Numerical prediction of blast‐induced stress wave from large‐scale underground explosion

This paper presents a numerical model for predicting the dynamic response of rock mass subjected to large‐scale underground explosion. The model is calibrated against data obtained from large‐scale field tests. The Hugoniot equation of state for rock mass is adopted to calculate the pressure as a function of mass density. A piecewise linear Drucker–Prager strength criterion including the strain rate effect is employed to model the rock mass behaviour subjected to blast loading. A double scalar damage model accounting for both the compression and tension damage is introduced to simulate the damage zone around the charge chamber caused by blast loading. The model is incorporated into Autodyn3D through its user subroutines. The numerical model is then used to predict the dynamic response of rock mass, in terms of the peak particle velocity (PPV) and peak particle acceleration (PPA) attenuation laws, the damage zone, the particle velocity time histories and their frequency contents for large‐scale underground explosion tests. The computed results are found in good agreement with the field measured data; hence, the proposed model is proven to be adequate for simulating the dynamic response of rock mass subjected to large‐scale underground explosion. Extended numerical analyses indicate that, apart from the charge loading density, the stress wave intensity is also affected, but to a lesser extent, by the charge weight and the charge chamber geometry for large‐scale underground explosions. Copyright © 2004 John Wiley & Sons, Ltd.     

Vicissitude of Sogo Nur and environmental-climatic change during last 1500 years

Lakes in arid zone are sensitive to climatic changes. The lacustrine sediment sequence in Sogo Nur has well and truly recorded climatic events such as the Sui-Tang Dynasty Warm Period, the Song-Liao Dynasty Cold Period, the Medieval Warm Period, the Little Ice Age and the 20th Century Warm Period. Commonly, the climate in warm Periods was relatively humid,accordingly the lake area extended and water level rose, and vice versa. Apart from climatic change, human activity is also an important factor of influencing lake vicissitude, and they played the dominant role alternatively during different periods; the factor of climatic change predominated in historical period, while since the beginning of the 20th century the utilization of water resources by human has became decisive.     

从安徽气候变化看2003年洪涝和高温的必然性

利用近 50年温度和降水资料研究了安徽夏季气候变化特征 ,解释了 2 0 0 3年夏季洪涝、高温等极端气候事件出现的必然性。研究结果表明 :(1 )近 50年来安徽夏季温度呈下降趋势 ,降水则呈增加趋势 ,两者变化是相协调的。目前夏季温度处于较低的气候基本态 ,降水处于高基本态。 (2 )无论是温度还是降水 ,其变率都在 2 0世纪80年代中后期开始上升 ,目前均处于高气候变率时期。降水的“两高”(高基本态和高气候变率 )结合决定了 2 0 0 3年夏季洪涝出现的必然性 ;温度的较低基本态决定了“凉夏”背景 ,但由于基本态的回升和变率的加大 ,仍会出现像 2 0 0 3年夏季的若干高温天气。 (3)最大熵谱估计表明 ,安徽夏季降水变化的主周期为 2 5年 ,反映了降水的准两年振荡特征     

Changes of precipitation extremes over South Korea projected by the 5 RCMs under RCP scenarios

The change of extreme precipitation is assessed with the HadGEM2-AO - 5 Regional Climate Models (RCMs) chain, which is a national downscaling project undertaken cooperatively by several South Korean institutes aimed at producing regional climate change projection with fine resolution (12.5 km) around the Korean Peninsula. The downscaling domain, resolution and lateral boundary conditions are held the same among the 5 RCMs to minimize the uncertainties from model configuration. Climatological changes reveal a statistically significant increase in the mid-21st century (2046- 2070; Fut1) and the late-21st century (2076-2100; Fut2) precipitation properties related to extreme precipitation, such as precipitation intensity and average of upper 5 percentile daily precipitation, with respect to the reference period (1981-2005). Changes depending on the intensity categories also present a clear trend of decreasing light rain and increasing heavy rain. In accordance with these results, the change of 1-in-50 year maximum precipitation intensity over South Korea is estimated by the GEV method. The result suggests that the 50-year return value (RV50) will change from -32.69% to 72.7% and from -31.6% to 96.32% in Fut1 and from -31.97% to 86.25% and from -19.45% to 134.88% in Fut2 under representative concentration pathway (RCP) 4.5 and 8.5 scenarios, respectively, at the 90% confidence level. This study suggests that multi-RCMs can be used to reduce uncertainties and assess the future change of extreme precipitation more reliably. Moreover, future projection of the regional climate change contains uncertainties evoked from not only driving GCM but also RCM. Therefore, multi-GCM and multi-RCM studies are expected to provide more robust projection.     

涡北河网区三维地震采集技术

涡北勘探区属于河网地带,难以进行正常的地震施工。为此,本文提出了一种以规则束状观测为基础和特殊观测系统相结合的数据采集方法。该方法适应了这种复杂的地表条件,获得了"空白区"的地震资料,为今后类似地表条件地区的三维地震勘探提供了经验。      

基于实测波浪的单桩式海上风电基础波浪力计算研究

基于实测波面的波浪力获取作为结构动力响应分析以及数字孪生模型建立的必备环节,对海上风电数字化运维至关重要。为了满足更大的装机容量需求,单桩式海上风电基础趋于大型化,其尺度因子D/L也随之增大;并且实际海域均为非规则波,以尺度因子划分波浪力计算理论的方法对非规则波的适用性尚不明确。通过建立数值水槽,依据实际工况对不规则波与桩基的作用进行数值模拟,得到入射波浪场与桩基所受波浪力,在此基础上,基于入射波浪场分别采用Morison方程以及绕射理论求解波浪力并将之与数值模拟结果进行对比,分析了不同波浪力计算理论关于尺度因子的适用性,同时探究了波浪要素对计算精度的影响。结果表明：Morison方程在波高较大时精度下降;相对于Morison方程,绕射理论在该尺度下的精度更高。最后,通过分析实测数据进一步探讨了典型工况下的波浪力特征,以期通过实测波面计算波浪力的方法为实际服役风机波浪力计算提供技术支持。     

“一国两制”下香港居民跨境消费行为特征和影响因素研究

深港边界是全球跨境活动最频繁的地区之一。以通过深圳湾口岸前往蛇口消费的香港居民为研究对象,采用定性、定量和空间计量相结合的方法分析香港居民来往深圳的消费模式和行为影响因素,发现在蛇口的跨境港人多来自“新界西”的屯门、元朗、荃湾三地,呈现以公交出行为主、出行频率高、消费低、时间短、老龄化、女性多的特点,其跨境行为主要受到个人年龄及收入、出行距离、区位等因素影响;港人在深港边界的跨境活动开始出现与收入、年龄相关的空间分异现象,呼吁展开针对不同过境群体的进一步研究,厘清其行为特点和影响因素,这将有助于建构粤港“优质生活圈”、促进粤港两地间更便利的跨境活动和更深层次的协作。     

新疆耕地时空变化特征

以新疆1990年、2000年、2005年和2008年4期土地利用数据库及其遥感影像为数据源,利用GIS空间分析提取3期耕地动态变化数据。从现状分析、发展动态对新疆3期耕地开发利用的空间格局、面积变化和类型结构进行了分析。结果表明,耕地总面积持续增加,耕地年均净增和开垦速度呈先增后减的趋势,耕地年均流失速度持续递减;耕地开垦由绿洲地区向沙漠、戈壁延伸,而耕地流失则主要集中在绿洲地区,中东、西北和西南的边缘地区的耕地面积变化相对较大(Rid>1.02);耕地开发结构由草地和林地为主转向草地和未利用地为主,未利用地的开发结构由裸土地、盐碱地为主转向沙地、戈壁和盐碱地为主,耕地的利用结构以草地、建设用地和未利用地为主;耕地与建设用地的相互转化始终是负转化,与草地间的转化是正转化。     

休闲旅游——国内外研究现状、差异与内涵解析

休闲旅游是当前我国旅游业发展的热点,政府和业界都对休闲旅游的发展高度重视,国内学术界也对这一问题进行了大量研究,但迄今为止有关休闲旅游的内涵仍缺乏统一的认识,这不利于人们对休闲旅游做进一步的深入研究。该文基于对国内外研究现状的分析,阐释了休闲旅游与休闲、旅游、观光旅游和度假旅游等概念之间的关系,并结合我国旅游发展的情境和特点,尝试性地对休闲旅游的内涵进行了解析,以期能够为休闲旅游未来的研究和实践发展提供一定的理论指导。     

面向全域全要素的广州市国土空间规划传导体系研究

建立科学清晰的传导体系是保障规划治理效力的重要前提。随着全国各层级国土空间规划编制与改革的推进,空间规划体系雏形初显,明确各级、各类规划编制内容、管理权限和传导路径,已成为各级政府十分关切的问题。文章基于广州国土空间规划试点的编制实践,针对原有规划体系中指标分解难、控制线管控标准不一、用地管控尺度和精度不一、设施管控缺乏分级等问题,以全域全要素管控为目标,提出了广州建立“四级三类”规划传导体系及实施评估监督的建议,认为一是要在纵向传导上,强化规划编制和“市—区—街道”行政管理体系的衔接,构建“市域—区—单元—地块”4个纵向传导层级,重点围绕“目标战略、底线管控、功能与用地管控、设施管控”4类核心管控内容明确各层级编制内容和深度;二是要在横向传导上,构建专项规划与各层级规划的“联系-反馈”机制,推进专项规划与总体层面规划同步编制,达成管控要求、核心指标等方面的共识,并加强详细规划层面的设施评估反馈,细化详细规划在指标、名录、位置、结构4个方面的传导要求。