降雨对滑坡的影响与基于ANSYS的滑坡数值模拟研究

分析了四川理县一处山体滑坡2014-08～2015-08的监测数据。结果表明,滑坡处于缓慢发生中,滑移的主要方向指向山体旁的学校;1 a中3个监测点在该方向上的累积位移量分别为180 mm、262 mm和448 mm。分析降雨量资料发现,降雨对山体滑坡有延迟的影响。利用ANSYS软件对滑坡发生的过程进行数值模拟,并计算监测点的位移,结果与实际观测情况吻合较好,得到降雨量与弹性模量、密度、粘聚力、内摩擦角之间的关系。该数值模拟实验提供了一种预测滑坡的新方法。     

基于有效降雨阈值的澧源镇滑坡灾害危险性分析

以湖南省澧源镇为例,利用证据权模型和灰色关联度模型分别计算了坡度、地层岩性、斜坡形态、土地利用类型、人类工程活动5个因子二级状态证据权值和一级因子权重;综合2种模型确定全区滑坡易发性指数后,完成基于斜坡单元的全区滑坡易发性区划;根据研究区岩土体类型（碎屑岩类、碳酸盐岩夹碎屑岩类、碳酸盐岩类和松散岩土体类）分组研究不同滑坡发生概率下的有效降雨阈值曲线（I-D曲线）。研究降雨时间为3日、有效强度为22.4 mm/d的降雨工况下各岩土体类型滑坡发生的时间概率。综合时间概率和易发性结果得到澧源镇基于有效降雨阈值的滑坡灾害危险性区划图。研究结果表明:澧源镇滑坡灾害高和极高易发区占研究区总面积的25%,主要沿澧河分布;极高危险区和高危险区占研究区总面积的14%,主要分布在澧河北侧。      

奉节县曾家棚滑坡时空差异性变形特征与成因机制分析

研究库水位波动和降雨影响下滑坡的位移变形特征并分析其破坏机制，对了解三峡库区滑坡的演化过程具有重要意义。以奉节曾家棚滑坡为例，基于GPS地表监测位移分析了滑坡在不同特征库水位运行阶段的变化规律，结合灰色关联度模型确定了滑坡不同部位的变形在不同阶段的主要控制因素，借助GEO-Studio软件模拟了曾家棚滑坡在历史降雨和库水位波动耦合作用下的稳定性变化，并与定量分析结果进行了交叉检验。结果表明:曾家棚滑坡的运动状态随时间变化，从缓慢蠕变状态进入阶跃变形状态。平面上，中东部坡体与西部坡体相比，运动更加强烈；剖面上，前缘变形早且变形量大。曾家棚滑坡变形失稳过程为初期蓄水启动了曾家棚古滑坡，前缘首先发生变形；降雨作为中后期主控因素，和库水位波动联合作用共同诱发了滑坡多次阶跃变形，使滑坡前中后部形成贯通裂缝；最终由二十年一遇的暴雨诱发滑坡发生整体破坏。      

基于多重分形特征和分项组合预测联合响应的滑坡预警预测研究

为准确掌握滑坡变形发展规律,基于滑坡变形监测成果构建滑坡预警预测模型,即先利用MF-DFA模型开展滑坡变形数据的多重分形特征分析,并进一步利用M-K分析构建双重判据（Δa指标判据和Δf(a)指标判据）进行滑坡预警研究;另外,在利用集成经验模态分解法对滑坡变形数据信息进行分离处理基础上,通过GOA-RNN-CT模型实现滑坡变形的分项组合预测。结果表明,h(q)值随波动函数q值减小而减小,说明滑坡变形数据具有多重分形特征,且预警分级研究表明,滑坡预警等级为Ⅱ级,即滑坡变形趋向不利方向发展;同时,通过变形预测分析认为,分项组合预测在滑坡变形预测中具有较优的预测效果和稳定性,且外推预测结果显示,滑坡变形会继续增加;最后,将多重分形特征研究结果和变形预测分析结果进行联合响应综合得出,滑坡现有预警等级相对不利,且后续变形仍会进一步增加,趋向不稳定方向发展,建议对滑坡采取必要防治措施。     

“6.1”芦山地震作用下宝兴新华村滑坡动力响应与失稳过程离散元模拟

斜坡浅表层是各类地震地质灾害发育的潜在破坏位置,坡面形态和坡体结构往往造成斜坡动力响应及破坏的复杂化。为探究不稳定斜坡浅表潜在滑动层动力响应特征与失稳过程,以芦山M_s6.1级地震触发的新华村滑坡为例,基于现场调查采用离散元方法建立了二维计算模型,分析了该斜坡潜在滑动层及坡面形态的动力响应特征并对其失稳过程进行了模拟。结果表明：(1)斜坡浅表潜在滑动层具有强烈动力放大效应;(2)微地貌对于潜在不稳定斜坡坡面的放大效应具有明显的影响,浅表潜在滑动层水平向及竖直向加速度在凸出部位的放大效应显著,凹陷部位相较于凸出部位放大效应较低;(3)研究揭示新华村滑坡在微地貌的作用下凸起地形呈现先于凹陷地形遭受破坏,其失稳过程分为震动放大局部震裂-凸出地形破坏-凹陷地形破坏-完全破坏整体下滑-重力堆积5个阶段。该研究结果有助于提升防灾人员对地震诱发潜在不稳定斜坡失稳的认识,为防灾减灾提供理论和数据支撑。     

基于S-变换的GNSS滑坡变形监测数据信息提取与抑噪

提出一种基于S-变换的变形监测数据抑噪方法。首先采用S-变换对监测数据进行时频分析,得到二维时频矩阵,再根据二维时频矩阵设计时频滤波器,最后利用时频分析反变换方法重构信号。采用模拟数据和滑坡变形实测数据对该方法的有效性进行验证。结果表明,相较于小波滤波方法,经该方法处理后的变形数据的RMSE和SNR均较优,可准确提取监测点的变形特征,为滑坡变形预测预报提供可靠的监测数据。     

青藏活动地块区运动与变形特征的数值模拟

利用二维有限元模型,以GPS测量的构造运动为约束条件,探讨了青藏活动地块在弹性应变积累过程中的运动与变形状态。模拟结果表明,青藏活动地块区在整体运动过程中,内部变形以大范围的分布为特征,其内部的应变分布和弹性应变能积累速率表明了Ⅱ级活动地块与活动边界带的显著变形差别：活动地块内部的应变和弹性应变能积累速率相对较小且分布较均匀;活动边界带上变形相对集中,应变和弹性应变能积累速率相对较高,并呈非均匀分布。这反映了青藏地块区内所含的各Ⅱ级活动地块的运动变形的整体性特征及彼此间的差异性特征,也揭示了活动地块构造通过边界带变形等方式对大陆强震的控制作用。     

Field investigations and numerical modeling of a giant landslide in the region of Eastern Himalayan Syntaxis:Jiaobunong landslide

Eastern Himalayan Syntaxis (EHS) is a tectonically active region that undergoes continuous geomorphic changes.Large landslides are predominant in this region.A ...     

降雨作用下青石镇政府后山堆积层滑坡渗流与稳定性

以黄冈地区青石镇政府后山堆积层滑坡为例，在分析了其工程地质特征及地质结构特征的基础上，采用有限元法研究了非饱和土瞬态体积含水量及孔隙水压力的分布，采用考虑孔隙水压力的Janbu法分析计算了降雨对堆积层滑坡安全系数的影响。研究结果表明:①降雨入渗导致坡体孔隙水压力升高，滑面抗剪强度降低，安全系数也随之逐渐降低，其中在降雨前期，两侧的抗剪强度下降速率比中部快，而到了后期中部的抗剪强度下降速率明显快于两侧；②安全系数变化表现为前19 d以0.008/d的速率缓慢下降，19~30 d以0.03/d的速率缓慢下降，30 d以后下降速度降低，至36 d之后不再发生变化，其中在0~11 d两侧抗剪强度变化对滑坡整体稳定性变化的贡献比中部大，19~36 d中部抗剪强度变化对滑坡整体稳定性变化的贡献要比两侧大；③降雨入渗过程中，地下水从坡体表层和两侧流向坡体中部，负孔压区面积向中部不断压缩，中部地下水变化受到两侧及上层的制约，体积含水量及孔隙水压力变化相对滞后；④该滑坡的防治重点是做好降雨前期坡体后缘地下水截流以及前缘地下水排泄工作，同时，做好地表排水，减少降雨入渗。      

On verification of the new criterion of adiabaticity by numerical simulation of acoustic propagation through the polar front

To assess the adiabaticity of acoustic propagation in the ocean is very important for acoustic field calculation (forward problem) and tomographic retrieving (inverse problem). A new criterion of adiabaticity is proposed recently (Shang et al., 2001). In this paper, numerical simulation has been conducted for acoustic propagation through the Polar Front to verify the new criterion. Numerical results on the f (frequency)-m (mode number) plan demonstrate that the new criterion works very well for this extremely non-gradual ocean structure.     

三峡库区麻柳林滑坡变形特征及演化模拟

在库水位波动和降雨作用的共同影响下，库岸滑坡的变形规律往往更为复杂。以三峡库区麻柳林滑坡为例，基于野外调查、钻探编录、深部位移监测以及数值模拟等手段，分析了库水位波动和降雨作用下滑坡变形特征及演化规律。结果表明:麻柳林滑坡在粉质黏土层和块石层交界处发育一个次级滑带，目前该滑坡主要沿次级滑带运动，导致次级滑动的原因与坡体物质的差异性有关；S_i(S_f)指标分析法揭示滑坡的滑带还未完全破坏，滑坡仍处于蠕变状态；根据三峡水库水位调度规律，将一个完整水文年划分为6个阶段，数值模拟结果表明滑坡在库水位缓慢下降阶段变形速率较小、在快速下降阶段和低水位阶段变形速率持续增大、在快速上升阶段和缓慢上升阶段以及高水位阶段变形速率则保持平稳。其中，降雨的直接影响和降雨导致库水位波动进而对滑坡变形造成的间接影响，使得麻柳林滑坡在低水位阶段的变形显著增加、稳定性最差，应加强该时段内滑坡的监测和预警。      

Study on numerical simulation and dynamic mechanism of winter-time circulation in the eastern China seas

An MOM2 based 3-dimentional prognostic baroclinic Z-ordinate model was established to study the circulation in eastern China seas, considering the topography, inflow and outflow on the open boundary, wind stress, temperature and salinity exchange on the sea surface. The results were consistent with observation and showed that the Kuroshio intrudes in large scale into the East China Sea continental shelf East China, during which its water is exchanged ceaselessly with outer sea water along Ryukyu Island. The Tsushima Warm Current is derived from several sources, a branch of the Kuroshio, part of the Taiwan Warm Current, and Yellow Sea mixed water coming from the west of Cheju Island. The water from the west of Cheju Island contributes approximately 13% of the Isushima Warm Current total transport through the Korea Strait. The circulation in the Bohai Sea and Yellow Sea is basically cyclonic circulation, and is comprised of coastal currents and the Yellow Sea Warm Current. Besides simulation of the real circulation, numerical experiments were conducted to study the dynamic mechanism. The numerical experiments indicated that wind directly drives the East China Sea and Yellow Sea Coastal Currents, and strengthens the Korea Coastal Current and Yellow Sea Warm Current. In the no wind case, the kinetic energy of the coastal current area and main YSWC area is only 1% of that of the wind case.Numerical experiments also showed that the Tsushima Warm Current is of great importance to the formation of the Korea Coastal Current and Yellow Sea Warm Current.     

Failure mechanism and stability analysis of the Zhenggang landslide in Yunnan Province of China using 3D particle flow code simulation

Based on the principle of 3D particle flow code, a numerical landslide run-out model is presented to simulate the failure process of the Zhenggang landslide (in southwestern China) under the effect of water after a rainfall. The relationship between the micro-mechanical parameters and the macro-shear strength of the grain material is determined through numerical calibrations. Then the rainfall effect is considered in numerical simulations and rain-induced sliding processes are performed, which help us to discuss the mechanism of deformation and failure of this landslide together with field observations. It shows the Zhenggang landslide would most likely be activated in Zone I and would gain momentum in Zone II. In order to prevent the potential disaster, a tailing dam is advised to be designed about 175 m downstream from the current landslide boundary of Zone II. Verified by field observations, the presented landslide model can reflect the failure mechanism after rainfall. It can also provide a method to predict the potential disaster and draft disaster prevention measures.     

Fine-resolution simulation of surface current and sea ice in the Arctic Mediterranean Seas

A fine-resolution model is developed for ocean circulation simulation in the National Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Chinese Academy of Sciences, and is applied to simulate surface current and sea ice variations in the Arctic Mediterranean Seas. A dynamic sea ice model in elastic-viscous-plastic rheology and a thermodynamic sea ice model are employed. A 200-year simulation is performed and a dimatological average of a 10-year period (141st-150th) is presented with focus on sea ice concentration and surface current variations in the Arctic Mediterranean Seas. The model is able to simulate well the East Greenland Current, Beaufort Gyre and the Transpolar Drift, but the simulated West Spitsbergen Current is small and weak. In the March climatology, the sea ice coverage can be simulated well except for a bit more ice in east of Spitsbergen Island. The result is also good for the September scenario except for less ice concentration east of Greenland and greater ice concentration near the ice margin. The extra ice east of Spitsbergen Island is caused by sea ice current convergence forced by atmospheric wind stress.     

NUMERICAL SIMULATION OF INTERANNUAL AND INTERDECADAL VARIABILITY OF SURFACE WIND OVER THE TROPICAL PACIFIC

A global atmospheric general circulation model (L9R15 AGCMs) forced by COADS SST was integrated from 1945 to 1993. Interannual and interdecadal variability of the simulated surface wind over the tropical Pacific was analyzed and shown to agree vey well with observation. Simulation of surface wind over the central-western equatorial Pacific was more successful than that over the eastern Pacific. Zonal propagating feature of interannual variability of the tropical Pacific wind anomalies and its decadal difference were also simulated successfully. The close agreement between simulation and observation on the existence of obvious interdecadal variability of tropical Pacific surface wind attested to the high simulation capability of AGCM.     

Panzhihua airport landslide (Oct. 3rd 2009) and an emergency monitoring and warning system based on the internet of things

Panzhihua city(26°05’-27°21’N,101°08’102°15’E),located in a mountainous area,is one of the large cities in Sichuan province,China.A landslide occurred in the filling body of the eastern part of the Panzhihua airport on October 3,2009(hereafter called the 10.3 landslide).We conducted field survey on the landslide and adopted emergency monitoring and warning models based on the Internet of Things(IoT) to estimate the losses from the disaster and to prevent a secondary disaster from occurring.The results showed that four major features of the airport site had contributed to the landslide,i.e,high altitude,huge amount of filling rocks,deep backfilling and great difficulty of backfilling.The deformation process of the landslide had six stages and the unstable geological structure of high fillings and an earthquake were the main causes of the landslide.We adopted relative displacement sensing technology and Global System for Mobile Communications(GSM) technology to achieve remote,real-time and unattended monitoring of ground cracks in the landslide.The monitoring system,including five extensometers with measuring ranges of 200,450 and 700 mm,was continuously working for 17 months and released 7 warning signals with an average warning time of about 26 hours.At 10 am on 6 December 2009,the system issued a warning and on-site workers were evacuated and equipment protected immediately.At 2:20 pm on 7 December,a medium-scale collapse occurred at the No.5 monitoring site,which justified the alarm and proved the reliability and efficiency of the monitoring system.     

THREE-DIMENSIONAL BAROCLINIC NUMERICAL SIMULATION OF THE SOUTH CHINA SEA CIRCULATION＇S SEASONAL CHARACTERISTICS II. MIDDLE AND DEEP CIRCULATION

A three-dimensional baroclinic shelf sea model‘ s numerical simulation of the South China Sea (SCS) middle and deep layer circulation structure showed that: 1. In the SCS middle and deep layer, a seulhward boundary current exists along the east shore of the Indo-China Peninsula all year long.A cyclonic eddy (gyre) is formed by the current in the above sea areas except in the middle layer in spring, when an anticyclonic eddy exists on the eastern side of the current. In the deep layer, a larges-cale anticyclonic eddy often exists in the sea areas between the Zhongsha Islands and west shore of southern Luzon Island. 2. In the middle layer in snmmer and autumn, and in the deep layer in autumn and winter, there is an anticyclonic eddy (gyre) in the northeastern SCS, while in the middle layer in winter and spring, and in the deep layer in spring and snmmer, there is a cyclonic one. 3. In the middle layer,there is a weak northeastward current in the Nansha Trough in spring and snmmer, while in autumn and winter it evolves inl~ an anticyclonic eddy ( gyre), which then spreads westward l~ the whole western Nansha Islands sea areas.