关于三峡库区周边坡体岩石特性的考察

Consideration on the Characteristics of Rock in the Landslide Area Around the Three Gorges Reservoir

岩石强度的载荷速率相关性与岩石的时间相关性特性及粘弹性性质密切相关,而且强度的载荷速率相关性越大,越容易发生蠕变破坏。对于坡体来说,如果构成坡体的岩石的时间相关性很显著,那么即使在比较低的应力下仅施加一点载荷,也容易发生变形。针对三峡库区周边滑坡多发,采集了组成滑坡坡体的4类主要岩石-泥岩、灰岩、泥质砂岩及砂岩。通过室内岩石力学强度试验,获得了不同岩石的强度特性曲线及表示载荷速率相关性的参数n。利用一个试件通过载荷速率交替变换获得了不同应变速率下的应力-应变曲线,从而根据强度的变化率不仅获得了峰值强度的载荷速率相关性,而且还求得了残余强度的载荷速率相关性。在单轴压缩试验中,残余强度的n值与峰值强度的n值有较大的差异,但在三轴压缩试验中两者的差异却不太明显。而且在气干状态下,不管是峰值强度还是残余强度的n值均随着围压的增加而增加。

The loading rate dependency of rock strength is well related to time dependent properties of rocks. For example, if the loading rate dependency is larger, it is easier to bring about creep failure under relatively low stress. Concerning slope stability, if the time dependency of rock consisting of slope is prominent, it is easy to deform even under a low stress/just a small load. The rocks including muddy rock, limestone, sandstone and muddy sandstone, collected from landslide area near the Three Gorges reservoir were examined in lab. The stress-strain curves of rocks were obtained and the parameters n related to loading rate dependency were calculated. In order to obtain the parameter n, just one stress - strain curve was enough obtained by just one small specimen with the loading rate alternately switching during a test. With this method, the parameter n not only of peak strength but also of residual strength can be obtained. Under uniaxial compression test, the parameter n of residual strength was found to be lower than that of peak strength. However, under triaxial compression test, the parameter n of residual strength was almost the same as that of peak strength. In air-dried condition, the parameter n increased with the increase of confining pressure for both peak and residual strength.