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   

昆明大板桥岩溶地下水系统污染边界及其防污性能研究   总被引：2，自引：2，他引：0  

彭淑惠  王宇  黄成  李芹  王裕琴 《中国岩溶》2015,34(4):362-368

大板桥岩溶地下水系统是滇东断陷盆地区较典型的裸露—覆盖型岩溶地下水系统,文章中定义了岩溶地下水系统污染边界,进行了大板桥岩溶地下水系统分级,即大板桥裸露—覆盖型岩溶水一级系统及横山—龙泉寺裸露型子系统和大板桥—阿地村覆盖型子系统两个二级子系统,确定了大板桥岩溶地下水系统侧向边界、裸露区顶界、裸露型子系统与覆盖型子系统的边界及覆盖区顶界四种裸露—覆盖型岩溶地下水系统污染边界,并对边界防污性能进行了研究,认为裸露区顶界防污性能弱、裸露型子系统与覆盖型子系统的侧向边界防污性能较弱,覆盖区顶界防污性能强。   相似文献   

Assessment of various CPT based liquefaction severity index frameworks relative to the Ishihara (1985) H1–H2 boundary curves     

《Soil Dynamics and Earthquake Engineering》2015

The objective of the study presented herein is to develop an understanding of the predictive trends of four different liquefaction severity index frameworks, with emphasis on the utility of the frameworks for assessing liquefaction vulnerability in Christchurch, New Zealand. Liquefaction induced land damage was widespread following the four major earthquakes in Christchurch (M_w 5.9–7.1) between 4 September 2010 and 23 December 2011. As part of the rebuilding effort, a major focus, to date, has been on assessing/developing approaches for evaluating vulnerability to liquefaction induced damage in future events. The four liquefaction severity index frameworks that are evaluated herein are: the one-dimensional volumetric reconsolidation settlement (S_V1D), the Liquefaction Potential Index (LPI), and two new liquefaction severity indices developed following the major earthquakes in Christchurch, namely the Ishihara inspired LPI (LPI_ISH) and the Liquefaction Severity Number (LSN). To assess the predictive trends of the four severity index frameworks, the H₁–H₂ boundary curves developed by Ishihara (1985) are used as a reference of comparison. In large part, the severity index frameworks serve the same purpose as the Ishihara boundary curves, but they alleviate some of the difficulties in implementing the Ishihara boundary curves for assessing the highly stratified soil profiles that underlie much of Christchurch. A parametric study was performed wherein relatively simple soil profiles are evaluated using all the procedures and contour plots of calculated S_V1D, LPI, LPI_ISH, and LSN values were superimposed onto the Ishihara boundary curves. The results indicate that the LPI_ISH and LSN indices yield similar trends as the Ishihara boundary curves, whereas the S_V1D and LPI indices do not. Furthermore, little field data is available to assess the severity indices for the scenarios where the trends in the LPI_ISH and LSN indices differ.  相似文献   

含方形凹陷半无限非均匀介质波动问题FDM模拟          下载免费PDF全文

杨在林  孙铖  王耀  李志东 《地震工程学报》2015,37(2):553-558

采用规则网格有限差分方法对二维平面弹性波动方程进行差分离散,得到相应的弹性波动方程的有限差分方程,再将弹性波动方程的差分格式与吸收边界、自由边界的离散形式结合形成弹性波动方程有限差分方程解决问题的主体,将其应用于含方形凹陷半无限非均匀介质的模型中进行数值模拟,得到此离散化模型中不同时刻不同节点的位移值。针对具体算例,运用上述方法结合科学计算软件MATLAB和结果后处理软件DIFEM ISOLINE PLOTER得到不同时刻的水平方向位移等值线图与接收器测量点处的合成位移记录,讨论非均匀介质、吸收边界、方形凹陷等对波动特性的影响。  相似文献   

浅剖数据解译中淤泥层层界提取方法   总被引：2，自引：0，他引：2  

胡梦涛  蒋廷臣  李佳琦  刘志强  董春来 《测绘通报》2017,(6):72-76

港口与航道淤泥层层界确定对于港航建设开发与工程实施有着重大意义。本文针对港口航道浅地层剖面仪原始采集数据模糊的问题,分析了影响原始数据真实性的主要原因,实施了中值滤波法多次波压制与消噪处理,取得了清晰可靠的真实数据图像文件,根据海底声波不同层界反射特征,对比分析了脉冲信号声强图像变化情况,探讨了基于浅剖数据声强图像提取淤泥层厚的方法。试验证明该方法可以达到当前钻孔资料所能达到的精度范围。  相似文献   

High-resolution calcareous nannofossil biostratigraphy of the Santonian/Campanian Stage boundary,Western Interior Basin,USA     

《Cretaceous Research》2017

The base of the Campanian Stage does not have a ratified Global Stratotype Section and Point (GSSP); however, several potential boundary markers have been proposed including the base of the Scaphites leei III ammonite Zone and the base of the paleomagnetic Chron C33r. Calcareous nannofossil assemblages from the Smoky Hill Member of the Niobrara Formation in the central Western Interior Seaway, USA were analyzed from two localities to determine relevant biohorizons and their relationships to these potential boundary markers. In a previous study, the Aristocrat Angus 12-8 core (Colorado) was astrochronologically dated and constrained using macrofossil zonations and radiometric ages. The Smoky Hill Member type area (Kansas) provides an expanded interval with good to excellent nannofossil preservation.Five biohorizons are useful for recognition of the Santonian/Campanian transition within the Smoky Hill Member type area, and three are useful in the Aristocrat Angus 12-8 core. The first occurrences (FOs) of Aspidolithus parcus parcus and Aspidolithus parcus constrictus, as well as the last occurrences (LOs) of Zeugrhabdotus moulladei, Helicolithus trabeculatus specimens larger than 7 μm, and Zeugrhabdotus biperforatus are in close stratigraphic proximity to the base of the Scaphites leei III Zone and the base of Chron C33r.  相似文献   

A 2.5-D coupled FE–BE model for the dynamic interaction between saturated soil and longitudinally invariant structures     

《Computers and Geotechnics》2017

A two-and-a-half-dimensional (2.5-D) coupled finite element–boundary element (FE–BE) model is presented to simulate the three-dimensional dynamic interaction between saturated soils and structures with longitudinally invariant geometries. A regularized 2.5-D boundary integral equation for saturated porous media is derived that avoids the evaluation of singular traction integrals. The 2.5-D coupled FE–BE model is established by using the continuity conditions on the soil–structure interface. The developed model is verified through comparison with an existing semi-analytical method. Two case studies of a tunnel embedded in a poroelastic half-space and the efficiency of a vibration isolating screen are presented.  相似文献   

Discovery of Iapetognathus fauna from far western New South Wales: towards a more precisely defined Cambrian–Ordovician boundary in Australia     

Y. Y. Zhen  I. G. Percival  B. D. Webby 《Australian Journal of Earth Sciences》2017,64(4):487-496

Conodont species Iapetognathus fluctivagus and Iapetonudus ibexensis are documented for the first time from Australia. The former is the primary marker internationally defining the base of the Ordovician, and the latter is also a distinctive species previously recorded only from the base of the Ordovician in North America. Both species were recovered from a single sample in the Kandie Tank Limestone of the Kayrunnera Group, located about 50 km west of White Cliffs in far western New South Wales. Other species recovered from this sample include Prooneotodus spp., Cordylodus lindstromi, Cordylodus proavus, Hirsutodontus simplex, Teridontus nakamurai and Variabiloconus sp. Recognition of the Iapetognathus fluctivagus Biozone in the Kandie Tank Limestone supports its correlation with the Green Point section (Global Stratigraphic Section and Point for the base of the Ordovician) in western Newfoundland and the Lawson Cove section of Utah (Auxiliary Stratigraphic Section and Point), as well as sections in Asia and South America. Review of other sections in Australia and elsewhere spanning the Cambrian–Ordovician boundary confirms that, in the absence of I. fluctivagus, the presence of C. lindstromi is a good proxy for this level.  相似文献   

吐哈盆地硫磺山铜多金属矿床表生黄钾铁矾~(40)Ar/~(39)Ar定年及对风化、地貌演化及古气候的启示     

杨静  郑德文  陈文  武颖  许英霞  杨莉 《地质力学学报》2017,23(2):232-242

黄钾铁矾是干旱—半干旱地区硫化物矿床氧化带中一种常见表生含钾硫酸盐矿物,对其进行~(40)Ar/~(39)Ar年代学研究,不仅可以直接限定硫化物矿床次生富集的时间,还可以为区域地貌形成演化和古气候演变等重大地质事件提供关键的年代学信息。本文对中国新疆吐哈盆地硫磺山铜多金属矿床氧化带中三个表生黄钾铁矾样品进行了~(40)Ar/~(39)Ar定年,第一次获得了始新世的风化矿物的年龄。结合已发表的年龄数据显示:在吐哈盆地,海拔较高的矿床氧化带剖面(如硫磺山矿床)记录了基岩的持续和较完整的区域风化事件,这些老的风化年龄的存在证明了剥蚀并不是均匀的,即其地貌演化遵循的是斜坡后退模型。对于吐哈盆地的古气候,这些表生硫酸盐的年龄表明:始新世以来吐哈盆地曾多次出现过有利于化学风化和硫化物矿床次生富集的干旱—半干旱气候,且主要集中在以下几个时期:27.7~23.3 Ma、16.4~14.7 Ma、11~7.8 Ma,之后气候开始向极端干旱气候转变,4.1~3.3 Ma之后吐哈盆地可能已经流行大规模的极端干旱气候。  相似文献   

大运河环境景观与变化分析     

胡朵朵  李春霞  舒高雪 《地理信息世界》2017,24(2)

基于第一次地理国情普查成果,结合高分辨率遥感影像、遗产保护区划图、遗产要素统计信息,获取、分析了大运河申遗之前(2009年为主)、申遗成功当年(2014年)、申遗成功一年之后(2015年)三个时点的环境景观及变化信息,为大运河调查、评估、规划、管理、监测提供理论和地理信息支撑.通过本研究探索,对地理国情普查成果有效转化应用起到很好的示范作用,并为其他世界文化遗产和不可移动文物监测提供了有效借鉴.  相似文献