A smoothed particle hydrodynamics modelling of soil–water mixing and resulting changes in average strength

Soil–water interaction is a pivotal process in many underwater geohazards such as underwater landslides where soil sediments gradually evolve into turbidity currents after interactions with ambient water. Due to the large deformations, multiphase interactions and phase changes this involves, investigations from numerical modelling of the transition process have been limited so far. This study explores a simple numerical replication of such soil–water mixing with respect to changes in average strength using smoothed particle hydrodynamics (SPH). A uniform viscoplastic model is used for both the solid-like and fluid-like SPH particles. The proposed numerical solution scheme is verified by single-phase dam break tests and multiphase simple shear tests. SPH combinations of solid-like and fluid-like particles can replicate the clay–water mixture as long as the liquidity index of the solid-like particles is larger than unity. The proposed numerical scheme is shown to capture key features of an underwater landslide such as hydroplaning, water entrainment and wave generation and thus shows promise as a tool to simulate the whole process of subaquatic geohazards involving solid–fluid transition during mass transport.     

Dynamic propagation criteria for catastrophic failure in planar landslides

Quantitative assessment of the risk of submarine landslides is an essential part of the design process for offshore oil and gas developments in deep water, beyond the continental shelf. Landslides may be triggered by a reduction in shear strength of subsea sediments over a given zone, caused for example by seismic activity. Simple criteria are then needed to identify critical conditions whereby the zone of weakness could grow catastrophically to cause a landslide. A number of such criteria have been developed over the last decade, based either on ideas drawn from fracture mechanics, or considering the equilibrium of the initial weakened zone and adjacent process zones of gradually softening material. Accounting for the history of the weak zone initiation is critical for derivation of reliable propagation criteria, in particular considering dynamic effects arising from accumulating kinetic energy of the failing material, which will allow the failure to propagate from a smaller initial zone of weakened sediments. Criteria are developed here for planar conditions, taking full account of such dynamic effects, which are shown to be capable of reducing the critical length of the softened zone by 20% or more compared with criteria based on static conditions. A numerical approach is used to solve the governing dynamic equations for the sliding material, the results from which justify assumptions that allow analytical criteria to be developed for the case where the initial softening occurs instantaneously. The effect of more gradual softening is also explored. Copyright © 2016 John Wiley & Sons, Ltd.     

基于贝塞尔曲线法线的太阳圆心求取方法

针对测日定向中获取的残缺不完整太阳图像难以确定其圆心的问题,本文提出了一种新的基于贝塞尔曲线法线的太阳圆心求取方法.该方法通过将图像上太阳的轮廓信息还原成贝塞尔曲线,利用轮廓点筛选由贝塞尔曲线的多个法线交点计算得来的圆心和半径,来确定太阳圆心的精确位置.实验结果表明该方法在太阳完整或残缺的情况下,均能精确可靠地求取太阳圆心.     

基于主成分分析和因子分析的宁夏水资源承载力研究

为了探求宁夏水资源承载力状况,利用主成分分析法和因子分析法,在分析宁夏2004~2014年水资源承载力状况的基础上,对宁夏5市2013年水资源承载力分水资源支持力、社会经济技术水平和社会生活水平3个方面进行综合考虑,得到宁夏5市的水资源利用状况指数和分级标准。具体得到以下几个结论:(1)2004~2014年间,宁夏水资源承载力仅在2005~2006年有所波动,其余年份两种方法结果一致,11年间保持稳定上升;(2)对于宁夏5市2013年水资源承载力状况,主成分分析结果由大到小排序为吴忠市、银川市、石嘴山市、固原市和中卫市,因子分析结果由大到小排序为吴忠市、银川市、固原市、石嘴山市和中卫市;(3)建立宁夏5市水资源承载力状况分级阈值,主成分分析下吴忠市和银川市的水资源利用状况高,石嘴山市的水资源利用状况中等,固原市和中卫市的水资源利用状况低;因子分析下吴忠市和银川市的水资源利用状况高,其余3市水资源利用状况都较低。     

南方煤田绳索取心钻进的配套问题

南方（湖南、贵州、四川、云南、重庆等）煤田在绳索取心钻进时,遇到的问题及解决办法有一定的普遍性。针对该区的地层特点,提出了合理的钻进方法及钻具配套方案;根据施工区的条件及孔深要求,进行了设备配套的研究;从研究区内事故发生的普遍性入手,摸索出一套较为合理的事故处理方案和工艺配套措施。通过多方面的研究,形成了一套比较合理的配套方案,据此方案在云贵川湘等地施工,均取得了较好的经济效益与社会效益方面。     

冻融干湿交替下灰绿板岩矿质元素释放特征及释放模型

针对宁夏中部干旱带压砂地土壤肥力下降、灰绿板岩矿质元素淋溶释放规律不明等问题,通过室内模拟灰绿板岩冻融干湿循环交替试验,采用修正的Elovich方程、抛物线方程、双常数速率方程、一级动力学方程对各矿质元素的累积释放曲线进行拟合,研究不同粒径板岩在冻融干湿循环作用下的释放动力学特征及最优动力学方程。结果表明：两种粒径灰绿板岩淋溶液中矿质元素淋溶总量随循环次数增大而增大,1 cm粒径灰绿板岩矿质元素累积淋溶总量、淋溶速率在不同循环次数下均大于3 cm粒径。灰绿板岩矿质元素淋溶释放是多因素共同控制的物理、化学过程,其释放过程可大致分为快速反应阶段和反应趋于平衡阶段;压砂地土壤中Ca、K、Mg、P元素的供给量运用修正的Elovich方程预测结果较好,抛物线方程更适用于描述S元素的释放规律。研究结果可为宁夏中部干旱带旱作农田土壤肥力调控提供决策参考。     

天地一体全景影像快速获取与应用技术

天地一体的高分辨率全景影像快速获取与应用技术,采用移动采集车、船舶、定制背包等多种交通设备载体,以及普通相机、定制化全景相机和GPS、运动传感器等配套设备,快速地获取空中、地面、水面等复杂场景的高分辨率全景影像。本文利用全景拼接融合软件、FlyPano处理软件、Krpano发布软件实现了全景影像实时处理与发布,同时结合天地图、行业应用系统接口等,提供了API接口形式与专业应用进行结合与集成,真正实现了复杂场景的全景影像标准化、规模化生产,以期在各行业中得到快速应用。     

Effect of climate changes and water‐related human activities on annual stream flows of the Shiyang river basin in arid north‐west China

The change of annual stream flow in the Shiyang river basin, a typical arid‐inland basin in north‐west China, was investigated using hydrological, meteorological and water‐related human activities' data of the past 50 years. The long‐term trends of the hydrological time series were examined by non‐parametric techniques, including the Pettitt and Mann–Kendall tests. Double cumulative curves and multi‐regression methods were used to separate and quantify the effects of climate changes and human activities on the stream flows. The results show that the study area has been experiencing a significant upward warming trend since 1986 and precipitation shows a decreasing trend in the mountainous region but an increasing trend in the plains region. All stream flows in the upper reach and lower reaches of the Shiyang river exhibit decreasing tendencies. Since 1970, human activities, such as irrigation, have had a significant effect on the upstream flow, and account for 60% of total flow decreases in the 1970s. However, climate changes are the main reason for the observed flow decreases in the 1980s and 1990s, with contributions to total flow decrease of 68% and 63%, respectively. Before 1975, flow decreases in the upper reaches were the main factor causing reduced flows in the lower reaches of the Shiyang river. After 1975, the effect of human activities became more pronounced, with contributions of 63%, 68% and 56% to total flow decreases in the lower reaches of the Shiyang river in the periods 1975 to 1980, 1980s and 1990s, respectively. As a result, climate change is responsible for a large proportion of the flow decreases in the upstream section of the catchment during the 1980s and 1990s, while human activities have caused flow decreases downstream during the same period. Copyright © 2007 John Wiley & Sons, Ltd.     

基于烈度指标的核电厂地震预警停堆参数研究

核电厂在遭遇超设计基准地震时需要考虑安全停堆,以避免造成核泄漏事故。采用地震动的峰值加速度参数(PGA)作为判别停堆的参数具有一定的局限性,PGA参数不能反映地震动的频谱和持时特征,因而可能引起不必要的停堆。针对此问题,基于我国本土大量实际强震记录,遴选出7种典型的工程相关地震动参数,进而基于地震烈度指标,分析发现地震动的标准累计绝对速度参数能更好地表征地震对核电厂的整体潜在破坏能力,适合作为判别停堆的参数,然后提出两种确定预警参数阈值的方法,最终建议考虑我国强震数据特征的核电厂判别停堆的预警参数阈值,为我国核电厂的地震安全停堆参数的确定提供了参考。