三峡库区杨家水井滑坡变形失稳机理研究

DEFORMATION AND FAILURE MECHANISM OF YANGJIA WELL LANDSLIDE IN THREE GORGES RESERVOIR AREA

2015年4月11日,受持续降雨影响,三峡库区秭归县沙镇溪镇发生了大型的反倾岩质滑坡,滑坡面积约2.5×104m^2,体积约25.0×10~4m^3,造成道路及大量房屋、管道设施破坏。基于现场地质调查第一手资料,详细阐述了滑坡特殊的地质地貌及岩体结构特征,分别从地质因素和环境因素两方面进行了滑坡成因分析,基于地貌学与工程地质力学理论推断滑坡形成演化过程,并对其变形发展趋势进行了预测。得出如下结论:(1)杨家水井滑坡为持续降雨触发的牵引式反倾岩质滑坡;(2)特殊的地质构造及地形地貌条件是滑坡形成的长期孕育内在条件,持续降雨则是滑坡发生的直接诱发因素;(3)河谷下切,伴随着高应力释放及斜坡岩体卸荷回弹,层状岩体发生弯曲倾倒变形,顺向纵张节理发育,尤其是弯折带底面陡倾顺向裂隙逐步形成软弱结构面对滑坡变形失稳起着至关重要的控制作用;(4)现阶段正值汛期,后续滑坡变形以局部失稳破坏为主,而产生堰塞湖和泥石流的可能性较小,建议汛期结束后实施治理工程为宜。

On April 11, 2015, affected by the continuous rainfall, a large-scale counter-dipping rock landslide occurred at Shazhenxi village of Zigui County. The landslide of about 25×10^4m^3 in volume and about 2. 5×104m^2 in area damaged the town road and a large number of facilities seriously. It is named as Yangjia Well Landslide. On the basis of the first-hand field investigation, the special geological features and rock mass structure characteristic of the landslide are studied in detail. The origin of the landslide is analyzed from two aspects including geologic origin and the environment origin. The formation mechanism and evolution process of the landslide is proposed tentatively by utilizing the theories of geomorphy and engineering geology mechanics. It is also predicted the deformation trend of the landslide. Conclusions as follows ： （ 1 ） This landslide is continuous rainfall-induced counter-dipping rock landslide, and has traction sliding deformation mode. （ 2） The particular geological structure is the long-term breeding inner condition of landslide formation ; the continuous rainfall is the main and direct triggering factors of landslide formation. （ 3 ） With valley incised, high stress released and the unloading and rebound of slope, layered rock mass bent and toppled to outside of the slope, producing fissures parallel to slope surface ; with the development of consequent tension joints gradually, the undersurface of bending belt formed a weak structure plane which plays an important role in landslide deformation. （4） During the flood season, local deformation may happen in a certain time, but barrier lake and debris flow is almost impossible; it is advised that the corresponding engineering management should be carried out after the flood season.