甘肃通渭“9·14”常河滑坡成因机理

doi:10.19657/j.geoscience.1000-8527.2020.073

现代地质 ›› 2021, Vol. 35 ›› Issue (03): 732-743.DOI: 10.19657/j.geoscience.1000-8527.2020.073

甘肃通渭“9·14”常河滑坡成因机理

王浩杰¹^,²(), 孙萍¹^,²(), 韩帅¹^,², 张帅¹^,², 李晓斌³, 王涛¹^,², 辛鹏¹^,², 郭强⁴

1.中国地质科学院地质力学研究所,北京 100081
2.新构造运动与地质灾害重点实验室,北京 100081
3.中国地质大学(北京) 工程技术学院,北京 100083
4.西安理工大学岩土工程研究所,陕西西安 710048

收稿日期:2020-03-02 修回日期:2020-09-10 出版日期:2021-06-23 发布日期:2021-06-24
通讯作者: 孙萍
作者简介:孙萍,女,研究员,博士生导师,1978年出生,地质工程专业,从事地质灾害方面的研究工作。Email: sunpingcgs@foxmail.com。
王浩杰,男,博士研究生,1992年出生,地质工程专业,从事工程地质学研究。Email: wanghaojie9219@qq.com。
基金资助:
国家自然科学基金项目(41472296);中国地质调查局地质调查项目(DD20190717)

Failure Mechanism of the Changhe Landslide on September 14, 2019 in Tongwei, Gansu

WANG Haojie¹^,²(), SUN Ping¹^,²(), HAN Shuai¹^,², ZHANG Shuai¹^,², LI Xiaobin³, WANG Tao¹^,², XIN Peng¹^,², GUO Qiang⁴

1. Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing 100081, China
2. Key Laboratory of Neotectonic Movement & Geohazard, Beijing 100081, China
3. School of Engineering and Technology, China University of Geosciences, Beijing 100083, China
4. Institute of Geotechnical Engineering, Xi’an University of Technology, Xi’an, Shaanxi 710048, China

Received:2020-03-02 Revised:2020-09-10 Online:2021-06-23 Published:2021-06-24
Contact: SUN Ping

摘要/Abstract

摘要：

2019年9月14日11时,受多日降雨影响,甘肃省定西市通渭县常家河镇小庄村发生大规模黄土滑坡,体积约800万m³。滑坡造成部分农田、公路及阳坡大桥损毁,直接经济损失约2 347.2万元。在对滑坡现场进行大量地面调查的基础上,通过无人机航拍、现场测绘、走访调查和数值模拟等手段对滑坡的变形破坏特征进行了分析,并在此基础上探讨了其成因机制。结果表明:斜坡体是在震裂、蠕变、软化、水动力等多种条件下按照一定的先后顺序由稳态逐步演化至失稳;该滑坡的失稳演化过程和灾变机制可以概括为原始斜坡(黄土、泥岩二元层状结构)-地震触发(滑坡堆积体、坡体震裂损伤)-蠕变弱化(层间剪切带、裂缝和落水洞扩展)-降雨激发(滑带软化、泥化,水压力作用)-失稳滑动(滑面贯通)5个阶段;由于长期的蠕变和雨水的渗透冲蚀,坡体上的落水洞和地下暗河十分发育,且是控制本次滑坡边界的关键因素;滑坡后缘和前缘变形剧烈,中部变形相对稍弱,推断该滑坡为受地形及地下水作用控制明显的牵引-推移式复合滑坡。

关键词: 甘肃通渭, 黄土地区, 降雨滑坡, 地震滑坡复活, 成因机理

Abstract:

A large loess landslide occurred in Xiaozhuang Village (Tongwei, Gansu Province) at around 11:00 am on September 14, 2019. About 800×10⁴ m³ of a historical sliding mass was reactivated by rainfall, and slipped down along a weak interface. The sliding mass destroyed several roads and the Yangpo bridge. Preliminary estimation of 2,975 people in one township and two villages of Tongwei County were affected, causing a direct economic loss of 23.47 million yuan in agriculture, water conservancy, power supply, and infrastructure. Based on site investigation, unmanned aerial vehicle photography and numerical simulation, the deformation and failure characteristics of this landslide are described in detail, and the failure mechanism are preliminarily assessed. The main factor that affected the slope stability is the post-seismic interaction of rainfall and creep, and the failure process comprise five stages: pre-earthquake, earthquake damage, creep weakening, rainfall triggering and final sliding. Sinkholes and underground rivers were well developed in the slope, and represent the key control of the landslide boundary. Strong deformation and failure occurred at the trailing and leading edges of the landslide, but the deformation in the middle was relatively weak. We infer that the landslide was a traction-movement composite one controlled by topography and ground water. Understanding the conditions and mechanism of the Changhe landslide is hugely important for the early identification and risk prevention of similar landslides in the loess region of northwestern China.

Key words: Tongwei, Gansu, loess region, rainfall-induced landslide, revival of seismic landslide, failuremechanism

中图分类号:

P642.22

王浩杰, 孙萍, 韩帅, 张帅, 李晓斌, 王涛, 辛鹏, 郭强. 甘肃通渭“9·14”常河滑坡成因机理[J]. 现代地质, 2021, 35(03): 732-743.

WANG Haojie, SUN Ping, HAN Shuai, ZHANG Shuai, LI Xiaobin, WANG Tao, XIN Peng, GUO Qiang. Failure Mechanism of the Changhe Landslide on September 14, 2019 in Tongwei, Gansu[J]. Geoscience, 2021, 35(03): 732-743.

图/表 17

图1 滑坡范围及特征 (a)地理位置;(b)航拍影像图;(c)滑坡后壁;(d)滑体表面阶梯状陡坎;(e)砖厂损毁;(f)(g)道路破坏;(h)桥梁垮塌;(i)前缘堆积体

Fig.1 Location map and aerial photos of the landslide

图2 研究区地质地貌概况 (a)构造剥蚀黄土低山丘陵区;(b)侵蚀堆积河谷区;(c)地层概况

Fig.2 Geomorphologic images and geological map of the study area

表1 黄土物性性质试验结果

Table 1 Physical properties of loess in the study area

土样编号	含水率/%	密度/(g/cm³)	干密度/(g/cm³)	比重G_S	孔隙比e₀	湿陷系数	渗透系数K/(cm/s)	塑性指数
原状土1	8.31	1.60	1.57	2.67	0.57	0.04	8.37×10^-8	7.17
原状土2	9.63	1.72	1.65	2.67	0.39	0.03	9.92×10^-8	10.22
滑带土1	20.48	1.65	1.33	2.67	0.67	0.01	1.34×10^-7	9.13
滑带土2	17.89	1.57	1.33	2.67	0.70	-	1.19×10^-7	8.08

图3 通渭地区断裂展布图

Fig.3 Topographic map showing the distribution of structures in Tongwei area

图4 滑坡整体特征 (a)滑坡平面图;(b)主滑方向纵剖面图

Fig.4 Image showing the overall characteristics of the landslide

图5 滑坡上部变形破坏特征 (a)滑坡上部航拍图;(b)滑坡后缘拉张裂缝;(c)滑坡后壁;(d)滑坡后缘地下暗河;(e)滑体冲沟;(f)滑体表面阶梯状陡坎;(g)砖厂变形破坏特征;(h)道路损毁;(i)滑坡侧壁落水洞

Fig.5 Photos showing deformation characteristics of the landslide (upper part)

图6 滑坡中部变形破坏特征 (a)滑坡中部航拍图;(b)(d)道路损毁;(c)冲沟内泥岩出露;(e)积水洼地;(f)滑体表面阶梯状陡坎

Fig.6 Photos showing deformation characteristics of the landslide (middle part)

图7 滑坡下部变形破坏特征 (a)滑坡下部航拍图;(b)道路被错断;(c)桥梁受挤压垮塌;(d)南侧壁边界处落水洞;(e)滑坡前缘

Fig.7 Photos showing deformation characteristics of the landslide (lower part)

表2 岩土体物理力学参数

Table 2 Physical and strength properties of rock and soil mass

岩土体	密度/(kg/m³)	弹性模量/MPa	泊松比	黏聚力/kPa		抗拉强度/kPa		内摩擦角/(°)
岩土体	密度/(kg/m³)	弹性模量/MPa	泊松比	天然	饱和	天然	饱和	天然	饱和
黄土堆积体	1 650	50	0.25	35	15	5	2	25.0	21.0
滑体	1 600	45	0.25	20	12	3	1	20.5	18.0
泥岩	2 120	300	0.18	500	500	100	100	35.0	35.0

图8 天然及降雨条件下滑体水平位移云图及塑性区分布图 (a)监测点布置图;(b)天然条件下位移云图;(c)降雨条件下位移云图;(d)降雨条件下塑性区分布图

Fig.8 X-displacement and plastic zone of sliding body under natural conditions and rainfall conditions

图9 监测点(M1—M6位置见图8(a))孔隙水压力(a)、塑性剪应变(b)和水平位移(c)变化曲线 (a)孔隙水压力;(b)塑性剪应变;(c)水平位移

Fig.9 Monitoring (M1-M6 location shown in Fig.8 (a)) curves of pore water pressure(a), plastic shear strain (b) andX-displacement (c) of monitor points

图10 常河滑坡失稳演化模式

Fig.10 Failure process of Changhe landslide

图11 研究区及周边历史地震滑坡群

Fig.11 Historical seismic landslide distributions in/around the study area

图12 不同含水率条件下泥岩蠕变试验成果(σ3=800 kPa)

Fig.12 Rheologic curves of mudstone specimens under different moisture contents (σ3=800 kPa)

图13 研究区日降雨量和小时降雨量 (a)20190801—20190923日降雨量;(b)20190909—20190914小时降雨量

Fig.13 Daily and hourly precipitation in the study area

表3 天然和饱和状态下黄土强度试验结果

Table 3 Strength properties of natural and water-saturated loess

土体编号	天然状态			饱和状态			天然状态				饱和状态
土体编号	黏聚力 /kPa	内摩擦角 /(°)		黏聚力 /kPa		内摩擦角 /(°)	压缩系数 /MPa^-1	压缩模量 /MPa			压缩系数 /MPa^-1	压缩模量 /MPa
原状土1	35.3	25.0	14.3		20.9		0.08		20.20	0.31		5.10
原状土2	36.6	19.9	18.6		18.0		0.05		29.85	0.94		1.48
滑带土1	19.0	20.5	12.0		17.8		0.17		9.80	0.48		3.48
滑带土2	16.5	19.5	9.8		17.4		0.07		22.73	0.68		2.51

图14 西北黄土区降雨诱发黄土滑坡类型 (a)(b)浅层黄土层内滑坡;(c)黄土-泥岩(红层)接触面滑坡;(d)老滑坡复活

Fig.14 Types of rainfall-induced loess landslides in the loess region of northwestern China

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甘肃通渭“9·14”常河滑坡成因机理

Failure Mechanism of the Changhe Landslide on September 14, 2019 in Tongwei, Gansu

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