新型预应力路基坡面法向附加应力扩散规律分析     

冷伍明  张期树  徐方  聂如松  杨奇  艾希 《岩土力学》2019,40(10):3987-4000

以新型预应力路基为研究对象,基于弹性理论推导预应力加固结构（侧压板和预应力筋）作用下路堤内沿坡面法向的附加应力扩散系数计算公式,并获得侧压板正下方及其2个外延方向的预应力扩散规律。研究表明：（1）理论公式适用的边界条件为侧压板（边长为0.9 m）离路肩距离不小于1倍板宽;（2）法向分解力产生的扩散作用显著大于切向分解力;（3）由于切向荷载作用,侧压板正下方土体的总扩散应力随深度由“腹鼓形”差异分布逐渐过渡呈“腹平状”较均匀分布;（4）各深度平面上最大扩散系数位置随深度发展在作用区中轴线上不断变动;（5）不同区域的扩散效果为板体正下方>上边界外侧>左右边界外侧>下边界外侧,板体两外延方向的平均有效扩散深度达1.6 m。基于ABAQUS有限元软件建立三维精细化路堤模型对理论解进行验证,发现二者结果（包括路肩处）吻合良好,论证了扩散系数理论公式的正确性及适用条件。最后,基于多块侧压板作用下附加应力的分布情况,探寻侧压板的合理布置间距,保障路堤内一定深度处形成一道连续、有效且较为均匀的预压区,改善路堤土的受力状态,并对路堤边坡提供侧向强制约束,利于路基长期稳定。  相似文献   

扬子地块东缘新元古代造山后构造转化:瓮安穹隆构造岩石与年代学限定     

宋志冬  颜丹平 《现代地质》2019,33(5):937-956

扬子地块Rodinian造山后向伸展作用转化的过程与时间,一直是扬子地块新元古代构造演化的重要科学问题。扬子地块东南瓮安穹隆保存了新元古界板溪群至南华系的完整地层层序与角度不整合接触关系,是回答和理解新元古代造山后构造转化问题的理想区域。对新元古代浅变质板溪群沉积岩和南华纪南沱组沉积层序进行了调查,并采取系列样品进行碎屑锆石U-Pb定年分析和岩石地球化学分析。野外调查表明,南华纪南沱组角度不整合于板溪群之上;年代学分析结果表明,板溪群的沉积时代应在772 Ma之前,而南华纪南沱组沉积时代晚于691 Ma。瓮安穹隆新元古代板溪群沉积岩SiO₂含量中等,SiO₂/Al₂O₃平均值为5.53,K₂O/Na₂O平均值为7.14,TFeO+MgO平均值为3.47%。板溪群物源可能来自上地壳,原岩以长英质物源为主,为活动大陆边缘构造背景,其物源主要来自扬子地块西缘。南沱组沉积岩样品SiO₂含量中等,SiO₂/Al₂O₃平均值为4.69,K₂O/Na₂O平均值为20.41,TFeO+MgO含量平均值为6.64%;碎屑沉积岩稀土元素球粒陨石标准化曲线与上陆壳相似,以轻稀土富集、显著的铕负异常和重稀土平坦为特征。南沱组沉积岩物源可能来自上地壳,原岩以长英质物源为主,有少量中性岩混入,具有裂谷背景特征。综上所述,认为瓮安穹隆板溪群—南沱组地层层序代表了从造山作用向造山后伸展裂谷转化过程,其中板溪群可能与碰撞造山作用对应,主体约在772 Ma结束,而造山后裂谷的形成在691 Ma之后,因此,从造山作用向造山后伸展转化的时间大约为772~691 Ma。  相似文献   

跨孔电波衰减成像初始振幅估算方法比较     

倪建福  刘四新 《物探与化探》2019,(3):634-641

跨孔电磁法衰减层析成像是一种利用电磁波振幅信息的方法,通过发射端到接收端电磁波的振幅变化来反演介质衰减常数分布。发射端振幅也就是初始振幅,一般情况下是未知的,它的精度很大程度上影响到层析成像结果,需要在反演前得到或者通过特殊反演方法来处理。本文总结了4种初始振幅处理方法——线性拟合法、矩阵反演法、双频电磁波法以及相邻道比值法,通过合成数据验证了这四种方法的可行性,并且指出了每种方法的优缺点:线性拟合法适合物性变化不大的情况;矩阵反演法对物性情况要求不高,但计算量较大;双频电磁波法能直接得到电导率分布,但只适合良导体情况;相邻道比值法适用情况最广,但容易受干扰影响。  相似文献   

华南大陆东部赣闽地区地壳厚度与泊松比研究     

赵延娜  段永红  魏运浩  邹长桥  林吉焱  邱勇 《大地测量与地球动力学》2017,37(3):261-266

通过收集江西省和福建省共58个固定台站记录到的2011-01～2012-12的远震数据,利用接收函数H-κ扫描叠加方法得到台站下方平均地壳厚度和波速比估计,并通过插值得到华南大陆东部赣闽地区整体的地壳厚度变化趋势以及泊松比分布情况。结果表明,研究区地壳厚度约为28～34 km,由内陆向沿海有起伏地逐渐减薄,赣南地区同福建沿海地区地壳厚度较薄,江西东部和福建西北部地壳较厚;泊松比约为0.21～0.28,由内陆向沿海逐渐增加,赣北地区泊松比值最低,低于0.23（波速比低于1.70）,沿海地区泊松比较高,可达0.28（波速比为1.83）。并探讨了造成地壳厚度和泊松比变化的构造因素。  相似文献   

Physical constraints on c13 and δ for transversely isotropic hydrocarbon source rocks          下载免费PDF全文

Fuyong Yan  De‐Hua Han  Qiuliang Yao 《Geophysical Prospecting》2016,64(6):1524-1536

Based on the theory of anisotropic elasticity and observation of static mechanic measurement of transversely isotropic hydrocarbon source rocks or rock‐like materials, we reasoned that one of the three principal Poisson's ratios of transversely isotropic hydrocarbon source rocks should always be greater than the other two and they should be generally positive. From these relations, we derived tight physical constraints on c₁₃, Thomsen parameter δ, and anellipticity parameter η. Some of the published data from laboratory velocity anisotropy measurement are lying outside of the constraints. We analysed that they are primarily caused by substantial uncertainty associated with the oblique velocity measurement. These physical constraints will be useful for our understanding of Thomsen parameter δ, data quality checking, and predicting δ from measurements perpendicular and parallel to the symmetrical axis of transversely isotropic medium. The physical constraints should also have potential application in anisotropic seismic data processing.  相似文献   

From Zipf's law to hypsometry: seeking the ‘signature’ of elevation distribution     

Lan Mu 《International journal of geographical information science》2013,27(7):1312-1328

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Quasi indicatrix approach for distortion visualization and analysis for map projections     

Ibrahim Oztug Bildirici 《International journal of geographical information science》2013,27(12):2295-2309

Tissot’s indicatrix or ellipse of distortion is a diagram that is the projection of an infinitesimal circle on the original surface. It is normally an ellipse of which elongation depends on the amount of distortion caused by map projection. It provides a medium for analyzing existing projections and developing new ones. The ellipse can be scaled and depicted on the map for visualization purposes. This paper presents an alternative approach, in which the projection of a finite small circle on the sphere is used. Its projection is normally an ellipse that can be very close to Tissot’s indicatrix, and is called quasi indicatrix, here. Its parameters can be derived from the forward projection equations without using partial derivatives. Therefore, it is a useful and practical approach from a programmer’s point of view. The quasi indicatrix approach is also numerically tested on Aitoff–Hammer projection with a set of points. The indicatrix parameters obtained by using this approach deviate 0.5% from the ground truths at most, being the average less than 0.2%.  相似文献   

In search of Thule children: Construction of playing houses as a means of socializing children     

Mariane Hardenberg 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):201-214

Geografisk Tidsskrift—Danish Journal of Geography 110(2):201–214, 2010

During the last decade, the subject of the individual agent and the conveyance of knowledge have become essential concerns in prehistoric archaeology. However, children are often entirely absent or passive in archaeological interpretation when considering their participation in a variety of economic or social tasks. This paper examines the miniature playhouse structures of Thule children that date from the pre-contact Thule period of approximately 1400–1800 AD. Implemented during the 2008field season, the study explored the region of Wollaston Forland in Northeast Greenland. Previous research suggested the arrangement of these features most likely referenced superstitious or spiritual activity. However, this study reveals the concept and organization of these features in the landscape, and offers insight into specifically arranged constructions that depict miniature versions of Thule houses.  相似文献   

Up Against the Law: Legal Structuring of Political Opportunities in Neighborhood Opposition to Group Home Siting in Massachusetts     

Deborah G. Martin 《Urban geography》2013,34(4):523-540

Abstract

Conflicts over siting of group homes for people transitioning out of homelessness or struggling with addiction illustrate the multiscalar dynamics at play between locally-based activism and supra-local laws. In Massachusetts, the state-scale legal environment limits the effectiveness of opposition to group housing; nonetheless, such opposition occurs at the municipal level. Drawing on media accounts, official documents, and interviews with stakeholders in conflicts over group home siting in Worcester, Massachusetts, I investigate the dynamics between neighborhood place claims, the responses of the local state, and the state-wide laws governing group home siting. Examining the legal frameworks relevant to social movement grievances demonstrate that law structures the political opportunities available for protest and local government response.  相似文献   

Phase Changes in Linear Solar-Terrestrial Relationships and a Review of the Electrification Hypothesis     

John M. Harlin 《自然地理学》2013,34(2):108-125

It appears that relatively strong linear relationships between solar activity and various weather phenomena are forthcoming only if the analyses relate to specific solar periods or are con ducted for specific geographic locations. Solar periods in this instance are defined according to the amplitude of the 11-year sunspot cycle. The sign for correlation coefficients between weather ele ments under investigation and solar activity often change according to solar amplitude. However, these phase changes may not weaken arguments in favor of sun-weather hypotheses.

Atmospheric teleconnection provides a logical explanation for phase changes over space within specific time frames, and variations in solar-amplitude relate to reversals in phase with space held constant. Previous research of large pressure systems in the tropics and mid-latitudes as well as re gional variations in annual precipitation outlined in this research indicate that a change in sign for the linear sun-weather relationship occurred between 1930 and 1940. Between 1930 and 1940, the amplitude of the solar cycle also changed. The incredibly complex nature of the climatic change equation along with the lack of an explicit physical link between solar-activity and the lower atmo sphere are serious deterrents for broad acceptance of a solar-weather connection. It is suggested, however, that recent research on a possible electrical stimulus might go far in establishing the solar hypothesis as a credible one.  相似文献