Overbreak and underbreak in underground openings Part 2: causes and implications   总被引：7，自引：0，他引：7  

J. A. Ibarra  N. H. Maerz  J. A. Franklin 《Geotechnical and Geological Engineering》1996,14(4):325-340

Summary The newly developed light sectioning method has been used to investigate some of the causes and costs of overbreak and underbreak. Investigations at the Aquamilpa Hydroelectric Project in Mexico have shown decreased overbreak and increased underbreak as a result of increased rock quality and decreased explosive energy. A new measure of explosive energy, the perimeter powder factor (PPF), has been defined and shown to be useful in the context of tunnel-wall rock damage. Tentative results indicate that explosive energy (PPF) may be a more important factor in producing underbreak, whereas rock quality may be a greater factor in producing overbreak. A site-specific equation is given for predicting overbreak or underbreak as a function of rock quality and explosive energy, with an evaluation of the cost of underbreak and overbreak.  相似文献   

基于遥感影像大数据、卷积神经网络的福建省有效致灾雷电分布模型及应用     

张烨方  刘冰  冯真祯  朱彪 《气象科技》2021,49(6):953-959

为了研究福建省有效致灾雷电的分布情况，基于福建省2004—2012年闪电定位数据及雷击人员伤亡数据、福建省L17级谷歌遥感影像瓦片，引入卷积神经网络模型对遥感影像所在区域是否属于人员活动的属性进行建模、训练和预测，得到福建省人员活动属性的格点产品，结合福建省历史雷电数据对有效致灾的雷电分布情况进行了分析，结果表明：①设计的遥感影像+CNN识别模型具有一定的可行性和准确率，通过显著性水平为0.01的假设检验；②福建省有63.55%的格点为无人员活动区域；③平均有45.36%的闪电落在无人员活动的区域，因地制宜地对其他致灾闪电进行预警是提高应急减灾服务效果的可行途径；④有效致灾雷电密度与历史雷击人员伤亡数据的相关性远大于常规雷电密度与历史雷击人员伤亡数据的相关性，有效致灾雷电分布在表征雷电灾害上比常规雷电分布更具有指示意义。  相似文献   

基于FPN Res-Unet的高分辨率遥感影像建筑物变化检测     

王明常  朱春宇  陈学业  王凤艳  李婷婷  张海明  韩有文 《吉林大学学报(地球科学版)》2021,51(1):296-306

针对城市土地资源变化检测工作繁杂、工作量大、自动化程度低等问题，本文提出一种基于深度学习模型的高分辨率遥感影像建筑物变化检测方法，将语义分割的思想引入到遥感变化检测。基于残差结构特征较卷积层提取性能更优和特征金字塔网络多尺度预测的特点，将残差结构和特征金字塔网络融合到Unet模型中，建立FPN Res-Unet模型。该模型以Unet为基础，引入ResNet18的残差结构作为编码路径特征提取层，在每次卷积后使用边界填充，使得输入图像和输出图像尺寸一致；在解码路径每级上采样过程中，拓展支路径将特征金字塔网络融合到模型的网络主干中，将残差结构、Unet及特征金字塔网络的优点相互融合，增强了Unet的特征提取，弥补了语义分割网络对小目标检测的欠缺；在获取深层语义信息的同时关注细节信息，提高建筑物变化检测精度。实验表明，该方法在所用数据集，准确率、召回率、F₁ 3种指标均达到90%以上。  相似文献   

论Eppley PIR精密红外辐射仪的测量精度   总被引：1，自引：0，他引：1  

江灏  沈志宝 《高原气象》1992,(4)

本文依据红外辐射表(PIR)的结构、性能和工作原理讨论了测量精度及有关影响因素,比较了粗测和精测两种方法的特点,在此基础上提出了各测量方法的适用范围和精度范围以及提高测量精度的措施,同时也给出了一些特定场合下的测量实例及提高测量精度的具体方法。分析表明:精测方法具有很好的测量精度以及很强的环境适应性。粗测在限定的温度范围内具有测量简单、换算方便、易于实现自动化等优点,精度尚能满足一般要求,但在限定的温度范围以外,测量精度急剧恶化。在影响测量精度的各因素中以温度响应中表体热辐射测量的影响最大,在粗测方法中表内电池的性能与测量精度关系重大。强烈日射对测量精度有一定影响,经订正后可基本消除。  相似文献   

Grain size and grain shape analysis of fault rocks   总被引：4，自引：0，他引：4  

Rene Heilbronner  Nynke Keulen 《Tectonophysics》2006,427(1-4):199

  相似文献   

GIS技术支持下的招远市金矿区崩塌遥感调查     

吴泉源  姜春玲  邹敏  杨圣军  张祖陆 《山地学报》2006,24(6):672-677

在总结前人研究成果的基础上,全面系统地分析了诱发招远市金矿区崩塌的自然和人为因数,然后运用遥感技术对金矿区遥感图像进行处理,提取诱发崩塌的条件因子,聘请有经验的专家对各项诱发因子进行诊断分析,以此作为判断条件,在G IS技术的支持下对诱发崩塌的条件因子进行空间分析,预测出招远金矿区发生崩塌的危害程度,为防治崩塌提供科学依据。预测结果表明,招远金矿区崩塌有进一步发展的可能,其中,高危险区有36820 m2,中易发区有50 610 m2,低易发区有67 200 m2,需要采取有效措施加以防治。  相似文献   

1993～2003年厦门市湿地动态变化及其驱动因素分析   总被引：1，自引：3，他引：1  

林巧莺  林广发  陈志鸿  杨陈照  游丽平 《湿地科学》2006,4(4):298-303

通过对厦门市1993年TM遥感影像和2003年ETM 遥感影像的解译分析和数据统计,从湿地面积动态变化和湿地消长情况等方面,用单一土地利用动态度等指标对1993~2003年期间厦门市的湿地变化进行了研究。结果表明,1993~2003年期间厦门市天然湿地面积减少了2103hm2,其中有954hm2(滩涂864hm2)转变为非湿地,有1149hm2转变为人工湿地;而人工湿地面积增加了2775hm2,其中养殖场面积从1993年的5778hm2迅猛增加到2003年的9768hm2,年均增长率为6.91%,水库与水塘和盐田则分别减少了961hm2和254hm2。有27.74%、11.41%、9.33%和3.63%的养殖场面积分别是由非湿地、滩涂、盐田和水库与水塘转变而来的;有54.37%的盐田转变成了养殖场,有33.24%、30.24%的红树林转变为非湿地、养殖场,有10.35%、8.64%的滩涂转变为养殖场、非湿地。对社会经济驱动因素的分析表明,经济发展、人口增长和农业生产比较利益因素极大影响着厦门市湿地的动态变化。  相似文献   

A Practical Procedure for the Measurement of Fragmentation by Blasting by Image Analysis   总被引：1，自引：0，他引：1  

J. A. Sanchidrián  P. Segarra  L. M. López 《Rock Mechanics and Rock Engineering》2006,39(4):359-382

Summary. The operation of a digital image analysis system in a limestone quarry is described. The calibration of the system, required in order to obtain moderately reliable fragmentation values, is done from muckpile sieving data by tuning the image analysis software settings so that the fragmentation curve obtained matches as close as possible the sieving. The sieving data have also been used to extend the fragment size distribution curves measured to sizes below the system’s optical resolution and to process the results in terms of fragmented rock, discounting the material coming from a loose overburden (natural fines) that is cast together with the fragmented rock. Automatic and manual operation modes of the image analysis are compared. The total fragmentation of a blast is obtained from the analysis of twenty photographs; a criterion for the elimination of outlier photographs has been adopted using a robust statistic. The limitations of the measurement system due to sampling, image processing and fines corrections are discussed and the errors estimated whenever possible. An analysis of consistency of the results based on the known amount of natural fines is made. Blasts with large differences in the amount of fines require a differentiated treatment, as the fine sizes tend to be the more underestimated in the image analysis as they become more abundant; this has been accomplished by means of a variable fines adjustment factor. Despite of the unavoidable errors and the large dispersion always associated with large-scale rock blasting data, the system is sensitive to relative changes in fragmentation.  相似文献   

东南极格罗夫山GPS控制网的布设与数据处理   总被引：2，自引：0，他引：2       下载免费PDF全文

张胜凯  鄂栋臣  闫利  姜卫平 《极地研究》2006,18(2):123-129

为了给中国南极野外考察队提供DEM卫星影像图,在2002/2003年南极度夏期间,中国第19次南极考察队的大地测量工作者,在东南极Grove山地区,进行了地面控制测量。在覆盖面积达8000km~2的2000多米高的内陆冰盖高原区,在直升机和雪地车的支持下,利用Trim- ble4000ssi GPS接收机,与中山站GPS跟踪站联测,测量了7个GPS控制点,并埋设了永久性测量标志。数据处理采用GAMIT/GLOBK软件解算,获得了较好的定位精度,能够满足该地区制图所需。  相似文献   

Traction image method for irregular free surface boundaries in finite difference seismic wave simulation   总被引：16，自引：1，他引：16  

Wei Zhang  Xiaofei Chen 《Geophysical Journal International》2006,167(1):337-353

In this study, we propose a new numerical method, named as Traction Image method, to accurately and efficiently implement the traction-free boundary conditions in finite difference simulation in the presence of surface topography. In this algorithm, the computational domain is discretized by boundary-conforming grids, in which the irregular surface is transformed into a 'flat' surface in computational space. Thus, the artefact of staircase approximation to arbitrarily irregular surface can be avoided. Such boundary-conforming gridding is equivalent to a curvilinear coordinate system, in which the first-order partial differential velocity-stress equations are numerically updated by an optimized high-order non-staggered finite difference scheme, that is, DRP/opt MacCormack scheme. To satisfy the free surface boundary conditions, we extend the Stress Image method for planar surface to Traction Image method for arbitrarily irregular surface by antisymmetrically setting the values of normal traction on the grid points above the free surface. This Traction Image method can be efficiently implemented. To validate this new method, we perform numerical tests to several complex models by comparing our results with those computed by other independent accurate methods. Although some of the testing examples have extremely sloped topography, all tested results show an excellent agreement between our results and those from the reference solutions, confirming the validity of our method for modelling seismic waves in the heterogeneous media with arbitrary shape topography. Numerical tests also demonstrate the efficiency of this method. We find about 10 grid points per shortest wavelength is enough to maintain the global accuracy of the simulation. Although the current study is for 2-D P-SV problem, it can be easily extended to 3-D problem.  相似文献