如美水电站坝址区碎裂松动岩体成因机制

Genetic Mechanism of Cataclastic Loose Rock Mass in Dam Site Area of Rumei Hydropower Station

以澜沧江如美水电站坝址区为研究对象,在工程地质定性分析碎裂松动岩体成因机制的基础上,运用离散元UDEC软件,建立了地质概化模型,模拟了岸坡在自重应力场和构造应力场共同作用下的河谷下切和碎裂松动岩体的形成过程,综合分析了碎裂松动岩体的成因机制。研究结果表明:坝址区岸坡岩体卸荷形式多样,其中以“推移-错动”型卸荷影响范围最大,卸荷机制最为复杂;随着河谷的下切,岸坡岩体地应力发生重分布,主应力减小,剪应力增大,近坡表岩体应力出现明显松弛卸荷现象,岸坡沿上部顺坡向中倾结构面产生较大变形,且对下部尖灭部位岩体产生了较大的推力,岩体沿反坡向陡倾节理出现反向错动,并在坡表形成外高内低的错台现象,岸坡岩体出现明显的倾倒变形特征,形成典型的“推移-错动”型卸荷模式,并叠加强烈的风化作用,最终形成碎裂松动岩体。

The genetic mechanism of cataclastic loose rock mass in the dam site area of Rumei Hydropower Station on the Lancang River was first analyzed through qualitative analysis of engineering geology.On this basis,a geological generalization model was established using the discrete element UDEC software to simulate the combined influence of self-weight stress field and tectonic stress field on the formation process of river valley downcutting and bank slope cataclastic loose rock mass.Results revealed diverse unloading forms in the dam site area,with“push dislocation”having the largest impact and the most complex mechanism.As the river valley undergoes downcutting,the in-situ stress of bank slope rock mass is redistributed,resulting in decreased principal stress and increased shear stress.This causes significant relaxation and unloading of the rock mass near the slope surface.The bank slope also exhibits large deformation characteristics along the upper slope to the mid dip structural plane,while the rock mass at the lower pinch out part experiences a large thrust.A dislocation of being high outside and low inside is formed on the slope surface in the reverse slope direction,indicating reverse dislocation along steep joints.Bank slope rock mass displays obvious dumping deformation characteristics,forming a typical“push dislocation”unloading mode.With the addition of strong weathering,cataclastic loose rock mass is finally formed.