Nearly four decades have passed since the Xintan Landslide in China made its mark, and the mechanics of its rapid movement continue to warrant scrutiny and interest. This research focuses on in on the engineering geological factors pertinent to the landslide’s movement. It suggests a model where the Xintan Landslide is structured with an active sliding section with significant mobility which is stabilized by supporting arches and essentially stable passive sliding section. The distinctive bend and constriction, coupled with the change in soil types and the structural integrity of the supporting arch, have positioned Jiangjiapo as the critical demarcation and incipient point of the Xintan Landslide’s movement. Drawing upon a thorough review of historical imagery and an analytical assessment of the forces at play based on failure indicators, we have constructed a mechanical model representing the Xintan Landslide. Employing the 2D DEM model within the open-source software DualSPHysics, we have simulated the entire progression of the Xintan Landslide’s movement. Post-collapse of the supporting arch, the central and leading sliding masses within the active sliding section rapidly reached velocities of approximately 13.8 m/s, engaging in multiple intense impacts with the passive sliding section. The most significant impact force recorded was around 7.19 × 106 N/m. Through collisions and subsequent loading, the active sliding section imparted energy to the passive zone, which in turn reached a peak velocity of roughly 12.98 m/s. The passive sliding section demonstrated clear traits of rear-driven motion, along with the crushing, shearing, and overriding effects stemming from the collisional propulsion. The swift movement of the Xintan Landslide is intrinsically linked to the collision-driven propulsion mechanism in the middle of the landslide collision-rear-driven propulsion mechanism. This research facilitates a more profound comprehension of the Xintan Landslide and similar debris flows, offering insights for the prevention and mitigation of similar landslide events.

The research establishes topographic recognition criteria for four types of bedding landslides in the clastic rock area of the Three Gorges Reservoir region, including groove side boundaries, isolated closed contour lines, linearly distributed gullies, rock walls, cliffs, tensile trough terrain lines, and wavy terrain lines. Using these markers, 38 potential landslides were identified in the Shazhenxi area, of which 27 are already included in the database. These findings indicate that the proposed topographic recognition features are effective for identifying bedding landslides in the region and can reflect the topographic characteristics of historical landslides. The study recommends further field verification and monitoring of the remaining 11 landslides not yet included in the local landslide database. This research provides a scientific basis for the early identification and disaster prevention of bedding landslides in the Three Gorges Reservoir area and similar regions. The established criteria can be applied to identify similar types of landslides in other areas, offering appropriate technical support for geological hazard prevention and mitigation.

Economically and effectively managing the risk of landslide-generated impulse waves (LGIWs) presents a significant challenge following the impoundment of newly constructed reservoirs in western China. To address this issue, we selected the Wangjiashan (WJS) landslide in the Baihetan Reservoir area as a case study to evaluate LGIW hazards and develop corresponding mitigation strategies. Using 2D physical model tests and 3D numerical simulations, we established a 3D hazard assessment method for LGIWs based on 2D experimental results. This method confirmed the effectiveness of slope-cutting engineering in mitigating LGIW hazards. Based on this assessment framework, we proposed a novel approach for LGIW risk reduction. The results showed that the maximum wave amplitude reached 19.64 m in the Jinsha River channel, and the maximum run-up was 11.5 m in the XiangBiLing (XBL) community, indicating a substantial LGIW threat to the area. By reducing the rear edge of the sliding mass to 920 m above sea level (asl), the LGIW risk to the XBL community could be lowered to a tolerable level. Compared with traditional landslide prevention and control measures, the proposed mitigation scheme can reduce excavation costs by approximately 37 million CNY, making it a more scientifically sound and economically feasible solution. We explored the concept and the implementation of LGIW risk mitigation in depth, offering new insights for global LGIW risk management. This case study enhances our understanding of LGIW hazard prevention and provides valuable guidance for policymaking and engineering practices in similar geological settings worldwide.

Since the initial partial impoundment of the Baihetan Hydropower Station in Jinsha River watershed in early April 2021, many landslides have started undergoing rapid deformation. The Wangjiashan landslide has been the most active and dangerous landslide in the Baihetan Reservoir area. Based on road deformation data, the overall average displacement rate of the landslide before impoundment was estimated to be in the range of 11–14 cm/year. After impoundment, particularly after the water level rose to approximately 790 m above sea level (asl) between September to October 2021, the average displacement rate at various monitoring sites ranged from 200 to 600 mm/day, and the maximum value was 1002.6 mm/day. When the water level decreased to approximately 796 m asl, the landslide displacement rate immediately decreased to a range of 2–3 mm/day. The deformation of the Wangjiashan landslide was positively correlated with the rise in water level. The landslide mechanism before impoundment was active–passive failure, and soil mass damage accumulated in the transition zone (Prandtl wedge) between the active and passive blocks. The landslide was strongly affected following reservoir impoundment, with the failure mechanism transforming into a composite active–passive impoundment-accompanied failure. Under the high water level during partial impoundment in 2021, the soil mass in the transition zone of the landslide had yielded and was already in the critical sliding failure stage. Studying the Wangjiashan landslide is significant to understand the response of reservoir-induced landslides in Jinshajiang River valley and similar reservoir-induced landslides around the world.

Landslide-generated impulse waves in reservoirs can overtop and even breach the dam and cause flooding of the downstream area, leading to catastrophic events with hazardous consequences. The Xiaodongcao (XDC) landslide located on the right bank of Daning River in Chongqing, China, at the anti-dip carbonate bank slope 2 km away from the Zhongliang Dam only, has an overall volume of about 1400 × 104 m3. After the reservoir impoundment, the XDC landslide began to topple violently. Based on the survey and monitoring results from this study, the front Donghuatian part, with a volume of 130 × 104 m3, has the highest probability of instability. The front Lanbandeng part, with a volume of 360 × 104 m3, a deformation area, will lead to the worst-case scenario. A fully coupled numerical model of fluid–solid-structure interaction is established to predict the landslide -water-dam interaction dynamic processes, under the four most probable and worst conditions. In the most likely scenario, about 48 buildings of the resettled town would be hit by a 6-m-high flow, causing hazardous consequences. In the worst-case scenarios of high water-levels in this study without considering dam break, 1.09 × 106 m3 of water will overtop the dam, leading to the complete destruction of about 150 buildings. Meanwhile, some measures, such as slope reinforcement, monitoring and early warning, are discussed to reduce the risk of landslide-generated impulse wave in the study area. This study is helpful for geological disaster prevention and mitigation for Zhongliang dam reservoir and provides reference for similar case studies in the world.

On October 2017, due to continuous rainfall, there was a massive river blockage induced by a landslide in Guang’an Village, Chongqing, China. Long-term monitoring analysis has shown that there remain four strong deformation areas on the slope, which seriously threaten the life and property of nearby residents. In this paper, a granular flow model and an elasto-visco-plasticity model were applied to reproduce and predict the landslide event that hit Guang’an Village. The results showed that the landslide gradually moved along the sliding surface, pushing loose deposits and blocking the Xixi River. The numerical reproduction results of the 2017 event are consistent with the actual slope deformation and failure process and deposit morphology. The simulated maximum depth-averaged velocity of this landslide was approximately 1.89 m/s, and the height of the landslide dam was approximately 10 m. After the landslide occurred in 2017, several large deformation areas appeared in the vicinity of the sliding area, and the right rear side of the sliding mass in area III has the largest deformation volume, accompanied by the most developed surface crack and the most intense deformation. There is a risk that the Xixi river will be blocked again. Therefore, with the same parameter and numerical model, a sliding–pushing–blocking dynamic prediction analysis of the strong deformation area III was conducted. The pushing motion of the mass in this area will reactivate the landslide mass observed in 2017. The maximum depth-averaged velocity of deformation area III was 0.5 m/s, and the maximum depth-averaged velocity of landslide deposition was 0.45 m/s. The length of the blocking dam formed by the mass of deformation area III along river was approximately 780 m, 30 m longer than that in 2017. The predicted height of the landslide dam was 14.5 m, approximately 4.5 m higher than that in 2017. The length of the landslide dam reservoir was predicted to be 2.55 km along the Xixi River, which may submerge the Waping Village. This study supports the landslide hazard prevention, reveals the whole movement process of sliding-pushing-blocking, and provides a new research idea and method for the landslide movement prediction. Hence, this study can serve as a reference for the hazard prevention and mitigation of such chain disasters.

Impulse waves generated by the collapse of pillar-shaped rock masses in Three Gorges, China, have attracted the attention of both researchers and local authorities owing to their catastrophic consequences. In this work, particle imaging velocimetry (PIV) was used to study impulse waves generated by the collapse of granular pillars during a series of physical experiments. Subsequently, the scenes of particles collapsing into water and the resulting impulse waves were analysed in terms of the solid/fluid fields. The energy obtained by the water during this process is mainly derived from the volume encroachment and continuous thrusting of particles. As indicated by the experimental results, as the aspect ratio (a) of the pillar and water depth increased, the potential energy of the granular pillar became more prone to reduction, whereas the efficiency of energy conversion to the liquid phase reduced. At constant water depth and granular pillar width, the maximum amplitude generated by the collapse of the granular pillar remained essentially the same (i.e., "saturation" was achieved) once the aspect ratio exceeded a certain threshold. The maximum impulse wave (the primary wave) formed before the main body of particles collapsed, resulting in the "saturation" of the maximum amplitude. When the kinetic energy of the particles reaches the maximum, the ratio of energy dissipation of the particles is the lowest; as the energy of water reaches the maximum, the particle collapse process does not end. The dynamic analysis of the impulse waves generated by the collapse of granular pillars provides a new approach to obtain an in-depth understanding of landslides and impulse waves. This can provide technical guidelines for disaster prevention and mitigation of impulse waves generated by bank collapse or coastline collapse.

The columnar dangerous rock mass is well developed in the Three Gorges Reservoir area. The change of water level accelerates the deterioration of the pedestal rock mass of the columnar dangerous rock mass and increases the risk of its crushing failure collapse. The potential surge disaster threatens the safety of shipping. According to the survey data of relevant dangerous rock masses in the Three Gorges Reservoir area, a dynamic observation system and experiment platform for particle column collapse was constructed, and physical model experiments on granular column collapse surge were carried out. The experiment results show that the crushing failure mode of dangerous rock mass is similar to that of the composite movement of collapsing-sliding of the experimental granular column. The staged motion of the granular column can be analyzed by the velocity of gravity center, which can represent the velocity of the particles. Formulas are derived by the nonlinear regression to estimate the water entry velocity of the particle and the maximum amplitude of surge. The Froude number is the main sensitive factor of the formula. Compared with the prediction formula of rigid block subsidence, the experimental formula in this paper is more suitable for crushing failure mode and has higher prediction accuracy. This research will provide the technical support for the prediction of the surge caused by the instability of the columnar dangerous rock mass in the reservoir area.

为弄清河谷下切面和软弱层组合特征对顺层斜坡的破坏失稳模式和成因机制的影响,采用UDEC建立了相应的数值模型,结合该区域内顺层滑坡的工程地质特征进行了深入探讨.研究结果表明:顺层斜坡坡脚河谷下切面与坡脚处软弱夹层的空间位置关系造成了滑坡失稳的3种变形破坏模式,滑移-剪切、滑移-剪断、滑移-弯曲-溃屈.得出了在坡脚河谷不同下切深度下岩质顺层斜坡变形破坏模式的转化过程及成因机制,并结合三峡库区实际案例验证了相应的变形破坏模式和成灾机制.

碎屑流具有冲程远、危害范围大等特性,难以进行有效预测防范.颗粒级配被认为是影响碎屑流运动距离的重要因素之一.开展了一系列基于单面临空不同颗粒级配颗粒柱体崩塌运动的物理模型试验研究.结果表明:颗粒柱体崩塌后,颗粒运动斜向箱体外,水平板上的颗粒运动呈放射状,堆积平面形式为圆形态,颗粒静止轮廓可分别用抛物线、圆的方程拟合,效果较好;颗粒类型相同时,随着颗粒柱体高度的增加,崩塌后颗粒堆积成圆形态的圆心位置有沿着y轴向前移动趋势;颗粒柱体高度相同时,小颗粒的运动距离比大颗粒的运动距离远;颗粒粒径小时,松散堆积区范围小,颗粒的影响区域为密集堆积区范围;反之,颗粒的影响区域为密集堆积区范围+松散堆积区范围.试验研究成果对预测碎屑流堆积区范围具有一定的参考价值.

长江两岸高耸的危岩体对航道、 沿岸居民带来巨大安全隐患.大宁河属于长江一级支流,龙门寨危岩体位于大宁河上,距离巫山县城仅1 km.利用FLOW-3D软件,模拟了145 m、175 m两种水位工况下龙门寨危岩体崩塌产生涌浪过程和涌浪传播过程.模拟结果表明,涌浪在145 m水位工况下最大浪高约为17.9 m,175 m水位工况下最大浪高约为11.6 m;在巫山县的五个码头处,两种水位工况最大涌浪爬高分别约为10.9 m、3.8 m;根据涌浪高度,对大宁河进行危险分区,145 m水位工况下极高危险区长度约4.4 km,很高危险区长度约1.9 km;175 m水位工况下极高危险区长度约3.0 km,很高危险区长度约1.0 km.研究结果有助于防控龙门寨危岩体潜在涌浪灾害危害,保障大宁河航道和巫山县码头安全,同时也为三峡库区滑坡涌浪灾害提供了预警依据.

柱状危岩体是三峡库区常见的一种典型地质灾害隐患,其崩塌产生涌浪给库区航运、 旅游、 生产生活以及人员财产造成巨大威胁和损害.文章基于野外柱状危岩体的成生及运动边界条件,开展了颗粒柱体崩塌产生涌浪的物理试验和数值模拟.结果表明:该数值模型能较好地模拟崩塌涌浪的形成过程、矢量信息以及与水体的相互作用;速度曲线定量地展示了能量的传递;物理试验和数值模拟涌浪高度偏差约3～4 cm;数值模拟堆积区堆积角比物理试验大5％;比前缘运动距离小7％.为柱状危岩体崩塌产生涌浪灾害的预测和预警提供了重要依据.

高密度颗粒流动现象与许多崩滑碎屑流类似,颗粒柱体崩塌试验一直是崩滑碎屑流动力研究的有效方法.基于野外柱状危岩体的成生及运动边界条件,在颗粒图像测速技术支持下,开展了一系列单面临空的颗粒柱体三维崩塌-堆积试验.结果 表明:颗粒柱体的高宽比a值决定了其失稳模式和堆积形式,当a＜1.5时,柱体临空侧颗粒沿着库伦破坏角运动,但柱体底部一部分颗粒仍保持不动,当a≥1.5时,颗粒体发生下沉-剪切-推出破坏,随后发生复杂的崩塌流动-堆积过程;柱体内颗粒呈近似的二维运动,柱体外则呈类扇体的扩展堆积,且圆心在X轴上往前移动,颗粒的运动与堆积的相关参数均可采用a的多个幂指数函数来定量刻画.高柱体的崩塌堆积试验结果可为压溃式柱状危岩体的运动评估及防治提供较多启示.

三峡水库峡谷区矗立着大量岩溶不稳定库岸,危及长江黄金水道安全.采用野外勘查和力学分析,对三峡库区碳酸盐岩区岩溶作用与斜坡破坏关系进行深入研究.野外勘查发现,三峡库区碳酸盐岩库岸存在许多与溶洞、溶隙、溶蚀带、溶槽、溶沟等表层岩溶作用有关的斜坡不稳定现象.巫峡段库岸内共发育岩溶地质灾害及隐患点186处,其中滑坡隐患点37处,大型以上危岩体6个.岩体力学分析表明:强降雨、蓄水和岩体劣化会因为有效应力减少、强度下降而造成破裂的节理/裂隙逐渐扩大.同时,水位变动带岩体劣化的裂缝扩展速率比三峡的平均溶蚀率高出约1300倍,极大地加快了已经进入屈服状态的不稳定岩体的演化进程.溶蚀作用是岩溶岸坡中最基本的作用,库水长期波动加快了岩溶岸坡演化.本次研究将为三峡库区峡谷段不稳定库岸识别和防灾减灾提供技术支撑.

Columnar dangerous rock mass is widely developed in many high and steep mountain areas around the world. It often collapses, disintegrates and produces debris flow, which is disastrous. The collapse process of the columnar dangerous rock mass is very similar to the collapse of granular column. In this paper, we report the results of an experimental investigation of the flow induced by the collapse of a column of granular material over a horizontal surface. Two different setups are used, namely, a channelized granular column collapse (i.e., two-dimensional) and an unchannelized granular column collapse (i.e., three-dimensional), allowing us to compare channelized and unchannelized collapses flows. The experimental data suggest that our experimental findings were markedly different from those reported by previous authors (i.e., include the channelized and unchannelized collapse flows showed differences in energy conversion and dissipation). In channelized collapse flows, the maximum vertical speed appears in the free fall regime, while, the maximum speed in the vertical direction of unchannelized collapse flows appears in the spreading regime. During the whole collapse process, i.e., in channelized and unchannelized collapse flows, the conversion of potential energy and kinetic energy does not occur uniformly, and the maximum kinetic energy of the channelized collapse flows is higher than that of the unchannelized collapse flows, and compared with the unchannelized collapse flows, the dissipation energy in the channelized collapse flows is lower. A series of experiments was performed to predict the behaviour of different granular columns (characterized by different initial aspect ratio (a), varying from 1 to 4). The data obtained from 2D experimental model and 3D experimental model have certain amount of difference, such as the particle runout distance (d1), the maximum central height (h2), and the deposition angle (i.e., β1, β2). These differences show that the 2D experimental model does not fully represent the 3D conditions (i.e., the role of side-walls on the channelized collapse flows characteristic is non-negligible). Accordingly, care must be taken when validating 3D models with 2D experimental data. The movement of the tower dangerous rock masses with collapse failure mode could be evaluated using this channelized and unchannelized granular column experimental results.

Towering in many gorges of reservoirs and coastal zones, pillar rock masses may collapse and fall due to foundation crushing, and the impact on water by debris leads to impulse waves. In this study, the process of impulse wave induction by the gravitational collapse of granular piles was investigated using particle image velocimetry. The experimental results showed that the collapse process of partially submerged particles was significantly different from that of dry particles. Near the water surface, particles moved outward in a reversed “S” shape. In the presence of water at the slope foot, the time and the distance traveled by the particles were reduced. The hydraulic effects such as water entrainment, vortex, rolling, and viscous drag exacerbated the energy dissipation of the granular piles, thus reducing particle mobility. Thirty five experiments suggested that the impulse waves induced by granular piles could be categorized as bores, solitary waves and nonlinear transition waves according to the functional inequality, which consisted of the aspect ratio and the relative thickness. The fitted formula for the run-out of partially submerged granular piles and the corresponding maximum wave amplitudes was derived by nonlinear regression of the experimental data. In comparison with previous formulas, these formulas are power functions consisting of aspect ratio and relative thickness and are highly suitable for predicting the collapse of granular piles and the impulse waves induced as the correlation coefficients of calculated results by these formulas and the measured values exceeded 0.93.

The high-density gravitational collapse of granular columns is very similar to the movements of large collapsing columns in nature. Based on the development of dangerous columnar rock mass in fields, granular column collapse boundary condition in the physical experiments of this study is a new type of boundary conditions with a single free face and a three-dimensional deposit. Physical experiments have shown that the mobility of small particles during the collapse of granular columns was greater than that of large particles. For example, when particle size was increased from 5 to 15 mm, deposit runout was decreased by about 16.4%. When a column consisted of two particle types with different sizes, these particles could mix in the vicinity of layer interfaces and small particles might increase the mobility of large particles. In the process of collapse, potential and kinetic energy conversion rate is fluctuated. By increasing initial aspect ratio a , the ratio of the initial height of column to its length along flow direction, potential and kinetic energy conversion rate is decreased. For example, as a was increased from 0.5 to 4, the ratio of maximum kinetic energy obtained and total potential energy loss was decreased from 47.6% to 7.4%. After movement stopped, an almost trapezoidal body remained in the column and a fanlike or fan-shaped accumulation was formed on the periphery of column. Using multiple exponential functions of the aspect ratio a, the planar morphology of the collapse deposit of granular columns could be quantitatively characterized. The movement of pillar dangerous rock masses with collapse failure mode could be evaluated using this granular column experimental results.

滑坡-涌浪灾害威胁沿河两岸居民生产生活安全和航道安全.当前尚缺乏同步提供流固两相运动矢量的相关物理试验分析系统,以深刻分析滑坡-涌浪产生机制.文章提出了基于流固两相识别的粒子图像测速(PIV)技术和试验实现方法.利用2560×1024像素的工业相机,该PIV技术可实现在3 m×1.5 m视窗下最小1.17 mm的空间分辨率和0.01 s内最小0.117 m/s的观测速度.同时,提出了与该系统方法有关的误差来源和克服相关问题的解决方法.利用相关硬件设施示范性构建了滑坡-涌浪两相运动观测平台,并编制了专门的解算软件.对三维柱体颗粒崩塌、 二维柱体颗粒崩塌及其涌浪和水下崩塌-涌浪进行了展示性试验,取得了良好效果.该系统可以揭示广泛的岩土体及水体运动全过程,具有很好的应用前景;将为滑坡-涌浪及相关动力学领域研究提供强有力的研究工具.

三峡水库周期性水位变动造成了部分消落带岩体劣化,其具体表现为强度下降和宏观裂隙增多,这使得一些柱状危岩体被发现或需要重新认识,包括箭穿洞、曲子滩和棺木岭等危岩体.这些柱状危岩体三维边界清晰,由“硬-相对软”的岩性组成,主要受控于相对软的硬岩基座岩体.采用伪时间增量的方式模拟岩石强度的时间相关劣化效应,数值分析了多水位变动周期下棺木岭危岩体裂缝和破坏区的扩展情况.危岩体初始破坏区主要集中在基座趾部岩体.随着水位变动周期增多,裂缝和破坏区由危岩体踵部和趾部相对扩展,破坏区主要集中在危岩体踵部.10次水位周期计算所得破坏区比相同时步、没有劣化效应时增加了近4倍,且以拉张破坏为主.周期性水位变动造成的岩体劣化强烈加快了柱状危岩体演化进程,同时影响了其破坏机理.从数值分析来看,棺木岭危岩体的变形破坏模式从原来的倾倒为主将转为以压溃崩塌为主.水位变动条件下岩石强度的时间相关劣化效应及其对柱状危岩体的影响研究将为三峡水库危岩体防治提供重要技术支撑.

三峡库区侏罗系顺向岸坡堆积体滑坡众多,其滑动模式存在一定差异.首先统计分析了192个三峡库区侏罗系层位发育的堆积体滑坡滑体及碎石土的工程地质性质和强度参数.在此基础上,运用数值分析软件对堆积体厚度变化引起的滑坡变形机制进行模拟分析.结果表明:堆积体厚度范围在15 m及以下滑坡会沿着岩土界线面滑动、15～35 m时滑坡会沿着层内剪切面滑动;厚度范围在35 m以上时,堆积体滑坡内部可能存在着多层滑带,即滑坡可能沿着层内剪切面滑动或者沿着岩土界线面滑动.堆积体厚度范围在15 m及以下时滑坡的治理措施可采用布置抗滑桩;厚度范围15～35 m时可采用排水+布置抗滑桩的滑坡治理措施;厚度范围在35 m以上时,可采用滑坡前期监测预报+后期根据滑坡发育情况相结合的滑坡防治措施.