从黄土灾害链看溃决型泥石流形成——以叶城柯克亚乡六村为例
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摘要
集中分布于昆仑山北坡2 500～4 000 m高度上的风积土因形成时代新、搬运距离短、成壤作用弱而多为松散多孔的灰黄色粉土或黄土状土。造成重大人员伤亡的叶城"7.6泥石流事件"为近年来日益重视的黄土灾害链发生机理研究提供了一个独特案例。采用遥感影像分析、现场调查、走访、高密度电法勘探等技术方法,研究发现该事件从斜坡高位长达10～15 a发育弧形张拉裂缝开始,短时强降雨诱发破坏,产生浅层远距离滑坡,堵塞河沟成堰塞湖,土坝溃决形成稀性泥石流乃至下游洪水。本文所揭示的柯克亚乡黄土地质灾害链发生机理在南疆较常见,或可称叶城模式。研究发现,突发破坏以滑坡而非水土流失形式,缘于中高山区斜坡上的风积土厚度一般小于20 m、坡脚与侧蚀河床距离有限。本研究解释了下游河谷突然断流,次日突发洪水现象原因:中上游堰塞湖形成、滞后溃决和瞬时泥石流、洪水损害环链生性灾害。
The aeolian soils in southern Xinjiang concentrated at 2 500～4 000 m height on the northern slope of Kunlun Mountains are mostly gray-yellow silt or loess-like soils due to their newly occurrence,short migration distance and weak soil formation.Yecheng 7.6 debris flow event provides a rare case for disclose the mechanism of geohazard chain in loess,which has been paid more and more attention in recent years.It was found that the event began with the development of arc tension cracks at the high slope for 10～15 years.Short-term rainstorm induced damage,resulted in shallow long-distance landslides,blocked rivers and became dammed lakes,and caused outburst debris flow and afterwards floods in the downstream.The mechanism of loess geohazard chain within Kekeya Town revealed in this paper is more common in South Xinjiang, or it can be called Yecheng Model.It is also found that the sudden slope failure is in the form of landslide rather than soil erosion, because the thickness of eolian soil on the high slopes in middle and high mountain areas is generally less than 20 m,and the distance between the foot of the slope and the scoured side-eroded river bed is limited.This paper studies and explains the causes of outburst debris flow in the gully and sudden flood in the lower reaches of the next day:formation of barrier lakes in the upper and middle reaches,delayed outburst of the landslide dam,instantaneous debris flow and afterwards floods.
The aeolian soils in southern Xinjiang concentrated at 2 500～4 000 m height on the northern slope of Kunlun Mountains are mostly gray-yellow silt or loess-like soils due to their newly occurrence,short migration distance and weak soil formation.Yecheng 7.6 debris flow event provides a rare case for disclose the mechanism of geohazard chain in loess,which has been paid more and more attention in recent years.It was found that the event began with the development of arc tension cracks at the high slope for 10～15 years.Short-term rainstorm induced damage,resulted in shallow long-distance landslides,blocked rivers and became dammed lakes,and caused outburst debris flow and afterwards floods in the downstream.The mechanism of loess geohazard chain within Kekeya Town revealed in this paper is more common in South Xinjiang, or it can be called Yecheng Model.It is also found that the sudden slope failure is in the form of landslide rather than soil erosion, because the thickness of eolian soil on the high slopes in middle and high mountain areas is generally less than 20 m,and the distance between the foot of the slope and the scoured side-eroded river bed is limited.This paper studies and explains the causes of outburst debris flow in the gully and sudden flood in the lower reaches of the next day:formation of barrier lakes in the upper and middle reaches,delayed outburst of the landslide dam,instantaneous debris flow and afterwards floods.
引文
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[3]冯玉涛,肖盛燮.崩滑流地质灾害链式机理及其优化防治[J].灾害学,2009,24(3):22-26.
[4]崔云,孔纪名,倪振强.强降雨在滑坡发育中的关键控制机理及典型实例分析[J].灾害学,2011,26(3):13-17.
[5]彭建兵,林鸿州,王启耀,等.黄土地质灾害研究中的关键问题与创新思路[J].工程地质学报,2014,22(4):684-691.
[6]朱兴华,彭建兵,同霄,等.黄土地区地质灾害链研究初探[J].工程地质学报,2017,25(1):117-122.
[7]曾庆利,尚彦军,胡桂胜,等.新疆叶城7.6滑坡泥石流灾害调查与形成机理研究[J].工程地质学报,2016,24(6):1145-1156.
[8]胡桂胜,尚彦军,曾庆利,等.新疆叶城7.6特大灾害性泥石流应急科学调查[J].山地学报,2017,35(1):112-116.
[9]高存海,张青松.中昆仑山北坡黄土特征及其环境[J].地理研究,1991,10(4):40-50.
[10]杨小平.塔里木盆地边缘山地的黄土沉积[J].干旱区地理,2000,(1):13-18.
[11]方小敏,吕连清,杨胜利,等.昆仑山黄土与中国西部沙漠发育和高原隆升[J].中国科学(D辑),2001,31(3):177-184.
[12]乃尉华,张磊.新疆叶城县地质灾害分布及其防治对策.中国地质灾害与防治学报,2009,20(3):138-141.
[13]古丽孜巴·艾尼.提孜那甫河流域气候变化及其对径流的影响[D].新疆师范大学硕士生论文,2014.
[14]毛丽旦木·吐尔干尼.新疆叶城县泥石流灾害易发性评价[D].新疆大学硕士生论文,2018.
[15]叶城县地方志编委员会.叶城县志[M].乌鲁木齐:新疆人民出版社,1999.
[16]杨莲梅.新疆极端降水的气候变化[J].地理学报,2003,58(4):577-583.
[17]张振山.浅谈叶城县水土流失现状与防治对策[J].内蒙古水利,2009,(3):43-44.
[18]河南省地质调查院.1:25万地质图(叶城县)[M].2005.
[19]梁瀚,汪新,陈伟,等.西昆仑山前和田-柯克亚挤压构造带新生代变形时序及其地质意义[J].大地构造与成矿学,2014,38(1):27-37.
[20]肖安成.塔里木盆地西南缘西昆仑前陆逆冲-褶皱带主滑脱面深度[J].江汉石油学报,1996,18(1):19-23.
[21]陈瑞银,徐思煌,杜晓峰.柯克亚油气田烃源岩特征与油源对比[J].新疆石油学院学报,2002,14(2):1-5,14.
[22]王大纯,张人权,史毅虹,等.水文地质学基础[M].北京:地质出版社,1995.