紫坪铺水电站2^#泄洪洞进水口边坡变形特征及其机理研究

CHARACTERISTICS AND MECHANISM OF SLOPE DEFORMATION AT INTAKE OF FLOOD-DISCHARGE TUNNEL NO.2 OF ZIPINPU HYDROPOWER STATION

四川省紫坪铺水电站2#泄洪洞进水口高边坡地质条件复杂,坡脚和中部的L9,L10软弱岩带上盘均出现明显倾倒变形迹象,并发生过几次垮塌。通过对该边坡的物质组成、结构特征、以及边坡开挖等因素的分析研究,阐述了其变形机理说明这类由下软上硬岩性组成的反倾边坡,其变形破坏模式为压缩–倾倒和滑移复合型。变形首先以层间软弱岩的不均匀压缩变形为先导,进而引起上部岩体倾倒,沿顺坡向结构面拉裂。采用二维有限元数值模拟,分析了这类边坡在开挖过程中的应力和变形的特征及其变化规律,进一步验证了上述的机理模型。

The geological condition of high rock slope at the intake of flood-discharge tunnel No.2 at Zipinpu hydropower station in Sichuan is very complex. There appears evidently the toppling deformation above the soft rock strata (L9, L10) in the lower part of slope, and collapses took place many times. Through studying lots of factors, such as different substantial components of slope, character of geological structure, excavation etc., this paper illuminates mechanism of deformation at the intake of flood-discharge tunnel No.2. Meanwhile, the mode of deformation and destruction of this kind of anti-inclined slope, which is composed of a series of soft rock layers in its lower part and hard rock layers in its upper part, is the compressed-toppling going with sliding. It is demonstrated that the deformation of this slope is always initiated by the non-uniform compression of the soft rock layer, leading to toppling of the upper hard rock layer; finally, the tensile fracture of sliding appears along discontinuities paralleling with slope. Besides, two-dimensional finite element calculation is used to analyze the regularities of stress field and displacement during the excavation and to demonstrate the mechanism of this deformation.