美国佛罗里达州岩溶塌陷保险法案及启示

通过保险将风险予以转嫁是风险管理的重要手段,设置地质灾害保险独立险种是保险业的趋势。岩溶塌陷是六大地质灾害之一,我国可溶岩面积占国土面积的1/3,其中尤以西南各省岩溶较为发育,岩溶塌陷发生频繁,导致房屋坍塌破裂,土地下陷,交通路线受损,影响人们正常生活和财产生命安全。对于岩溶塌陷造成的损失,发达国家已经有一套比较完善的保险体制,而我国在岩溶塌陷保险方面的研究还是一片空白。本文对佛罗里达州的塌陷保险体制从立法、确定评估指数到判断灾后损失几个方面进行了阐述,希望对我国岩溶塌陷保险发展有所启示。      

Sinkhole subsidence due to mining

This paper reviews the modes of formation of sinkhole subsidence associated with mining activities, drawing on examples in India. Sinkhole (pot-hole) subsidence is an abrupt local depression at the surface which can be hazardous to life and property due to its tendency to occur without warning. Shallow extraction, weak overburden and geological discontinuities are the main factors which cause them. Sinkholes occur due to the failure of a mine roof which migrates through the overlying strata until the failure zone intercepts the unconsolidated overburden. Alternatively they may occur by the creation of cavities in the overburden following the inflow of sand and soil from the overlying weathered and friable strata through faults. Overburden cavities eventually cave in and sinkholes appear at the surface. Sinkholing phenomena can be controlled to some extent by proper design of mining supports and construction of walls to create a barrier around an area prone to sinkholes in bord and pillar workings. Backfilling and grouting can be used to stabilize abandoned underground workings.     

Sinkhole hazard assessment in Minnesota using a decision tree model

An understanding of what influences sinkhole formation and the ability to accurately predict sinkhole hazards is critical to environmental management efforts in the karst lands of southeastern Minnesota. Based on the distribution of distances to the nearest sinkhole, sinkhole density, bedrock geology and depth to bedrock in southeastern Minnesota and northwestern Iowa, a decision tree model has been developed to construct maps of sinkhole probability in Minnesota. The decision tree model was converted as cartographic models and implemented in ArcGIS to create a preliminary sinkhole probability map in Goodhue, Wabasha, Olmsted, Fillmore, and Mower Counties. This model quantifies bedrock geology, depth to bedrock, sinkhole density, and neighborhood effects in southeastern Minnesota but excludes potential controlling factors such as structural control, topographic settings, human activities and land-use. The sinkhole probability map needs to be verified and updated as more sinkholes are mapped and more information about sinkhole formation is obtained.     

Sinkhole characterization in the Dead Sea area using airborne laser scanning

Since the early 1980s, the Dead Sea coast has undergone a near catastrophic land deterioration as a result of a rapid lake-level drop. One conspicuous expression of this deterioration is the formation of sinkholes fields that puncture the coastal plains. The evolution of sinkholes along nearly 70-km strip has brought to a halt the regional development in this well-known and toured area and destroyed existing infrastructures. Great efforts are being invested in understanding the phenomena and in development of monitoring techniques. We report in this paper the application of airborne laser scanning for characterization of sinkholes. We demonstrate first the appropriateness of laser scanning for this task and its ability to provide detailed 3D information on this phenomenon. We describe then an autonomous means for their extraction over large regions and with high level of accuracy. Extraction is followed by their detailed geometric characterization. Using this high-resolution data, we show how sinkholes of 0.5 m radius and 25 cm depth can be detected from airborne platforms as well as the geomorphic features surrounding them. These sinkhole measures account for their embryonic stage, allowing tracking them at an early phase of their creation.     

The macungie Sinkhole,Lehigh valley Pennsylvania: Cause and repair

A dramatic sinkhole collapse measuring some 100 feet in diameter by 41 feet deep occurred suddenly in the Borough of Macungie on June 23, 1986. The sinkhole collapse resulted in a major disruption of traffic, utility services, as well as a major health and safety hazard. Continual growth of the sinkhole could have resulted in almost certain damage or loss to more than 17 residences adjacent to the sinkhole collapse. Stabilization and repair costs totaled some $450,000 and required almost three months to restore utility services, roadway, and parking areas.     

Sinkhole formation and subsidence along the Dead Sea coast,Israel

More than 4,000 sinkholes have formed since the 1980s within a 60-km-long and 1-km-wide strip along the western coast of the Dead Sea (DS) in Israel. Their formation rate accelerated in recent years to >400 sinkholes per year. They cluster mostly in specific sites up to 1,000 m long and 200 m wide, which align parallel to the general direction of the fault systems associated with the DS Rift. The abrupt appearance of the sinkholes reflects changes to the groundwater regime around the shrinking DS. The eastward retreat of the shoreline and the lake-level drop (1 m/year in recent years) cause an eastward and downward migration of the fresh/saline groundwater interface. Consequently, a subsurface salt layer, which was previously enveloped by saline groundwater, is gradually being invaded and submerged by relatively fresh groundwater, and cavities form due to the rapid dissolution of the salt. Collapse of the overlying sediments into these cavities results in sinkholes at the surface. An association between sinkhole sites and land subsidence is revealed by interferometric synthetic aperture radar (InSAR) measurements. On a broad scale (hundreds of meters), subsidence occurs due to compaction of fine-grained sediments as groundwater levels decline along the retreating DS shoreline. At smaller scales (tens of meters), subsidence appears above subsurface cavities in association with the sinkholes, serving in many cases as sinkhole precursors, a few weeks to more than a year before their actual appearance at the surface. This paper overviews the processes of sinkhole formation and their relation to land subsidence.     

Assessment of climate change impacts on flooding vulnerability for lowland management in southwestern Taiwan

Taiwan suffers from losses of economic property and human lives caused by flooding almost every year. Flooding is an inevitable, reoccurring, and the most damaging disaster in Taiwan since Taiwan is located in the most active tropic cyclone formation region of the Western Pacific. Flooding problem is further worse in land subsidence areas along southwestern coast of Taiwan due to groundwater overdraft. Increasing number of people is threatened with floods owing to climate change since it would induce sea level rise and intensify extreme rainfall. Assessments of flooding vulnerability depend not only on flooding severity, possible damage of assets exposed to floods should also be simultaneously considered. This paper aims at exploring how climate change might impact the flooding vulnerability of lowland areas in Taiwan. A flooding vulnerability evaluation scheme is proposed in this study which incorporates flooding severity (the maximum inundation depth determined by a two-dimensional model) and potential economic losses for various land uses. Effects of climate change on flooding vulnerability focus on alterations of rainfall depth for various recurrence intervals. The flood-prone Yunlin coastal area, located in southwestern Taiwan, is chosen to illustrate the proposed methodology. The results reveal that reducing flooding vulnerability can be achieved by either reducing flooding severity (implementation of flood-mitigation measures) or decreasing assets exposed to floods (suspension of land uses for flood-detention purpose). Performance of currently implemented flood-mitigation measures is insufficient to reduce flooding vulnerability when facing with climate change. However, the scenario suggested in this study to sustain room for floods efficiently reduces flooding vulnerability in both without- and with climate change situations. The suggestions provided in this study could support decision processes and help easing flooding problems of lowland management in Taiwan under climate change.     

校园雨涝灾害风险因素影响机制研究

洪涝灾害作为当前最严重的水患问题影响着校园安全,但目前针对该尺度下的风险研究较少。如何降低灾害风险,提升韧性成为当下校园可持续研究的重要议题。以HER框架为基础,在现有研究的基础上综合运用DEMATEL-ISM法,明确各因素间的影响机制及作用程度,构建多级递阶结构模型。结果表明：（1）校园雨涝灾害风险影响机制为五级三阶结构,其中排水设施排涝能力是最关键的根本致因,极端日降水量、暴雨频率、相对高程差是最有效的直接致因。（2）校园雨涝灾害风险最关键的作用路径是排水设施排涝能力-排水管网设置率-校园排水设施维养频率-植被覆盖率-暴雨频率。研究可为校园雨涝灾害防治提供参考。     

Morphostructural analysis of Jamaica

To Jamaica, macroblock in differential ascent in the plate boundary zone of the Caribbean—North America, a set of morphostructural and geological methods and procedures was applied that permitted its neostructure to be explained. It is composed of two mesoblocks, 11 blocks, 29 microblocks, and 65 nanoblocks. This group configures a heterogeneous network of morphoalignments and knots; knot N1 (Montego) and N11 (Kingston) being the most active. The main watershed was delimited, with an E-W strike, that reflects in its inflections the influence of a shear tectonic, mainly ancient, and that watershed divides the insular territory into two sectors (of rectangular figures) to the north and to the south. The river network is conditioned, in sectors and fundamentally, by tectonic factors. From a morphometric point of view the greater levels of uplifting (>1000 m) are located in the eastern part, in the Blue Mountains, though the estimated raising sectors denote that on its edges the recent intensity reaches values of ∼500 m. The contemporary faulting is more important in the marine parts of the north and of the south zones where the strongest earthquakes are located; however, this element is linked differently with the disruptive structures inherited, modified and active of the emerged part, those which determined that they are neither vast nor homogeneous. The seismic activity is justified by its space—time location in a transpression area of the plate boundary zone and where six relevant seismogenetic zones exist. In these elements the larger geological hazard is framed.     

The Liquefaction-Collapse Sinkhole Formation and Assessment of Its Danger to Buildings and Structures

Doklady Earth Sciences - A poorly studied genetic type of sinkhole formation, which is typical for areas where karstified rocks are covered by water-saturated or unsaturated cohesionless soils is...     

Drainage and flooding in karst terranes

Flooding in karst terranes is a commonly occurring geo-hazard. It causes damage to property, businesses, and roadways. It can lead to the formation of cover-collapse sinkholes and groundwater contamination. Generally, three types of flooding or their combinations are related to karst: recharge-related sinkhole flooding, flow-related flooding, and discharge-related flooding. Understanding of the type of flooding is essential for solving the flooding problem. Areas prone to karst flooding should be recognized, and restrictions and laws on land use should be implemented. Runoff and erosion control plans should address the unique characteristics of karst features. Digging out clogged sinkholes, creating retention basins, or installing Class V Injection Wells are possible solutions to improve drainage of storm water. Solutions to flooding problems in karst areas should also be coordinated with the water quality control to prevent groundwater contamination.     

Heavy metals distribution in Jamaica Bay sediments

Ninety-two sediment samples collected at 53 stations in Jamaica Bay from November 1970 to October 1973 were analyzed for Pb, Cr, V, Cu, Cd, Zn, Ni, Co, and percent organic carbon (ORC). Selected samples were analyzed for Hg. The concentrations of all metals correlate with each other and with organic carbon. Vanadium, cobalt, and nickel stand out as a separate component and are enriched relative to other metals in areas affected by petroliferous pollution. The metal concentrations are strongly influenced by the strength of tidal currents and proximity to pollution sources. Amount of rainfall and/or season affects metal concentrations in Grassy Bay (a deep restricted body of water within Jamaica Bay).     

Holocene flooding and species diversity in southwestern Amazonia

A thick blanket of Holocene alluvium lies over southwestern lowland Amazonia, and may possibly occur throughout much of the Amazon Basin. These deposits resulted from massive, seasonal flooding from about 11,000 to about 5000 yr B.P. that was followed by two cycles of erosion and deposition. Interpretations based on these geologic data suggest that southwestern lowland Amazonia is ecologically an “island” in a state of supersaturated disequilibrium as a result of colonization from Pleistocene refugia on its perimeter, and that habitats of highest diversity may be the most recent in origin. Conservation efforts and studies of Amazonian biogeography, soils, and paleoethnography should be reevaluated in light of the geologic data.     

Geological excursion guide 9: Jamaica

Apart from its obvious attractions for the visiting tourist, Jamaica is geologically significant, with a rock record dating from the Cretaceous and occupying a position at the north–east end of the Nicaraguan Rise, adjacent to the North Caribbean Plate Boundary Zone. During the Cretaceous, Jamaica was part of an island arc, but since the Eocene the rock record has been dominated by limestones.     

Geochemistry and petrogenesis of Cretaceous oceanic plateau lavas in eastern Jamaica

Basaltic lavas of Turonian to Coniacian age belonging to the Bath–Dunrobin Formation occur with intercalated island arc tuffs in the south of the Blue Mountain inlier, have been interpreted as being derived from the Caribbean oceanic plateau. This study presents new major and trace element and Sr–Pb–Nd–Hf isotopic data for these igneous rocks. The Jamaican rocks are altered by tropical weathering, hydrothermal and metamorphic processes, which have mobilised many of their elements (e.g. K and Ba). Consequently, the basalts and dacitic tuffs have been classified by using immobile trace elements. The trace element and _Hf(i)–_Nd(i) geochemistry suggests that the basaltic lavas are derived from a chemically similar source region by variable degrees of partial melting. The Caribbean plateau basalts lie on a mixing line between a depleted plume component and HIMU in Nd–Hf isotopic space. The Pb isotope data also demonstrate that the Jamaican plateau lavas are composed of a larger HIMU component than the other plateau lavas within the Caribbean region. The intercalated island arc tuffs are the first to be found in any oceanic plateau succession in the Caribbean and imply that the Caribbean oceanic plateau at  90 Ma was relatively close to the subduction zone along South America and the Great Arc of the Antilles.     

稠油油藏注超临界二氧化碳驱油影响因素分析

本文以辽河油田某断块油藏为研究对象,基于室内实验,结合正交设计试验,以提高原油采收率程度为评价指标,开展了稠油油藏注超临界CO_2驱影响因素研究,并分析了不同变量对注超临界CO_2驱油效率的影响权重。结果表明:CO_2驱油效率随渗透率、气体注入量、油藏温度的增加而增加,随原油粘度的增加而降低,其中:渗透率对原油采收率的影响程度最大,其次是原油粘度、气体注入量、油藏温度、压力。最后,本文总结并分析了我国注CO_2驱油提高原油采收率技术存在的主要问题,并提出拟解决措施。     

Diving deep on a Pleistocene reef in eastern Jamaica

Exhumed early Pleistocene reefs along the eastern coast of Jamaica expose deep-water environments downslope from the more familiar, shallow-water reef frameworks. Such environments have quite different faunas from the shallow parts of the reefs, including common 'Palaeozoic-type' biotas like the brachiopods and crinoids. These animals are found in deeper-water settings around the Caribbean today; however, these biotas are not readily available nor easily studied. The slightly older Pleistocene faunas are much more accessible and informative. Here the past may be the key to the present.     

An occurrence of cadmiferous phosphorite soil concretions in Jamaica

Bauxite exploration drilling revealed the presence of phosphate minerals through the chemical and XRD analysis of recovered drill hole samples at Spitzbergen, in Manchester Parish, Jamaica. A subsequent pit led to the discovery of phosphorite concretions composed of hard competent masses of finely crystalline fluorapatite, with some minor crandallite. The phosphorite contains anomalously high levels of Zn (>5000 mg kg⁻¹), Cd (>1.1%), Ag (>20 mg kg⁻¹), Be (>80 mg kg⁻¹) and, to a lesser extent, U. Textural and geochemical evidence indicates that the phosphorite concretions were most likely formed by the replacement of limestone by secondary deposition proximal to fossil guano deposits, postulated to be Late Miocene or Pliocene sea-bird colonies. Mechanical dispersion of the phosphorite concretions through karst weathering processes has led to their wider spatial distribution than the original guano deposits. Subsequent weathering of the concretions and the admixture of their decomposition products into the bauxitic and Terra Rossa soils is postulated to be the cause of the widespread anomalous levels of Zn, Cd and Be in these soils in central Jamaica, and the elevated levels of P in the bauxite.     

Sinkhole hazards along the eastern Dead Sea shoreline area, Jordan: a geological and geotechnical consideration

For the last four decades, the level of the Dead Sea has been subjected to continual variation which, among other important factors, has led to the occurrence of much subsidence and many sinkholes in the southern Dead Sea area. Sinkhole activities occurred repetitively and were observed in open farms, across roads, near dwellings and near an existing factory, thus causing a serious threat to the locals and farmers of the area and their properties. This paper presents the main results from detailed geological and geotechnical studies of this area. Aerial photo interpretation and borehole drilling aided these studies. Parallel geophysical investigations (vertical electrical sounding and seismic refraction) and hydrological and hydrogeological studies were made by others in the same area to also investigate this phenomenon. It was found that sinkholes are aligned to and follow old water channels and are concentrated parallel to the recent shoreline of the Dead Sea. The development of subsurface cavities is associated mainly with the variation in the level of the Dead Sea over the four past decades, the presence of regional salt intrusion under the surface of salt beds, the fluctuation of the water table and continuous dissolution and the active tectonism of the area. Moreover, this work showed that the area is still under active sinkhole hazards and other parts of the area will be inevitably affected by sinkholes in the future.No practical engineering solution to this problem is feasible. Received: 1 July 1999 / Accepted: 11 October 1999