张溪滑坡--台风诱发滑坡成因分析

14号台风“云娜”造成我国东部沿海地区发生多处滑坡地质灾害,张溪滑坡便是其中个案。通过对张溪滑坡成因进行分析,得出了张溪滑坡是在一定厚度覆盖层、特定地形条件、植被条件下,台风风力加载作用及暴雨的淘蚀、软化、增重等一系列过程共同作用下滑动失稳的滑坡。它与暴雨型滑坡的形成机理有显著不同,这一分析成果对类似滑坡的研究和防治具有一定的意义。     

Modeling an irrigation ditch opens up the world. Hydrology and hydraulics of an ancient irrigation system in Peru

Ancient Peruvian irrigation systems have been studied extensively, but much remains unknown about technical and hydrological aspects of these irrigation systems. The Pampa de Chaparrí irrigation system in Peru is used as an example to show how modeling approaches for hydrological and hydraulic features of irrigation can yield results to improve our understanding of irrigation in the area. Analysis focuses on water availability compared demand, the way available water may have been applied to crops and whether the water needed could be delivered through the canal system. Results suggest that on the Pampa some 2500 hectares may have been cultivated within certain security limits for acceptable yields. The rhythm with which the irrigation requirement was applied to crops most likely influenced yields and thus food security. Furthermore, the influence of groundwater on crop growth may have been considerable. The hydraulic behavior of the irrigation system suggests that it should not be taken for granted that theoretically required water flows could actually be diverted and/or distributed to water users. The many questions coming out of the results define important items for a joint research agenda of archeologists and irrigation scientists.     

Debris flow initiation and sediment recharge in gullies

Landslides that enter gullied low-order drainages can either initiate debris flow or stop, depositing sediment in the channel. This process is one of the most common ways that debris flows initiate, but little attention to date has been paid to evaluating the factors that affect whether or not the initial landslide will become a debris flow or deposit sediment in the channel. Statistically significant parameters that determine whether slope failures become debris flows or act to recharge in-channel sediment are channel gradient, angle of entry of failure into the channel, initial failure volume, and the amount of in-channel stored sediment. Steeper channels, low angles of entry, lower volumes of in-channel sediment, and larger initial failures were more likely to result in debris flows. This study found that as the volume of in-channel stored sediment increased, the volume of initial failure required to initiate a debris flow also increased. This result calls into question the simple supply-limited model of cyclical debris recharge and debris flow in low-order gullied drainages and suggests a negative feedback mechanism between debris accumulation and debris flow susceptibility.     

Electromagnetic sounding of geothermal zones

Electromagnetic (EM) data provide a substantial contribution to the geophysical mapping and monitoring of geothermal reservoirs. This paper presents an up-to-date picture of the achievements of EM methods for geothermal exploration as they have emerged over the last few years. It has been proved that EM sounding of geothermal zones and distant monitoring macro-parameters of the reservoirs, fluid-filled faults and other elements of the geothermal system are possible provided that modern 3-D inversion is used along with techniques that reduce the effects of industrial and geological noise. In addition, geological and petrophysical data also need to be included in the analysis.     

Loss estimation in Istanbul based on deterministic earthquake scenarios of the Marmara Sea region (Turkey)

The rapid urban development in Istanbul has lead to an increase in the exposure levels of the urban vulnerability. Due to the steadily increasing population, with improper land-use planning, inappropriate construction techniques and inadequate infrastructure systems, associated with an existing high hazard level, Istanbul is one of the most risky cities in the Mediterranean region. Estimations of casualties and losses, expected for given earthquake scenarios, are necessary to develop sustainable rehabilitation programs and for improving preparedness. Deterministic hazard scenarios and time-dependent probabilistic hazard assessment were used as input to a GIS-based loss estimation model, to evaluate the earthquake risk for Istanbul.     

滑坡临滑预报的态矢量方法研究

态矢量是统计物理学中对连续场进行粗粒化描述的一种方法。将其引入滑坡预报中,通过将滑坡危险区划分为n个子区域,在各个时间窗内对一系列子区域的监测数据进行态矢量分析,将监测数据与降雨量态矢量的模等归一化后叠加,研究一段时间内滑坡位移态矢量的发展变化规律,并提出利用态矢量进行滑坡预报的新方法。以新滩滑坡为例,对累计水平位移进行态矢量分析,发现在滑坡前态矢量的模和态矢量增量的模均发生了明显突变,按态矢量曲线的变化规律,依据滑坡预警分级方法提出3级滑坡预警,最高预警级别预报的滑坡时间比实际滑坡时间提前2天。研究结果表明,态矢量的急剧突变是滑坡发生的前兆,可以用来进行滑坡的短期和临滑预报。     

Determining landslide susceptibility in Central Taiwan from rainfall and six site factors using the analytical hierarchy process method

This work provides a landslide susceptibility assessment model for rainfall-induced landslides in Central Taiwan based on the analytical hierarchy process method. The model considers rainfall and six site factors, including slope, geology, vegetation, soil moisture, road development and historical landslides. The rainfall factor consists of 10-day antecedent rainfall and total rainfall during a rainfall event. Landslide susceptibility values are calculated for both before and after the beginning of a rainfall event. The 175 landslide cases with detailed field surveys are used to determine a landslide-susceptibility threshold value of 9.0. When a landslide susceptibility assessment value exceeds the threshold value, slope failure is likely to occur. Three zones with different landslide susceptibility levels (below, slightly above, and far above the threshold) are identified. The 9149 landslides caused by Typhoon Toraji in Central Taiwan are utilized to validate the study's result. Approximately, 0.2%, 0.4% and 15.3% of the typhoon-caused landslides are located in the three landslide susceptibility zones, respectively. Three villages with 6.6%, 0.4% and 4.9% of the landslides respectively are used to validate the accuracy of the landslide susceptibility map and analyze the main causes of landslides. The landslide susceptibility assessment model can be used to evaluate susceptibility relative to accumulated rainfall, and is useful as an early warning and landslide monitoring tool.     

水位骤变触发库岸堆积层滑坡的物理模型试验及机理分析

库区水位骤变容易引起库岸边坡堆积层滑坡,而水库库岸滑坡往往会直接造成水工建筑物的损毁、减少有效库容,因此深入研究其诱发机理和变形破坏模式具有重要意义。本试验在模型箱内进行,其净空尺寸为100cm60cm60cm（长宽高）,内设不透水底板模拟基岩体,通过水闸可以实现水位的骤降。在不透水底板上填筑有厚度约为20cm的堆积层,并在堆积层内部埋设传感器,用于测量土压力和孔隙水压力的变化过程,并在试验全过程中用摄像机记录了滑坡的变形位移情况。试验结果表明：在水位上升过程中堆积层表面会形成张拉裂缝,边坡前缘涉水区域发生局部破坏,主要是由于库水入渗后,水对岩土体会造成抗剪强度弱化; 水位骤降时,堆积层会沿着基岩面发生整体下滑,滞留在土体中的孔隙水压引起的渗流力是导致该滑坡发生的主要因素; 由于水库库岸堆积层滑坡是在渗流力牵引作用下发生,故滑坡失稳模式一般为牵引式滑坡。     

某多次治理滑坡的变形机理和经验教训

玻璃沟滑坡位于薛家湾镇玻璃沟左岸,为一牵引式堆填土滑坡。 2009～2012年数次治理工程失效,不得已对该滑坡再次进行勘察设计和整治工程。本文通过进一步勘测研究,剖析了玻璃沟滑坡的坡体结构和变形机理：人为改变自然坡体形态是滑坡形成的先天条件; 特殊的坡体结构为滑坡变形提供了物质基础; 地表水下渗、后山地下水及河床淤塞抬升是滑坡变形的诱发因素; 坡脚开挖进一步加剧滑坡变形。在对滑坡机理准确分析的基础上,提出了治理工程措施,取得了成功。同时本文对该滑坡多次治理失效进行了反思,该滑坡屡治不愈的根本原因在于没有重视滑坡工程地质勘察,导致对滑坡的变形机理认识不足,尤其是滑动面的埋深判断失误,而且又弱化了地下水对滑坡的作用; 在对滑坡变形机理分析不到位的情况下,盲目实施抗滑工程,导致滑坡多次治理失效。因此应采取必要的工程地质勘测手段,查明滑坡区的工程地质条件和坡体结构,准确分析滑坡的变形机理和发生发展过程是滑坡地质灾害根治的重要前提。     

三峡库区万州驸马滑坡基本特征及形成演化机制分析

基于驸马滑坡的地理位置及地质环境条件,从滑坡周界、滑体与滑带的物质结构特征,滑坡变形迹象等,深入分析了驸马滑坡的基本特征,在此基础上进一步探讨了驸马滑坡的成因机制及后期演变趋势,为其后进行滑坡稳定性研究及治理方案优化设计提供地质依据。