Monitoring subsidence at Messara basin using radar interferometry

The Messara valley is the largest and most productive region in the island of Crete, Greece. Over the last 20 years, extensive exploitation of the aquifer mainly for agricultural purposes has led to a 40-m decrease in the level of groundwater. This investigation aims at mapping ground subsidence that might be induced by such overpumping of groundwater using conventional differential interferometry. A total of 29 ERS-1 and 2 SAR and 7 ALOS PALSAR images have been used for forming interferograms. The images used cover the period from 1992 to 2000 and 2007 to 2010, respectively. Processing of ALOS L-band data (λ = 23.6 cm) has revealed a ground motion away from the Line of Sight of the satellite (LOS direction) that amounts to at least 3 cm/year for the period 2007–2010. Piezometric measurements and other geological parameters have also been analyzed.     

On the impact of rockfall catch fences on ground-based radar interferometry

Rockfalls are major natural hazards in mountainous regions and as such monitored if they pose a high risk to people or infrastructure. Ground-based radar interferometry is a relatively new technique suitable for such monitoring. It offers the potential for determining sub-mm- to mm-level displacements by remote measurements under various weather conditions. To avoid damage from smaller rocks and debris, critical surfaces are often protected by rockfall catch fences. We present an experimental investigation proving that the radar measurements are indeed significantly affected by a catch fence made of steel even if its mesh size is larger compared to that of the wavelength of the radar. A stable rock wall in a quarry was monitored by means of a ground-based synthetic aperture radar for 2 days. Different fences varying in shape, size, and density of mesh and in various geometrical configurations were erected at different locations for short periods of time during the experiment. We show that for surfaces observed through the fence, the reflected power can be reduced by 20 dB and thus the signal-to-noise ratio is significantly deteriorated. We also observed spurious interferometric phase shifts. Even parts of the rock wall not covered by the fences are affected. Side lobes and mixed pixels result, e.g., in severe loss of coherence and thus potentially mask actual displacements.     

Monitoring surface elevation changes in Jharia coalfield,India using synthetic aperture radar interferometry

This paper investigates surface elevation changes that occurred during 1996–2004 in the Jharia coalfield through the digital elevation model (DEM) generated using synthetic aperture radar interferometry (InSAR) using ERS-1/2 (European Remote Sensing Satellite) tandem and RADARSAT-1 data. The comparison of elevation values derived from the InSAR DEM and topographic height data shows a bias of 23.08 m with root-mean-square error of ±2.31 m (5.8 %). The accuracy of the DEM was investigated by comparing the elevation profiles with the digitized elevation contour data at four different locations. The profile comparison shows a mean bias of 22.68 m. Local topography shows changes in elevation up to ±40.00 m due to mining activities on the 8-year time period. The results of InSAR-derived heights and topographic heights were comparable and well-matched except at a few locations where topographic data were unavailable. DEM generated using InSAR due to its high spatial details is ideal for the detection and estimation of surface elevation changes in mining areas.     

Monitoring and early warning of the 2012 Preonzo catastrophic rockslope failure

In this paper, we describe the investigations and actions taken to reduce risk and prevent casualties from a catastrophic 210,000 m³ rockslope failure, which occurred near the village of Preonzo in the Swiss Alps on May 15, 2012. We describe the geological predisposition and displacement history before and during the accelerated creep stage as well as the development and operation of an efficient early warning system. The failure of May 15, 2012, occurred from a large and retrogressive instability in gneisses and amphibolites with a total volume of about 350,000 m³, which formed an alpine meadow 1250 m above the valley floor. About 140,000 m³ of unstable rock mass remained in place and might collapse partially or completely in the future. The instability showed clearly visible signs of movements along a tension crack since 1989 and accelerated creep with significant hydromechanical forcing since about 2006. Because the active rockslide at Preonzo threatened a large industrial facility and important transport routes located directly at the toe of the slope, an early warning system was installed in 2010. The thresholds for prealarm, general public alarm, and evacuation were derived from crack meter and total station monitoring data covering a period of about 10 years, supplemented with information from past failure events with similar predisposition. These thresholds were successfully applied to evacuate the industrial facility and to close important roads a few days before the catastrophic slope failure of May 15, 2012. The rock slope failure occurred in two events, exposing a compound rupture plane dipping 42° and generating deposits in the midslope portion with a travel angle of 39°. Three hours after the second rockslide, the fresh deposits became reactivated in a devastating debris avalanche that reached the foot of the slope but did not destroy any infrastructure. The final run-out distance of this combined rock collapse–debris avalanche corresponded to the predictions made in the year 2004.     

Monitoring playa sedimentation using sequential radar images

A series of ERS-1 radar images of the Chott el Djerid playa in Tunisia obtained at intervals of 35 days demonstrates the ability to monitor geological change from space. The C-band radar backscatter is shown from field measurements to be sensitive to changes in surface roughness at millimetric scale due to evaporative growth of halite and gypsum crystals. Backscatter increases gradually during the dry summer months and decreases rapidly in early winter as the rains begin. Episodic hydrogeological and sedimentological events including lake development, channel flow and aeolian deposition can also be detected in addition to the seasonal pattern. Multitemporal, spaceborne radar offers the prospect of being able to map the dynamics of evaporite sedimentation in continental playas.     

三角形网络和判据图法在地质灾害气象预警中的应用

本文以改进的综合判据图法为理论依据,提出了应用判据计算预警结果的权重系数和预警指数的预警方法,通过应用Delaunay三角网和边界条件限定自动剖分三角网进行地质灾害气象预警,实现了地质灾害气象预警自动计算、判别的新方法,建立了一套地质灾害气象预警自动计算软件系统,并应用于张家口市2007～2008年地质灾害气象预警,取得了一定的成果。     

基于实例推理系统的滑坡预警判据研究

为研究滑坡预警预报指标,建立了31个典型岩质滑坡组成的滑坡数据库,基于滑坡数据库、工程类比和模糊综合评判方法开发了滑坡实例推理系统。首先将滑坡特征属性分为6大项:破坏模式、滑面倾角、滑面类型、边坡岩体结构、边坡倾角、滑坡的诱发因素(降雨、地下水、水库蓄水、开挖、爆破、地震),用11个特征值表示边坡的特征属性;其次采用比值法相似度计算理论在滑坡数据库中搜索与目标边坡最相似的滑坡,通过工程类比给出滑坡预警判据建议值;最后依据模糊综合评判模型修正建议值,得到预警判据确认值,形成滑坡实例推理系统。以锦屏一级水电站为例,通过计算找到了滑坡数据库中与锦屏一级水电站左岸边坡最为相似的5个滑坡实例;其中大冶铁矿狮子山滑坡和安家岭露天矿滑坡有较为完整的变形监测数据,深入分析类似边坡变形破坏过程,分4个阶段给出了锦屏一级水电站左岸边坡预警判据建议值;并建立边坡预警判据修正的模糊综合评判模型,修正相似边坡预警判据,给出锦屏一级水电站左岸边坡进入加速变形阶段的位移速率阀值的精确区间为1.0～1.2 mm/d。     

地质灾害预报预警的研究现状及发展趋势

目前国内外较为成功的地质灾害预报预警方法可分为现象监测预报法、数理统计预报法、非线性系统论预报法和地球内外动力耦合法。在对各类方法以及存在问题进行概述的基础上,指出在方法应用的同时,集成和融合迅速发展起来的“3S”技术,建立集观测、研究、风险评估、预报预警、预防和治理一体化的灾害预报系统是未来发展的方向和趋势。     

滑坡灾害预测预报分类

有人主张滑坡灾害的空间和时间预测预报应是并存的,即脱离时间预测预报的空间预测是不可取的。但也有人认为两者可以相互独立而又互为补充。事实上,空间预测是时间预测预报的先决条件,只有在明确了预测的对象之后,方可有目的地开展滑坡灾害的时间预测预报。因而,一般地讲,滑坡灾害空间和时间预测具有先后序次关系。但从减灾的角度考虑,二者又具有相对的独立性。即可以在时间预测之外进行空间预测。目前对滑坡灾害预测预报分类的系统研究不多,所开展的预测预报事例报导基本上属于个例研究。论文将滑坡灾害预测预报分为空间和时间2大类,并进一步将空间预测划分成区域空间预测、地段空间预测和场地空间预测;将时间预测预报划分成长期时间预测、短期时间预测和临滑时间预测预报。文章针对滑坡灾害时间预测预报的特点,对预测预报的信息源进行了分析和分类。并对不同的工程阶段所要预测的滑坡灾害问题进行了分类归纳。     

基于Web的地质灾害预警信息发布与反馈系统研究

对河南省地质灾害预警预报系统,县（市）地质灾害调查与区划成果资料进行分析研究,以商城县地质灾害预警为例,将预警网格作为关联字段,对地质灾害预警结果库、地质灾害基础数据库进行关联处理,建立带有空间预警网格及地质灾害基础信息的地质灾害数据库,按照省国土资源厅统一制定的地质灾害上报表格,以河南省地质环境信息网为系统平台,采用asp动态网页设计语言,设计预警结果区地质灾害信息查询以及地质灾害反馈等页面,从而建立基于Web的地质灾害预警信息发布与反馈系统。     

基于多普勒天气雷达的冰雹云早期识别与预警方法研究

利用C波段新一代多普勒天气雷达监测资料和探空数据,对新疆南疆阿克苏地区西部绿洲2009-2015年28个降雹个例、32个对流风暴降雹单体进行分析,把发生在该区域的暴雹单体分为弱、中、强等三种类型,并综合分析不同强度降雹单体的“初生”、“跃增”和“酝酿”三个冰雹云生命史关键阶段的空间分布、演变规律以及不同温度层之间的关系,筛选出了能够提前识别各类冰雹云的雷达回波特征参量及指标阈值,并以此作为判识因子,建立了三种冰雹云提前识别及预警概念模型,同时对其识别能力进行验证,获得了三类冰雹云80%以上的识别准确率和合适的早期识别与有效作业指挥时间提前量,为该区域强冰雹云的早期识别与有效实施人工防雹作业决策提供科学依据。     

重庆涪陵区谷水溪滑坡监测与预警

重庆地区属红层分布区,经常遇到紫红色、灰色泥岩与杂色砂岩组成的层状岩体斜坡或软弱基座斜坡,为全国滑坡灾害严重的地区之一.文章以重庆涪陵区谷水溪滑坡监测为例,对裂缝观测法在滑坡监测中的应用做了探讨.通过布设裂缝观测标志,按监测周期采集数据,对裂缝观测数据进行统计分析,并成功地做出预警预报,使100余人安全撤离;减少财产损失1500余万元,运用裂缝观测法监测滑坡收到了较好的效果.裂缝观测法是地质灾害群测群防中一种有效的基础方法.     

基于Visual Basic及Access的工程资料档案管理系统开发

在社会日趋发展和信息技术取得巨大进步的今天，许多勘查设计单位原有的工程资料管理方法已不能完全满足社会各方面工程实践的要求，使用先进的工程资料管理系统是必不可少的。因此，工程资料档案管理系统是一卜具有重要理论研究意义及广阔应用前景的研究课题。文章结合鹧鸪山隧道这一重大工程，利用visual Basic和Access开发了一个适用于广大工程建设资料管理的软件。在系统开发过程中，解决了以下问题，即利用WinRAR软件实现文，牛的压缩及解压缩，利用SQL语言实现文件多种查询方法。通过调用文件存放地址实现文件的打开功能。工程资料卡当案管理系统的使用将解决工程实际中存放、保管资料的各种问题，消除了传统资料保存方式的弊端。工程资料档案管理系统具有使用方便、查询快捷等优点，具有实用价值和推广价值。     

滑坡监测预警国内外研究现状及评述

本文从降雨临界值研究、监测技术方法、区域性监测预警系统三个方面对滑坡监测预警的国内外研究现状进行了回顾和总结。首先归纳了国内外28个国家或地区的滑坡降雨临界值及统计方法,三个模型——日降雨量模型、前期降雨量模型和前期土体含水状态模型,基本概括了当前降雨诱发滑坡临界值的确定方法;但由于降雨入渗触发滑坡的复杂性,不同机理的滑坡"需要"不同的降雨临界值;目前的研究趋势是对雨量雨强雨时—土体渗流场动态变化—土体抗剪强度变化的耦合关系进行研究。按监测对象的不同,滑坡监测可分为四大类,即位移监测、物理场监测、地下水监测和外部诱发因素监测;按监测手段的不同,则可分为人工监测、简易监测、专业监测三大类;目前国内外在滑坡监测技术、方法、手段上并无太大差距,专业仪器已成为常规设备,只是由于价格因素得不到普及;一些新技术如InSAR、三维激光扫描等能很快应用到滑坡监测领域;监测数据的采集和传输也都实现了自动化和远程化;监测和预警系统有向Web—GIS发展的趋势。利用一个地区的滑坡易发区划或危险区划,结合降雨临界值,可以设定不同的预警级别,在区内布设一定数量的雨量站,监测雨量加上预报雨量,就可进行滑坡预警预报,国内外的区域性降雨型滑坡监测预警大体都是这个思路和做法,该方法在对公众进行警示方面起到了良好效果,但由于预警的范围太大,在具体的单点防治上,难以做到有效。我国在近10年开展了大量的监测预警工作,并取得了丰硕的成果,但根据统计数据,其成功预警率却并不理想,这一方面表现在成功预警实例中专业预警所占比例过低,另一方面同时表现在发生的大量的地质灾害在已有的预警点之外。制约目前工作有效性的主要问题是滑坡隐患点的排查和识别问题,因为只有识别出了隐患点才能进行下一步的监测和预警,它是一切工作的基础。而解决这一问题的重要途径是分析区域上的滑坡发育规律,找到有效的隐患点识别技术方法,以及引进风险管理的概念,进行监测资源的合理分配和有效预警。     

中国锂资源安全评估与预警

锂是中国重要的战略性矿产资源,在锂资源需求快速增加、进口依赖严重的背景下,对中国锂资源安全进行评估与预警具有必要性和紧迫性。构建了以资源禀赋、进口安全、市场风险和地缘政治为一级指标的中国锂资源安全评估指标体系,利用常权和变权模型对2009—2021年中国锂资源安全状况进行了评估,采用ARIMA-BP组合模型对2022—2035年中国锂资源安全进行了预警。研究发现,①进口依赖度、进口集中度和运输通道风险对锂资源安全的影响最大;②2009—2021年中国锂资源安全等级由黄色—基本安全等级波动下降至橙色—不安全等级,资源禀赋和进口安全是导致锂资源安全等级较低的主要原因;③2022—2035年中国锂资源安全评分总体呈下降趋势,除2026年处于黄色—基本安全等级外,其余年份均处于橙色—不安全等级。     

全断面隧道掘进机护盾受力监测及卡机预警

全断面隧道掘进机(简称TBM)在穿越深部软弱地层时围岩收敛变形较大,围岩容易挤压护盾,导致TBM卡机,影响TBM正常掘进。通过分析TBM卡机灾害孕育过程,得到了预测TBM卡机的重要条件：一是围岩变形量大于预留的空间,二是额定推力不能克服摩擦阻力。为了监测实际工程TBM卡机状态,提出了一种监测护盾变形的方案以及护盾受力的计算方法,可通过监测得到的变形估算护盾的受力,进而计算出护盾受到的摩擦阻力,得到TBM卡机的状态。根据TBM受到的摩擦阻力、TBM正常掘进时所需推力和TBM额定推力之间的关系,将TBM卡机状态分为4个等级,即无卡机、轻微卡机、卡机和严重卡机,并提出了对应的处理措施。结合TBM卡机条件以及护盾受力监测方案,提出了TBM卡机灾害预警流程。在兰州水源地输水隧洞工程中应用了该监测方案和卡机灾害预警流程,应用结果表明,预测的卡机状态与TBM实际状态基本一致,说明该方法具有一定的可靠性,对指导TBM隧道施工具有重要意义。     

预报预警在地质灾害防治中的应用

本文介绍了江西地质灾害气象预报模型的建立、计算方法,以及预警预报在地质灾害防治工作中获得的成功,对类似条件地区的地质灾害防治工作,具有一定的借鉴作用.