[关键词]
[摘要]
汶川县雁门沟雁洛村发育一大型堆积体,其成因类型、形成时序及成灾过程在川西北峡谷区具有代表性,因此对其形成过程的研究具有理论与现实意义。基于详细的野外调查,对堆积体的形成及演化过程进行较深入研究,得出如下结论:(1)雁洛堆积体为早—中更新世黄土堆积基础上,中更新世以来河谷强烈下切,峡谷期滑坡堆积与早期堆积体复合形成的大型堆积;(2)中更新世以前,河流缓慢下切形成宽谷并堆积西北吹来的黄土;(3)中更新世以来河流快速下切形成峡谷,陡立临空面与强烈卸荷松弛使陡倾坡外的软硬相间岩体发生倾倒变形,继续发展后失稳形成滑坡曾经阻塞沟谷;(4)近年来因强降雨洪水冲刷坡脚以及进村公路对坡脚的开挖,老滑坡堆积体中下部出现牵引式变形。
[Key word]
[Abstract]
The Yanluo deposit, located in Yanluo village, Wenchuan county, is an ancient giant deposit, whose formation mechanism, sequence and evolution are of great value for understanding the mechanism of similar deposit in southwest Sichuan. Based on detail field investigations and comprehensive analysis, this study carries out a study on the formation and evolution of Yanluo deposit. The results show (1) the Yanluo deposit is a giant complex deposit that made up of loess deposit in early-middle Pleistocene, landslide deposit in canyon area due to rapid river incision. (2) Before mid-Pleistocene, the valley was turned into wide canyon due to river incision, and accumulated loess deposits whose sources are from NW direction. (3) Since middle Pleistocene, the valley was turned into deep canyon, the steep free surface, intensive unloading relaxation and soft and hard alternated rock mass make the slopes topple frequently, the deposits, produced by continuous topple failure, collapsed and blocked the river. (4) In recent years, the incision of extreme flood and road construction make middle-lower part of ancient deposits appear tractive deformation.
[中图分类号]
P642.22
[基金项目]
国家重点研发计划项目(2017YFC1501000);国家自然科学基金(41877235);国家创新研究群体科学基金(41521002);地质灾害防治与地质环境保护国家重点实验室自主课题基金 (SKLGP2015Z001)