Snow disaster characteristics in Palongzangbu River Basin and mitigation countermeasures for road engineering

The Palongzangbu River Basin contains the highest number of maritime province glaciers in China.There are 130 glacial lakes,64 snow avalanche sites and 28 glacial debris flow gullies distributed within the basin.Snow disasters play a controlling role in the Sichuan-Tibet Highway construction,due to the terrain's special characteristics of high altitude and large height differential.Segmentation mitigation countermeasures for the Sichuan-Tibet Highway are presented based on snow disaster severity level and damage mode of the road.In the Ranwu to Midui section,snow avalanches are regional disasters, so the line should be placed in sunny slopes.In the Midui Gully to Yupu section,the line should be placed in shady slopes and at higher elevations to reduce the risk of glacial lake outburst.In the Yupu to Guxiang section,all three snow disasters are minimal.In the Guxiang to Tongmai section,glacier debris flows are the major threat,thus the road should be placed in shady slopes.     

南极普里兹湾附近海域表层海流特征分析

利用第29次南极科考期间在普里兹湾海区释放的8个Argos漂流浮标所获的总计662 d的数据,对普里兹湾及其邻近海域的表层海流特征进行了分析,并和以前的研究结果进行对比,结果表明:普里兹湾西部和北部表层海流基本呈现向西的流动,说明此地区的表层海流以沿南极大陆的逆时针沿岸流为主。普里兹湾东部海流呈现先向南再向西或先向南再向北的流动,普里兹湾西北部海流呈现向南的流动。8个浮标平均流速在0.02—0.20 m·s~(-1)之间,最大流速为1.57 m·s~(-1),流速1.0 m·s~(-1)的大流速区主要集中在普里兹湾、克洛斯角外侧、达恩利角外侧海域,流速1.5 m·s~(-1)的大流速区只出现在普里兹湾、克洛斯角外侧两处海域。     

辽河盆地东部凹陷热历史及构造—热演化特征

根据辽河盆地东部凹陷大地热流测量和镜质体反射率数据,恢复了该区的热历史,结果表明:东部凹陷热流呈现古热流高现今热流低的变化特征,沙河街组三段沉积期到东营组沉积期(距今43～25Ma)盆地热流为66～82mWm2,现今热流值为47～70mWm2。构造沉降史分析显示,盆地经历了早期的裂谷阶段(距今43～25Ma)和后期的热沉降阶段,裂谷阶段包含了两个裂谷亚旋回。盆地现今较低的大地热流和较高的古热流及典型的裂谷型构造沉降样式为东部凹陷的构造—热演化提供了重要认识。     

河流生态系统结构功能整体性概念模型

在完善与整合现有河流生态系统结构功能概念及模型的基础上,提出河流生态系统结构功能整体性概念模型。水文情势、水力条件和地貌景观格局是对河流生态系统结构与功能具有关键影响的3大生境要素,结构功能模型的核心是建立以3大生境要素为构架的生命支持系统与河流生命系统之间的相互作用和相互制约关系,同时考虑由于人类活动引起生境要素变化对于河流生态系统的影响。河流生态系统结构功能整体性概念模型由以下4种模型组成:河流四维连续体模型、水文情势-河流生态过程耦合模型、水力条件-生物生活史特征适宜模型以及地貌景观空间异质性-生物群落多样性关联模型,这4种模型的一体化整合,基本概括了河流生态系统结构功能的整体特征。     

The evolution of pore pressure fields around standard and ball penetrometers: influence of penetration rate

Rate effects are examined in the steady pore pressure distribution induced as a result of penetration of standard and ball penetrometers. The incompressible flow field, which develops around the penetrometer is used to define the approximate soil velocity field local to the penetrometer tip. This prescribes the Lagrangian framework for the migration of the fluid saturated porous medium, defining the advection of induced pore pressures relative to the pressure‐monitoring locations present on the probe face. In two separate approaches, different source functions are used to define the undrained pore fluid pressures developed either (i) on the face of the penetrometer or (ii) in the material comprising the failure zone surrounding the penetrometer tip. In the first, the sources applied at the tip face balance the volume of fluid mobilized by the piston displacement of the advancing penetrometer. Alternately, a fluid source distribution is evaluated from plasticity solutions and distributed throughout the tip process zone: for a standard penetrometer, the solution is for the expansion of a spherical cavity, and for the ball penetrometer, the solution is an elastic distribution of stresses conditioned by the limit load embedded within an infinite medium. For the standard penetrometer, the transition from drained to undrained behavior occurs over about two orders of magnitude in penetration rate for pore pressures recorded at the tip (U1) and about two‐and‐a‐half orders of magnitude for the shoulder (U2). This response is strongly influenced by the rigidity of the soil and slightly influenced by the model linking induced total stresses to pore pressures. For the ball penetrometer, the transition from drained to undrained behavior also transits two‐and‐a‐half orders of magnitude in penetration rate, although it is offset to higher dimensionless penetration rates than for standard penetration. Copyright © 2012 John Wiley & Sons, Ltd.     

东江径流年内分配特征及影响因素贡献分解

基于1956~2009年实测径流、天然径流和面降水的月系列,选用集中度和不均匀系数,分析东江径流年内分配特征的时空变异规律。通过对比降水和径流年内分配特征指标的阶段变化差异,量化分解气候变化、土地利用/覆被变化、水利工程水量调节和用水消耗等主要因素对东江径流年内分配特征变化的影响贡献。结果表明:东江实测径流的集中度和不均匀系数年变化过程均有显著下降趋势,且1973年为时序变点。降水及天然径流的年内集中程度阶段变化较小,但2000~2009年降水及天然径流的年内不均匀性要明显大于20世纪80年代和90年代。降水及天然径流的年内集中度和不均匀系数由上游向下游逐渐增大,显示集水面积越大降水及径流的年内集中程度和不均匀性越大。水利工程水量调节和土地利用/覆被变化降低了径流的年内集中程度和不均匀性,而用水消耗和气候变化增加了径流的年内集中程度和不均匀性。水利工程水量调节、土地利用/覆被变化、用水消耗和气候变化,对东江径流分配特征的影响贡献率分别约为-33.5%、-9.0%、4.5%和1.0%,新丰江水库、枫树坝水库和白盆珠水库的影响贡献率分别约为-21%、-10%和-2%,且近30年来土地利用/覆被变化和用水消耗的影响贡献有逐渐增加趋势。     

长江口九段沙下段冲淤演变水动力机制分析

概述了长江口深水航道整治一期工程及工程对九段沙下段地形冲淤的影响.根据已建立的σ坐标系下三维非线性水流数学模型,用新测水文资料对模型进行验证.利用所建立的模型,结合由现场测量得到一期工程前后九段沙下段近期地形演变,数值模拟了北槽区域流通量、底层欧拉余流和北槽中下段平面水流特征,以综合分析北槽水域水动力变化对九段沙下段地形冲淤变化的影响.     

贵州都匀马达岭地质灾害链的自动化监测

贵州省都匀市马达岭地灾体自2003年起间歇发生小规模崩塌,2006年5月18日持续降雨诱发大规模滑坡。崩滑体产生的碎屑流被采空区内蓄积的老窑水卷携并铲刮沟道残坡积物冲向下游形成泥石流。该地质灾害由崩塌、滑坡以及次生泥石流所组成,呈现连锁反应,形成了崩滑流灾害链。以贵州省马达岭地质灾害链为研究对象,基于现场地质环境条件调研和地质灾害链发育规律研究,确定以雨量、相对位移、倾角、渗压水头、泥位、次声为监测指标,在崩滑体后缘和泥石流沟口部位分别布置了相应的自动化监测仪器,形成了集自动采集、无线传输、数据解析、分析决策和预警预报为一体的地质灾害链自动化监测系统。监测系统运行状况显示,该监测系统能够较好地反映该地质灾害链的变形特征,可为该地质灾害链的预警预报提供技术支撑。     

不同墙体位移方式下被动土压力的颗粒流模拟

用二维颗粒流程序（PFC2D）对各种移动模式的刚性挡墙被动土压力进行了模拟。再根据已有的模型试验建立颗粒流模型,分别让刚性墙体朝土体一侧平移、绕墙体顶部转动和绕墙体底部转动,给出了这三种情况下墙后被动土压力的分布图形以及相应的竖向应力的分布图形,同时给出了墙后被动土压力随墙体位移的变化规律。最后,将计算结果与实验结果进行了对比表明,颗粒流数值模拟方法不仅使用方便,而且能较好地模拟墙后被动土压力的分布规律。