An improved analytical approach for simulating the lateral kinematic distress of deepwater offshore pipelines     

《Applied Ocean Research》2019

Offshore pipelines are critical infrastructures and any possible damage may have devastating financial and environmental consequences. Earthquake-related geohazards (such as strong ground motion, active seismic faults, submarine landslides and debris flows) consist crucial threats that an offshore pipeline has to overcome. The main aim of the current study is to examine analytically a seabed-laid offshore pipeline subjected to a lateral kinematic distress due to a submarine landslide or a debris flow. Extra emphasis is given on the impact of pipe-soil interaction on the pipe response, by the realistic representation of the soil resistance via a tri-linear model. Firstly, the proposed analytical model is validated with a numerical model utilizing the finite-element method. Subsequently, various combinations of soil parameters and loading conditions that affect the examined problem are investigated with realistic input data taken from the offshore section of the high-pressure natural-gas pipeline TAP (Trans Adriatic Pipeline) in the Adriatic Sea. Finally, useful conclusions are drawn regarding the applicability and the efficiency of the proposed approach.  相似文献   

Dynamic modelling of retrogressive landslides with emphasis on the role of clay sensitivity          下载免费PDF全文

Xue Zhang  Scott W. Sloan  Eugenio Oñate 《国际地质力学数值与分析法杂志》2018,42(15):1806-1822

This paper presents a detailed numerical study of the retrogressive failure of landslides in sensitive clays. The dynamic modelling of the landslides is carried out using a novel continuum approach, the particle finite element method, complemented with an elastoviscoplastic constitutive model. The multiwedge failure mode in the collapse is captured successfully, and the multiple retrogressive failures that have been widely observed in landslides in sensitive clays are reproduced with the failure mechanism, the kinematics, and the deposition being discussed in detail. Special attention has been paid to the role of the clay sensitivity on each retrogressive failure as well as on the final retrogression distance and the final run‐out distance via parametric studies. Moreover, the effects of the viscosity of sensitive clays on the failure are also investigated for different clay sensitivities.  相似文献   

汶川地震同震滑坡物质在震区的滞留和运移及其对龙门山地形演化的影响   总被引：1，自引：1，他引：0       下载免费PDF全文

王伟  刘静  Vincent Godard  张金玉  许冲  李志刚  徐心悦  许强  王鹏  谢克家 《地球物理学报》2018,61(5):1970-1983

2008年M_W7.9汶川地震导致龙门山断裂发生强烈地壳变形，同时引发的巨量同震滑坡加速了该地区的地表剥蚀和河流侵蚀.然而，目前尚缺少系统的数据定量研究滑坡物质的运移以及河流侵蚀速率随时间的演化规律，这些对理解龙门山前缘物质的再分配以及强震对活动造山带地形塑造的作用至关重要.为此，本研究在汶川地震后的6年间，对震区沱江上游3条支流湔江、石亭江、绵远河流域进行了多期次的定点现代河沙采样.通过系统测量河沙中的石英¹⁰Be浓度，并与震前已发表的数据进行对比，发现如下基本特点：（1）震后河沙¹⁰Be浓度均有明显降低，表明同震滑坡物质对河沙的稀释作用；（2）震后河流对河沙的运移量增加为震前的1.3~18.5倍，因此震后龙门山地区侵蚀速率短期显著增加；（3）初步估计得到汶川地震产生的滑坡物质被完全运移出造山带所需要的时间至少为100~4000年，接近龙门山地区强震复发周期；（4）震间和同震产生的构造变形和地表剥蚀在空间上具有互补性.考虑到地表剥蚀引起的地壳均衡反弹效应，认为类似汶川地震的强震有利于龙门山的隆升.认识震前、震时和震后的地壳变形及侵蚀过程有助于更好地理解单次强震事件对高原边界龙门山地形演化的作用.  相似文献   

Dating of paleolandslides in western Finnish Lapland          下载免费PDF全文

Antti E.K. Ojala  Mira Markovaara‐Koivisto  Maarit Middleton  Timo Ruskeeniemi  Jussi Mattila  Raimo Sutinen 《地球表面变化过程与地形》2018,43(11):2449-2462

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Hillslopes in humid-tropical climates aren't always wet: Implications for hydrologic response and landslide initiation in Puerto Rico     

Matthew A. Thomas  Benjamin B. Mirus  Joel B. Smith 《水文研究》2020,34(22):4307-4318

The devastating impacts of the widespread flooding and landsliding in Puerto Rico following the September 2017 landfall of Hurricane Maria highlight the increasingly extreme atmospheric disturbances and enhanced hazard potential in mountainous humid-tropical climate zones. Long-standing conceptual models for hydrologically driven hazards in Puerto Rico posit that hillslope soils remain wet throughout the year, and therefore, that antecedent soil wetness imposes a negligible effect on hazard potential. Our post-Maria in situ hillslope hydrologic observations, however, indicate that while some slopes remain wet throughout the year, others exhibit appreciable seasonal and intra-storm subsurface drainage. Therefore, we evaluated the performance of hydro-meteorological (soil wetness and rainfall) versus intensity-duration (rainfall only) hillslope hydrologic response thresholds that identify the onset of positive pore-water pressure, a predisposing factor for widespread slope instability in this region. Our analyses also consider the role of soil-water storage and infiltration rates on runoff generation, which are relevant factors for flooding hazards. We found that the hydro-meteorological thresholds outperformed intensity-duration thresholds for a seasonally wet, coarse-grained soil, although they did not outperform intensity-duration thresholds for a perennially wet, fine-grained soil. These end-member soils types may also produce radically different stormflow responses, with subsurface flow being more common for the coarse-grained soils underlain by intrusive rocks versus infiltration excess and/or saturation excess for the fine-grained soils underlain by volcaniclastic rocks. We conclude that variability in soil-hydraulic properties, as opposed to climate zone, is the dominant factor that controls runoff generation mechanisms and modulates the relative importance of antecedent soil wetness for our hillslope hydrologic response thresholds.  相似文献   

The impact of storm-triggered landslides on sediment dynamics and catchment-wide denudation rates in the southern Central Range of Taiwan following the extreme rainfall event of Typhoon Morakot     

Chia-Yu Chen  Sean D. Willett  A. Joshua West  Simon Dadson  Niels Hovius  Marcus Christl  J. Bruce H. Shyu 《地球表面变化过程与地形》2020,45(3):548-564

Extreme erosion events can produce large short-term sediment fluxes. Such events complicate erosion rates estimated from cosmogenic nuclide concentrations in river sediment by providing sediment with a concentration different from the long-term basin average. We present a detrital ¹⁰Be study in southern Taiwan, with multiple samples obtained in a time sequence bracketing the 2009 Typhoon Morakot, to assess the impact of landslide sediment on ¹⁰Be concentrations (N¹⁰Be) in river sediment. Sediment samples were collected from 13 major basins, two or three times over the last decade, to observe the temporal variation of N¹⁰Be. Landslide inventories with time intervals of 5–6 years were used to quantify sediment flux changes. A negative correlation between N¹⁰Be and landslide areal density indicates dilution of N¹⁰Be by landslide sediment. Denudation rates estimated from the diluted N¹⁰Be can be up to three times higher than the lowest rate derived from the same basins. Observed increases imply that, 3 years after the passage of Typhoon Morakot, fluvial channels still contain a considerable amount of sediment provided by hillslope landslides during the event. However, higher N¹⁰Be in 2016 samples indicate that the contribution from landslide sediment at the sampled grain size has decreased with time. The correlation between changes in N¹⁰Be and landslide area and volume is not strong, likely resulting from the stochastic and complex nature of sediment transport. To simultaneously evaluate the volume of landslide-derived sediment and estimate the background denudation rate, associated with less impulsive sediment supply, we constructed a sediment-mixing model with the time series of N¹⁰Be and landslide inventories. The spatial pattern of background erosion rate in southern Taiwan is consistent with the regional tectonic framework, indicating that the landscape is evolving mainly in response to the tectonic forcing, and this signal is modified, but not obscured by impulsive sediment supply. © 2019 John Wiley & Sons, Ltd.  相似文献   

Comparing threshold definition techniques for rainfall‐induced landslides: A national assessment using radar rainfall          下载免费PDF全文

Benjamin Postance  John Hillier  Tom Dijkstra  Neil Dixon 《地球表面变化过程与地形》2018,43(2):553-560

Translational landslides and debris flows are often initiated during intense or prolonged rainfall. Empirical thresholds aim to classify the rain conditions that are commonly associated with landslide occurrence and therefore improve understating of these hazards and predictive ability. Objective techniques that are used to determine these thresholds are likely to be affected by the length of the rain record used, yet this is not routinely considered. Moreover, remotely sensed spatially continuous rainfall observations are under‐exploited. This study compares and evaluates the effect of rain record length on two objective threshold selection techniques in a national assessment of Scotland using weather radar data. Thresholds selected by ‘threat score’ are sensitive to rain record length whereas, in a first application to landslides, ‘optimal point’ (OP) thresholds prove relatively consistent. OP thresholds increase landslide detection and may therefore be applicable in early‐warning systems. Thresholds combining 1‐ and 12‐day antecedence variables best distinguish landslide initiation conditions and indicate that Scottish landslides may be initiated by lower rain accumulation and intensities than previously thought. © 2017 The Authors. Earth Surface Processes and Landforms published by John Wiley & Sons Ltd.  相似文献   

Hazard Assessment of Co-seismic Landslides Based on Information Value Method: A Case in 2018 MW6.6 Hokkaido Earthquake, Japan     

WEN Boyu  XU Chong  HE Xiangli  MA Siyuan  SHAO Xiaoyi  LI Kai  ZHANG Zhongjian  LI Zhengfang 《中国地震研究》2020,34(1):64-80

An M_W6.6 earthquake occurred in eastern Hokkaido, Japan on September 6^th, 2018. Based on the pre-earthquake image from Google Earth and the post-earthquake image from high resolution (3 m) planet satellite, we manually interpret 9 293 coseismic landslides and select 7 influencing factors of seismic landslide, such as elevation, slope, slope direction, road distance, flow distance, peak ground acceleration (PGA) and lithology. Then, 9 293 landslide points are randomly divided into training samples and validation samples with a proportion of 7:3. In detail, the training sample has 6 505 landslide points and the validation sample has 2 788 landslide points. The hazard risk assessment of seismic landslide is conducted by using the information value method and the study area is further divided into five risk grades, including very low risk area, low risk area, moderate risk area high risk area and very high risk area. The results show that there are 7 576 landslides in high risk area and very high risk area, accounting for 81.52% of the total landslide number, and the landslide area is 22.93 km², accounting for 74.35% of the total area. The hazard zoning is in high accordance with the actual situation. The evaluation results are tested by using the curve of cumulative percentage of hazardous area and cumulative percentage of landslides number. The results show that the success rate of the information value method is 78.50% and the prediction rate is 78.43%. The evaluation results are satisfactory, indicating that the hazard risk assessment results based on information value method may provide scientific reference for landslide hazard risk assessment as well as the disaster prevention and mitigation in the study area.  相似文献   

芦山地震崩滑灾害空间分布及相关问题探讨   总被引：2，自引：1，他引：1       下载免费PDF全文

周庆  江亚风  吴果  陈国光 《地震地质》2014,36(2):344-357

由于逆断层作用，2013年芦山M_S 7.0地震诱发的崩滑地质灾害分布表现出了明显的上盘效应与方向效应。在震后应急科考中未发现发震断层的地表破裂带，然而灾区大量出现的地震诱发滑坡、崩塌，加之密集的余震分布、地震烈度调查结果等，提供了确定芦山地震宏观震中、地震动错动方向以及研究地震发震构造等的诸多线索。 统计结果表明，芦山地震诱发的滑坡、崩塌具有明显的优势滑动方向（135°～144°），该方向揭示了地震断层的错动方向，与震源机制解反映的一致，大体垂直于发震断层的走向；从地震诱发崩塌、滑坡灾害点的分布与密度判断，宏观震中位于宝盛乡北，在仪器记录震中东北约3.6km处；从余震群分布、地震诱发滑坡分布特点及地震等烈度线等，结合以往强震如汶川地震等的调查经验，推测当震级足够大时，发震断层地表破裂带可能通过地质灾害、余震密集区东侧的边缘地带，总体平行于双石-大川断裂。另外，通过分析地层岩性与崩滑地形条件之间的关联性，发现崩滑灾害在某些地层岩性中易发，灾害点呈线性排列的原因是不同地层岩性之间抗风化能力的差异性，造成在地层分界线上形成线性陡崖或高坡度地带，使之在强震作用下容易发生崩塌、滑坡。  相似文献   

Solid–fluid transition modelling in geomaterials and application to a mudflow interacting with an obstacle     

Noémie Prime  Frédéric Dufour  Félix Darve 《国际地质力学数值与分析法杂志》2014,38(13):1341-1361

Given the contrasting behaviour observed for geomaterials, for example, during landslides of the flow type, this contribution proposes an original constitutive model, which associates both an elasto‐plastic relation and a Bingham viscous law linked by a mechanical transition criterion. This last is defined as the second‐order work sign for each material point, which is a general criterion for divergence instabilities. Finite element method with Lagrangian integration points is chosen as a framework for implementing the new model because of its well‐known ability to deal with both solid and fluid behaviours in large deformation processes. A first boundary model considering a sample of initially stable soil, a slope and an obstacle is performed. The results show the power of the constitutive model because the consistent evolution of initiation, propagation and arrest of the mudflow is described. A parametric study is led on various plastic and viscous parameters to determine their influence on the flow development and arrest. Finally, forces against the obstacle are compared with good agreement with those of other authors for the same geometry and a pure viscous behaviour. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献