Hazard assessment by 3D stability analysis of landslides due to reservoir impounding

The Yudonghe landslide is located in a upcoming reservoir region of a 233-m-high Shuibuya rockfill dam, 2,300 m away from the dam site. It consists of a massive landslide with upper and lower segments and two secondary slides, i.e. an eastern secondary slide and a western secondary slide. In this paper, values of factor of safety (FS) for various masses were calculated in a scenario of reservoir impounding-induced increase in groundwater levels, using a method of three-dimensional (3D) limit equilibrium. Results showed that the smallest value of FS for the massive landslide is 1.12 computed on the presupposition of reactivating along a bottom slide zone in case of an earthquake. The smallest FS value of the lower slide mass is 1.12 in a possible direction, given earthquake occurrence and a groundwater level of 225 m above the sea level. This FS value shows that the lower slide mass is stable in case of groundwater increasing. In addition, by the calculation of the 3D limit equilibrium method, the FS value of the east secondary slide is approximately 1.0 in different groundwater levels under consideration of earthquake occurrence, which reflects that this mass is prone to reactivate when external factors are taken into effect.     

贵州省岑巩县大榕滑坡特征及形成机制研究

2012年6月29日,岑巩县思旸镇大榕村突发大型滑坡灾害,约310104m3。大榕滑坡为古滑坡堆积区失稳。基于滑坡破坏特征分析和地质原型分析,定性判断滑坡失稳模式为蠕滑-拉裂-牵引式滑移。滑坡启动区在不合理人工填土及强降雨作用下,坡脚蠕滑并发展为失稳,由此导致主滑区坡脚支撑作用明显减弱,主滑区中下部因此滑移失稳,并牵引右侧主滑体中上部坡体逐步失稳。滑带主要位于下伏强风化基岩中。主滑体左侧向西滑移,右侧主体向SW向滑移。基于渗流场-应力场耦合数值分析,再现了滑坡失稳过程及发生机理。大榕滑坡形成机制深入研究对于西部山区类似滑坡分析及识别具有重要的参考价值。     

Characteristics and remediation of a landslide complex triggered by the 2008 Wenchuan, China earthquake-case from Yingxiu near the earthquake epicenter

During the 2008 Wenchuan earthquake, the river valley from Yingxiu to Wenchuan experienced numerous landslides and became a prominent area of landslide complexes. The present large landslide complex near the earthquake epicenter consisted of Laohuzui slide 1, Laohuzui slide 2 and Douyaping slide. The scale, geology, morphology, sliding process, and failure mechanism of the landslide complex are analyzed by means of field investigation, aerial photograph and stereographic projection technique. Characteristics of these three slides including seismic response of slope, landslide debris, damage and potential failure are discussed: the convex slope and the upslope of fractured granitic rock at high altitude are highly prone to landsliding under earthquake; the high source altitude and long travel path determine grain sizes and the deposit angle of the slide debris; the landslide complex completely buries the G213 roadway and dams up the Minjiang River in these sections; after the earthquake, rainfall, aftershocks and river erosion may retrigger new failures, such as retrogressive slide of weathered fractured rock, colluvial landslide, debris flow, embankment failure and rockfall. The following are presented as suggested remedial measures to protect the roadway and stabilize the slope: the removing and trenching, protective concrete/rock blocks against erosion, retaining structure, rockfall stopping wall, rockfall restraining net, rock bolt, and the planting of vegetation.     

金沙江上游沃达滑坡发育特征与堵江危险性分析

金沙江上游沃达滑坡自1985年开始出现变形,现今地表宏观变形迹象明显,存在进一步失稳滑动和堵江的风险。采用遥感解译、地面调查、工程地质钻探和综合监测等方法,分析了沃达滑坡空间结构和复活变形特征,阐明了滑坡潜在复活失稳模式,并采用经验公式计算分析了滑坡堵江危险性。结果表明:沃达滑坡为一特大型滑坡,体积约28.81×106 m3,推测其在晚更新世之前发生过大规模滑动;滑坡堆积体目前整体处于蠕滑变形阶段,局部处于加速变形阶段;复活变形范围主要集中在中前部,且呈现向后渐进变形破坏特征,复活区右侧变形比左侧强烈。滑坡存在浅层和深层两级滑面,平均埋深分别约15.0,25.5 m,相应地可能出现两种潜在失稳模式:滑坡强变形区沿浅层滑带滑动失稳时,形成的堵江堰塞坝高度约87.2 m;滑坡整体沿深层滑带滑动失稳时,形成的堵江堰塞坝高度约129.2 m。沃达滑坡存在形成滑坡-堵江-溃决-洪水链式灾害的危险性,建议进一步加强滑坡监测,针对性开展排水、加固等防治工程。     

青藏高原大型深层蠕滑型滑坡变形机制研究进展与展望

大型深层蠕滑型滑坡在青藏高原怒江、澜沧江、金沙江、岷江等地形地貌和地质构造复杂区极为发育,具有规模大、滑带深、渐进变形破坏显著等特点,按照滑坡空间结构主要有后缘洼地蠕滑型、顺层基岩蠕滑型和厚层松散堆积物蠕滑型等3种类型,往往表现为长期蠕滑-间歇性复活-整体滑动.通过梳理大型深层蠕滑型滑坡稳定性影响因素、滑带土工程地质力学性质、地下水渗流场特征与降雨诱发滑坡滞后性以及渐进变形破坏机制和动态稳定性等4个方面的研究进展,提出了3个关键科学问题与4个主要研究方向.建议加强深层滑带土在渗流场-应力场等多场耦合作用下的工程地质力学特性研究、加强剖析滑坡岩土体的非均质渗透特性及地下水分布特征分析,研究不同雨强和历时条件下降雨有效入渗机理,研究大型深层蠕滑型滑坡的降水入渗响应过程和降水诱发滑坡变形的滞后性,提出基于渐进变形破坏的滑坡动态稳定性评价方法,为地质灾害早期判识和综合防范提供理论依据.     

Failure processes in a full-scale landslide experiment using a rainfall simulator

A full-scale landslide experiment was conducted to clarify the failure process of a landslide triggered by rainfall, using a loose sandy soil. The experiment used a 23-m long and about 8-m high flume, consisting of three parts: an upper 30° slope section, a lower 10° slope section, and a horizontal section at the foot of the slope. The flume was sprinkled at a constant intensity of 100 mm/h. The landslide occurred first in the upper slope about 154 min after the sprinkling started, following a creep movement within 41 min. The sliding mass slid to a stop in about 5 s, compressing soils in the lower gentle slope and horizontal sections. The dynamic process related to slide movement and the fluctuation of subsurface water pressures during failure were measured and analyzed. Sequential visual observations provided a clear record of the slip surface during failure. The rapid increase of subsurface water pressure in the slope and horizontal soil layers was also recorded during failure. It was inferred that the increased water pressures in the upper slope resulted from collapse of loose soil structure during shearing in the translational slide, whereas those in the lower portion of the slope and horizontal sections resulted from a mix of soil compression and shearing by the sliding mass.     

甘肃舟曲县牙豁口滑坡发育特征与成因分析

2019年7月16日,位于舟曲—化马深大活动断裂带的舟曲县牙豁口发生滑坡,滑坡长1 920 m,宽50~190 m,体积212×10⁴ m³,为典型的推移式大型长条状断层破碎带堆积层滑坡。滑坡自上而下沿原老滑道分级分块逐步发育形成,滑动历时近50天,最大滑距500 m,滑坡破坏X414县道、养鸡场等,并使岷江呈半堵塞状态,影响汛期行洪安全。通过现场调查、监测、无人机测量、岩土试验和收集历史滑坡资料,对牙豁口滑坡形成的地质环境、滑坡发育历史、滑坡分级分块特征、滑动过程和成因进行了系统研究。牙豁口滑坡分为上、下相对独立的两级滑坡。上级滑坡又可分为南支滑块和北支滑块两部分,在老滑坡的基础上长期孕育发展,上级滑坡北支滑块在2013年前就已活动,2019年7月16日上级滑坡南支滑块开始剧烈滑动,并推挤北支滑块前部一同复活滑动。上级滑坡约10×10⁴ m³滑体下滑加载于下级滑坡,下级滑坡于7月24日由上向下逐步扩展变形和滑动,下级滑坡又可分为上、中、下三段滑体,滑坡前缘于8月10日达到岷江边,使岷江呈半堵状态。牙豁口滑坡总体具有孕育历史悠久、滑动历时长、滑动速度较低、分级分块差异性滑动的特点。长期活动的深大断裂带及凹槽状地形、软弱易滑的灰黑色风化破碎炭质板岩、地下水和大气降水的强烈作用、两侧崩滑体的堆积加载是滑坡发生的主要原因。     

降雨诱发填方路堤边坡变形机制物理模拟研究

填方路堤变形失稳是西部山区工程建设的常见问题。重庆某高速公路边坡为典型的堆载条件下降雨诱发型滑坡,填方堆载后,填方边坡在连续降雨条件下,沿基岩之上的软弱面产生滑动破坏。定性分析认为,降雨在滑坡形成中起着关键作用,为了研究填方边坡在降雨条件下的变形破坏机制及孔隙水压力与变形之间的关系,采用物理模拟方法研究边坡变形失稳的全过程,分析孔隙水压力随降雨时间的变化规律及其与变形破坏的关系。研究结果表明：边坡后缘大方量堆载,改变了其应力条件,是滑坡产生的主要因素。场地施工改变了原有的地表水环境,连续强降雨致使大量下渗的雨水,不仅显著改变坡体应力条件,而且雨水沿着滑面运移软化滑带,是滑坡产生的重要诱发因素。孔隙水压力在坡体失稳过程中起着关键作用,填方体土碎屑、泥质含量大,下渗的雨水携带上部细小颗粒及滑带泥质成分至滑带附近,堵塞地下水消散通道,表现为坡体变形积累,孔隙水压力增加;边坡变形陡增,孔隙水压力降低。该滑坡破坏分为降雨下渗、滑带饱水软化、后缘产生裂缝、裂缝贯通-整体滑动4个阶段,为蠕滑-拉裂式滑坡。     

Description of dynamics of the Tuzla Landslide and its implications for further landslides in the northern slope and shelf of the Cinarcik Basin (Marmara Sea, Turkey)

Seismic and multi-beam bathymetric data from the northern shelf and slope of the Cinarcik Basin, which is generated by the North Anatolian Fault Zone (NAFZ) located in the easternmost basin in the Marmara Sea, were re-interpreted to better understand the future sub-marine landslide susceptibility. Seismic data indicate that upper surface of the sub-marine extension of the Paleozoic rocks has an NNE–SSW oriented basin and a ridge type morphology controlled by the secondary faults of the NAFZ. Basins are fulfilled by Plio-Quaternary sediments, which are cut by strike-slip faults on the shelf and slope. The thickness of basin deposits reaches up to 130 m toward the linear northern slope of the Cinarcik Basin. A relatively recent sub-marine landslide, the Tuzla Landslide, cuts the slope of the Cinarcik Basin. The detailed morphological investigation indicates that the Tuzla Landslide is a deep-seated rotational landslide, which was likely triggered by activity of the NAFZ. Morphological analyses also indicate that the thick Plio-Quaternary deposits on the Paleozoic basement slid during the Tuzla Landslide event. This landslide is considered as a key event to understand the dynamics of the potential landslides on the northern shelf and slope of the Cinarcik Basin. Two areas locating on the eastern and the western sides of the Tuzla Landslide are considered as the potential areas for future sliding due to similarities of geological and geomorphological features with the Tuzla Landslide such as similar thick Plio-Quaternary deposits, similar slope morphology, and similar fault activity cutting the sediments. Considering this information, the purposes of the present study are to determine the dynamics of the possible landslide areas and to discuss their effects on the sub-marine morphology. In the light of the interpretations, the amounts of possible displaced material are obtained. Three different landslide scenarios due to possible slide surfaces for future landslides are developed and assessed. The first scenario is sliding of the sediments at the shelf break. The third scenario is a mass movement of almost whole basin deposits on the Paleozoic rocks. The latter one is evaluated as less important because of the volume of the displaced material, and the latter one is accepted as lowest possible event. Among the scenarios, the second scenario is accepted as the most critical and possible because of the amount of the slipped material and existence of faults rupture, which is considered as further sliding surfaces. These landslides will result in important changes in shelf, slope and basin floor in the study area.     

牵引式滑坡推力计算方法研究

三峡工程运行期间引发大量库区滑坡地质灾害,由于库区水位及降雨等联合影响,使得牵引式滑坡在库区滑坡中占有相当的比例。通过对库区牵引式滑坡形成机制研究,根据变形破坏模式,把牵引式滑坡分为牵引区（初始滑动区）和被牵引区,分析牵引式滑坡在演化过程中牵引区滑体与被牵引区滑体之间的相互依存关系,针对其相互作用力学特征建立合理的物理和数学力学计算模型,初步推导牵引式滑坡推力计算公式,为抗滑桩设计提供合理的设计推力。以三峡库区朱家店牵引式滑坡为例,在确定被牵引区滑体对牵引区滑体存在推力作用情况下,通过推力计算表明,推导出的公式计算得到牵引区滑体的设计推力比单独计算牵引区滑体设计推力更大,相比将牵引区滑体和被牵引区滑体视为整体计算设计推力更小,说明此方法计算的推力用于抗滑结构设计可以达到既安全又经济的效果,为牵引式滑坡治理设计提供新的思路。     

柳家凹黄土滑坡滑动机制研究

以豫西山区柳家凹黄土滑坡为研究对象,采用现场地质勘探和调绘的方法确定了滑坡的形态和性质;利用原位试验和室内试验确定了滑带土的强度衰减的影响因素和影响规律;采用现场监测等技术手段,确定了滑动深度。在此基础上,分析了柳家凹滑坡的活动历史、成因、范围和影响因素。调查和分析表明,柳家凹黄土滑坡的滑动机制可概括为古滑坡因路堑开挖和降雨而局部复活。古滑坡黄土体结构相对松散,抗剪强度较差。当古滑坡前缘土体被开挖后,古滑体失去前缘支挡,在自重应力和地下水共同作用下,古滑坡体前缘沿黄土层与砾石层交接面滑动带滑移破坏。根据古滑坡复活情况分析,柳家凹黄土滑坡为牵引式滑坡,当滑体前缘滑动后,后面的滑体陆续出现滑动,裂缝向纵深方向发展。     

西藏帕里河2004-06-22滑坡卫星监测

2004-06-22滑坡位于我国西藏自治区的最西端,中印边界附近的帕里河流域中部。以多时相高分辨率卫星图像为信息源,以Orbview立体像对制作的高精度DEM为地理控制,采用数字滑坡技术研究和监测该滑坡自滑坡前至2007年7月的活动。遥感解译表明,滑坡前该处为由弧形裂缝与山体分割的滑前危岩,2004-06-22发生的堵河事件为一高速顺层基岩滑坡,基于RS+GIS求得滑坡体积为63。7万m3。遥感监测显示自2004年9月至2007年7月共35个月内,滑坡边界及滑面各细部均没有明显变化,期间该处未见发生过任何新的滑坡活动。该滑坡是一次在新构造活动强烈的高山峡谷区自然形成的重力侵蚀活动过程,能量释放充分,近期除原滑体四周有一些泄荷及调整活动外不会有大的活动。     

岩质顺层边坡的平面滑移破坏机制分析

沿岩层层面的平面滑动破坏是顺层边坡发生最多、规模很大的一种破坏模式,根据其顺层滑移的力学机制将平面破坏分为滑移-拉裂型和水力驱动型两种类型。根据平面刚体模型,给出了滑移-拉裂型滑坡的失稳判据,即滑坡的条件为边坡高度要大于临界高度。地下水在顺层边坡后缘张裂隙和滑动面形成的渗流通道中运动时,对滑体将产生3个方面的力学作用：张裂隙静水压力、滑动面扬压力和拖曳力。根据水力-驱动型滑坡的计算分析表明,边坡后缘张裂隙充水高度直接决定了3种水压力的大小,当张裂隙充水高度达到临界值后,边坡在水压力作用下发生滑移破坏。     

Identification of failure slip surfaces for landslide risk assessment using smoothed particle hydrodynamics

ABSTRACT

Location of failure slip surfaces plays a critical role in landslide risk assessment and mitigation, particularly for unstable slopes, because it is a key input to design of stabilisation measures for unstable slopes and it determines the volume of the sliding soil mass (i.e. landslide consequence). The failure slip surfaces in the numerical analysis (e.g. finite element/different method, FEM/FDM) are often identified using shear strength reduction (SSR) method. A careful examination of FEM results showed that, although the SSR method performs well for stable slopes, it might provide misleading results for unstable slopes. To properly locate failure slip surfaces for unstable slopes, this paper presents a particle-based numerical method called smoothed particle hydrodynamics (SPH), which is mesh-free, immune to the mesh distortion problem in FEM/FDM, and able to directly simulate large deformation of soils that occurs during landslides. A series of slope stability analyses is performed using an in-house SPH programme. Failure slip surfaces are properly identified by SPH for both stable and unstable slopes. Furthermore, because SPH provides a spatial distribution of the post-landslide large displacement of soils, the failure slip surfaces can be identified conveniently using soil displacement. A displacement-based criterion is proposed to locate the failure slip surfaces.     

The Portuguese bend landslide

The Portuguese Bend landslide, in coastal southern California, is an active, slow-moving mass of blocks and debris that extends from the shoreline to moderate altitudes along part of the southerly margin of the Palos Verdes Hills. These hills form a peninsula that is underlain by Cenozoic sedimentary and volcanic rocks draped anticlinally over a core of Mesozoic schist. In the southerly parts of the peninsula, inherently weak units in the Altamira Shale Member of the Miocene Monterey Formation dip seaward in general concordance with the ground surface. Ground failure has been widespread in this area. It evidently began in mid- to late-Pleistocene time, and it has continued intermittently to the present.

The Portuguese Bend landslide represents a reactivation of movement of the eastern part of a complex of prehistoric landslides occupying an area of approximately two square miles. This latest episode of movement began in 1956, presumably in response to placement of fill during a road construction project. The active slide subsequently was enlarged by sequential failure of adjoining blocks of ground, and by September 1969 about 54,500,000 metric tons of debris was slowly moving downslope in an area of approximately 104 ha. Movement has been continuous since recent failure began in 1956, although the velocity of the active slide decreased markedly after that year. Between 1962 and 1972 the velocity fluctuated only slightly about an average value of about 1 cm per day.

The active slide is an irregular prism, roughly triangular in plan view. The southern side of the triangle trends approximately 1100 m east-west along a stretch of shoreline that essentially coincides with the toe of the slide. The other two sides of the triangle trend northeast and northwest from the ends of the toe and meet about 1200 m north of the shoreline. The thickness of the moving mass differs considerably from one place to another, reflecting both topographic irregularities and major undulations in the underlying surface of movement. The maximum thickness is approximately 75 m.

Movement is occurring along a distinct basal failure surface. The eastern part of the slide is underlain by bedrock, and is bordered by bedrock with a general structure that limits further deep-seated propagation of failure to the east and northeast. In contrast, the western part of the slide is underlain and bordered by extensive ancient landslide deposits that are marginally stable. Further encroachment of the active slide westward and northwestward into these materials was viewed as a distinct possibility at the time the dissertation was prepared and has occurred since then.

Continued movement of the Portuguese Bend landslide since 1956 has been due to four main factors. A rise in the water table during the period 1957–1968 has been documented in the northwestern part of the moving mass and is attributable mainly to infiltration of surface runoff entering numerous open fissures that cut the surface of the slide. The toe of the active slide daylights along the shoreline and is subjected to storm-wave erosion, so that any natural build-up of resisting forces is prevented in this area. The redistribution of mass as the slide has moved along an undulatory failure surface has been responsible for local fluctuations in the driving and resisting forces. Finally, smoothing of irregularities in the failure surface by the moving slide mass must have decreased some of the forces resisting movement.     

阳鹿高速公路K52新滑坡变形特征与成因机理分析

阳鹿（阳朔—鹿寨）高速公路K52新滑坡为古滑坡堆积体中局部复活的滑坡,处于急剧变形状态,需进行抢险性处治。复工后对该滑坡进行了详细的地质勘察及变形监测,借助FLAC3D软件对其成因、变形过程及变形机理进行了研究,得到了以下结论:（1）古滑坡堆积体形成于顺层岩质滑坡,堆积体内部发育软-可塑状软弱夹层风化页岩,为新滑坡的主要滑带土;（2）导致新滑坡变形的主要内因为不良地质、微地貌、特殊的岩土结构,主要外因为在中后部堆载、填土改变地表水径流路径、向滑坡排放生活用水及降雨;（3）新滑坡具有三层滑面,失稳前底部滑面为主滑面,失稳阶段中部滑面为主滑面,属前段推移后段牵引型复合式滑坡,具多级、逐级及渐进滑动特点;（4）新滑坡变形进程为:后缘拉张变形-中部剪切蠕变-滑体A、B推移剪出失稳-滑体C前缘临空牵引失稳;（5）新滑坡处治重点应防止顶部、中部及底部三个滑动面继续变形,也应防止古滑面及古滑坡堆积体内部其余风化页岩夹层产生次级滑动。     

隧道-洞口滑坡体系受力特征及变形模式

随着我国高速铁路在西部地区的大规模建设,隧道在线路中所占的比例越来越高,洞口隧道在滑坡作用下产生的病害越来越严重。然而,我国目前在隧道-洞口滑坡体系设计中没有可供参考的受力变形模式,因此本文以隧道-洞口滑坡为研究对象,通过对云南功东高速公路中隧道-滑坡工程实例的总结及工程地质模型的建立,对滑坡推力作用下的隧道变形模式进行研究,得到如下结论:(1)将隧道-洞口滑坡分为与滑面相交和下穿滑体两种模式,与滑面相交的隧道直接受到剩余滑坡推力的作用,而下穿滑体的隧道主要承受附加荷载的影响;(2)位于滑体内隧道承受围岩压力、滑坡推力和岩土抗力的作用,可将洞口有刚性支撑的隧道-滑坡结构简化为简支梁,无刚性支撑作用下的隧道-滑坡结构简化为悬臂梁;(3)下穿滑体隧道在附加荷载的影响下,拱部承受多余的压力而受到偏压作用,拱顶形成受拉区域,出现拉张裂缝。     

The 2007 Fox Creek landslide,Peace River Lowland,Alberta, Canada

Fox Creek is a small tributary of the Saddle River, a tributary of the Peace River in northwestern Alberta. It has several dormant landslides with degraded scarps and grabens. A new, reactivated landslide on the north bank of the Fox Creek occurred on 5 May 2007. The landslide formed two major sliding blocks. A rapid translational block slide, it mobilized 47 Mm³ of displaced materials, blocked the creek, and made a natural dam with a maximum height of 19 m at the tips of the displaced blocks. The rupture surfaces of the 2007 landslide were within the advance phase glaciolacustrine sediments. The residual friction angles are about 10° similar to those of the previous landslides in the Peace River Lowland. Precipitation and snow melt prior to the landslide are likely triggers of the 2007 Fox Creek landslide. The farmlands on the crest of the river valley and timber resources were impacted. The current landslide dam in Fox Creek does not have any evidence of seepage downstream; it may last for many years. Eventually, the creek will overtop and erode the dam. The same cycle of actions, landsliding, damming, and erosion will continue in the foreseeable future.     

Yielding mechanism of shallow mass movements in completely decomposed Norwood Tuff: the Zigzag Sign landslide,Utah

Over the past decade, land development activities on hillsides in northern Utah have resulted in a significant increase in landslide activity throughout the region. The majority of recent landslides are shallow and they occurred on cut gentle slopes especially during spring and early summer due to snowmelt induced elevated groundwater tables. The geologic material documented at numerous landslide sites is a soft gray-green completely decomposed Norwood Tuff. The present study addresses the mechanism of a shallow landslide in completely decomposed Norwood Tuff based on field, laboratory and numerical investigations. Detailed slope surface geometry obtained from laser-scan surveys together with strength and stress–strain parameters derived from laboratory triaxial tests on undisturbed samples of completely decomposed Norwood Tuff collected from the landslide site are employed with finite-element modeling to examine the effects of ground surface deformation patterns on the yielding behavior of the slide mass. The numerical results indicate a gradual retreat of the yield zone with progressive landslide deformation, which eventually becomes concentrated within the accumulation zone of the landslide, compared to a well-developed yield zone within the entire slide mass at the onset of landslide movement. Limit equilibrium stability analyses along potential sliding surfaces of extent limited within the yield zone of the displaced slide mass produce lower safety factors than an analysis based on the original sliding surface comprising the entire slide mass.     

Characteristics and Formation Mechanism of Giant Long‐Runout Landslide: A Case Study of the Gamisi Ancient Landslide in the Upper Minjiang River,China

The upper reaches of the Minjiang River are in the eastern margin of the Tibetan Plateau, where active faults are well developed and earthquakes frequently occur. Anomalous climate change and the extremely complex geomechanical properties of rock and soil have resulted in a number of geohazards. Based on the analysis of remote sensing interpretations, geological field surveys, geophysical prospecting and geological dating results, this paper discusses the developmental characteristics of the Gamisi ancient landslide in Songpan County, Sichuan Province, and investigates its geological age and formation mechanism. This study finds that the Gamisi ancient landslide is in the periglacial region of the Minshan Mountain and formed approximately 25 ka BP. The landslide initiation zone has a collapse and slide zone of approximately 22.65×106–31.7×106 m3 and shows a maximum sliding distance of approximately 1.42 km, with an elevation difference of approximately 310 m between the back wall of the landslide and the leading edge of the accumulation area. The landslide movement was characterized by a high speed and long runout. During the sliding process, the landslide body eroded and dammed the ancient Minjiang River valley. The ancient river channel was buried 30-60 m below the surface of the landslide accumulation area. Geophysical prospecting and drilling observations revealed that the ancient riverbed was approximately 80-100 m thick. After the dam broke, the Minjiang River was migrated to the current channel at the leading edge of the landslide. The Gamisi ancient landslide was greatly affected by the regional crustal uplift, topography, geomorphology and paleoclimatic change. The combined action of periglacial karstification and climate change caused the limestone at the rear edge of the landslide fractured, thus providing a lithological foundation for landslide occurrence. Intense tectonic activity along the Minjiang Fault, which runs through the middle and trailing parts of the Gamisi ancient landslide, may have been the main factor inducing landsliding. Studying the Gamisi ancient landslide is of great significance for investigating the regional response to paleoclimatic change and geomorphologic evolution of the Minjiang Fault since the late Pleistocene and for disaster prevention and mitigation.