金沙江寨子村巨型古滑坡的工程地质特征及其发生机制

 通过现场调查，对金沙江寨子村巨型古滑坡的工程地质特征及形成机制进行较为深入的探讨。该滑坡后缘与前缘高差638 m，体积2.5×108 m3。主断壁外围发育有宽30～100 cm的冠裂缝，滑坡断壁为高5～30 m的石灰岩峭壁。滑源区地形起伏较大，内部发育有规模不一的冲沟，覆盖有发育植被的坡积物、倒石堆和直径1～6 m的巨石。滑坡主体为程海断裂带，断裂带背景地层主要为C2+3石灰岩，岩性为碎裂石灰岩和岩溶角砾岩。寨子村滑坡曾诱发严重的滑坡堵江事件，滑源区对面岸坡残留滑坡坝坝顶高出江面118 m，体积180×104 m3，由70%的粒径在30 cm以下的灰岩碎块和30%的粒径30 cm以上的灰岩、岩溶角砾岩块石组成。长200 km的程海断裂带是一条规模巨大的岩石圈断裂，长期活动导致带内及其两侧岩体质量降低。沿断裂带北西侧顺其走向流过的金沙江的底蚀作用使得右岸岸坡越来越陡，为其大规模失稳奠定基础。程海断裂带还是一条活动性断裂，其自身活动产生的地震是寨子村滑坡的诱发因素。

ENGINEERING GEOLOGICAL CHARACTERISTICS OF ZHAIZICUN GIANT ANCIENT LANDSLIDE ALONG JINSHA RIVER AND ITS OCCURRENCE MECHANISMS

Height difference between the crown and the toe of rupture surface of Zhaizicun landslide in Jinsha river is 638 m，with about 2.5×108 m3 total rock displaced. The width of crown cracks surrounding the main scarp，which is limestone cliffs with a height of 5–30 m，is 30–100 cm. Slip source area with gullies is covered by colluvial deposit with vegetation，talus and separate giant rock blocks with a diameter of 1–6 m. The landslide occurred in Chenghai fault zone，which developed in the limestone dating to C2+3；and the landslide deposit is mainly made of cataclastic limestone and karst breccia. The Zhaizicun landslide once dammed Jinsha river and the crest of the residual landslide dam with a volume of 180 × 104 m3 opposite slip source area is 118 m high above the river. The relic landslide dam is mainly composed of 70% of limestone block with a diameter of less than 30 cm and 30% of blocks of limestone and karst breccia with a diameter of more than 30 cm. Chenghai fault zone with a length of 200 km is normal and lithospheric fault and its long-term activities make the quality of the rockmass in fault zone decrease. The undercutting of the Jinsha River flowing along the left side of the fault zone make the right bank slope increasingly steep and laid the foundation for the bank slope failure on a large scale. Chenghai fault zone is an activity fracture and the earthquake caused by its own activities is the inducing factor of Zhaizicun landslide.