| 泸定韧性剪切带泸定段及其工程效应 |
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| 引用本文： | 王运生,苏毅,冯卓,吴德超,王道永.泸定韧性剪切带泸定段及其工程效应[J].地球科学,2022,47(3):794-802. |
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| 作者姓名： | 王运生 苏毅 冯卓 吴德超 王道永 |
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| 作者单位： | 成都理工大学地质灾害评价与地质环境保护国家重点实验室,四川成都 610059 |
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| 基金项目： | 国家自然科学基金项目(No.41877235);;国家创新研究群体科学基金(No.41521002); |
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| 摘 要： | 泸定韧性剪切带为南北向大渡河断裂中段,为川滇“Y”字构造重要组成部分.川藏铁路泸定特大桥在泸定县白日坝附近横跨泸定韧性剪切带,且左岸隧洞穿越⑤号糜棱岩带,该韧性剪切带组成及活动性直接影响重大基础工程建设.基于平硐、公路开挖剖面精细编录,配合薄片鉴定,对泸定韧性剪切带展布特征、组成特征及断裂活动性进行了研究,主要结论如下:（1）泸定韧性剪切带从西向东可区分为5个带,其中①、③、⑤为长英质糜棱岩带,②、④为糜棱岩化斜长角闪岩带,泸定韧性剪切带泸定段展布于桥位区河谷底部及左岸,总宽约1 000 m.①、③带由南向北横穿桥位区,产状N15°~20°E/NW∠55°~65°,带宽500 m,以灰色长英质糜棱岩、千糜棱岩为主,⑤带沿太阳沟-五里沟向东延伸,横穿左岸隧道,产状N43°E/NW∠54°,带宽500 m,糜棱岩为长英质糜棱岩、带状-小眼球状糜棱岩;（2）受断层带切割影响,河段构造节理密度大、组数多、期次多,岩体破碎、完整性较差;（3）泸定韧性剪切带晋宁期受韧性剪切变形影响,中生代以来受脆性破裂改造,但未形成大规模脆性破裂带,对泸定特大桥影响总体较小,工程效应主要表现为大渡河两岸隧洞进出口边坡稳定性较差及左岸洞内围岩完整性差.
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| 关 键 词： | 泸定段 泸定韧性剪切带 组成特征 新活动性 工程效应 工程地质 |
| 收稿时间： | 2021-12-20 |
Luding Section of Luding Ductile Shear Zone and Its Engineering Effects |
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| Abstract: | The Luding ductile shear zone is the middle section of the north-south Daduhe fault and is an important part of the "Y" structure in Sichuan and Yunnan. The Sichuan-Tibet Railway Luding bridge spans the Luding ductile shear zone near Bairiba, Luding County, and the tunnel on the left bank crosses the No.5 mylonite belt. The composition and activity of the ductile shear zone directly affect major foundation projects. Based on the fine cataloguing of excavation profiles of flat tunnels and highways, and the identification of thin sections, the distribution characteristics, composition characteristics and fault activity of the Luding ductile shear zone were studied. The main conclusions are as follows: (1) The Luding ductile shear zone can be divided into five zones from west to east, among which ①, ③ and ⑤ are felsic mylonite belts, and ② and ④ are mylonitized amphibolites. The Luding segment of the Luding ductile shear zone is distributed at the bottom of the valley and the left bank of the bridge area, with a total width of about 1 000 m. The belts ① and ③ traverse the bridge site from north to south, the fault occurrence is N15°-20°E/NW∠55°-65°, the fault width is 500 m, mainly gray felsic mylonite and thousand mylonite. The belt ⑤ extends along the Taiyanggou-Wuligou and crosses the tunnel on the left bank. The occurrence is N43°E/NW∠54°, and the fault width is 500 m. Mylonite is felsic mylonite, zonal-small eyeball mylonite. (2) Cut by the fault zone, the structural joint density of the river reach is high, the number of groups and stages are many, the rock mass is broken, and the integrity of the rock mass is poor. (3) The Luding ductile shear zone was deformed by ductile shear in Jinning Period, and was transformed by brittle fractures since the Mesozoic, but no large-scale brittle fracture zone was formed. The overall impact on the Luding bridge was small, and the engineering effect was mainly manifested in the tunnels on both sides of the Dadu river. The stability of the inlet and outlet slopes is poor and the integrity of the surrounding rock in the left bank cave is poor. |
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