摘要
位于四川茂县南新镇的周场坪滑坡是一大型古滑坡,曾于1982年发生大规模快速复活,目前滑体半堰塞岷江。野外地质调查表明,周场坪滑坡在平面上呈不规则长舌形,长约850 m,滑体前后缘高差约350 m;在剖面上发育3级滑动,钻探揭露滑带埋深以50~70 m为主,推测潜在失稳滑坡体积为1500×10^(~4)~2000×10^(~4) m^(~3)。周场坪滑坡在平面上分为4个变形区,在滑体中后部和前缘坡脚发育大量拉裂缝与下错陡坎,拉裂缝宽度以0.2~3.0 m为主,陡坎下错高度2~10 m。在野外调查和钻探分析的基础上,对该滑坡开展了地表位移(GNSS)、深部蠕滑变形(钻孔测斜仪)和雨量等监测。监测分析表明,目前周场坪滑坡后缘变形速率达0.80m/a,中部和前缘分别为0.69m/a和0.51m/a,呈推移式滑动变形,整体向NW310°方向滑动;地表位移速率在监测期内基本在1~3mm/d之间波动,波动主要受降雨量影响,且略滞后于降雨量;滑移加速度基本在0~6mm/d^(~2)范围波动。ZK2钻孔测斜仪监测数据表明,滑坡在80 m深度内主要沿2层滑带蠕滑,其中浅层滑带埋深在22 m左右,深层滑带埋深在46 m左右,滑移速率在0~5mm/d范围波动。综合研究认为,周场坪滑坡目前处于缓慢变形的深层蠕滑中,其变形速率受降雨和河流侵蚀等因素的影响,在极端内、外动力条件下,可能会加速滑动,并再次整体复活,造成堵塞岷江等危害。
The Zhouchangping landslide in Nanxin Town(Mao County,Sichuan Province)is a large-scale ancient landslide,which had an extensive and rapid reactivation in 1982.At present,the sliding body appears as irregular tongue-shaped on the surface,with a length of about 850 m and height difference of about 350 m between its frontal and rear edge.Three levels of sliding were developed on the profile.Drilling revealed that the burial depth of slip zone is mainly 50-70 m,and the volume of potential unstable landslide is estimated to be about 1,500×10^(~4)-2,000×10^(~4) m^(~3).The Zhouchangping landslide is divided into four deformation zones.A large number of tensile cracks and downward dislocation scarps are developed at the toe of the middle-rear part and front-edge of the sliding body.The tensile cracks are mainly 0.2-3.0 m wide,and the downward dislocation of the scarps is 2-10 m.Based on field investigation and drilling,we monitored the surface displacement(GNSS),deep-creep deformation(borehole inclinometer)and rainfall on the landslide.Our data(collected across one year)demonstrate that the current deformation rate of the rear edge of the landslide is 0.80 m/a,and those of the middle and frontal edges are 0.69 m/a and 0.51 m/a,respectively,showing a push-type sliding deformation toward 310°.The surface displacement rate fluctuates from 1 to 3 mm/d during the monitoring period,and the fluctuation was mainly influenced/delayed by rainfall.The slip acceleration fluctuates from 0 to 6 mm/d^(~2).Data from ZK2 borehole inclinometer shows that the landslide mainly crept along two layers of slip zones in the 80 m depth,of which the burial depth of shallow and deep slip zone is about 22 m and about 46 m,respectively,with the slip rate fluctuating between 0 and 5 mm/d.Comprehensive study shows that Zhouchangping landslide is currently in the deep-creep stage with slowing deformation.Its deformation rate is affected by factors such as rainfall and river erosion.Under extreme internal and external dynamic conditions,the slope sliding may accelerate and reactivate again,causing incidents such as blocking of the Minjiang River.
作者
金继军
郭长宝
沈亚麒
杨志华
任三绍
李雪
JIN Jijun;GUO Changbao;SHEN Yaqi;YANG Zhihua;REN Sanshao;LI Xue(Institute of Geomechanics,Chinese Academy of Geological Sciences,Beijing 100081,China;Key Laboratory of Neotectonic Movement and Geohazards,Beijing 100081,China;Geokon Instrument Co.,Ltd.,Beijing 102488,China)
出处
《现代地质》
CAS
CSCD
北大核心
2021年第1期103-113,共11页
Geoscience
基金
国家自然科学基金项目(41877279,41731287)
中国地质调查局项目(DD20160271,DD20190319)。
关键词
岷江上游
周场坪滑坡
古滑坡复活
深层蠕滑
变形监测
Minjiang River(upper reach)
Zhouchangping landslide
ancient landslide reactivation
deep-seated creeping
deformation monitoring
