基于物理模型试验的多层滑带滑坡变形演化特征

滑坡变形演化特征一直是滑坡灾害预测与防治领域急需解决的关键问题,但对于多层滑带滑坡的变形演化特征却少有研究。以物理模型试验为手段建立了三层滑带滑坡物理试验模型,完成了多层滑带滑坡变形演化全过程的模拟。基于PIV技术获取坡表位移数据,通过柔性测斜仪监测滑坡深部位移,同时布设土压力盒获取滑坡内部土压力的变化情况,实现了多层滑带滑坡演化过程多参量数据分析。试验结果表明,多层滑带滑坡破坏过程可分为初始、等速、加速和破坏4个阶段。不同破坏阶段滑坡的主要变形区域不同,下层滑体受到上层滑体牵引作用,在重力和推力作用下滑坡变形逐渐向浅层发展。变形过程中滑坡应力逐渐向滑带集中,滑坡推力沿埋深方向呈多级梯形分布。加速变形阶段滑带处应力迅速增大,滑坡体内产生多层应力集中带,滑带位置推力变化与滑坡位移显著相关。     

基于模型试验的动水驱动型顺层岩质滑坡启滑机制初探

动水驱动型顺层岩质滑坡数量多、灾害频发、危害大, 是滑坡地质灾害领域的研究重点, 但目前对于滑坡启滑机制的认识仍不充分, 滑坡的准确预报还面临巨大挑战。鉴于此, 以含软弱夹层的中倾角顺层岩质滑坡为研究对象, 通过构建理想的单层滑带滑坡物理模型, 开展了一系列动水作用下的滑坡模型试验研究。结果表明, 动水作用下顺层岩质滑坡从开始变形至失稳滑动需经历初始变形、缓慢变形、加速变形和失稳破坏4个阶段, 而各个阶段的演化特征与滑面粗糙度和倾角密切相关。滑面倾角越大或粗糙度越小, 滑坡体从开始变形至失稳滑动所需的时间则越短; 相应地, 坡体加速变形阶段越不明显, 滑坡破坏的突发性越强。滑带内的渗流冲蚀作用会使滑带土中的骨料流失, 导致其抗剪强度降低, 进而引发坡体滑动。与此同时, 上覆坡体的压剪作用以及变形演化过程亦将反过来影响冲蚀强度。基于滑带土黏聚力随水力梯度和冲蚀时间的变化关系, 提出了渗流驱动下滑带土黏聚力演化模型, 可较好地描述滑带土黏聚力的退化过程。滑面粗糙度的存在不仅显著影响了滑带的冲蚀劣化规律, 还改变了滑带不同区域的破坏模式。此外, 通过考虑滑面粗糙度对滑带不同区域破坏模式的影响, 开展了动水多效应关联分析, 建立了滑坡地质体力学分析模型, 实现了动水作用下顺层岩质滑坡动态稳定性的有效评估。本研究成果可为实际动水驱动型顺层岩质滑坡的预测和防治提供理论参考。      

Field testing innovative differential geospatial and photogrammetric monitoring technologies in mountainous terrain near Ashcroft,British Columbia,Canada

This paper presents a novel approach to continuously monitor very slow-moving translational landslides in mountainous terrain using conventional and experimental differential global navigation satellite system(d-GNSS)technologies.A key research question addressed is whether displacement trends captured by a radio-frequency“mobile”d-GNSS network compare with the spatial and temporal patterns in activity indicated by satellite interferometric synthetic aperture radar(InSAR)and unmanned aerial vehicle(UAV)photogrammetry.Field testing undertaken at Ripley Landslide,near Ashcroft in south-central British Columbia,Canada,demonstrates the applicability of new geospatial technologies to monitoring ground control points(GCPs)and railway infrastructure on a landslide with small and slow annual displacements(<10 cm/yr).Each technique records increased landslide activity and ground displacement in late winter and early spring.During this interval,river and groundwater levels are at their lowest levels,while ground saturation rapidly increases in response to the thawing of surficial earth materials,and the infiltration of snowmelt and runoff occurs by way of deep-penetrating tension cracks at the head scarp and across the main slide body.Research over the last decade provides vital information for government agencies,national railway companies,and other stakeholders to understand geohazard risk,predict landslide movement,improve the safety,security,and resilience of Canada’s transportation infrastructure;and reduce risks to the economy,environment,natural resources,and public safety.     

Long-term kinematics and mechanism of a deep-seated slow-moving debris slide near Wudongde hydropower station in Southwest China

Long-term kinematic research of slowmoving debris slide is rare despite of the widespread global distribution of this kind. This paper presents a study of the kinematics and mechanism of the Jinpingzi debris slide located on the Jinsha river bank in southwest China. This debris slide is known to have a volume of 27×106 m3 in active state for at least one century. Field survey and geotechnical investigation were carried out to define the structure of the landslide. The physical and mechanical properties of the landslide materials were obtained by in-situ and laboratory tests. Additionally, surface and subsurface displacements, as well as groundwater level fluctuations, were monitored since 2005. Movement features, especially the response of the landslide movement to rainfall, were analysed. Relationships between resisting forces and driving forces were analysed by using the limit equilibrium method assuming rigid-plastic frictional slip. The results confirmed a viscous component in the long-termcontinuous movement resulting in the quasioverconsolidated state of the slip zone with higher strength parameters than some other types of slowmoving landslides. Both surface and subsurface displacements showed an advancing pattern by the straight outwardly inclined(rather than gently or reversely inclined) slip zone, which resulted in low resistance to the entire sliding mass. The average surface displacement rate from 2005 to 2016 was estimated to be 0.19~0.87 mm/d. Basal sliding on the silty clay seam accounted for most of the deformation with different degrees of internal deformation in different parts. Rainfall was the predominant factor affecting the kinematics of Jinpingzi landslide while the role of groundwater level, though positive, was not significant. The response of the groundwater level to rainfall infiltration was not apparent. Unlike some shallow slow-moving earth flows or mudslides, whose behaviors are directly related to the phreatic groundwater level, the mechanism for Jinpingzi landslide kinematics is more likely related to the changing weight of the sliding mass and thedownslope seepage pressure in the shallow soil mass resulting from rainfall events.     

Mechanical analysis for progressive failure of debris landslide

It is of significance to research failure mechanism of debris landslides that are widespread in the Three Gorges Reservoir Area. Based on the statistical analysis of the developmental law and failure mode of debris landslides in the Three Gorges Reservoir, the mode of progressive failure is found. The mechanical model for progressive failure of debris landslides with two slip bands is also established by applying slice method. According to the results of the downslide force between adjacent slices, if the downslide force of lower slice is larger than zero, the slice fails along the major sliding surface, otherwise it is stable. In result, the failure range is obtained. The stress function can be determined through dimensional analysis of failure slice. According to static boundary conditions of the slice, stress state of any point in the slice can be obtained. Then stress state of any point in the secondary slip band can also be established. The failure of the secondary slip band is judged on the basis of Mohr-Coulomb failure criterion. Therefore, a mechanical method is proposed to analyze the progressive failure of debris landslide with two slip bands.     

考虑降雨滑坡多级滑动的改进传递系数法研究

在多级滑坡的渐进破坏过程中, 滑带不同部位的屈服程度和破坏模式不同, 强度参数也不同。在强降雨条件下, 坡表产生的张拉裂缝充水, 会产生静水压力。当前广泛应用的传递系数法对滑带不同位置取同一强度参数, 也尚未考虑到静水压力作用。为此提出了一种考虑静水压力作用和滑带不同部位强度参数差异的改进传递系数法, 对降雨引起的西安市柳西村南部的牛角沟滑坡进行了计算。结果表明: 与不考虑静水压力和滑带不同部位强度参数差异的计算方法比, 改进传递系数法计算的抗滑力相对较小, 剩余下滑力计算结果相对较大, 各级滑坡稳定性系数分别减小了约33.26%、17.92%、24.95和16.94%;而改进前的稳定性系数偏高, 可能会导致支挡工程的安全储备不足。本研究提出的改进传递系数法可为多级滑坡处置提供更安全的参考。      

基于物理力学机制的滑坡数值预报模式: 综述、挑战与机遇

滑坡预测预报是地质灾害防治领域长期以来备受关注的前沿科学问题。当前的研究框架专注于滑坡的变形行为特征与外动力因素, 面临着普适性不强与预报精准度不高的双重瓶颈问题。基于目前研究现状, 系统梳理了滑带流变力学行为与强度弱化效应的内涵, 阐述了滑坡渐进破坏演化机制, 总结了滑坡预测预报模型所包含的类型, 并介绍了其中的典型模型, 指出当前研究主要存在如下问题: ①滑坡演化物理力学模型尚需扩展; ②预测预报模型未能充分结合滑坡演化过程和物理力学模型; ③物理力学模型预测与多场监测数据间的兼容性问题未能实际解决。针对上述问题, 阐述了基于物理力学过程的滑坡预测预报所面临的挑战, 并立足多学科融合与交叉, 提出了开展滑坡预测预报研究的新思路。新思路要求从滑坡滑带介质特性与流变力学行为出发, 建立滑坡演化过程物理力学模型, 紧密结合实时多场监测数据, 建立滑坡数值预报模式, 实现滑坡物理力学过程实时动态更新, 以期实现理论与技术的突破。      

Tectonic control on slow-moving Andean landslides in the Colca Valley,Peru

The Colca Valley in the Central Andes is a region characterized by the occurrence of large slow-moving landslides and a high level of seismic activity.In this study,we aimed to determine passive and active tectonic control on the formation of selected five large landslides in the Colca Valley and to assess geohazard associated with these features.For that purpose,we performed a post-landslide field survey,applied remote sensing techniques,and obtained eyewitness accounts.Recently,the need to understand mass movement processes in this region is even higher due to the establishment of the Colca y Volcanes de Andagua Geopark(Colca and Andagua Volcanoes Geopark).Our results suggest that the studied landslides usually represent a complex failure mechanism,dominated by translational sliding or rotational displacements,commonly associated with the formation of horst-and-graben like structures.We found a spatial correlation between the distribution of landslides and inherited fault network.The head scarps appear to be limited by the WNW-to NW-striking faults,whereas the lateral extent of some of the reported features seems to be connected with the NNE-striking normal faults,common in both,the Mesozoic strata and the Pleistocene-Holocene deposits.     

水库滑坡成因机制研究进展与展望

滑坡是水库库区主要地质灾害类型之一,开展水库滑坡成因机制研究具有重要理论意义和工程应用价值.利用WebofScience(WoS)数据库和VOSviewer文献计量工具对1999-2018年已发表的969篇以水库滑坡为主题的相关论文进行研究趋势分析.文献计量分析表明三峡库区滑坡稳定性和变形研究是未来水库滑坡成因机制研究主要趋势.从库水对滑坡的宏观力学作用方式、库水作用下岩土体渗流应力耦合机理和库水对岩土体劣化作用过程等方面,对国内外水库滑坡成因机制研究的主要成果与进展进行了综述.综合现有的研究成果指出水库滑坡在精细化地质建模、岩土体多场耦合特征参数获取和岸坡长期演化评价等方面尚存在不足.基于上述问题,提出水库滑坡成因机制研究应以多场信息监测为重要手段,立足多学科交叉,采用大数据融合与挖掘和人工智能技术等解决水库滑坡长期演化趋势难题.考虑水库滑坡所处地质环境的复杂性,建议未来应在水库滑坡立体精细地质建模、多场关联监测、地质结构多场多尺度演变过程、基于监测数据大数据分析的滑坡预警阈值确定和原位试验综合平台构建等方面进一步深入研究.     

Large-scale rock landslide slip surface location analysis and strength parameters evaluation

Large-scale rock landslides have huge impacts on various large-scale rock engineering and project operations. They are also important aspects evaluating geological disasters. In the initial evaluations on the stability of large-scale rock landslides, in most cases, it is difficult to conduct evaluation or to have accurate evaluations because most of large-scale rock landslides are huge in size, high in slopes, and located in the canyon of mountains, which makes the exploration very difficult and thus hard to get credible data on slip surface form, location, depth and strength. This paper describes the Badi landslide happened along the Lancang River, and systematically introduces methods to analyze and verify large-scale slip surface form using terrain conditions surrounding the large-scale landslide, shape of the slide walls, and development patterns of streams and gully. This paper also introduces ways to obtain strength parameters of slip surface with the soil in the slide zone by using the principles of stress state, principles of gravity compaction, structure regeneration and strength regeneration. It is confirmed that analyzed results to the slip surface are basically consistent with the exploration results. The methods introduced here have been successfully applied to evaluate the stability of Badi large-scale rock landslide and have been applied in engineering practices.     

广西河池五圩矿田构造应力场划分及力源探讨

五圩矿田位于广西南丹-河池锡多金属成矿带的南端,主干构造为NNW向的不对称短轴背斜,其上叠加了NE、SN、EW 3个方向的褶皱,它们在丹池带上都有表现.文章通过大量共轭节理、层面擦痕、断层派生小构造、次级褶皱等构造要素野外观测,室内计算,恢复了五圩矿田中生代(印支-燕山期) 4期构造应力场,各期主压应力方位依次为NEE、NW-SE、N WW-SEE及NNE向,前两期为印支期,后两期为燕山期.并探讨了其力源:印支期来源于古特提斯板块向北俯冲与江南古陆向南推移形成的SN向顺时针区域力偶;燕山期来源于丹池断裂的右旋或左旋走滑活动.     

不同环剪条件下三峡库区童家坪滑坡滑带土强度特性

研究不同环剪条件下库岸堆积层滑坡滑带土强度特性对滑坡稳定性评价具有重要意义。针对目前在库岸堆积层滑坡滑带土力学特性方面研究薄弱的问题, 以三峡库区童家坪滑坡滑带土为研究对象, 采用ARS-E2环剪仪开展了不同剪切速率下的剪切试验, 研究了等速剪切、加速剪切以及减速剪切作用下滑带土强度变化特征。试验结果表明: 滑带土试样在恒定的低速剪切条件下更容易得到稳定的残余强度, 并且达到峰值强度后易出现"应变软化"现象; 在相同剪切应力条件下, 滑带土加速环剪和减速环剪的剪应力变化趋势基本一致, 与法向应力均呈正相关关系; 剪切速率的变化会显著影响滑带土峰值黏聚力的大小。研究成果揭示了不同环剪条件下滑带土力学特性, 可以为揭示库岸堆积层滑坡变形破坏的力学机制提供理论依据。      

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Evaluation of mountain slope stability considering the impact of geological interfaces using discrete fractures model

The stability of rock slope is often controlled by the existing discontinuous surfaces, such as discrete fractures, which are ubiquitously distributing in a geological medium. In contrast with the traditional approaches used in soil slope with a continuous assumption, the simulation methods of jointed rock slope are different from that of in soil slope. This paper presents a study on jointed rock slope stability using the proposed discontinuous approach, which considers the effects of discrete fractures. Comparing with traditional methods to model fractures in an implicit way, the presented approach provides a method to simulate fractures in an explicit way, where grids between rock matrix and fractures are independent. To complete geometric components generation and mesh partition for the model, the corresponding algorithms were devised. To evaluate the stability state of rock slope quantitatively, the strength reduction method was integrated into our analysis framework. A benchmark example was used to verify the validation of the approach. A jointed rock slope, which contains natural fractures, was selected as a case study and was simulated regarding the workflow of our framework. It was set up in the light of the geological condition of the site. Slope stability was evaluated under different loading conditions with various fracture patterns. Numerical results show that fractures have significant contributions to slope stability, and different fracture patterns would lead to different shapes of the slip surface. The devised method has the ability to calculate a non-circular slip surface, which is different from a circular slip surface obtained by classical methods.     

一种方向和度量关系组合描述模型

为在统一的框架下研究方向和度量关系,在改进的锥形模型表达方向关系、定性度量关系表示的基础上,本文提出一种新的方向和度量关系组合描述模型。在对方向关系和度量关系定性描述基础上,采用7×7的矩阵和简化后的3×3的矩阵,分别表达方向和度量关系组合模型,并对组合模型的取值范围和数量进行分析。在方向和度量关系组合模型基础上,定义了组合描述模型的5个有效性规则,用于排除不可能的组合关系;设计了方向和度量关系组合描述模型的实例,用于验证模型的有效性。方向和度量关系组合描述模型将方向关系和度量关系有机地结合在一起,提高了空间关系描述的准确性和有效性。     

Seismic stability analysis of slopes with pre-existing slip surfaces

In analyzing seismic stability of a slope with upper bound limit analysis method, the slip surface is often assumed as a log-spiral or plane slip surface. However, due to the presence of a weak layer and unfavorable geological structural surface or a bedrock interface with overlying soft strata, the preexisting slip surface of the slope may be irregular and composed of a series of planes rather than strictly log-spiral or plane shape. A computational model is developed for analyzing the seismic stability of slopes with pre-existing slip surfaces. This model is based on the upper bound limit analysis method and can consider the effect of anchor bolts. The soil or rock is deemed to follow the Mohr-Coulomb yield criterion. The slope is divided into multiple block elements along the slip surface. According to the displacement compatibility and the associated flow rule, a kinematic velocity field of the slope can be obtained computationally. The proposed model allows not only calculation of the rate of external work owing to the combined effect of self-weight and seismic loading, but also that of the energy dissipation rate caused by the slip surface, interfaces of block elements and anchorage effect of the anchors. Considering a direct relationship between the rate of external work and the energy dissipation rate, the expressions of yield acceleration and permanent displacement of anchored slopes can be derived. Finally, the validity of this proposed model is illustrated by analysis on three typical slopes. The results showed that the proposed model is more easily formulated and does not need to solve complex equations or time consuming iterations compared with previous methods based on the conditions of force equilibrium.     

利用最小二乘支持向量机的短临降雨预测模型构建

针对传统降雨预测理论错报率高及算法拟合精度低等缺陷,将与降雨过程相关的多种气象参数(温度、相对湿度、露点温度、气压等)及时间参数(年积日和天积时)引入短临降雨预测模型的构建.将新加坡2个GNSS和气象并址的测站(NTUS、SNUS)2010?2012年的气象数据及降雨数据作为样本,研究气象参数与降雨数据的时变特征,结果...     

Displacement characteristics and prediction of Baishuihe landslide in the Three Gorges Reservoir

In order to reach the designated final water level of 175 m, there were three impoundment stages in the Three Gorges Reservoir, with water levels of 135 m, 156 m and 175 m. Baishuihe landslide in the Reservoir was chosen to analyze its displacement characteristics and displacement variability at the different stages. Based on monitoring data, the landslide displacement was mainly influenced by rainfall and drawdown of the reservoir water level. However, the magnitude of the rise and drawdown of the water level after the reservoir water level reached 175 m did not accelerate landslide displacement. The prediction of landslide displacement for active landslides is very important for landslide risk management. The time series of cumulative displacement was divided into a trend term and a periodic term using the Hodrick-Prescott(HP) filter method. The polynomial model was used to predict the trend term. The extreme learning machine(ELM) and least squares support vector machine(LS-SVM) were chosen to predict theperiodic term. In the prediction model for the periodic term, input variables based on the effects of rainfall and reservoir water level in landslide displacement were selected using grey relational analysis. Based on the results, the prediction precision of ELM is better than that of LS-SVM for predicting landslide displacement. The method for predicting landslide displacement could be applied by relevant authorities in making landslide emergency plans in the future.     

基于形变资料开展地震预测研究需关注的问题及展望

总结基于形变资料的与地震预测相关的物理模型发展过程,并对当前形变观测资料在地震预测研究中的应用进行介绍。在此基础上,给出基于形变资料的强震综合预测思路及需要关注的问题。未来一段时间,建议从形变监测角度解决典型构造区密集观测与通用大地测量模型的构建问题;从科研角度开展高分辨率应力/应变场获取方法及其与地震关系的研究,深入研究并获得我国地壳粘滞性结构分布,强化研究活动地块/典型构造区的变形机理,开展断层滑动速率、闭锁程度/滑动亏损分布的可靠获取方法及模型研究,强化典型部位连续观测异常模式识别及机理研究。监测和科研的核心问题是为断层变形机理提供有效的观测约束并构建定量力学模型,相关工作是深入理解地震过程和推进强震物理预测的关键所在。
     

A generalized limit equilibrium method for the solution of active earth pressure on a retaining wall

In this paper, a generalized limit equilibrium method of solving the active earth pressure problem behind a retaining wall is proposed. Differing from other limit equilibrium methods, an arbitrary slip surface shape without any assumptions of pre-defined shapes is needed in the current framework, which is verified to find the most probable failure slip surface. Based on the current computational framework, numerical comparisons with experiment, discrete element method and other methods are carried out. In addition, the influences of the inclination of the wall, the soil cohesion, the angle of the internal friction of the soil, the slope inclination of the backfill soil on the critical pressure coefficient of the soil, the point of application of the resultant earth pressure and the shape of the slip surface are also carefully investigated. The results demonstrate that limit equilibrium solution from predefined slip plane assumption, including Coulomb solution, is a special case of current computational framework. It is well illustrated that the current method is feasible to evaluate the characteristics of earth pressure problem.