坡面松散砾石土侵蚀过程及其特征研究

砾石土因其含砾、粉细砂和粘性土,具有级配宽、不均匀系数大、透水性强等特点,在土石坝防渗体土料和工程防渗墙中得到广泛应用。目前的研究多针对砾石土在工程应用方面,对于坡面松散砾石土降雨淋滤作用导致土体细粒成分流失、土体组构改变以至影响土体力学性质变化以及坡面物质稳定性变化等系列研究并不多见。利用人工降雨装置,进行了人工降雨坡面松散砾石土降雨淋滤试验,开展了砾石土侵蚀过程及其特征初步试验研究。试验表明,降雨作用下砾石土斜坡表面土体形态变化具有明显的阶段性特征,随着坡长的增加,产流率和侵蚀模数成线性增加,径流量随降雨时间跳跃和波动性增加,径流泥沙含量随降雨时间的增加以近似幂函数曲线关系递减。     

Flood frequency analysis based on simulated peak discharges

Flood frequency approaches vary from statistical methods, directly applied on the observed annual maximum flood series, to adopting rainfall–runoff simulation models that transform design rainfalls to flood discharges. Reliance on statistical flood frequency analysis depends on several factors such as the selected probability distribution function, estimation of the function parameters, possible outliers, and length of the observed flood series. Through adopting the simulation approach in this paper, watershed-average rainfalls of various occurrence probabilities were transformed into the corresponding peak discharges using a calibrated hydrological model. A Monte Carlo scheme was employed to consider the uncertainties involved in rainfall spatial patterns and antecedent soil moisture condition (AMC). For any given rainfall depth, realizations of rainfall spatial distribution and AMC conditions were entered as inputs to the model. Then, floods of different return periods were simulated by transforming rainfall to runoff. The approach was applied to Tangrah watershed in northeastern Iran. It was deduced that the spatial rainfall distribution and the AMCs exerted a varying influence on the peak discharge of different return periods. Comparing the results of the simulation approach with those of the statistical frequency analysis revealed that, for a given return period, flood quantiles based on the observed series were greater than the corresponding simulated discharges. It is also worthy to note that existence of outliers and the selection of the statistical distribution function has a major effect in increasing the differences between the results of the two approaches.     

Drought in the Sahel

The Sahel region of West Africa is well known as a region of environmental degradation. The reported incidence of desertification has been challenged but persistent and widespread drought is still widely accepted. Drought, defined solely as a function of rainfall, is believed to have commenced in the early 1970s and continued through to the present. It is usually defined as a meteorological phenomenon and standardised rainfall anomalies are employed to indicate the severity of negative departures from the ‘norm’. There are several difficulties with this approach. The period of standardising rainfall has changed from 1931–1960 to 1961–1990 but the impacts on drought occurrence have not been fully determined. The spatial aggregation of rainfall anomalies may mask important local variation and the purely statistical approach to defining drought takes little account of human impact. The first two issues, averaging period and spatial aggregation, are investigated through an analysis of rainfalls in Continental Sahel (Bukina Faso, Mali and Niger). A new classification of drought classes is suggested. Despite the clear evidence of negative rainfall anomalies for rainfalls aggregated across the Sahel region, it is found that the averaging period has a significant impact on our perceptions of the occurrence of what can be considered to be meteorological drought according to the definition employed and that there is significant spatial variation. This revised version was published online in July 2006 with corrections to the Cover Date.     

Experimental analysis and modelling of shallow landslides

The paper presents the results of some experimental tests reproducing the triggering mechanism of a special kind of shallow landslides induced by rainfalls (soil slip) in a physical 1-g model. The experimental data have been employed to verify the capability of a simplified stability model to describe the phenomenon and to back-analyse its occurrence in a case history (Pizzo d’Alvano, Campania Region 1998). The method enables a direct correlation between the safety factor of a slope and rainfall intensity, as well as antecedent rainfalls.     

Debris flow impact assessment caused by 14 April 2012 rainfall along the Al-Hada Highway,Kingdom of Saudi Arabia using high-resolution satellite imagery

The Al-Hada highway that descends towards the west of the city of At-Taif is a major connecting highway in the western part of the Kingdom of Saudi Arabia. It is one of the series of descending roads connecting the holy city of Makkah and the city of Jeddah with the city of At-Taif and the cities farther south along the escarpment. The length of the Al-Hada highways is about 22 km. The Al-Hada highway has been historically exposed to landslides and other geohazards since the day it was opened to public some 60 years ago. The road has been reconstructed and many slope instabilities have been remediated and the road has been expanded to two lanes in each direction. Heavy rainfalls occurred on the 14th of April 2012 in the province of At-Taif, causing huge debris flows in two places along the Al-Hada highway. As a result of that, these debris flows closed all four lanes of the highway for 2 weeks in order to remove the debris. The current research deals with mapping of all debris flows along Al-Hada highway and determining their volumes and their impact on the road. Finally, suitable solutions have been suggested to address these critical sites to minimize and/or avoid the debris flow hazards in the future.     

Linear system techniques applied to the Fuenmayor Karst Spring, Huesca (Spain)

Black box identification techniques are very useful tools to study the relationship between rainfall and the discharge of karst aquifers. Autocorrelation, cross-correlation, cross-spectral, impulse response identification (Wiener–Hopf and error minimization methods) and parametric identification of transfer functions techniques have been used by different authors. A review of these techniques has been realized to assess the possibilities and limitations. The reviewed techniques are applied to a time rainfall–discharge series of Fuenmayor karst spring, (southern central Pyrenees, Spain) to establish the relative quality of the obtained models. The quality is evaluated with the Nash–Sutcliffe model efficiency coefficient. In addition, effective rainfall has been used to improve the performance of every model. The whitening technique has been used in the cross-correlation technique with good results. The studied spring shows a Fontestorbes type behavior. The linearity of the system has been analyzed by the coherence function. Fuenmayor has an acceptable linear response, except for high frequency events. The parametric identification provides the best efficiency value E = 0.8164 and provides a proper transfer function, with five parameters (one zero, two poles, the gain and the delay). The prediction power of this transfer function is validated with another time series, with an efficiency value of E = 0.7904.     

A probabilistic model for the prediction of meteorological droughts in Venezuela

Droughts occur when rainfalls diminish or cease for several days, months or years. In the last five years several meteorological droughts have occurred in Venezuela, impacting negatively water supply, hydro-power and agriculture sectors. In order to provide institutions with tools to manage the water resources, a probabilistic model has been developed and validated to predict in advance the occurrence of meteorological droughts in the country using monthly series of 632 rainfall stations. The standardized precipitation index (SPI) was used to identify dry events of each rainfall series. A principal component analysis associated to a geographic information system was used to define geographically continuous homogeneous sub-regions (HS) for the values of SPI. For each HS a representative station was selected (reference station, RS). A lagged correlation analysis was applied to the SPI series of the RS and the corresponding series of anomaly indices of 10 macroclimatic variables (MV). The four MV with higher correlation in each RS were organized into three levels (-1, 0 and +1), using the quartiles Q₂ and Q₄ as values of truncation. The SPI series are expressed in four ranges: non-dry, moderately dry, severely dry and extremely dry. The conditional probability of occurrence of the four ranges of SPI was determined in every combination that can occur in the four VM best correlated. The resulting model in each RS was validated using the SPI series from 20 meteorological stations operated by the Servicio de Meteorología de la Fuerza Aérea Venezolana (Meteorological Service of the Venezuelan Air Force) which were not used in the development of the models. Results indicate that models detected the occurrence of ES with an accuracy ranging from 85.19 to 100%; the success is directly proportional to the length of records used in the development of the model. This methodology could be applied in any country that has long, continuous and homogeneous rainfall series.     

晚三叠世中卡尼期极端气候事件:研究进展及存在问题

作为三叠纪最显著的气候变化事件,全球性的卡尼期气候事件以幕次降雨量增多为特征,在西北特提斯洋地区表现较为明显,主要反映了从碳酸盐岩到黑色页岩的岩性变化,近年来这一地质事件在美国、中国、日本等地的卡尼阶地层中也有识别.其成因一直是学者研究的重点,有人认为是板块构造运动促使大气或大洋循环发生了变化,或是超级大陆聚合碰撞而触发大火成岩省喷发致使全球气候发生了紊乱,也有人认为是地球系统综合因素相互作用的结果.联系到中国西南部地区卡尼阶现状,认为超级季风、构造运动和卡尼期气候变化的关系值得深入研究,此外卡尼期气候事件过程中碳酸盐补偿深度上升问题、卡尼期黑色页岩事件反映的大洋生产力以及多幕卡尼期气候事件反映的气候波动事件等科学问题也是今后的研究中值得重视的.     

Multipath interference cancelation in GPS time series under changing physical conditions by means of adaptive filtering

Multipath, a highly autocorrelated signal is observable phenomena during time periods longer than the sidereal period of Global Positioning System (GPS) satellites in their constellations. Multipath pattern and sidereal repeat time interaction are examined in terms of time series correlations of topocentric coordinates using GPS code and phase observations collected at high and low frequencies. The horizontal and vertical components at 5 and 30 s sampling rates are analyzed to detect and remove multipath classified by their M P ₁ levels and baseline lengths. For the selected 11 stations that have 24-hour data from CORS stations in the USA and Turkey, the repeat times of the GPS constellation were identified as a function of maximum cross-correlation of adjacent time series. The multipath interference signal from two-day time series data is removed by an adaptive filter to improve time series of coordinate estimates. After the filtering process, an effective epoch based position tracking has been accomplished, especially in the height component. The position errors disappeared to maximum possible extent in the pseudo-range measurements. Up to 70% improvement for the phase derived coordinates in reflective environment has been achieved over the baselines ranging from 1 km to 175 km. For the phase observables, the filter success directly related to the multipath level which is specific to the station.     

Estimates of source parameters of <Emphasis Type="Italic">M</Emphasis>4.9 Kharsali earthquake using waveform modelling

This paper presents the computation of time series of the 22 July 2007 M 4.9 Kharsali earthquake. It occurred close to the Main Central Thrust (MCT) where seismic gap exists. The main shock and 17 aftershocks were located by closely spaced eleven seismograph stations in a network that involved VSAT based real-time seismic monitoring. The largest aftershock of M 3.5 and other aftershocks occurred within a small volume of 4 × 4 km horizontal extent and between depths of 10 and 14 km. The values of seismic moment (M _∘) determined using P-wave spectra and Brune’s model based on f ² spectral shape ranges from 10¹⁸ to 10²³ dyne-cm. The initial aftershocks occurred at greater depth compared to the later aftershocks. The time series of ground motion have been computed for recording sites using geometric ray theory and Green’s function approach. The method for computing time series consists in integrating the far-field contributions of Green’s function for a number of distributed point source. The generated waveforms have been compared with the observed ones. It has been inferred that the Kharsali earthquake occurred due to a northerly dipping low angle thrust fault at a depth of 14 km taking strike N279°E, dip 14° and rake 117°. There are two regions on the fault surface which have larger slip amplitudes (asperities) and the rupture which has been considered as circular in nature initiated from the asperity at a greater depth shifting gradually upwards. The two asperities cover only 10% of the total area of the causative fault plane. However, detailed seismic imaging of these two asperities can be corroborated with structural heterogeneities associated with causative fault to understand how seismogenesis is influenced by strong or weak structural barriers in the region.     

贵州省地质灾害气象预警系统

从降水（特别是暴雨）是地质灾害的主要自然诱因这一基本事实出发，通过对地质灾害和对应气象资料的分析，探讨地质灾害的发生与气象条件之间的关系，提出了一套基于降雨量指标的地质灾害气象预警方法。作者综合考虑前期累积雨量、降雨类型和实时雨量等关键指标，建立了一定地质环境条件下灾害的气象预警模型。在此基础上，应用先进的软件技术开发研制了贵州省地质灾害气象预警系统，并于2003午汛期投入业务试运行，开展地质灾害气象预警眼务。该系统实时运行在气象业务网络环境中，高效稳定、功能全面．自动进行全省地质灾害气象条件的动态监测和模型计算，利用精细化乡镇雨量观测网和地质灾害隐患点资料，可实现对全省各地到乡镇一级的地质灾害气象条件预警，每日制作发布全省地质灾害气象条件预警报告，提供生动直观的预警图、表及相应的地质灾害隐患点信息：该系统经过在实践应用中不断改进完善，形成了以应用全省精细化乡镇雨量观测资料和针对地质灾害隐患分布的特色。该系统投入业务运行以来建立了汛期业务值班制度，向省委首政府、国土民政等有关部门进行有效的地质灾害气象预警服务，对系统运行情况进行地质灾害实例检验取得了较好的预警效果，服务工作取得了明显的社会效益。由于该系统的开发主要是从气象条件的角度出发，虽考虑了地质灾害隐患的分布情况，但对导致地质灾害发生的地喷环境条件的分析应用还显不够。最后，作者也指出了需要进一步改进的方向。     

200 years of mining activities at La Paz/San Luis Potosí/Mexico - Consequences for environment and geochemical exploration

The Ag---Pb---Zn---Cu---Au mining district of Santa María de La Paz has been extensively exploited for approximately 200 years. Consequences of these activities are several deposits of tailings with high As and heavy metal concentrations, which are completely unstable. The climate is semiarid and as the dumps have no protective cover, material from the dumps is dispersed by strong winds. It is also washed out during seasonally heavy rainfalls. By these processes approximately 100 km² of surrounding have been contaminated by dump material. The As and heavy metal content of the soils was determined as well as their level in crops (Zea Maize) from agricultural lands in the vicinity of the dumps. In the direction of prevailing winds concentrations up to 1000 ppm Zn, 400 ppm Pb, 16 ppm Cd, 550 ppm Cu and 300 As have been detected in top soils. Using fuzzy cluster analysis the different contamination sources could be identified. Grains of corn from contaminated sites showed no critical concentrations, but leaves which are also used tor fodder, have As-concentrations up to 20 ppm.     

全国航放数据库的建设

全国航放数据库系统成功地解决了不同类型航放测量数据源的录入、重复数据检索等关键技术问题并已录入30多个测区的航放(部分含航磁)数据；研究、应用概率论数理统计学原理，解决连片(重复)数据的标准化方法与实现；完成了检索的库原始数据、查询计算的标准化数据或比值计算数据等直接网格化的程序设计；探索了图形数据与标量数据库的接口技术，开发了屏幕绘图及与相关软件接口程序，做到了图并茂。使全国航放数据库具有：灵活、可靠的数据录入／导入功能，方便、可视性强的查询(统计)功能，实用、快捷的数据处理应用功能，适时、完备的输出功能，易用、可扩展的系统维护功能，严密、安全的数据保密功能。     

基于多元线性回归的表层岩溶泉流量预测

利用贵州省安顺市普定县陈旗小流域泉流量动态变化及降雨观测资料,根据泉流量系列自相关和偏自相关以及降雨-泉流量系列互相关分析,确定泉流量系列以及降雨-泉流量响应滞时,建立泉流量与降雨及前期泉流量的多元线性回归模型。率定期(模型参数率定的时段)模型的输出结果与实测流量过程线较为吻合,效率系数为0.996,均方误差为3.0×10-7m3/s,平均相对误差为2.12%。验证期效率系数为0.985,均方误差为3.96×10-7m3/s,平均相对误差为5.36%。研究也同时表明,随着预测时段的增长,泉流量消退阶段的预测误差增大,因此文中所建模型用于10小时之内泉流量预测较为可靠,六场降雨后泉流量退水过程预测的泉流量相对误差平均值小于5%。      

Monitoring ground deformation at the decade volcano Gunung Merapi,Indonesia

Pressure changes within a volcano lead to deformations of his edifice. To discriminate local and regional ground movements, four deformation stations with clusters of continuous borehole tiltmeters have been installed at the hillsides of Gunung Merapi. In addition, recording local environmental parameters allows the recognition of interfering local tilt signals. First analyses of the data records show: The significant tidal variations of the tilt signal validate the successful coupling between the instruments and their surroundings. Transient tilt signals correlated to rainfalls are probably caused by poroelastic deformation of the hillsides. Four volcanic events occurred during the observation period; all of them were accompanied, if not triggered, by heavy rainfalls. Tilt anomalies, considerably larger than the rain induced tilts, were recorded around the event of October 31, 1996, coincident with an extraordinary high seismic activity. If this activity reflects internal fracture processes prior to the eruption, the accompanying deformations might partially explain the observed tilt signal.     

干湿循环条件下煤矿砂岩分离式霍普金森压杆试验研究

由于降雨、季节引起地下水位升降等原因,地壳中岩体常处于干湿循环状态。为研究干湿循环对岩石动态力学性能的影响,以安徽恒源煤矿北风井-259 m处砂岩为研究对象,采用?50 mm变截面分离式霍普金森压杆试验装置,对长径比为0.5的煤矿砂岩试件经干湿循环作用后实施单轴冲击压缩试验,获得了砂岩动态单轴压缩应力-应变曲线。研究发现,由于自由水的Stefan效应,干湿循环1次对砂岩具有增强作用,单轴动态抗压强度最高;其后,随着干湿循环次数的增加,砂岩受水侵蚀物理弱化作用,砂岩动态单轴抗压强度呈乘幂关系降低,砂岩试件的冲击破碎块度逐渐变小。试验结果表明,干湿循环12次时砂岩动态抗压强度比干湿循环1次降低约24%,表现出较强的劣化效应。     

A simple numerical procedure for timely prediction of precipitation-induced landslides in unsaturated pyroclastic soils

In the last 20 years, several catastrophic precipitation-induced landslides have hit villages, towns and roads in Campania (southern Italy), causing extensive damage and many fatalities. Although such phenomena have occurred since time immemorial, recent urbanisation and infrastructural development have produced a major increase in landslide risk. Due to climatic changes and further unavoidable increases in exposure, in the near future, the risk will become even greater. It is therefore high time to develop reliable criteria for landslide prediction. The paper discusses the main factors which affect the triggering of precipitation-induced landslides, highlighting the key role played by antecedent rainfalls which cannot be precisely accounted for using empirical criteria. We propose a simple 1D numerical approach able to predict the evolution of the key factors governing slope stability as a tool to predict the onset of slope failure, with potential benefits for early warning systems. The approach is calibrated through a well-documented case history.     

中国历史文献档案中的古环境记录

我国的历史文献记录是古气候、古环境信息的重要来源,对古全球变化（PAGES）研究计划的目标时段——近2000年（人文记录和自然记录并存的时段）来说,尤其具有重要的科学价值。介绍了我国古文献中的古气候、古环境记录的概况和各项记录如水、旱、雨、雪等的数量统计,综述了这些记录被用于重建定量的气候序列、绘制历史气候复原图、编制古环境事件年表、获取高分辨率的古气候信息诸方面的主要进展。     

Univariate modelling of summer-monsoon rainfall time series: Comparison between ARIMA and ARNN

The present article reports studies to develop a univariate model to forecast the summer monsoon (June–August) rainfall over India. Based on the data pertaining to the period 1871–1999, the trend and stationarity within the time series have been investigated. After revealing the randomness and non-stationarity within the time series, the autoregressive integrated moving average (ARIMA) models have been attempted and the ARIMA(0,1,1) has been identified as a suitable representative model. Consequently, an autoregressive neural network (ARNN) model has been attempted and the neural network has been trained as a multilayer perceptron with the extensive variable selection procedure. Sigmoid non-linearity has been used while training the network. Finally, a three-three-one architecture of the ARNN model has been obtained and after thorough statistical analysis the supremacy of ARNN has been established over ARIMA(0,1,1). The usefulness of ARIMA(0,1,1) has also been described.     

基于小波的时序改进法在深基坑监测中的应用

结合润扬长江公路大桥南汊悬索桥南锚碇采用排桩冻结法新技术的工程实际,对深基坑支撑轴力监测数据提出了基于小波技术的时间序列改进法,将时间序列分析的多步预报功能与小波对信号精加工的功能相结合,研究结果表明,采用小波改进时间序列分析方法建立的时间序列动态预测模型,其预测精度大大提高,为基坑的安全施工提供了保障,为基坑的信息化施工提供了依据。