陕西省宝鸡市地质灾害发育特征

根据近7年来陕西省宝鸡市12区县地质灾害详细调查资料,总结宝鸡地区地质灾害主要类型、空间分布规律、发育特征及其危害性。研究结果显示,宝鸡市地质灾害发育类型主要包括滑坡、崩塌、泥石流及不稳定斜坡等4类,总体发育特征具有群发性、突发性、周期性和链生性。其中,滑坡和崩塌数量多、危害大,泥石流相对发育较少,不稳定斜坡多与崩塌相伴生,大多发展为崩塌灾害。每年汛期在强降雨作用下,都可能诱发表层小型滑坡和崩塌,特别是城镇居民房前屋后的小型黄土滑坡和崩塌,以及山区公路切坡导致的残坡积层滑坡崩塌频繁发生,是宝鸡市地质灾害群测群防和减灾防灾关注的重点。     

Non-stationary realisation of CPT data: considering lithological and inherent heterogeneity

ABSTRACT

The main sources of uncertainty in the soil specification and mechanical behaviour consist of the lithological and heterogeneous randomness of soil deposits. It is quite obvious that the cone penetration testing (CPT) data and the variation of soil characteristics are not stationary. Hence, this paper investigates a new approach to realise a CPT data, taking both sources of uncertainty into consideration. In this regard, the first part of this study illustrates a simple approach to stratify the CPT data, using the Eslami–Fellenius chart of classification. In the second part, the non-stationary algorithm of generating random field is introduced to generate a multi-layer random field. This algorithm takes account of each layer’s statistical properties (i.e. standard deviation, mean, and the trend value), separately. To validate the proposed approach, 41 case histories from different worldwide sites, have been regenerated by considering both the stationary and non-stationary algorithms. The correlation coefficient between real and realised CPT data has been employed to show that the proposed non-stationary algorithm can simulate the CPT data more accurately in comparison with the stationary algorithm.     

Effect of the Dead Sea–Red Sea canal modelling on the prediction of the Dead Sea conditions

A project to link the Dead Sea to the Red Sea via a canal is undergoing extensive study. In previous works, a generalized mathematical model describing the state of the Dead Sea and a simulation model to implement it have been developed. The model is extended to include the proposed canal project and investigates two alternative modelling canal scenarios: (1) introducing the canal water inflow into the bottom layer or (2) the top layer of the sea. The predicted general effects of the canal are the restoration of the water level of the sea to pre‐1970s level; an increase in the total evaporation rate and a decrease in the top layer salinity. Implementing scenario 1, the model predicts that: the water level of the Dead Sea will exceed the desired level design value and therefore shorter filling time can be used; seasonal stratification will persist; total evaporation rate will increase Modestly; there will a small decrease in the salinity of the top layer but a substantial decrease in the salinity of the bottom layer, which will hurt industries severely; there will be a continuation of seasonal crystallization of aragonite and gypsum. Implementing scenario 2 the model predicts that: the water level of the Dead Sea will be maintained at the desired level design value; stratification will be re‐established, with the formation of a permanent two‐layer system; there will be a substantial increase in the total evaporation rate; the salinity of the top layer will decrease significantly but there will be continuous slower salinity increase in the bottom layer; the crystallization of aragonite will cease, but seasonal gypsum crystallization can be expected to continue as soon as the filling period ends and the canal shifts into normal operation. Copyright © 2003 John Wiley & Sons, Ltd.     

Sun-perturbed earth-to-moon transfers with low energy and moderate flight time

We construct a spacecraft transfer with low cost and moderate flight time from the Earth to the Moon. The motion of the spacecraft is modeled by the planar circular restricted three-body problem including a perturbation due to the solar gravitation. Our approach is to reduce computation of optimal transfers to a non-linear boundary value problem. Using a computer software called AUTO, we solve it and continue its solutions numerically to obtain the optimal transfers. Our result also shows that the use of the solar gravitation can further lower the transfer cost drastically.     

“威马逊”台前飑线环境场及多普勒雷达回波特征

利用常规观测资料、多普勒天气雷达资料、地面自动站加密资料、NCEP 1°×1°的再分析资料等对2014年7月18日发生在湘赣地区一次台前飑线过程的环境条件及多普勒天气雷达特征进行研究。结果表明:台前飑线产生前,对流层低层较好的水汽条件、条件不稳定层结以及两者结合形成的高CAPE值均为其发生发展提供了良好的条件;台风倒槽是此次台前飑线过程主要影响系统,露点锋、地面辐合线为其提供了抬升触发和维持加强机制;台前飑线西移北上的过程中出现"弓形"回波、中层径向辐合(MARC)、速度大值区、阵风锋。本次台前飑线和以往研究的西风带飑线存在以下差异:本次飑线低层垂直风切变主要是以风速差为主;中高层的冷空气侵入并不明显;在成熟阶段,气压场上也没有明显的雷暴高压,但有明显正变压;本次飑线过程是发生在暖湿的环境条件下,后侧入流为相对湿度较大的东南急流,雨水蒸发并没有西风带飑线强烈;雷达速度图上虽有MARC特征但最大正负速度差值并不是很大(15~27 m/s)。上述特征可能是该台前飑线过境湖南过程中没有造成极端大风的主要原因之一。     

An analysis of extreme intraseasonal rainfall events during January–March 2010 over eastern China

The precipitation over eastern China during January–March 2010 exhibited a marked intraseasonal oscillation (ISO) and a dominant period of 10-60 days. There were two active intraseasonal rainfall periods. The physical mechanisms responsible for the onset of the two rainfall events were investigated using ERA-interim data. In the first ISO event, anomalous ascending motion was triggered by vertically integrated (1000–300 hPa) warm temperature advection. In addition to southerly anomalies on the intraseasonal (10–60-day) timescale, synoptic-scale southeasterly winds helped advect warm air from the South China Sea and western Pacific into the rainfall region. In the second ISO event, anomalous convection was triggered by a convectively unstable stratification, which was caused primarily by anomalous moisture advection in the lower troposphere (1000–850 hPa) from the Bay of Bengal and the Indo-China Peninsula. Both the intraseasonal and the synoptic winds contributed to the anomalous moisture advection. Therefore, the winter intraseasonal rainfall events over East Asia in winter could be affected not only by intraseasonal activities but also by higher frequency disturbances.     

层化对东海大陆架潮流垂向结构的影响

利用ADCP对东海大陆架定点(26°30.052′N,122°35.998′E)连续观测6个多月的海流数据进行分析研究,结果表明:层化对该海域潮流的垂向结构有显著影响,层化导致潮流流速、潮流椭圆长轴、椭圆率和倾角在通过密度跃层时发生较大改变。9月份,东海大陆架存在较强的密度跃层,层化加强,海流流速、M2分潮潮流倾角和M2分潮潮流椭圆率在跃层深度以浅随深度显著增大,跃层处达最大,跃层以深随深度迅速减小;2月份,上层海洋混合较强,密度跃层强度最弱,潮流流速、潮流椭圆长轴、椭圆率和倾角在垂向上变化不大。     

多目标渔业资源科学调查的分层方案设计优化

渔业资源科学调查常用于收集高质量的生物学和生态学数据以进行渔业资源评估与管理。渔业资源调查设计优化十分必要,其有助于在经济有效的采样努力量下提高调查估计量的精度。对于估计单鱼种资源量指数和物种多样性指数为主的多目标渔业资源调查设计,本研究应用模拟方法评价和优化了分层随机采样设计的分层方案。在不同月份,对于不同调查目标,分别比较了不同分层方案设计的表现。对于大多数指标,与简单随机采样设计相比,分层方案设计可以提高调查估计量的精度。目前采用的具有5层的分层随机采样设计表现最好。通过分层方案设计可以补偿由于采样努力量降低造成的估计量精度的下降,采样努力量的减少有助于降低调查成本、减轻调查拖网对于种群数量较低鱼种的不利影响。本研究表明对于不同的调查目标,最优化的分层方案设计不同。调查后分析有助于改善渔业资源调查的分层方案设计。     

2020年“1·24”广西大范围冰雹天气过程分析

2020年1月24-25日,广西出现近20年来范围最大的一次冰雹天气过程。利用常规观测资料、雷达、卫星以及再分析资料,对此次天气过程进行分析和诊断。结果表明:(1)500hPa宽槽、高空急流、低层切变、地面冷锋以及辐合线相配合提供有利环流背景,异常偏冷的中层导致大温度直减率,大气不稳定增强;(2)深层强垂直风切变、热力不稳定层结以及适宜的0℃、-20℃层高度为冰雹产生提供适宜的热动力条件;(3)对流云团呈“长椭圆”型,具有造成区域性冰雹天气的典型特征,雷达回波图上的回波悬垂结构、超过60dBz的强反射率因子、VIL跃增、持久深厚中气旋以及高层辐散低层辐合等特征,对于冰雹天气的识别和预警具有指示意义。     

三峡库区望霞危岩体孕灾地质环境条件分析

危岩体是一种典型的灾害地质体,其形成、变形与破坏受控于地质环境条件,地质基础要素在孕灾的过程中起着决定性作用,各基本地质要素与灾害形成的关系是研究危岩体变形规律和破坏机理的关键性问题。通过对三峡库区望霞危岩体区域地质构造作用分析,横石溪背斜构造解析,各类地质结构面发育特征统计和危岩体岩性组合方式及工程地质条件剖析,结合危岩体两次变形破坏过程,分析各因素对危岩体的形成及变形的关系。研究认为:孕育望霞危岩体的横石溪背斜雏形形成于印支期的隆升阶段,至燕山主期形成褶皱主体,后期则以继承性改造为主,危岩体的形成及孕育主要集中在背斜核部区域,枢纽位置尤为发育。控制危岩体变形的5条关键裂缝与顶部发育的"V"字形裂缝关系密切,其是在纵弯褶皱作用下背斜顶部脆性岩层受到强烈的拉裂影响,叠加台阶式层间滑动作用,形成与轴面近于平行的拉张裂缝。在望霞危岩体中发育多组地质结构面,其中原生结构面对各条关键裂缝及关键块体提供基础背景值,控制其规模、范围及变形强度。控制着变形关键部位特别是前缘软弱层变形位置、牵引区段及强烈程度。构造结构面主要控制关键裂缝的延伸方向、距离及样式,控制关键块体的变形方向,裂解范围及规模,掉块及崩裂位置,控制危岩体底部关键部位即压张裂缝的形成位置、张开度及位移方向。次生结构面主要控制后缘变形区,对各条关键裂缝控制其继承性变形,控制关键块体扩张,对岩体裂解破坏至关重要。同时,望霞危岩体在地层岩性上构成了典型的硬—软—硬岩性组合,为危岩体的变形提供了地质结构组合条件,其底部大面积的采空区控制着危岩体整体滑塌变形。