山地冰川流动模型探讨

近30 a来冰川动力学模型有了快速发展, 在南极、 格林兰冰盖预测中取得一系列重要成果, 对山地冰川的研究也初见端倪. 从冰川流动的力学过程出发, 利用本构方程、 理想冰川假设、 浅冰层近似(Shallow ice approximation)假设完整地推导了理想冰川流动的物理过程, 揭示了冰川流动的机理, 建立了气候变化和冰川自身重力引起的理想冰川物质和能量再分配的温度耦合三维流动模型. 结合山地冰川的冰床形态, 将理想冰川与实际冰川相结合, 使理想冰川流动模型更好地近似山地冰川的流动.     

线性工程建设对地下水流场的影响分析

出于降低高速公路坡度的目的, 团结桥连接线高速公路路基开挖在Ⅱ级阶地前缘处排水盲沟最大开挖段基本将原来连续的天然含水层切穿, 导致地下水排泄基准面下降, 使得地下水流场发生改变, 部分民井出现水位下降或干涸现象. 得出路基开挖排水是导致工程区附近地下水含水层结构及流场改变、 水位下降或局部疏干的主要原因.     

Early subduction–exhumation and late channel flow of the Greater Himalayan Sequence: implications from the Yadong section in the eastern Himalaya

Based on metamorphic studies of the Yadong high-pressure (HP) granulite and multiple thermochronological investigations of granitoids from both upper and lower parts, the Yadong section in the eastern Himalaya constrains the Cenozoic tectonic evolution of the Greater Himalayan Sequence (GHS). The Yadong HP granulite, located at the top of the GHS, underwent a peak-stage HP granulite facies metamorphism and two stages of retrograde metamorphism. Granulite and hornblende facies retrograde metamorphism took place at 48.5 and 31.8 Ma, respectively, marking the time of exhumation of the subducted Indian slab to lower and middle crustal levels. Subsequently, an average young zircon U–Pb age obtained from the Yadong HP granulite indicated that this unit was captured by its surroundings in a partially molten condition at 16.9 Ma. In addition, three granitoids from both the lower and the upper parts of the GHS yielded biotite ⁴⁰Ar/³⁹Ar ages of 11.0, 11.3, and 11.5 million years. These consistent ages suggest that the GHS along the Yadong section was laterally extruded and synchronously cooled to ～300°C at ～11.3 Ma. Furthermore, the granitic gneisses yield apatite fission track ages of ～7 million years, documenting the cooling of the GHS to ～110°C. A two-stage model describes the Cenozoic tectonic evolution of the GHS: (1) the Indian slab had subducted under Tibet before ～55 Ma, and was exhumed to the lower crust (50-40 km) at 48.5 Ma, and to the middle crust (22-15 km) at 31.8 Ma; and (2) the partial melting occurred at middle crustal levels during the period 31.8 to 16.9 Ma, causing channel flow. In the late stage, the GHS was laterally extruded by ductile mid-crustal flow during the period 16.9 to ～7 Ma, characterized by a fast cooling rate of ～2 mm per year.     

汶川震区暴雨泥石流激发雨量特征

利用搜集的汶川震区典型泥石流暴发前后的降雨过程资料,分析了泥石流的激发雨量过程,获得了汶川震区的泥石流激发雨量特征,以期为泥石流的预测预报提供依据。结果表明,汶川地震区的泥石流激发雨型可分为快速激发型、中速激发型和慢速激发型3类,其差异主要体现在降雨的持续时间和强度方面。不同激发雨型下的泥石流形成过程的差别主要体现在松散土体饱和过程。雨型的差异(降雨的持续时间和强度)使得土体饱和产生超渗产流的时间出现差异,进而使得泥石流暴发的时间存在差异。激发雨强跟激发雨型存在一定的关系,激发雨强最大者为中速激发雨型,其次是慢速激发雨型,最小者为快速激发雨型。与地震之前相比,地震后的泥石流暴发时的累积雨量和临界雨量都有所降低。     

宁夏短期天气预报业务流程

介绍了以宁夏ＭＯＳ预报结果为基本指导产品、结合宁夏气象业务具体情况、通过二次开发建立在微机上的新型短期天气预报业务流程。该流程的建立,使宁夏短期天气预报人员基本摆脱了传统的纸上作业而转向新型的计算机预报平台,使宁夏短期天气预报的自动化水平上了一个新台阶。     

考虑Hansbo渗流的二维Biot固结有限元分析

为进一步深入研究弹性饱和黏性土地基的二维固结机制,引入Hansbo渗流方程描述固结过程中的非达西渗流,修正Biot二维固结方程。基于加权残数法,给出相应的有限元数值求解格式。通过和饱和黏性土一维非达西渗流固结理论有限体积法数值结果的对比,证明数值计算方法的有效性。在此基础上,探讨Hansbo渗流参数对二维地基固结进程的影响。计算结果表明,在固结初期,Hansbo渗流将增强Mandel-Cryer效应,增大孔压的峰值,并延长孔隙水压力达到峰值的时间;在固结中后期,整个土层存在孔隙水压力滞后现象。同时,Hansbo渗流将阻碍地基沉降的发展。而且,上述影响会随着Hansbo渗流参数的增大而更加明显。     

南海南部陆缘地质流体类型及其油气成藏意义

南海南部陆缘蕴藏着非常丰富的油气资源。为了解南海南部陆缘流体活动系统以及与油气藏之间的关系,以高精度2D地震资料为基础,对南海南部陆缘流体活动系统的类型、地震反射特征、以及对油气成藏的意义开展了研究。在南海南部陆缘发现了多种流体活动系统,包括:泥底辟/泥火山、气烟囱、管状通道、与构造断层相关的流体活动系统。这些流体活动系统具有不同的地震反射特征,常常出现含气强振幅异常带、弱振幅杂乱反射带以及\"下拉\"或者\"上拱\"地震反射形态等流体活动系统的标志特征。流体活动系统受到构造运动和沉积因素的影响,并且与深部高温高压塑性流体密切相关,流体活动系统优先发育在地层薄弱部位。流体活动系统及所伴生的断裂和裂隙常常作为油气富集区的运输通道;并且流体活动系统所运移的强溶蚀性流体和深部热液流体有利于油气储层的形成,特别是对于碳酸盐岩储层的改造尤为明显。因此,流体活动系统不仅能作为油气运移通道,也可以改善储层,对油气成藏具有重要意义。     

岩石单轴压缩下能量与损伤演化规律研究

能量变化是材料各参数变化的本质特征。通过颗粒流模拟岩石单轴压缩试验,从细观力学角度分析能量转化、裂纹扩展及损伤演化规律。颗粒流利用细观颗粒的运动克服了宏观力学理论不易实现试件多裂纹破坏形态的缺点,以此研究能量变化更加合理。应力-应变各阶段能量与微裂纹及损伤存在着相互对应的发展关系。通过3种工况论证了宏-细观力学参数对应关系,采用最小二乘法拟合得出微裂纹与轴向应变呈幂次函数关系。采用割线模量定义损伤变量,取模量加速下降处（对应裂纹加速扩展）为损伤门槛,对应损伤阈值为0.158。3种工况下微裂纹数量与损伤呈线性发展关系,为损伤演化的深入研究提供参考。     

甘肃舟曲三眼峪沟泥石流的形成条件与发展趋势

2010年8月8日,舟曲县城北侧三眼峪沟和罗家峪沟暴发的特大山洪泥石流,给舟曲县城人民生命财产造成了巨大损失。本文基于现场调查,分析了三眼峪沟泥石流的形成条件和未来泥石流的发展趋势。调查发现,独特的地形条件、极其丰富的固体物质储备和极端降雨条件,导致了"8.8"特大泥石流灾害。崩塌堆积体是三眼峪沟泥石流固体物质的最主要来源,受"8.8"泥石流的影响,沟内堆积物的稳定性进一步降低,一旦有强降雨发生,该沟很可能再次发生泥石流,并且泥石流的规模和活动性可能进一步增强。     

Dynamics of fluvial and slope processes in the changing geomorphic environment of singapore

The nature and rates of fluvial and slope processes change over time and space as urbanized areas replace forested land in Singapore. Storm-based and time-based data, from undisturbed rainforests, heavily disturbed construction sites, urban grass-covered slopes and an experimental plot, are collected to observe the impact of rainwater on the soil moisture conditions, surface microtopography, runoff generation, sediment movement, and ground lowering in the three different categories of land use. The undisturbed forested environment is characterized by high throughfall (58% of total rainfall) and frequent negative soil moisture suctions. The slow and unconcentrated overland flow during heavy storms is restricted by the forest floor microtopography. No rills develop. Ground lowering is recorded as 3·2–3·4 mm a^?1. But sediment movement is episodic and suspended sediment concentrations in overland flow are 172–222 mg l^?1. During urban construction, gully development is rapid on the bare slopes, runoff generation, voluminous, and sediment-laden discharges (5200–75498 mg l^?1) lead to sediment plumes at channel mouths. Ground lowering rates are measured at 132·4 mm a^?1. Once grass-covered, runoff carries less suspended sediment (800 mg l^?1) and ground lowering rates are reduced, but depend on the condition of the cover, ranging from 0·2 to 8·2 mm a^?1. As urban development continues, environments are altered both in time as well as spatially.