水文站水准基面关系分析   总被引：3，自引：3，他引：0  

刘琦  王峰  周珂  周宜富 《水文》2012,32(3):20-28

本文定义了基面关系式的概念,提出了基面与基本水准点考证的原则,分析了十六类基面关系式的计算方法,通过研究得出结论:基本水准点变动,冻结高程变动,基本水准点不变,冻结高程不变;绝对基面变化国冻差变化,绝对基面不变国冻差不变;冻结高程及国冻差有一项变动标准高程变动,冻结高程及国冻差都不变动标准高程不变。  相似文献   

物探方法在隧洞超前探测中的应用     

肖宽怀 《物探与化探》2012,(5):874-877

在云南厂口隧洞工程施工中,根据不同地质问题,采用高密度电法、洞地间地震波CT和超前预报三种物探方法进行探测,探测结果均对地质灾害有较明确的反映,说明作为基本技术手段的物探方法在隧洞超前探测中能发挥重要作用。  相似文献   

Mechanisms for avulsion on alluvial fans: Insights from high-frequency topographic data     

Anya Leenman  Brett Eaton 《地球表面变化过程与地形》2021,46(6):1111-1127

Avulsion is a key process in building alluvial fans, but it is also a formidable natural hazard. Based on laboratory experiments monitored with novel high-frequency photogrammetry, we present a new model for avulsion on widely graded gravel fans. Previous experimental studies of alluvial fans have suggested that avulsion occurs in a periodic autogenic cycle, that is thought to be mediated by the gradient of the fan and fan-channel. However, those studies measured gradients at low spatial or temporal resolutions, which capture temporally or spatially averaged topographic evolution. Here, we present high-resolution (1 mm), high-frequency (1-minute) topographic data and orthophotos from an alluvial fan experiment. Avulsions in the experiment were rapid and, in contrast to some previous experimental studies, avulsion occurrence was aperiodic. Moreover, we found little evidence of the back-filling observed at coarser temporal and spatial resolutions. Our observations suggest that avulsion is disproportionately affected by sediment accumulation in the channel, particularly around larger, less mobile grains. Such in-channel deposition can cause channel shifting that interrupts the autogenic avulsion cycle, so that avulsions are aperiodic and their timing is more difficult to predict.  相似文献   

黄土高原粮食生产空间重构过程中的生态系统服务权衡——以陕北榆林市为例     

杨海娟  孙来玎  周美君  李飞 《干旱区地理》2022,45(1):226-236

粮食生产空间重构集中了土地系统变化的主要矛盾,探索粮食生产空间重构过程中的生态系统服务权衡变化有利于明确粮食安全、生态修复与经济发展之间的矛盾,从而推进区域生态文明建设和高质量发展.采用生态系统服务评估模型及均方根偏差法,对2000—2018年陕北榆林市粮食生产空间重构过程中的固碳、食物供给、土壤保持和产水服务及其权衡...  相似文献   

花岗岩风化土崩岗破坏机理分析   总被引：6，自引：2，他引：4       下载免费PDF全文

颜波  汤连生  胡辉  王大志  林国威 《水文地质工程地质》2009,36(6):68-71

崩岗破坏是红层土中特有的破坏形式,在花岗岩风化土中发育更为强烈,这与花岗岩风化土自身的力学性质有关。本文认为花岗岩风化土自身的结构性、粒间吸力特性决定了其遇水软化和崩解的性质,花岗岩风化土软化主要表现为减压软化和损伤软化,花岗岩风化土颗粒粒径和孔隙大小不均匀性,以至土体在吸水过程中吸力不平衡导致其崩解作用。花岗岩风化土遇水发生软化和崩解是崩岗发生的内因,为崩岗破坏水土流失提供了物质来源,长期的水与重力作用是崩岗发生的外因,为崩岗持续发展提供了动力,在上述内因和外因作用下,最终形成了崩岗地貌。  相似文献   

用于数字地图自动综合的多边形合并算法   总被引：2，自引：0，他引：2  

王辉连  武芳  王宝山  邓红艳 《测绘工程》2005,14(3):15-18

从计算几何出发,实现了能考虑到空间关系和形态要求的一种新的多边形合并算法--"凸包演化"算法,并用于自动综合软伴中,取得了较好的效果.  相似文献   

大气环流模式和耦合模式模拟的降水-海温关系之比较   总被引：9，自引：6，他引：3  

李博  周天军  吴春强 《大气科学》2009,33(5):1071-1086

本文讨论了气候系统耦合模式FGOALS_s模拟的局地降水和海温的关系, 并通过与单独大气模式SAMIL的AMIP试验结果进行对比分析, 考察了海气耦合过程对局地降水和海温关系模拟的影响。结果表明, 耦合模式FGOALS_s和单独大气模式SAMIL在模拟局地降水和海温关系上各有优势。在赤道中东太平洋地区, 观测中局地降水和海温的关系是海洋强迫为主, FGOALS_s模拟的海洋对大气的强迫比观测偏弱, 因此, SAMIL相对于FGOALS_s更有优势。在西北太平洋东部地区, 观测中夏秋季节降水和海温的关系是大气强迫为主, 由于考虑了海气相互作用过程, FGOALS_s对降水和海温关系的模拟能力要优于单独的大气模式。此外, 由于大气模式SAMIL的云参数化方案导致的模拟偏差, 在赤道中东太平洋地区 (9～11月), 降水增加时入射的短波辐射通量也是增加的, 并且这种模拟的偏差在耦合后仍然保留了下来, 导致了与观测不符的云[CD*2]辐射反馈过程。因此, 改进大气模式的云参数化方案是未来工作重点之一。此外, 分析发现耦合模式模拟的潜热通量的变化过分依赖海气湿度差。  相似文献   

Cyclic Swell–Shrink Behaviour of a Compacted Expansive Soil     

Snehasis Tripathy  Kanakapura S. Subba Rao 《Geotechnical and Geological Engineering》2009,27(1):89-103

Laboratory cyclic swell–shrink tests were carried out on compacted expansive soil specimens to study in detail the effect of changes in shrinkage pattern on the swell–shrink behaviour of compacted expansive soils. Compacted soil specimens were allowed to swell and either shrank fully or partially shrank to several predetermined heights in each cycle. The tests were carried out at a surcharge pressure of 50 kPa. The test results revealed that shrinkage of compacted saturated soil specimens to predetermined height in each shrinkage cycle provides similar conditions as that of the controlled suction tests with an increasing number of swell–shrink cycles. The water content of soil specimens and hence soil suction was found to remain nearly constant for each pattern of shrinkage. For soil specimens equilibrated to a given swell–shrink pattern, suction at the end of shrinkage cycles was changed from a higher suction to a lower suction, and also from a lower to a higher suction. The experimental results showed that there may be an immediate equilibrium state attained by the soil in terms of swell–shrink potential if suction at the shrinkage cycles was less than the past suction; otherwise, the equilibrium state was accompanied by fatigue of swelling. The volumetric deformation of the soil specimen subjected greater shrinkage was found to be much larger than the corresponding vertical deformation. The compressibility index of microstructure, κ_m, was determined for several shrinkage patterns. It is shown that κ_m is heavily influenced by suction at the end of shrinkage cycles.  相似文献   

高武地区过铝花岗岩特征与构造环境   总被引：3，自引：1，他引：2  

舒永宽  杨宏辉  曾昭光  刘灵  李吉春 《贵州地质》2004,21(1):16-23

高武地区的过铝花岗岩主要为二长花岗岩及正长花岗岩,山德指数ALI>1 1,标准矿物刚玉分子(c)普遍>3,出现石榴石、原生白云母矿物组合,δ18O‰>10、87Sr/86Sr>0 707,属典型的S型过铝花岗岩。形成的高峰期为新元古代早中期(819-825Ma),是与Rodinia超大陆裂解背景有关的拉张构造环境的产物,而非形成于挤压构造体制。  相似文献   

Basin Structure and Numerical Simulation for the Mechanisms of Seismic Disasters     

ZHAO Zhixin  XU Jiren Institute of Geology  Chinese Academy of Geological Sciences  Beijing 《《地质学报》英文版》2004,78(4):954-959

In the present study seismic wave propagation in heterogeneous media is numerically simulated by using the pseudospectral method with the staggered grid RFFT differentiation in order to clarify the cause for the complicated distribution characteristics of strong ground motion in regions with basin structure. The results show that the maximum amplitudes of simulated ground acceleration waveforms are closely related to the basin structure. Interference of seismic waves in the basin strongly affects the distribution of maximum seismic waveforms, which may result in peak disasters during earthquakes. Peak disasters might be away from basin boundaries or earthquake faults. Seismic energy transmitted into the basin from the bedrock can hardly penetrate the bottom of the basin and then travel back into the bedrock region. The seismic energy is absorbed by basin media, and transferred into the kinematical energy of seismic waves with great amplitude in the basin. Seismic waves between basins may result in seriou  相似文献