Experimental study of extreme shear stress for shallow flow under simulated rainfall

The raindrop impact and overland flow are two major factors causing soil detachment and particle transportation. In this study, the turbulent characteristics of the shallow rain‐impacted water flow were investigated using a 2‐D fibre‐optic laser Doppler velocimetry (FLDV) and an artificial rainfall simulator. The fluctuating turbulent shear stress was computed using digital data processing techniques. The experimental data showed that the Reynolds shear stress follows a probability distribution with heavy tails. The tail probability increases with an increase of rainfall intensity or raindrop diameter, and it decreases with an increase of Reynolds number. A modified empirical equation was derived using both the raindrop diameter and rainfall intensity as independent variables to provide a better prediction of the Darcy‐Weisbach friction coefficient f under rainfall conditions. Copyright © 2009 John Wiley & Sons, Ltd.     

A multi-gene genetic programming model for estimating stress-dependent soil water retention curves

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.     

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.     

Simulation of Tsaoling landslide, Taiwan, based on Saint Venant equations over general topography

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, SHALTOP^2D, 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.     

临汾地震台垂直摆倾斜观测资料阶变异常分析

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。     

浅析有色金属浮选尾矿排放工艺与选矿生产用水重复利用率的关系

随着有色金属采选建设项目的增加,选矿生产的耗水量日渐为公众及管理部门所关注,在整个生产过程中,除精矿粉中会带走精矿重量约10%的水分外,绝大部分排放水是尾矿矿浆经输送至尾矿库澄清后排出的。因此从环境保护及提高水的利用率角度考虑,选矿废水应回用,而尾矿的排放方式又对生产用水回用率有着很大的影响。     

The tunnel seismic advance prediction method with wide illumination and a high signal-to-noise ratio

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.     

山东岚山I型与A型复合片麻状变质花岗岩：年代学、地球化学及其构造指示意义

在山东日照岚山地区,出露有原岩为新元古代岩浆活动产物的I型与A型复合的片麻状变质花岗岩体,前者特征矿物组合为石英+钾长石+斜长石+黑云母,而后者则为石英+钾长石+斜长石+霓石+亚铁钠闪石+黑云母。锆石LA-ICP-MS U-Pb定年结果表明,I型片麻状变质花岗岩的原岩成岩年龄为795±32Ma,而A型片麻状变质花岗岩的原岩年龄则为772±26Ma,二者均经历了早中生代的超高压变质作用,并在220Ma左右遭受强烈的角闪岩相退变质作用的改造。地球化学上,I型和A型片麻状变质花岗岩均具有高硅、富铁和贫镁的特征,但A型片麻状变质花岗岩更富碱贫铝,其铝饱和指数仅为0.88~0.94,表现为准铝质,而I型片麻状变质花岗岩则具有准铝-弱过铝的特点（A/CNK=0.94~1.01）。在微量和稀土元素方面,A型片麻状变质花岗岩较I型稀土总量高,且具有高场强元素富集的特征,富Ga,10⁴×Ga/Al值为2.77~3.89。二类片麻状变质花岗岩具有不同的Nd同位素组成,ε_Nd (t)值分别为-6.26 ~ -8.00和-3.73 ~ -5.20,指示它们应具不同的岩浆源区,元素结晶分异模拟显示二者岩浆演化的历程也存在差异。岚山片麻状变质花岗岩叠加有"弧"和"裂谷"双重岩浆活动的地球化学印记,它们与由地幔柱上隆所引发的主动裂谷背景下岩浆作用产物的特征存在明显差别。I型与A型复合片麻状变质花岗岩的产出指示扬子板块北东缘在片麻状变质花岗岩原岩形成时（795~770Ma）应处于弧后伸展引发的被动裂谷环境的初始阶段。     

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

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.     

基于粘弹性球体地球模型的震后位移与重力变化计算软件

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。