无限域横观各向同性岩体介质中折线裂纹边界元方法     

王炳军  肖洪天  孙凌志  岳中琦 《岩土力学》2015,36(3):885-890

岩体材料的各向异性导致其中的光滑裂纹在扩展后会变为折线裂纹。对于折线裂纹,其折线处裂纹面外法线方向不惟一,不能用连续单元离散。为此,在光滑裂纹问题方法的基础上,引入4种新的不连续单元来离散折线处裂纹面,建立了适用于折线裂纹问题的对偶边界元方法,该方法基于横观各向同性基本解。算例验证表明,该方法具有较好的精度。最后用该方法分析了横观各向同性岩体中的折线裂纹,得到了该类裂纹的应力强度因子。当裂纹面上作用法向均布力,横观各向同性岩体介质中的矩形光滑裂纹发生弯折时,折线两侧的裂纹面在张开时存在抑制效应,从而导致折线裂纹裂尖应力强度因子小于原光滑裂纹。同时还发现,随裂纹面的逐渐弯折,其裂纹面对各向同性面的倾角发生变化,因此,其裂尖断裂特性还受到岩体各向异性的影响。  相似文献   

双主卷扬配合“环形道活门机构”的快速提下钻系统          下载免费PDF全文

田炯  宋伟  刘虎  耿建璞  赵文涛  张西坤  高占听 《探矿工程》2017,44(1):61-64

为了提高快速提升钻具更换钻具的能力,研制了SPT-600D型拖车钻机。该钻机配置了SPS-600型双卷扬钻机及“环形道活门机构”。试验及应用情况表明,双卷扬配合“环形道活门机构”能够快速提升钻具更换钻具,缩短钻井施工的时间,可实现水文水井施工优质、高效、快速的要求。  相似文献   

不连续面在双重介质热-水-力三维耦合分析中的有限元数值实现   总被引：1，自引：0，他引：1  

赵延林  王卫军  曹平  王军  赵阳升 《岩土力学》2010,31(2):638-644

在建立双重介质热-水-力耦合微分控制方程的基础上,提出了裂隙岩体热-水-力耦合的三维力学模型,对不同介质分别建立以节点位移、水压力和温度为求解量的三维有限元格式,开发了双重介质热-水-力耦合分析的的三维有限元计算程序,在有限元数值分析中不连续面应力计算采用等厚度空间8节点节理单元进行离散,而不连续面渗流和热能计算时采用平面4节点等参单元进行离散,这样保证了不同介质之间的水量、热量交换和两类模型接触处节点水头、温度和位移相等。通过高温岩体地热开发算例,揭示了在热-水-力耦合作用下不连续面处于低应力区,其张开度随运行时间的延长呈非线性增加,非稳定渗流阶段不连续面显著地控制着渗流场的整体分布,它的水头远高于拟连续岩体介质的水头,而进入稳定渗流阶段不连续面的控渗作用不明显,由于高温岩体地热开发系统中存在大规模的热量补给,不连续面对岩体温度场分布的影响并不显著。  相似文献   

Foraging strategy of little auks under divergent conditions on feeding grounds     

Katarzyna Wojczulanis-Jakubas  Dariusz Jakubas  Nina J. Karnovsky  & Wojciech Walkusz 《Polar research》2010,29(1):22-29

A dual foraging strategy (long versus short trips) has been described for some species of seabirds, such as petrels, albatrosses (Procellariiformes) and penguins (Sphenisciphormes). Such a strategy has recently been reported for little auks ( Alle alle ) from the central coast of west Spitsbergen, Svalbard. This has been explained as a response to poor trophic conditions close to the breeding colony, and better conditions further away (150 km). In the present study, we investigated the foraging strategy of little auks in Hornsund, southern Spitsbergen, during two seasons with contrasting oceanographic conditions. During 2004, foraging conditions for little auks were good: cold Arctic waters rich in profitable high-energy food were dominant in their feeding grounds. Conversely, during 2006 there was a great influx of warm Atlantic water in the feeding area, inducing poor foraging conditions. In both seasons we examined the pattern of foraging trip lengths automatically with a video camera (both adults from four nests in each year), and by direct non-stop observation of 20–54 individually marked birds. Our results showed that the dual strategy and the ratio of short and long trips were consistent, regardless of the conditions in the feeding grounds. This suggests that the strategy is inherent and may be crucial for the self-maintenance of adults.  相似文献   

小肠空气灌肠双源CT检查与胶囊内镜小肠检查对比研究     

黄银平  沈比先  陈胜基  周娜  保莲  陈丽兴 《CT理论与应用研究》2010,19(3):123-129

目的:探讨小肠空气灌肠双源CT检查对小肠疾病的诊断价值。方法:15例临床怀疑小肠病变的患者,行双源CT检查前或后3天内行胶囊内镜检查。其中,男8例,女7例,年龄最大者42岁,最小者23岁。症状主要为腹痛10例,脓血便4例,不明原因消瘦1例,病程最长4年,最短1月。结果:胶囊内镜未见异常8例,双源CT检查亦未见异常;双源CT诊断克罗恩病4例,与胶囊内镜及临床诊断一致;胶囊内镜可疑肿瘤3例,双源CT发现2例并作出良恶性诊断,其中1例为空肠间质瘤,1例为回肠腺癌,经手术病理证实;仅1例胶囊内镜可疑3cm大小肿瘤,双源CT未见异常,结合MRI检查及临床,证实为假阳性。结论:小肠空气灌肠双源CT检查,不仅可以显示小肠器质性病变范围、与邻近结构的关系,而且可以结合临床鉴别炎性病变与肿瘤性病变,并对肿瘤性病变做出良恶性鉴别;还可以为胶囊内镜所见病变定位及排除假阳性问题。  相似文献   

损伤和剪胀效应对裂隙煤体渗透率演化规律的影响研究     

魏明尧  王春光  崔光磊  檀玉玲  张守文 《岩土力学》2016,37(2):574-582

煤层瓦斯渗透率是影响瓦斯抽采和动力灾害防治的重要参数。为了研究煤体损伤和剪胀变形对渗透率的影响,首先引入损伤变量反映煤体损伤破坏状态,建立了基于体应变增量的煤体损伤本构模型。并采用Hurst指数表征裂隙表面粗糙度,基于裂隙表面的分形特征,建立了裂隙渗透率在压缩和剪切作用下的演化模型。通过对TOUGH2和FLAC3D软件进行二次开发,建立了基于双重孔隙模型的TOUGH2(CH4)-FLAC气-固耦合数值分析工具。采用本软件对煤样单轴压缩过程进行模拟分析,结果表明：煤体的破坏是损伤单元累积和贯通的结果,最终形成贯通煤体的损伤带是造成煤体失稳破坏的主因;围岩内的渗透率增加区域与损伤区位置基本一致,其中裂隙系统的渗透率增加幅度最大可达2个数量级;剪切破坏区的裂隙发生剪胀变形,引起裂隙渗透率大幅增加。建立的理论模型与数值计算工具为制定瓦斯治理措施提供了理论指导。  相似文献   

热处理天然金红石的微结构研究   总被引：1，自引：0，他引：1  

庄伟  罗泽敏  刘迎新  吴婧  秦善  鲁安怀 《岩石矿物学杂志》2009,28(6):629-636

利用粉晶X射线衍射(XRD)、透射电镜(TEM)等分析手段对在氩气气氛中加热、退火的天然金红石样品的微结构进行了研究.研究表明样品在热处理后,晶格发生膨胀,并且在900 ℃和1000 ℃的样品中出现了钛铁矿物相.钛铁矿也是一种天然半导体矿物,沿与金红石(010)面网成大约31°夹角的方向生长,与金红石形成了二元复合半导体.紫外漫反射实验结果表明热处理后,金红石中出现的钛铁矿相有效地促进了光催化效果.  相似文献   

Generating hierarchical strokes from urban street networks based on spatial pattern recognition     

Bisheng Yang  Xuechen Luan  Qingquan Li 《International journal of geographical information science》2013,27(12):2025-2050

Strokes are products of a higher-level aggregation of street segments that can reflect functional importance and perceptual significance that is associated with them in human spatial mental conceptualizations, which is of vital importance for network analysis, street selection, and map generalization. Street properties (e.g., street names) and angles between street segments are the two main elements used for generating street strokes according to the continuity principle of perceptual grouping into networks. However, it is difficult to automatically generate strokes with good continuity from street networks with multiple lanes such as dual carriageways or complex street junctions. This article proposes a method for generating street strokes that maintain good continuity across multiple lanes and complex street junctions. The proposed method first detects dual carriageways and complex junctions in street networks and then generates strokes according to the continuity principle of perceptual grouping. Finally, it groups the generated street strokes across the dual carriageways and complex street junctions to maintain good continuity. Moreover, the generated strokes are hierarchically ranked based on stroke length and centrality measurements. Experimental studies demonstrate the validity and effectiveness of the proposed method. The result shows that the generated street strokes maintain good continuity and reflect well the hierarchical structure of the street networks.  相似文献   

Impact of lateral force-resisting system and design/construction practices on seismic performance and cost of tall buildings in Dubai, UAE     

Mohammad AlHamaydeh  Khaled Galal  Sherif Yehia 《地震工程与工程振动(英文版)》2013,12(3):385-397

The local design and construction practices in the United Arab Emirates(UAE),together with Dubai’s unique rate of development,warrant special attention to the selection of Lateral Force-Resisting Systems(LFRS).This research proposes four different feasible solutions for the selection of the LFRS for tall buildings and quantifies the impact of these selections on seismic performance and cost.The systems considered are: Steel Special Moment-Resisting Frame(SMRF),Concrete SMRF,Steel Dual System(SMRF with Special Steel Plates Shear Wall,SPSW),and Concrete Dual System(SMRF with Special Concrete Shear Wall,SCSW).The LFRS selection is driven by seismic setup as well as the adopted design and construction practices in Dubai.It is found that the concrete design alternatives are consistently less expensive than their steel counterparts.The steel dual system is expected to have the least damage based on its relatively lesser interstory drifts.However,this preferred performance comes at a higher initial construction cost.Conversely,the steel SMRF system is expected to have the most damage and associated repair cost due to its excessive flexibility.The two concrete alternatives are expected to have relatively moderate damage and repair costs in addition to their lesser initial construction cost.  相似文献   

基于随机二元指标的边坡稳定性分析          下载免费PDF全文

刘小强  周世良  尚明芳  李怡 《地震工程学报》2011,33(Z1)

考虑岩土体抗剪强度参数的变异性,综合极限平衡法和可靠性理论构建了安全系数概率密度分布函数模型。结合实际工程特点,以安全系数大于临界值为标准构建有效区,将有效区安全系数均值与对应可靠度相乘,得到以安全系数和可靠度为随机二元指标的有效安全系数。以有效安全系数为定量指标,将边坡宏观特征现象与定量分析相联系,构建意义更为明确的边坡稳定性分析及评价方法。通过工程实例对比了有效安全系数与传统评价指标之间的差异。所得结论可为工程建设提供参考和借鉴。  相似文献