THE JICHANG LANDSLIDE ON JULY 23, 2019 IN SHUICHENG, GUIZHOU: CHARACTERISTICS AND FAILURE MECHANISM
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摘要: 2019年7月23日20时40分许, 贵州省水城县鸡场镇坪地村岔沟组发生高位滑坡, 高速运动的碎屑物质沿途铲刮坡面原有松散崩滑堆积物, 最终形成体积约为191.2×104 m3的堆积体, 摧毁坡脚的居民区, 造成43人遇难, 9人失踪。通过对灾害发生现场进行详细的地质调查, 本文综合运用无人机航拍、现场测试等技术手段, 对鸡场滑坡特征进行了详细描述, 初步阐述了滑坡发生的动力学过程和成因机理, 并对残余滑坡堆积体的潜在危险性进行了分析。初步研究结果认为, 滑坡源区特殊的地形条件、风化碎裂的玄武岩体和不利的岩体结构面是滑坡形成的内因, 强降雨的饱水加载和下渗软化作用, 以及公路切坡扰动是导致滑坡发生的外因。鸡场滑坡发生前斜坡无明显的变形迹象, 表现出极强的隐蔽性和突发性。滑坡发生后碎屑流远程运动了约1.3 km, 造成了巨大的危害。深入研究鸡场滑坡的形成过程和成灾机理, 对我国西南山区存在类似条件的地质灾害隐患点的减灾防灾工作, 具有重要的指导意义。Abstract: A large scale of mountain rock avalanche occurred at about 20:40 on July 23, 2019 in Jichang town, Shuicheng county, Guizhou Province. The rock mass moved down and scraped the original loose deposits and finally formed deposits of 191.2×104 m3. It destroyed parts of Pingdi Village, resulted in the death of 43 persons and missing of 9 persons. Based on site investigation, unmanned aerial vehicle(UAV)photography and other technologies, this paper provides a detailed description on the characteristics and a comprehensive analysis on the dynamic process and failure mechanism of the long runout landslide. And there is still a risk that the accumulation of the landslide can be translated into debris flow during rainfall. The results indicate that the special geometry of the source area, the weathered and shattered basalt mass and favorable combination of discontinuities are the internal cause factors for sliding. The rainfall infiltrating and its softening effect, and the road construction cut-slope are the external cause factors for the landslide. There is no obvious signal before the occurrence of Jichang landslide. The masses have a long runout distance of 1300 m. When it occurred, it demonstrated the characteristics of confidentiality and strong paroxysm. It caused great danger in large range. There can be a big attribution if such case can be studied further. It can provide the significant experience on dealing with this kind of masses failure and how to provide advice on early warning and remediation project on similar cases in southwestern mountain areas of China.
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图 2 鸡场滑坡区附近地质图
1.乡镇; 2.公路; 3.水库; 4.河流; 5.鸡场滑坡; 6.岩层产状; 7.面理产状; 8.下三叠统飞仙关组第二段(T1f2); 9.下三叠统飞仙关组第一段(T1f1); 10.上二叠统宣威组第三段(P3x3); 11.上二叠统宣威组第二段(P3x2); 12.上二叠统宣威组第一段(P3x1); 13.中上二叠统峨眉山玄武岩第二段(P2-3em2); 14.中上二叠统峨眉山玄武岩第一段(P2-3em1)
Figure 2. Geological map of the investigated area showing the outline of Jichang landslide
图 11 鸡场滑坡碎屑流地质剖面图(a-e)
剖面线位置见图 10b; 1.上二叠统宣威组第二段(P3x2); 2.上二叠统宣威组第一段(P3x1); 3.中上二叠统峨眉山玄武岩第二段(P2-3em2); 4.中上二叠统峨眉山玄武岩第一段(P2-3em1); 5.粉砂岩; 6.泥质粉砂岩; 7.炭质黏土岩; 8.豆鲕粒含铁质黏土岩; 9.黏土岩; 10.杏仁状玄武岩; 11.凝灰岩; 12.现地面线; 13.原始地面线; 14.滑面; 15.堆积体; 16.出水点; 17.居民房屋
Figure 11. Cross section a-e of Jichang landslide
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