A new prediction model for rock slope failure time: a case study in West Open-Pit mine,Fushun, China

Establishing an accurate method for predicting the failure times of rock slopes subject to creep deformation is challenging, but at the same time crucial for preventing damage to properties and loss of life. In this paper, the Medium–short Term Prediction of Landslide by Polynomial (MsTPLP) model is proposed based on the Levenberg–Marquardt (LM) algorithm. The West Open-Pit mine in Fushun, NE China is currently the largest open-pit coal mine in Asia. The landslide on the southern slope of the West Open-Pit mine was selected as the study case. Global Positioning System (GPS) monitoring is employed in landslide displacement monitoring. Based on the analysis process of the MsTPLP model, the displacement time series derived from GPS monitoring points is selected as the input. The model parameters of the MsTPLP model are obtained using the Levenberg–Marquardt (LM) algorithm. The predicted failure time of a landslide, which is the output, can be determined according to the prediction criteria of the model. The prediction results show that the MsTPLP model can provide accurate landslide displacement predictions (correlation coefficient R ² > 0.98 and average relative error ARE < 17 %). The forecasting results of the landslide show that the estimated failure time is Mar 5, 2014. Based on field investigation and displacement analysis, the landslide on the southern slope of the West Open-Pit mine occurred on Mar 9, 2014. The predicted and actual failure times are significantly close, demonstrating the potential of the new method in landslide prediction.     

Mapping the susceptibility of rainfall and earthquake triggered landslides along China–Nepal highways

The 2015 Gorkha earthquake (Mw?=?7.8) caused significant earthquake triggered landslides (ETL) in a landscape that is heavily intervened by rainfall triggered landslides (RTL). China’s Belt and Road Initiative plan to boost South-Asian regional trade and mobility through two key highway corridors, i.e. 1) Longmu–Rasuwa–Kathmandu (LRK) and 2) Nyalam–Tatopani–Kathmandu (NTK) route, that dissect the Himalayas through this geologically unstable region. To understand the spatial characteristics and susceptibility of these ETL and RTL, we delineate the landslides by means of time variant satellite imageries, assess their spatial distribution and model their susceptibilities along the highway slopes. We use a coupled frequency ratio (FR) – analytical hierarchy process (AHP) model by considering nine landslide determinants, e.g. geomorphic type (slope, aspect, curvature, elevation), hydrologic type (erosive potential of gullies, i.e. stream power index and distance to streams), normalized difference vegetation index, lithology and civil structure type (i.e. distance to roads). The results demonstrate that elevation and slope predominantly control both these landslide occurrences. The model predicts locations of ETL with higher accuracy than RTL. On comparison, NTK was safer with 133.5 km² of high RTL or ETL (or both) landslide susceptible areas, whereas LRK has 216.04 km². For mapping the extent of these landslides, we constricted it to the slope units of highways to reduce the computational effort, but this technique successfully achieved an acceptable threefold average model prediction rate of 82.75% in ETL and 77.9% in RTL. These landslide susceptibility maps and route comparisons would provide guidance towards further planning, monitoring, and implementing landslide risk mitigation measures for the governments.

     

管网渗流系统对含碎石粘性土边坡的稳定作用

坡脚开挖或坡面堆载时,含碎石粘性土边坡经常发生滑坡。此类滑坡的发生机理不仅与边坡力学条件的改变有关,还与水文地质条件的改变有关。在含碎石粘性土边坡中常常发育有地下水管网渗流系统,它对控制坡体地下水位上升有重要的作用,是保持边坡稳定的重要因素。当坡脚开挖或坡面堆载引起坡体局部破坏时,原有的地下水管网渗流系统可能遭到破坏,从而导致坡体地下水位明显上升而产生滑坡。通过滑坡地质调查和稳定性计算分析,揭示了管网渗流系统的发育特点及其对边坡稳定性的影响,并通过物理模型试验再现了地下水管网渗流系统的形成过程及其对边坡渗透性的作用。     

Assessing landslide hazard in GIS: a case study from Rasuwa, Nepal

A slope stability analysis on a regional scale is presented for the northern part of the Rasuwa district in Nepal, covering 409 km². A physically based slope stability model coupled to a simplified groundwater flow model was used to estimate soil wetness, and safety maps were generated for three steady state and two quasi-dynamic conditions. The results show that only about half of the soils are unconditionally stable, characterised by slopes smaller than 22°. Some 7% of the study area is prone to failure under completely saturated conditions, where the slopes exceed 30° and the land-use is predominantly agricultural. Some deficiencies in the model are discussed, but nevertheless the study shows that based upon relatively coarse and limited data, useful landslide hazard information on a regional scale can be obtained.     

四川都江堰白依庵泥岩矿高陡边坡环境治理和生态修复

矿山创面高陡边坡是矿山地质环境治理与生态修复的难点。该文选取四川都江堰白依庵泥岩矿高陡边坡为研究对象,通过野外矿山地质环境详细调查,认为边坡失稳、滑坡灾害和创面边坡大面积裸露制约白依庵泥岩矿安全生产和环境保护的主要问题。识别出2处创面边坡滑坡,其中Ⅰ#滑坡堆积区岩土体处于欠稳定-稳定状态,Ⅱ#滑坡当前经历过整体失稳滑移,目前处于基本稳定-欠稳定状态。基于生态自循环理念,在创面边坡构建合理的土壤结构,以生态修复措施协助自然生态恢复。将创面边坡分为破碎岩面、完整岩面和滑坡面三种类型,根据泥岩面的特点分布设计生态修复方案和工艺流程。     

粘土矿物与斜坡失稳

作为微米级材料，粘土矿物的单晶尺寸及特殊晶体结构使其集合体-粘土呈现低渗透性、分散-凝絮性及粘滞性等重要工程特性。除沉积岩斜坡含粘土矿物外，76％以上的斜坡岩石造岩矿物还可形成次生粘土矿物。粘土矿物广泛分布于原生沉积岩、三大岩类风化带及第四系松散堆积物构成的斜坡中。泥屑岩因含粘土矿物而易于失稳，且水稳定性差。次生粘土矿物的形成将引起源矿物、矿物集合体及岩块的强度与变形特性的显著变化，诱发岩石向松散介质转化。宏观结构面是粘土矿物最主要的形成和聚集场所，结构面及其内侧一定范围内不同成因粘土矿物的淀积将导致结构面及岩体强度的衰减。粘土矿物是滑坡滑带的常见矿物组分；粘土滑带可以在滑体与滑床之间起到润滑作用。滑带中粘土矿物的含量越多，其润滑效应越显著。粘土型滑带还具有隔水边界之功效，可将滑体与周围介质隔离，使之成为独立水文地质单元，提高坡体拦截、吸收渗入水的能力及斜坡稳定对降雨过程的敏感度。粘土矿物可以促进斜坡时效变形，甚至成为斜坡破坏的关键因素，对斜坡演化及失稳的贡献是显著的。     

Geotechnical study for optimizing the slope design of a deep open-pit mine,India

The study was undertaken to determine the optimal overall slope angle of a lead–zinc mine, which could extend down to a depth of 170 m. Detailed geotechnical investigations were conducted, including geotechnical mapping of existing benches to establish the geometrical and mechanical properties of the discontinuities, the drilling of eight boreholes and the establishment of the physico-mechanical properties of the intact rock. Based on these data, limit equilibrium and numerical simulation techniques were applied to assess the stability of the slopes and determine an optimal slope angle. It was concluded that the overall foot-wall and hanging-wall slopes should be 42 and 48° respectively.      

Spatial distribution and failure mechanism of water-induced landslides in the reservoir areas of Southwest China

Water-induced landslides in hydropower reservoirs pose a great threat to both project operation and human life. This paper examines three large reservoirs in Sichuan Province, China. Field surveys, site monitoring data analyses and numerical simulations are used to analyze the spatial distribution and failure mechanisms of water-induced landslides in reservoir areas. First, the general rules of landslide development in the reservoir area are summarized. The first rule is that most of the landslides have rear edge elevations of 100–500 m above the normal water level of the reservoir, with volumes in the range of 10⁶–10⁷ m³. When the volume exceeds a certain amount, the number of sites at which the landscape can withstand landslides is greatly reduced. Landslide hazards mainly occur in the middle section of the reservoir and less in the annex of the dam site and the latter half of the reservoir area. The second rule is that sedimentary rocks such as sandstone are more prone to landslide hazards than other lithologies. Then, the failure mechanism of changes in the water level that reduces the stability of the slope composed of different geomaterials is analyzed by a proposed slope stability framework that considers displacement and is discussed with the monitoring results. Permeability is an essential parameter for understanding the diametrically opposed deformation behavior of landslides experiencing filling-drawdown cycles during operation. This study seeks to provide inspiration to subsequent researchers, as well as guidance to technicians, on landslide prevention and control in reservoir areas.     

Stability evaluation and optimal excavated design of rock slope at Antaibao open pit coal mine, China

Rock slope deformation stability for Antaibao open pit coal mine under mining was analyzed using finite difference technique (FLAC^3D). Optimal excavated scheme with relatively steeper slope angle of 47° instead of 30° was successfully implemented at the west wall on the geological section 73200 of the mine area, where the three-dimensional (3D) effect of nonlinear large deformation of the slope was taken into account. Physico-mechanical properties of the rock materials were obtained by laboratory tests conducted on samples cored from exploration drilling and rock blocks taken directly from the mine. A nonlinear Mohr–Coulomb material model with a tension cutoff was used in all present simulations. Nonlinear effect on excavated sequence was also discussed. It is demonstrated by dynamical response analysis that the action of earthquake magnitude VII (Richter) upon the relatively steeper excavated slope could not be more than that slope could bear.     

Hydraulic conductivity of bentonite-polymer geosynthetic clay liners to coal combustion product leachates

Hydraulic conductivity of seven geosynthetic clay liners (GCLs) to synthetic coal combustion product (CCP) leachates were evaluated in this study. The leachates are chemically representative of typical and worst scenarios observed in CCP landfills. The ionic strength (I) of the synthetic CCP leachates ranged from 50 mM to 4676 mM (TCCP-50, LRMD-96, TFGDS-473, LR-2577, HI-3179 and HR-4676). One of the GCLs contained conventional sodium bentonite (Na–B) and the other six contained bentonite-polymer (B–P) mixture with polymer loadings ranging from 0.5% to 12.7%. Hydraulic conductivity tests were conducted at an effective confining stress of 20 kPa. The hydraulic conductivity of the Na–B GCLs were >1 × 10⁻¹⁰ m/s when permeated with all six CCP leachates, whereas the B–P GCLs with sufficient polymer loading maintained low hydraulic conductivity to synthetic CCP leachates. All the B–P GCLs showed low hydraulic conductivity (<1 × 10⁻¹⁰ m/s) to low ionic strength leachates (TCCP-50, I = 50 mM and LRMD-96, I = 96 mM). B–P GCLs with P > 5% showed low hydraulic conductivity (<1 × 10⁻¹⁰ m/s) up to HI-3179 leachates. These results suggest that B–P GCLs with sufficient polymer loading can be used to manage aggressive CCP leachates.     

某煤矿工业场地东侧古滑坡复活机制及应力-应变特征分析

以某煤矿工业场地东侧古滑坡的工程地质特征为基础,在分析斜坡变形破坏的形成机制及模式的前提下,探讨古滑坡的复活机制,并采用二维弹塑性有限元数值模型分别分析了天然及工程开挖状况下滑坡体的稳定性。结果表明工程开挖将导致边坡失稳,对该滑坡进行治理非常必要,治理方案以"消坡压脚"为主,排水措施为辅。     

Applications of sewage sludge ash and nano-SiO2 to manufacture tile as construction material

In this study, various portions of potter’s clay and porcelain clay were replaced with incinerated sewage sludge ash (ISSA) to manufacture sludge ash tile specimens. We used these tiles to investigate the effect of introducing nano-SiO₂ particles as strengthening additives in the clay–ISSA materials. Percentages of ISSA in the porcelain or potter’s clay-based materials ranged from 0% to 50%, and fractions of nano-SiO₂ additives range from 0% to 3%. Tile specimens were manufactured from the different clay–ISSA–additive mixtures and sintered at kiln temperatures of 1000 °C and 1100 °C. Mechanical tests were performed to measure shrinkage, water absorption, abrasion, and bending strength. The sample microstructure was investigated using scanning electron microscopy (SEM). Chemical compositions of the tile specimens were characterized with X-ray diffraction. Results indicate that water absorption of porcelain and potter’s clay-based tiles was reduced when samples were fired at the higher kiln temperature, dropping to less than 12% in porcelain tiles at a kiln temperature of 1100 °C. Kiln temperature appeared to have less influence on the tiles made from potter’s clay. With the addition of nano-SiO₂ additive, the bending strengths of both types of tiles were increased, with the strengthening effect more pronounced in potter’s clay tiles when compared to porcelain clay tiles.     

滑坡地质灾害远程监测预报系统及其工程应用

 露天矿边坡稳定性监控预报技术研究,对滑坡地质灾害防控具有重要意义。以滑体、滑床和监控锚索相互作用力学原理为理论基础,提出滑体和滑床相对运动状态的力学监测原理,把多因素监测变为单一滑动力力学量监测,给出滑动力与监控预紧力的关系。通过滑坡物理模型试验得出,在滑坡发生前,边坡岩体内应力会连续发生变化,当滑动力大于抗滑力后,边坡岩体会发生变形和滑动,且捕捉边坡岩体内应力的变化优于对岩体位移的监测。基于上述原理和试验结果,开发了滑坡地质灾害远程监测预报系统,实现摄动力动态变化的远程实时监测。提出4种监测预警模型,通过对露天矿山边坡等的现场实践应用,该监控新技术成功地进行边坡稳态实时监控和预测预报。     

水位变化引起分层边坡滑坡的实验研究

通过对分层的边坡在水位变化时滑坡的模拟实验，起的滑坡，重点考察了水位涨落速度对坡体稳定的影响，考察了分层坡体的滑坡模式、坡体变形、破坏和渗流引以及坡面从产生张拉裂缝直到形成滑面的整个过程，并对这类滑坡中的现象给出了定性解释。最后用有限元对实验坡体进行了应力和位移的静力场分析，计算结果与实验结果基本一致。     

The 17 February 2006 Guinsaugon rock slide-debris avalanche, Southern Leyte, Philippines: deposit characteristics and failure mechanism

The Guinsaugon rock slide-debris avalanche was the most catastrophic single landslide event in Philippine history, with 14–18 M m³ of debris instantly burying an entire village. Hummocky topography, pressure ridges and other internal structures suggest that the landslide deposit was emplaced as a debris avalanche and debris flow. Susceptibility to planar and wedge failures as well as to toppling due to rock discontinuities were demonstrated using kinematic analysis and SMR. Limit equilibrium analysis on planar failures yielded factors of safety ranging from 0.8 to 1.5. The study showed that pore pressure on discontinuities had a more significant effect on the slope stability than seismicity. For wedge failures, there is a sudden drop in the factor of safety at pore water pressures of 258–306 kPa. At the site, the pore water pressure may have been as high as 490 kPa. The possibility of such a landslide event in the future is discussed.      

Apport d'une approche probabiliste de la stabilité pour la conception des talus de mine a ciel ouvert. Applciation à la mine de Carmaux,france

Slope stability problem in operacast mines is one that is often encountered by geotechnical engineers in the design of slopes in jointed rock masses. To resolve this problem, several elements such as the geometrical and the geotechnical parameters of the fracture set of the rock mass have to be considered. In this paper, the characterization of the statistical distribution of geometrical fracture parameters enable the simulation of the rock massive and thus provides a realistic approach to the analysis of failure mechanisms that may affect the rock mass. Computer programs were developed and applied to the opencast coal mine of Carmaux (France). Test results led to the proposal of different slope angles and bench widths for different slope orientations in the mine.     

The Gays River mine tailing revegetation study

The Gays River (NS) lead-zinc mine ceased operations in 1982. Seven ha of calcereous mine tailings were left which required stabilization. The tailings, variable in physical composition with depth, were devoid of organic matter, N and P. A potting experiment using the tailings, with and without fertilizer, established 6 plant species which could potentially revegetate the tailing site. Experimental plots (24) were established on the tailings in May 1983 using the same 6 species and 2 indigenous species (alder (Alnus rugosa) and bulbrush (Scirpus americanus Pers.)). The plots were maintained through June 1985; plant yield and tissue analysis for macro- and micronutrients followed each cutting or sampling data. The final recommendations for reclamation were to drill in alfalfa (Medicago sativa L.) and red clover (Trifolium pratense L.) seeds, cut and fertilize annually with 800 kg ha^-1 of 12-24-24 or transplant couchgrass (Agropyron repens) and fertilize periodically with 12-24-24.     

高速列车荷载下尾矿动力特性及坝体稳定性分析

高速列车荷载作用下尾矿库边坡的稳定与否直接影响着列车的安全运营。以福建某一尾矿库边坡为例,通过采集的尾矿材料进行动三轴和共振柱试验,得到尾粉砂和尾粉土的动力参数,并揭示了尾矿材料在不同围压下动剪切模量比(G/Gmax)和动阻尼比(λ)随动剪应变(γ)变化发展规律,定量给出相应参数的推荐值;借助实测的动力参数和高速列车加速度时程曲线,对尾矿库边坡进行液化特性和动力稳定性的定量分析评价,计算结果满足要求。该研究手段可为类似工程的安全评价提供有意义的参考。     

兰永一级公路顺层滑坡抗剪强度参数确定及应用

兰永一级公路工程修建过程中在路堑边坡开挖时形成了顺层边坡,以K23+520处的大型顺层滑坡最为典型。由于岩土体抗剪强度参数在边坡稳定性分析和加固设计中不可或缺,为了更好地实现其余类似边坡的加固设计和稳定性分析,以K23+520处的滑坡为研究对象,提出含有软弱夹层的顺层滑坡结构面上抗剪强度参数的确定方法:对已知一个滑动面位置的滑移–拉裂破坏模式下的顺层滑坡,通过结合顺层滑坡失稳条件(临界高度、局部稳定系数)及变形破坏特征对满足刚体滑移模型下的多组强度参数进行逐步修正,得到了满足工程应用要求的强度参数取值,并将结果用于类似边坡的加固设计和稳定分析。方法不仅适合兰永一级公路K23+520处顺层滑坡结构面上抗剪强度参数的确定,还适用于类似滑坡工程强度参数的确定,具有一定的工程实用价值。     

High-resolution lidar-based landslide hazard mapping and modeling,UCSF Parnassus Campus,San Francisco,USA

Airborne lidar (light detection and ranging) was used to create a high-resolution digital elevation model (DEM) and produce landslide hazard maps of the University of California, San Francisco Parnassus Campus. The lidar DEM consisted of nearly 2.8 million interpolated elevation values covering approximately100 ha and posted on an 0.6 m horizontal grid, from which a set of 16 maps was produced. The first subset of maps showed aspects of the topography useful for landslide mapping, an engineering geological map and a qualitative slope hazard map. The second subset consisted of physics-based probabilistic landslide hazard maps for wet static, wet seismic, and dry seismic conditions. This case history illustrates the utility of lidar-based products, supplemented by field-based geological observations and physics-based probabilistic slope stability modeling, for the evaluation of existing and potential slope stability hazards on a steep and heavily forested site.