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排序方式: 共有231条查询结果,搜索用时 15 毫秒
21.
A multi-gene genetic programming model for estimating stress-dependent soil water retention curves 总被引:1,自引:0,他引:1
Soil water retention curve (SWRC) is an important parameter required for seepage modelling in unsaturated soil and is used for analysing rainfall-induced slope failures, design of waste contaminant liners and cover, etc. The influence of stress, which is one of constitutive variables that governs unsaturated soil behaviour on the SWRC, has been well recognised by researchers. Stress is essential for study as it drastically alters the soil fabric which includes macropores, minipores and micropores and thus affects the ability of soil to retain water. Various computational modelling techniques that formulate models based on existing databases such as UNSODA, ISRIC and HYPRES for the estimation of SWRC do not take into account the stress influence on soil behaviour. In the present work, three artificial intelligence (AI) methods of support vector regression, artificial neural network and multi-gene genetic programming (MGGP) have been applied to formulate the mathematical relationship between the water content and input variables such as stress and suction (i.e. stress-dependent soil water characteristic curves (SDSWRCs)). The results indicate that the MGGP model outperforms the other two models and is able to extrapolate the water content values satisfactorily along the stress value of 800 kPa. This MGGP model can then be deployed by experts for the estimation of SDSWRCs, thus eliminating the need for conducting costly and time-consuming experiments. 相似文献
22.
Tai Ho Choo Soo Kwon Chae Hyeon Cheol Yoon Yeon Moon Choo 《Environmental Earth Sciences》2014,71(2):675-683
Discharge is an important factor in river design for water utilization, water control and hydraulic structures; therefore, an accurate estimation of the discharge is required. At present, a rating curve depicting the relationship between a stage and discharge is used to calculate the discharge from river systems. Although the rating curve has an advantage in that it can predict and use the discharge during the flood season in which the measurement is difficult, there is room for improvement as it does not reflect the hydraulic characteristics of rivers. Therefore, in this study, discharge was predicted using the convenient calculation method with empirical mediating variables of the Manning and Chezy equations which were proposed by the author’s previous research as a new methodology for estimating discharge in an open channel. This was proven, based on the data measured in a meandering open channel system in a lab at the Mississippi River in the US and at the Columbia Del Dique Canal, and an accuracy level at a coefficient of 0.8 was demonstrated. Thus, this method, which reflects the hydraulic characteristics and predicts the discharge in a simple manner, is expected to be convenient in practice. 相似文献
23.
Evolution of scouring process downstream of grade‐control structures under steady and unsteady flows
For many incised channels, one of the most common strategies is to install some hard structures, such as grade‐control structures (GCSs), in the riverbed to resist further incision. In this study, a series of experiments, including both steady and unsteady flow conditions, were conducted to investigate the scouring process downstream of a GCS. Three distinct phases, including the initial, developing and equilibrium phases, during the evolution of scour holes were identified. In addition, a semi‐empirical method was proposed to predict the equilibrium scour‐hole profile for the scour countermeasure design. In general, the comparisons between the experimental and simulated results are reasonably consistent. As the studies on temporal variation of the scour depth at GCSs caused by floods are limited, the effect of flood hydrograph shapes on the scour downstream of GCSs without upstream sediment supply was also investigated experimentally in this study. Based on the dimensional analysis and the concept of superposition, a methodology is proposed to simulate the time evolution of the maximum scour depth downstream of a GCS for steady flows. Moreover, the proposed scheme predicts reasonably well the temporal variations of the maximum scour depth for unsteady flows with both single and multiple peak. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
24.
C.Y. Kuo Y.C. Tai F. Bouchut A. Mangeney M. Pelanti R.F. Chen K.J. Chang 《Engineering Geology》2009,104(3-4):181-189
The 1999 Chi-Chi earthquake triggered the catastrophic Tsaoling landslide in Taiwan. The geomorphological change measured from the data of the 1989 and 2000 aerial photos reveals that the scar and deposit volumes are about 0.126 km3 and 0.15 km3 respectively. The debris material ran over a distance of 1.6 km with 500 m descent in elevation. In this paper, we use the continuum model of hydraulic flow, SHALTOP2D, based on the equations of Bouchut and Westdickenberg to simulate numerically the landslide dynamics. When the mass is moving, the flow is assumed hydrostatic with a basal Coulomb friction. The best fit is obtained using the basal friction angle equal to 6°, the only parameter of the simulation, uniformly applied in the calculation domain. The landslide front reaches the Chinshui river valley, the foothill of the slope, within only about 25 s after initiation and the motion settles in about 113 s. The maximum speed is estimated 75 m/s. The spreading of the deposit agrees well with the field measurement. 相似文献
25.
对临汾地震台垂直摆倾斜观测资料中记录到的阶变型异常图像进行分析,对异常成因进行探讨,希望对观测数据异常判断、数据预处理及地震预测预报的应用研究,提供一定参考。 相似文献
26.
27.
The tunnel seismic advance prediction method with wide illumination and a high signal-to-noise ratio
Xinglin Lu Xian Liao Yao Wang Guimei Wang Zhihong Fu HengMing Tai 《Geophysical Prospecting》2020,68(8):2444-2458
Tunnel seismic prediction is widely used in the field of tunnel seismic advance detection. The illumination of the target and the signal-to-noise ratio of the data are two key factors affecting the precision of data interpretation. Current seismic prospecting has shortcomings on sites: (1) The lighting shots are solely towards one side of the tunnel wall, (2) the geophones are placed far away from the tunnel face and (3) the surface waves from the tunnel wall dominate over the reflection waves, lowering the signal-to-noise ratio of the data at the tunnel wall. This paper proposes a tunnel symmetrical geometry to tackle the above challenges. The arrangement is to place 12 sources uniformly on each side of the tunnel wall and six geophones on the tunnel wall and face. Results of simulated data and measured data show that the proposed method enables (1) broad illumination of the target body, (2) the enhancement of illumination energy of the target body, and (3) higher data signal-to-noise ratio. The proposed symmetrical geometry method provides better interpretation in terms of broader coverage, higher quality and greater distance of investigation. 相似文献
28.
黄东海是太平洋重要的边缘海,拥有丰富的海洋生物多样性资源,但在气候变化及人类活动的双重胁迫下,黄东海面临生物多样性衰退等问题,亟需加强保护。保护区网络被认为可有效防止或减缓人类活动和气候变化对生物多样性的负面影响,但连通性作为保护区网络的重要参数却很难直接测量。因此,本研究希望通过梳理已发表的黄东海间遗传连通性文献来揭示黄东海区域内的保护区是否形成网络。通过搜集已发表的137篇文献,共获得175个研究案例。超过半数的案例(65.71%)认为黄东海之间具有显著的遗传分化,这也意味着跨生态区群体间具有较低的遗传连通性。在总结影响因素时发现长江冲淡水、生境异质性、空间距离、进化过程、生活史(较短的浮游幼体期)、洋流等6个因素阻碍了黄东海群体间的遗传连通性,而洋流、生活史(较长的浮游幼体期)等2个因素促进了遗传连通性。进一步分析发现黄东海群体间的遗传连通性与空间距离呈显著的负相关,而与浮游幼体期呈正相关。因此,根据本研究结果,建议未来保护区网络建设应针对黄、东海生态区分别构建网络,在网络设计时应考虑保护对象的扩散能力及保护区间的空间距离。本研究不仅为构建涵盖黄东海的海洋保护区网络提供理论基础,... 相似文献
29.
最近13万年以来洛川黄土剖面中固定铵态氮的古气候意义 总被引:1,自引:1,他引:0
对13万年以来洛川黄土-古土壤序列中固定铵态氮进行了分析.末次间冰期S1古土壤中固定铵态氮含量最高,其次为冰后期S0古土壤,末次冰期形成的马兰黄土最低;而且,固定铵态氮的分布在马兰黄土中也能体现出三次小的低-高值的波动特征.洛川黄土13万年以来固定铵态氮的分布与磁化率和<2μm组分的分布相似.在此基础上,利用马兰黄土中粒度与固定铵态氮的相关关系,计算了S1古土壤中固定铵的分布,并与实测结果进行了对比,推测S1古土壤中固定铵态氮有轻微的损失,尽管如此,S1古土壤中固定铵态氮含量仍然高于黄土.鉴于黄土-古土壤序列中固定铵态氮的分布与粉尘粒度有密切的关系,能与气候变化较好地对应,它可视为反映黄土高原区东亚冬季风强-弱周期性变化较好的替代性指标. 相似文献
30.
在考虑地球曲率、成层结构、可压缩性与自重的前提下,Tanaka等[1-2]提出一套较为完备的粘弹性球体位错理论,可计算全球任意位置由地震产生的同震与震后形变(含位移、重力变化、大地水准面变化)。Gao等[3]给出了与上述理论相匹配、界面友好的计算软件,能计算30个震后时间点对应的震后形变。本研究针对Gao等的软件进行改进,可计算震后任意时间点对应的震后形变。新软件由3个部分组成:1)与32个震后时间点相对应的32套离散格林函数数值框架;2)格林函数插值计算程序,可针对上述32套格林函数数值框架进行插值运算,输出任意震后时间点对应的格林函数数值结果;3)积分计算程序,调用上述格林函数数值结果,计算任意类型地震在地表任意位置产生的同震与震后形变。一般情况下,使用者只需按要求准备辅助文件,提供发震断层模型和观测站位置信息,以及震中周围地区地幔粘滞性因子,先后运行格林函数插值计算程序和积分计算程序,即可计算出目标地震在地表任意位置产生的同震与震后形变。本文基于粘弹球体位错理论与弹性球体位错理论,分别计算2011年日本MW9.0地震引起的远场同震位移,2套结果的高度一致性证明了新程序的正确性。最后,介绍需要注意的若干事项,便于使用者掌握该软件。 相似文献