西安地裂缝与地面沉降灾害经济损失评估

为了深入分析西安地裂缝与地面沉降灾害致灾特点及定量评价其经济损失,在中国地质调查局于2004-2006年开展的西安地区地裂缝与地面沉降调查所取得的成果资料基础上,通过综合分析研究得出,西安地裂缝与地面沉降的致灾特点具有直接性、三维破坏性、三维空间有限性、渐进性和持久性。采用终值法、影子工程法、统计推断法、重置成本法、建造成本或工程费用法、灾情对比法、间接损失与直接损失比例法和权重分解法评价得出地裂缝与地面沉降灾害在1976-2006年造成经济损失为117亿元,其中直接损失71亿元,间接损失46亿元。     

地面沉降研究的新进展与面临的新问题

通过国内外地面沉降研究历史概述 ,介绍了多方面的地面沉降原因。由于地下支撑物的移动导致地面标高损失是目前对地面沉降概念或原理的最新概括和总结。文章从监测技术、信息系统、图件编制、预测计算、损失评估和防治措施等方面概括了中国近年来地面沉降研究取得的新进展。同时提出淤泥质软土沉降问题、深部土层沉降问题、工程性沉降问题、长江三角洲地面沉降的严重性和系统性问题、地面沉降引起的全国性防汛能力降低问题和干涉合成孔径雷达 (InSAR)探测技术是中国当前地面沉降研究面临的新问题。最后指出 ,在中国城市化和工业化高速发展的 2 1世纪上半叶 ,中国东部的地面沉降问题将更大、更多、更复杂 ,需要认真规划和控制。     

江苏省徐州市睢宁县城区地面沉降稳定性分析与评价

根据江苏省徐州市睢宁县城区内可压缩土层的类型、空间分布特点及压缩变形等特征,建立了本区地面沉降计算地质模型。利用该模型计算出城区2013年累计地面沉降量3.08~380.60 mm,平均为162.41 mm,最大沉降量发生在城区西北部,该区域可压缩土层、黏性土的累计厚度大,地下水水位下降幅度较大。根据预测2030年地下水位埋深条件,采用地面沉降地质模型计算得出城区累计地面沉降量,在此基础上对区内地面沉降危险性进行分区,从而为地下水开采总量的控制及地面沉降监测控制提供相关建议措施,以避免城区2030年后地面沉降地质灾害逐步发展为特大型地质灾害。     

基于防治德城区地面沉降控制深层地下水开采的模拟研究

山东省德州市德城区由于地下水的大量开采,形成了大规模的地下水降落漏斗,地面沉降问题尤为突出。采用回归分析方法,从单井开采量、区域总开采量、不同深度开采等方面分析深层地下水开采与地面沉降的关系,全面分析深层地下水开采和地面沉降之间的关系,结果表明两者的线性趋势显著,由此得出地面沉降主要是由深层地下水开采量导致的。为控制地面沉降,采用水量均衡法方法计算城区深层地下水开采量应小于47 945 m3/d,该结果为后续的地面沉降防治工作提供了明确方向和理论基础,使得防治工作更具针对性。     

GPS城市沉降监测网数据处理方法研究

GPS技术在大地测量、维护大地坐标系和进行全球板块运动或区域地壳形变监测中已得到非常广泛的应用,但在城市地面沉降监测方面,仍存在基准选取、系统参数对高程形变影响等问题。比较了平差过程中的不同基准模型,分析了各自的适用性,讨论了系统参数对平差结果的影响,得出附加系统参数和附有约束条件的网平差计算模型,最后对西安地区布设的GPS地面沉降和地裂缝监测网进行计算,比较了不同的平差方案,得出系统参数和不同基准模型对地面沉降数据处理的影响和适用性。     

基于PS-InSAR技术的宁波市地面沉降监测研究

由大规模抽取地下水和工程建设引发的地面沉降广泛分布于世界各大平原,地面沉降地质灾害使城市损失标高,增加城市在洪涝灾害中的生命财产损失。基于60景Sentinel-1影像,采用PS-InSAR(永久散射体合成孔径雷达干涉测量)技术获取了宁波市2017～2021年平原区地表形变,利用同期水准数据进行了精度和可靠性评定,监测和分析结果表明工程建设是现阶段引发宁波市地面沉降的主要因素;杭州湾新区为代表的沿海围垦区地面沉降与围垦和工程建设时间密切相关;城市建成区地面沉降局限于近期的工程建设区域内,且沉降衰减相对较快。     

盾构施工中土体损失引起的地面沉降预测

土质软硬决定了隧道周围土体的移动方向,移动焦点在隧道中心点与隧道底部位置之间变动。采用两圆相切的土体损失模型,通过引入移动焦点的坐标参数,建立了统一的土体移动模型,该模型能将Park模型与Loganathan模型包括在内。假定土体不排水,利用源汇法推导了由土体损失引起的地面沉降通用计算公式,该方法适用于施工阶段。算例分析表明该方法的计算结果与实测值非常吻合,适用于各种土质条件。Loganathan公式只适用于土质较差的情况,当土质较好时计算得到的地面沉降量要比实测值偏小。     

顶管施工中土体损失引起的沉降预测

顶管施工过程中不可避免地会产生土体损失,进而引起地面沉降。对前人工作进行总结,提出一个可以计算土体中任一点沉降的通用经验公式。假定土体不排水,考虑土体泊松比以及采用椭圆形非等量径向土体移动模式,对Sagaseta公式进行了修正。算例分析表明,在开挖面后方较远处,修正Sagaseta公式与Peck公式和Loganathan公式的计算结果较吻合。修正Sagaseta公式与累积概率曲线的变形规律一致,开挖面上方地面沉降量都为最大地面沉降量的一半,但累积概率曲线的影响范围小、收敛速度快;该方法也适用于盾构法施工。     

地面出入式盾构法隧道施工引起的土体垂直变形

对地面出入式盾构法隧道施工引起的土体垂直变形计算方法进行研究。考虑盾构轴线与水平面的夹角 （即隧道埋深变化）,对林存刚公式进行修正,结合正面附加推力、盾壳摩擦力、附加注浆压力和土体损失的共同作用,提出全新的土体垂直变形计算公式。算例分析结果表明：在隧道埋深较浅工况下,新方法计算结果与林存刚公式的计算结果差异较大,新方法计算得到的开挖面前方地面隆起和后方地面沉降均较大;盾构上仰掘进时,随着 增大,由正面附加推力、盾壳摩擦力及土体损失引起的纵向土体垂直变形曲线呈上移趋势,由附加注浆压力引起的纵向土体垂直变形曲线则呈下移趋势;地面沉降最大值变小,但地面横向沉降槽范围逐渐变大。     

简述地面沉降的研究进展

分析引起地面沉降的人为因素和自然因素,综述抽取地下水、开采石油和水溶性气体及建筑荷载诱发地面沉降的三种机制.介绍全球定位系统、地下水位自动监测、合成孔径雷达干涉测量、分层标与自动监测四种地面沉降监测技术的特点、发展及应用.概述地面沉降预测和灾害损失评估研究及其治理进展的状况.     

Floodgate Operations and Fish Communities in Tidal Creeks of the Lower Fraser River (British Columbia,Canada)

Tidal creeks in large coastal deltas can be important habitat for fish but are often highly modified by human activities. Connectivity between tributary creeks and mainstem channels is often constrained by structures such as dikes and floodgates, designed to protect urban and agricultural areas from flooding. While they play important roles in flood mitigation, floodgates can diminish habitat quality and block fish from accessing tidal creeks. It is likely that floodgates differ in their operations and may consequently open for different amounts of time; however, floodgate operations and their effects are not well quantified. We asked the question: how does the mechanical functioning of these floodgates affect fish communities in tidal creeks? We used time-lapse cameras and quantified the timing of gate openings for 22 tributaries of the Lower Fraser River in British Columbia, Canada, and related these operational data to differences in fish communities above and below floodgates. Floodgate operations varied substantially, with some floodgates opening daily while others opened less than 20% of the day, on average. Sites with floodgates that seldom opened were associated with greater differences in fish communities and with reduced upstream native species richness by about one species on average. Where floodgates opened infrequently, we also found lower upstream dissolved oxygen concentrations than at sites where floodgates opened for longer periods of time. Thus, floodgate operations can influence fish communities as well as water quality. These data indicate a large scope for improving floodgate operations for connectivity.     

Managed Retreat of Saline Coastal Wetlands: Challenges and Opportunities Identified from the Hunter River Estuary,Australia

We analyse the potential impacts of sea-level rise on the management of saline coastal wetlands in the Hunter River estuary, NSW, Australia. We model two management options: leaving all floodgates open, facilitating retreat of mangrove and saltmarsh into low-lying coastal lands; and leaving floodgates closed. For both management options we modelled the potential extent of saline coastal wetland to 2100 under a low sea-level rise scenario (based on 5 % minima of SRES B1 emissions scenario) and a high sea-level rise scenario (based on 95 % maxima of SRES A1FI emissions scenario). In both instances we quantified the carbon burial benefits associated with those actions. Using a dynamic elevation model, which factored in the accretion and vertical elevation responses of mangrove and saltmarsh to rising sea levels, we projected the distribution of saline coastal wetlands, and estimated the volume of sediment and carbon burial across the estuary under each scenario. We found that the management of floodgates is the primary determinant of potential saline coastal wetland extent to 2100, with only 33 % of the potential wetland area remaining under the high sea-level rise scenario, with floodgates closed, and with a 127 % expansion of potential wetland extent with floodgates open and levees breached. Carbon burial was an additional benefit of accommodating landward retreat of wetlands, with an additional 280,000 tonnes of carbon buried under the high sea-level rise scenario with floodgates open (775,075 tonnes with floodgates open and 490,280 tonnes with floodgates closed). Nearly all of the Hunter Wetlands National Park, a Ramsar wetland, will be lost under the high sea-level rise scenario, while there is potential for expansion of the wetland area by 35 % under the low sea-level rise scenario, regardless of floodgate management. We recommend that National Parks, Reserves, Ramsar sites and other static conservation mechanisms employed to protect significant coastal wetlands must begin to employ dynamic buffers to accommodate sea-level rise change impacts, which will likely require land purchase or other agreements with private landholders. The costs of facilitating adaptation may be offset by carbon sequestration gains.     

依据重力与航磁资料对天津地区深大断裂深部特征的解释

依据重力与航磁异常,在地壳分层、正演模拟以及多种不同方法的处理结果基础上,重点认识天津断裂、沧东断裂与天津西部断裂等深大断层的深部延展特征,分析其活动规律,从不同侧面认识本区地壳在渤海湾裂谷盆地发育中的地质过程。研究结果认为:天津地区存在超壳断裂的可能性不大;天津断裂带西部新生代盖层下部存在规模较大的产状较陡的隐伏断裂,该断裂的活动性对本地区地壳稳定性影响更大。     

The effects of tidal buffering on acid sulphate soil environments in coastal areas of New South Wales

One-way floodgates installed on flood mitigation drains in regions affected by acid sulphate soils restrict carbonate/bicarbonate buffering, thereby creating reservoirs of acid water (pH < 4.5) that discharge during the ebb tide. The drain water quality and hydrodynamic conditions prior to and following floodgate modifications that allowed for controlled saline intrusion are described with reference to data collected from intensively drained and floodgated coastal lowlands located in southeastern New South Wales, Australia. Cl:SO₄ ratios taken from groundwater samples depicted an acidic environment with little soil buffering capacity. Prior to modification, water quality upstream of the one-way floodgate was consistently acidic (average pH 4.6) with high concentrations of aluminum and iron that fluctuated with precipitation. Over a two-week period before modifications, floodgate leakage permitted alkaline water to intrude upstream of the floodgate and react with H⁺ ions. This period showed the strongest supporting field evidence for tidal buffering via modified floodgates. After installing vertical lifting, two-way floodgates average drain water pH increased to 5.89 and aluminum and iron concentrations decreased by more than 30%. A large rainfall (131.8 mm) during the post-modification period caused acidic groundwater flushing, however, in comparison to the pre-modification period, recovery time and average pH were markedly improved. Preliminary investigations of groundwater salinity in response to tidal intrusion has shown that electrical conductivity fluctuates with rainfall and it is predominately limited to 10 m perpendicular to the drain.     

The ecological effects of structural flood mitigation works on fish habitats and fish communities in the lower Clarence River system of South-Eastern Australia

The effects of flood mitigation structures on the quality of estuarine and freshwater fish habitats in the lower Clarence River system of south-eastern Australia were investigated. Surrounding land use, fringing vegetation, overall level of habitat disturbance, distance from the sea, salinity, and water temperature were examined and compared between four sites on natural tributary streams, four sites on channelized flood mitigation drains gated at their mouths, and ten paired sites (five below and five above floodgates) on flood mitigation drains in this system, from mid 1988 to late 1990. Quantitative sampling of the fish fauna at each of these sites was conducted quarterly over this 21/2-yr period. Juvenile fishes were sampled using netting enclosures together with application of the ichthyocide rotenone, while subadults and adults were sampled using multiple-panel gill nets. In general, fish habitats in the flood mitigation drains, and especially those above flood gates, had more intensive surrounding land uses, less natural native fringing vegetation and, overall, were more highly disturbed than those in the natural tributaries. Salinity at the various study sites was largely dependent on the pattern of seasonal (mainly summer and autumn) rainfall and distance upstream from the sea. Salinities usually differed only slightly between gated and ungated sites at similar distances from the sea, indicating that the floodgates were generally ineffective in preventing the penetration of saline river water into the drains immediately above them. These gates were, however, very effective in preventing the establishment of fringing mangrove vegetation in the drains above them. The main ecological effects of these flood mitigation works have thus been to generally degrade the overall quality of available fish habitat, particularly in terms of reductions in natural fringing vegetation (mangroves in the more estuarine-dominated areas and overhanging terrestrial trees in the more freshwater-dominated areas often being replaced by grassess and rushes), and to increase the intensity of surrounding land use (natural forest often being cleared and wetlands drained for cattle grazing and sugarcane growing), both of these factors contributing to increases in generalized aquatic habitat disturbance. Results from the study of the fish assemblages in these natural and man-altered habitats revealed the following general patterns. Highest fish species numbers and abundances occurred in the ungated natural tributaries and in drains downstream of floodgates. These habitats also contained the largest proportions of both commercial fish species and individuals as well as the majority of species and individuals with marine-estuarine affinities. Both total and commercial fish species numbers generally declined with decreasing salinity and increasing distance of the sampling sites from the sea. Even through saline waters from the main river system penetrated the majority of the floodgates during most of the study period, fish passage through these gates was found to be very restricted. Fish assemblages above such gates were generally dominated by primarily freshwater species, as compared with primarily saltwater (estuarine-marine) species below. The conversion of the great majority of small mangrove-fringed tributaries in the lower reaches of this river system into uniform floodgated drainage channels has thus resulted in the destruction of, and impeded fish access to, large areas of previously available estuarine fish nursery and feeding habitat. These drainage changels are now dominated by terrestrial-freshwater vegetation above where they are cut off from the main river channels by the floodgates, and the period of their construction has coincided with that of reported declines in fish catches in this river system. On the basis of the above findings, it is recommended that these floodgates be left fully open at all times except immediately prior to and during floods in the river system, thus facilitating the re-establishment of fringing mangrove vegetation along the banks of the artificial drains in the lower reaches, generally improving flushing and thus water quality in these drains, and allowing the establishment of primarily estuarine-marine fish communities, including more species of economic importance, in them.     

Occurrence and consequences of acid sulphate soils and methods of site remediation

The oxidation of sulphides in acid sulphate soils (ASS) causes the acidification of many Australian coastal river systems. The acidity negatively impacts upon coastal ecosystems, aquaculture, agriculture and concrete and steel infrastructure. In the low-lying floodplains, relatively deep surface drains fitted with one-way floodgates lower the watertable, thereby exposing the sulphidic minerals to oxidation. On the Broughton Creek floodplain in SE Australia, four distinct remediation strategies have been developed to tackle the issue of acidification by ASS: (i) simple V-notch weirs that raise the level of the watertable surrounding the drains thereby submerging the pyrite and preventing the further formation of acidity; (ii) modified two-way floodgates that allow the inflow of tidal water into the drains, thereby buffering the acidity within the drain before it enters the river and raising the level of the watertable surrounding the drain; (iii) lateral impermeable lime barriers that both prevent oxidation of pyrite by stopping the downward movement of oxygen into the soil and neutralise the acidity in the groundwater; and (iv) permeable reactive barriers (PRB) that passively intercept the groundwater flow and neutralise the acidity. Each remediation strategy has a distinct role to suit the different terrain and groundwater conditions.     

高密度电法技术在牡蛎礁勘查中的应用效果

天津牡蛎礁是全新世以来海侵海退过程中在天津滨海平原留下的重要地质遗迹,是海陆变迁的佐证,对推演天津滨海平原的成陆史具有重要的科学价值。选用物探高密度电法探测手段对宁河县七里海罾口河南岸的牡蛎礁分布进行了试验研究,并布设了7个钻孔对高密度电法的探测结果进行验证。结果表明:高密度电法技术能经济、快速、有效地探测地下牡蛎礁的分布。     

基于ArcGIS Server的天津市突发性地质灾害信息网络发布平台建设设计与实现

天津市为进一步加强地质灾害防治工作,提出构建地质灾害监测预警信息共享平台,是防灾减灾工作的关键环节。本文探讨了基于网络技术、GIS技术、数据库技术并结合地质环境专业知识,建立集数据发布、管理、查询、共享等为一体的天津市突发性地质灾害数据网络发布与共享平台的设计过程,并以天津市突发性地质灾害发育特征、群测群防、预警预报、巡查与监测信息为数据源,实现了天津市突发性地质灾害信息网络发布平台的建设,进而为政府、社会公众等进行地质灾害工程治理、搬迁避让和应急处置提供依据。     

天津平原区地下水位动态特征与影响因素分析

天津市地下水位监测工作已经开展了将近40年,监测区覆盖整个平原区。根据多年地下水位监测资料,笔者对区内浅层地下水和深层地下水不同含水层组的水位动态特征及其影响因素进行了分析研究,认为：天津平原区地下水位动态受水文地质条件、降水和开采条件的控制,不同类型地下水动态规律在时空分布上有明显差异,除降水量、温度等自然因素外,开...     

洼地开采地下水的地质环境效应研究——以天津市黄港洼应急水源地为例

天津市是我国水资源缺乏、人均占有淡水资源最少的城市之一,也是我国地面沉降最为严重的地区之一。地面沉降现已成为天津市的主要地质灾害,并在一定程度上制约着天津城镇的可持续发展。天津市平原区洼地众多,这些洼地大部分是天津市的湿地分布区。在洼地内建设应急地下水水源地,既可以起到为城区供水,缓解城区的地面沉降,又可以改善洼地生态环境的作用。