川藏公路地质环境与整治改建方案的思考   总被引：3，自引：0，他引：3  

崔建恒 《工程地质学报》2003,11(1):100-104

川藏公路由于地质环境复杂、建设标准低、后遗病害多,抗灾能力差,泥石流、滑坡、山崩、雪害、水毁等自然灾害频繁发生,公路阻车断道严重。国家投入巨资进行整治改建,并取得了明显的效果,但由于自然环境特殊、影响因素复杂,许多特大型、大型工程地质病害问题还没有可行、可靠的解决方案。本文通过分析川藏公路沿线的地质环境和灾害特点,总结历年整治改建和经验的教训,提出川藏公路建设的途径、可能达到的目标和应采用的原则。  相似文献   

A method for assessing regional debris flow risk: an application in Zhaotong of Yunnan province (SW China)   总被引：6，自引：0，他引：6  

Xilin Liu  Junzhong Lei 《Geomorphology》2003,52(3-4):181-191

Based on the definitions of the United Nations, the assessment of risk involves the evaluation of both hazard and vulnerability. This forms the basis of a generalized assessment model of debris flow risk. Hazard is a measure of the threatening degree of an extreme event and is expressed theoretically as a function of event magnitude and frequency of occurrence. Mathematically, it is the definite integral area under the magnitude–frequency curve. Based on the need for a model applicable in regions that lack data, a new method that incorporates theoretical concepts with empirical analysis is presented to calculate the regional hazardousness of debris flows. Debris flow hazard can be estimated from gully density, mean annual rainfall and percentage of cultivated land on steep slope. Vulnerability is defined as the potential total maximum losses due to a potential damaging phenomenon for a specified area and during a reference period. On a regional scale, it is dependent on the fixed assets, gross domestic product, land resources and population density, as well as age, education and wealth of the inhabitants. A nonlinear, power-function model to compute the vulnerability degree is presented. An application of the proposed method to Zhaotong prefecture of Yunnan province, SW China, provides high accuracy and reasonable risk estimates. The highest risk of debris flow is in Zhaotong county with a value of 0.48; the lowest risk of debris flow is in Yanjin county with a value of 0.16. The other counties have debris flow risks ranging from 0.22 to 0.46. This provides an approach for assessing the regional debris flow risk and a basis for the formulation of a regional risk management policy in Zhaotong prefecture.  相似文献   

Work, persistence, and formative events: The geomorphic impact of landslides   总被引：1，自引：0，他引：1  

R.H. Guthrie  S.G. Evans   《Geomorphology》2007,88(3-4):266-275

Understanding the scale and frequency of physical processes that act upon and form the surface of the Earth is a fundamental goal of earth science. Here we determine the magnitudes of landslides that impact the landscape in terms of work, persistence, and formative events. A systematic analysis of rapid landsliding (the analysis did not consider creep and other slow semi-continuous processes) indicates that moderate-sized landslides do the most work transporting material on hillslopes. The work peak defines the moderate magnitude, and that magnitude varies based on local physiography and climate. Landslides that form the work peak are distinct from catastrophic landslides that are themselves formative and system resetting. The persistence time for debris slides/debris flows (P_DS) and rock slides/rock avalanches (P_RS) is calculated over six orders of magnitude. We consider an event catastrophic when it persists in the landscape, as described by a persistence ratio (P_F), an order of magnitude longer than the population of landslides that form the work peak.  相似文献   

Empirical modelling of the May 1998 small debris flows in Sarno (Italy) using LAHARZ   总被引：1，自引：0，他引：1  

D. Oramas Dorta  G. Toyos  C. Oppenheimer  M. T. Pareschi  R. Sulpizio  G. Zanchetta 《Natural Hazards》2007,40(2):381-396

The catastrophic events that occurred in May 1998 in the area of Sarno (Southern Italy) highlight the destructive potential of debris flows, even when they are of relatively low magnitude. More than 130 people were killed and severe property damage took place when volcaniclastic debris flows triggered by heavy rainfall inundated various towns located in piedmont areas. This work investigates the suitability of LAHARZ, a GIS-assisted method for the automatic delineation of lahar inundation areas, for reproducing the May 1998 flows at Sarno. It was found that recalibration of the empirical relationship employed by LAHARZ is required in order to realistically hind-cast the inundation areas of considered events. The potential for further improvements in prediction outputs for this type of geomorphic setting is discussed, taking into account the observed lower mobility of these small volcaniclastic debris flows as compared to lahars of similar size.  相似文献   

A GIS-based methodology for hazard mapping of small volume pyroclastic density currents     

G. P. Toyos  P. D. Cole  A. Felpeto  J. Martí 《Natural Hazards》2007,41(1):99-112

We present here a methodology implemented within a geographical information system (GIS) for hazard mapping of small volume pyroclastic density currents (PDCs). This technique is implemented as a set of macros written in Visual Basic for Applications (VBA) that run within GIS-software (i.e. ArcGIS). Based on the energy line concept, we calibrated an equation that relates the volume (V) and the mobility (ΔH/L) of single PDCs using data from Soufrière Hills volcano (Montserrat) and Arenal volcano (Costa Rica). Maximum potential run-outs can be predicted with an associated uncertainty of about 30%. Also based on the energy line concept and with data from Soufrière Hills volcano and Mt. St. Helens (USA), we were able to calibrate an equation that predicts the flow velocity as a function of the vertical distance between the energy line and the ground surface (Δh). Velocities derived in this way have an associated uncertainty of 3 m s⁻¹. We wrote code to implement these equations and allow the automatic mapping of run-out and velocity with the inputs being (i) the height and location of the vent (ii) the flow volume and (iii) a digital elevation model (DEM) of the volcano. Dynamic pressure can also be estimated and mapped by incorporating the density of the pyroclastic density current (PDC). This computer application allows the incorporation of uncertainties in the location of the vent and of statistical uncertainties expressed by the 95% confidence limits of the regression model. We were able to verify predictions by the proposed methodology with data from Unzen volcano (Japan) and Mayon volcano (The Philippines). The consistencies observed highlight the applicability of this approach for hazard mitigation and real-time emergency management.  相似文献   

Spatial correlation of shear-wave velocity in the San Francisco Bay Area sediments   总被引：1，自引：0，他引：1  

Eric M. Thompson  Laurie G. Baise  Robert E. Kayen 《Soil Dynamics and Earthquake Engineering》2007,27(2):144-152

Ground motions recorded within sedimentary basins are variable over short distances. One important cause of the variability is that local soil properties are variable at all scales. Regional hazard maps developed for predicting site effects are generally derived from maps of surficial geology; however, recent studies have shown that mapped geologic units do not correlate well with the average shear-wave velocity of the upper 30 m, V_s(30). We model the horizontal variability of near-surface soil shear-wave velocity in the San Francisco Bay Area to estimate values in unsampled locations in order to account for site effects in a continuous manner. Previous geostatistical studies of soil properties have shown horizontal correlations at the scale of meters to tens of meters while the vertical correlations are on the order of centimeters. In this paper we analyze shear-wave velocity data over regional distances and find that surface shear-wave velocity is correlated at horizontal distances up to 4 km based on data from seismic cone penetration tests and the spectral analysis of surface waves. We propose a method to map site effects by using geostatistical methods based on the shear-wave velocity correlation structure within a sedimentary basin. If used in conjunction with densely spaced shear-wave velocity profiles in regions of high seismic risk, geostatistical methods can produce reliable continuous maps of site effects.  相似文献   

Volcaniclastic debris-flow occurrences in the Campania region (Southern Italy) and their relation to Holocene–Late Pleistocene pyroclastic fall deposits: implications for large-scale hazard mapping     

M. Bisson  M. T. Pareschi  G. Zanchetta  R. Sulpizio  R. Santacroce 《Bulletin of Volcanology》2007,70(2):157-167

The Campania Region (southern Italy) is characterized by the frequent occurrence of volcaniclastic debris flows that damage property and loss of life (more than 170 deaths between 1996 and 1999). Historical investigation allowed the identification of more than 500 events during the last four centuries; in particular, more than half of these occurred in the last 100 years, causing hundreds of deaths. The aim of this paper is to quantify debris-flow hazard potential in the Campania Region. To this end, we compared several elements such as the thickness distribution of pyroclastic fall deposits from the last 18 ka of the Vesuvius and Phlegrean Fields volcanoes, the slopes of relieves, and the historical record of volcaniclastic debris flows from A.D. 1500 to the present. Results show that flow occurrence is not only a function of the cumulative thickness of past pyroclastic fall deposits but also depends on the age of emplacement. Deposits younger than 10 ka (Holocene eruptions) apparently increase the risk of debris flows, while those older than 10 ka (Late Pleistocene eruptions) seem to play a less prominent role, which is probably due to different climatic conditions, and therefore different rates of erosion of pyroclastic falls between the Holocene and the Late Pleistocene. Based on the above considerations, we compiled a large-scale debris-flow hazard map of the study area in which five main hazard zones are identified: very low, low, moderate, high, and very high.  相似文献   

Hazard rate estimation of a mixture model with censored lifetimes     

S. E. Ahn  C. S. Park  H. M. Kim 《Stochastic Environmental Research and Risk Assessment (SERRA)》2007,21(6):711-716

This paper is intended to compare the hazard rate from the Bayesian approach with the hazard rate from the maximum likelihood estimate (MLE) method. The MLE of a parameter is appropriate as long as there are sufficient data. For various reasons, however, sufficient data may not be available, which may make the result of the MLE method unreliable. In order to resolve the problem, it is necessary to rely on judgment about unknown parameters. This is done by adopting the Bayesian approach. The hazard rate of a mixture model can be inferred from a method called Bayesian estimation. For eliciting a prior distribution which can be used in deriving a Bayesian estimate, a computerized-simulation method is introduced. Finally, a numerical example is given to illustrate the potential benefits of the Bayesian approach.  相似文献   

自然灾害链的场效机理与区链观   总被引：2，自引：0，他引：2  

姚清林 《气象与减灾研究》2007,30(3):31-36,F0003

在分析2004年12月、2005年3月印尼苏门答腊9.0、8.7级巨震和2005年6月17—23日西江大洪水前后数千张卫星遥感图像,以及其他资料的基础上,提出了灾害链的场效机理与区链观。认为相邻异域链事件间不具备直接的传承关系。链事件的发生是由所在区域场的动力学环境、介质结构及诸多物理、化学因素组合的不均衡性与连续的、自然的系统演化过程决定的。前发链事件具有即时场效应和后期调整场效应,这些效应会以包含隐性、较小尺度事件的区域链接的方式向后传送。场中每点的动变皆有后效,且体现在或作用于过程、区域上,而非个别点上;或者说,作用于时空邻点上而非远程点上。各类动变效应在场与过程上的叠加与演化,会在条件"成熟"时导致较大链事件的发生。具有一定的内在联系,其结构特征、运动方式、动力环境、演化过程具有相对整体性的区域与其边界,是自然灾害链的发生背景,也是判定两事件间是否相关的重要判据。  相似文献   

Progress in NTHMP Hazard Assessment     

Frank I. González  Vasily V. Titov  Harold O. Mofjeld  Angie J. Venturato  R. Scott Simmons  Roger Hansen  Rodney Combellick  Richard K. Eisner  Don F. Hoirup  Brian S. Yanagi  Sterling Yong  Mark Darienzo  George R. Priest  George L. Crawford  Timothy J. Walsh 《Natural Hazards》2005,35(1):89-110

The Hazard Assessment component of the U.S. National Tsunami Hazard Mitigation Program has completed 22 modeling efforts covering 113 coastal communities with an estimated population of 1.2 million residents that are at risk. Twenty-three evacuation maps have also been completed. Important improvements in organizational structure have been made with the addition of two State geotechnical agency representatives to Steering Group membership, and progress has been made on other improvements suggested by program reviewers.  相似文献