镜及X射线定量分析结果表明风化较弱的泥质岩基本上含有石英与钙质矿物,后者由于易溶于水而导致岩石的孔隙率增加。孔隙的一部分连接形成了裂缝, 从而使岩石的强度下降。各岩石的单轴压缩试验结果表明砂岩的强度最高,发生了风化的泥质砂岩的强度最低。在饱和状态下紫红色泥岩及风化了的泥质砂岩的单轴压缩强度降低最显著,比自然干燥状态下降低了大约50%, 推测是受粘土矿物含量的影响。所有岩石都表现出在峰值强度之前应力与应变几乎呈线性关系,而峰值强度之后应力急剧下降的脆性特征。这种在饱和状态下岩石强度大幅度下降与脆性特征表明在治理滑坡时需要采取十分周密及复杂的预防措施。

CHARACTERISTICS OF ROCKS IN THE LANDSLIDE AREA AROUND THE THREE-GORGES RESERVOIR

In order to study the mechanical characteristics of rocks in the landslide area around the Three-Gorges Reservoir, rock samples including two muddy sandstones, a red mudstone, a limestone and sandstone were collected and examined. Laboratory work including microscope observation, X-ray diffraction analysis and uniaxial compression tests have been carried out. Under the air-dried condition, sandstone is strongest and weathered muddy sandstone is weakest. It is interesting to note that calcium contents (carbonate observed) in unweathered muddy sandstone are significantly decreased as compared with weathered one. The decrease in strength for the weathered rock may arise from the dissolution of calcium. For all rock samples, uniaxial compressive strength shows a remarkable decrease under the water-saturated condition. It may be attributed to the high contents of clay minerals. For all rock samples, stress increased almost linearly with strain up to the maximum and then dropped rapidly, indicating brittle feature. Weakening under water-saturated condition and high degree of brittleness indicate that very careful and sophisticated measures are necessary to prevent landslide in the area.