A new contact algorithm in the material point method for geotechnical simulations     

J. Ma  D. Wang  M.F. Randolph 《国际地质力学数值与分析法杂志》2014,38(11):1197-1210

Contact between stiff structural elements and soil is encountered in many applications in geotechnical engineering. Modelling of such contact is challenging as it often involves impact that would lead to large deformation and failure of the soil. The Material Point Method (MPM) is a mesh‐free method that has been applied to simulate such phenomena. However, the frictional contact algorithm commonly used in MPM only supports Coulomb friction and cannot model fully or partially rough contact conditions in terms of geotechnical engineering. Moreover, because of very different stiffness of contacting materials, the contact force predicted by the previous frictional contact algorithms usually suffers from severe oscillation when applied in structure–soil interaction. This paper presents a new contact algorithm, termed Geo‐contact, designed for geotechnical engineering. In Geo‐contact, a penalty function is incorporated to reduce the oscillation in contact computation, and a limited shear stress is specified along the contact interface. The proposed Geo‐contact algorithm has been implemented to simulate smooth, partially rough and rough contact in typical large deformation penetration problems. The resistance–displacement curves obtained using the Geo‐contact are compared with analytical solutions of limit analysis and large deformation finite element results to verify the accuracy and robustness of the proposed contact algorithm. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   

Erosional scours and meander development in response to river engineering: middle Tisza region, Hungary     

Ágnes Cserkész-Nagy  Tamás Tóth 《Proceedings of the Geologists' Association. Geologists' Association》2010,121(2):238-247

We present a case study on how riverbed morphology of the engineered and meandering Tisza River of the Pannonian Basin (Hungary) has changed during post-engineering times. The objectives were (1) mapping the location and morphology of scours and point bars, (2) reconstructing their changes in a 150 year time-scale in response to engineering work, (3) describing the differences of quasi-natural and engineered channels and (4) distinguishing of local and general causes, both natural and anthropogenic.Recent erosion and deposition have been traced on continuous ultrahigh resolution (UHR) seismic profiles. These results were matched up to channel cross-sections and to time-series planimetric and bathymetric maps. The topography of the riverbed is determined primarily by two factors: the plan view geometry of the channel and the lithology of the substratum. As well as naturally developing scours in the river bends, shallower and elongated, slightly refilled ones appear on straight reaches or in engineered channels. Elongated bed scours and extraordinary forms are related to local human effects. However, erosion is observed everywhere in the investigated 102 km long Middle-Tisza region. As a result of cut-offs the gradient increased and, as a consequence, the riverbed became incised.Sedimentation is reflected in accelerated point bar development, which resulted in intensive lateral migration and increasing sinuosity, which is enhanced in the vicinity of human interventions. Changes do not propagate far away. Channel adjustments happened in two phases: rapid incision was followed by a slower sinuosity increase in order to obtain a new dynamic equilibrium.  相似文献   

Upper limits on neutrino fluxes from point-like sources with AMANDA-II     

Markus Ackermann 《Astrophysics and Space Science》2007,309(1-4):421-427

The AMANDA-II telescope, operated by the IceCube collaboration, is currently the world’s most sensitive telescope to fluxes of neutrinos from individual sources. A data sample of 4282 neutrino induced events collected in 1001 days of detector livetime during the years 2000–2004 have now been analyzed looking for a neutrino signal from point-like sources. A sensitivity to fluxes of of d Φ/dE=1.0×10⁻¹⁰(E/TeV)⁻² TeV⁻¹ cm⁻²s⁻¹ was reached in the energy range between 1.7 TeV and 2.4 PeV. So far no statistically significant localized excess of events over the background of atmospheric neutrinos has been found, which would be ascribed to a neutrino source. However, the flux upper limits derived from the non-observation of a signal are comparable to observed fluxes of high energy gamma rays from blazars and within the range of current models for neutrino emission from selected sources. Possible constraints on these models are discussed.   相似文献   

Recently Ratified and Proposed Cambrian Global Standard Stratotype-section and Points     

PENG Shanchi  ZHU Xuejian  ZUO Jinxun  LIN Huanling  CHEN Yong’an  WANG Longwu 《《地质学报》英文版》2011,85(2):296-308

This paper briefly summarizes an officially ratified Global Standard Stratotype-section and Point (GSSP) and a proposed GSSP for global stages of the Cambrian System. The Luoyixi section near Luoyixi town, Guzhang, northwestern Hunan is ratified as the boundary stratotype for the base of the global Guzhangian Stage, which is the upmost stage of an unnamed series termed provisionally as Cambrian Series 3. The GSSP position lies 121.3 m above the base of the Huaqiao Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Lejopyge leavigata. The Duibian B section at Duibian village, Jiangshan, western Zhejiang, is proposed as the boundary stratotype for the base of the proposed global Jiangshanian Stage that is the second stage of the Furongian Series. The proposed GSSP position lies 108.12 m above the base of the Huayansi Formation in the section, coinciding with the first appearance of the cosmopolitan agnostoid trilobite Agnostotes orientalius. This horizon is also with the first appearance of the cosmopolitan polymerid trilobite Irvingella angustilimbata.  相似文献   

Correlation of the Tournaisian-Visean Boundary Beds     

HOU Hongfei  WU Xianghe  YIN Bao’an 《《地质学报》英文版》2011,85(2):354-365

With the definition and adoption of the Global Stratotype Section and Point (GSSP) for base of the Visean in China, the newly synthesized zonations and correlation of some significant fossil groups: foraminifera, conodont, coral and brachiopoda near the Tournaisian-Visean boundary beds are reviewed, which help in the recognition of the boundary in various sedimentary facies. The occurrence of two physical events, one pre- and one post- the Tournaisian-Visean boundary is emphasized, which allows for recognition of the position close to the Tournaisian-Visean boundary in the field. The regional correlation in southern China and international correlation throughout Eurasia around the Tournaisian-Visean boundary beds with the GSSP is proposed.  相似文献   

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陈俊勇  党亚明  程鹏飞 《大地测量与地球动力学》2007,27(5):1-4

?????????????????(GNSS)???GPS??????????????GLONASS???????GALILEO?????????????;????????μ?????????????????????????????????·??Ч??????????????????????????λ?????仯????????λ??????????????????λ????????;??????GPS???????λ(PPP)???????  相似文献   

长江中下游梅雨与北太平洋OLR关系的诊断分析     

郑皓文  毛文书 《山西气象》2011,(2):25-30

利用长江中下游流域25站1954年-2001年共48年逐日梅雨量资料和美国NCEP／NCAR同期逐月降水量资料和射出长波辐射（outgoing longwave radiation,简称OLR）资料,采用EOF分解、Z指数、合成分析和点相关分析等多种现代诊断分析方法,详细讨论了长江中下游梅雨与北太平洋OLR的关系。结果表明：长江中下游梅雨量与西太平洋暖池区及东太平洋漂流区OLR呈显著正相关,说明西太平洋暖池区及东太平洋漂流区OLR异常增强（减弱）,长江中下游梅雨异常偏多（偏少）。长江中下游梅雨量与西太平洋至东海、黄海一带OLR呈显著负相关,说明当西太平洋至东海、黄海一带OLR异常增强（减弱）时,长江中下游梅雨量异常偏少（偏多）。合成分析和点相关分析的结果完全一致,并且通过信度0．05的显著性水平检验。  相似文献   

浅水湖盆三角洲储层构型模式探讨   总被引：1，自引：0，他引：1       下载免费PDF全文

封从军  赵逸  贾鹏  颜佩丽 《地质科学》2013,48(4):1234-1245

针对浅水湖盆三角洲储层构型模式研究的不足,在考察鄱阳湖现代浅水湖盆三角洲沉积和解剖扶余油田扶余油层古代浅水湖盆三角洲储层构型的基础上,综合应用卫星照片、岩心、测井等资料,建立了浅水湖盆三角洲平原分流河道和三角洲前缘水下分流河道的沉积构型模式。研究结果表明:浅水湖盆三角洲主要发育三角洲平原上部曲流型分流河道、三角洲平原下部顺直型分流河道和三角洲前缘顺直型水下分流河道3种砂体类型,曲流型分流河道主要为侧积的点砂坝沉积构型模式,顺直型分流河道主要为垂积的心滩坝沉积构型模式,顺直型水下分流河道主要为垂积的分流砂坝沉积构型模式。同时从沉积亚相、砂体几何形态、夹层倾向及倾角、废弃河道、决口扇、粒度分析等几个方面总结了不同类型的分流河道及水下分流河道砂体的判别标志,为浅水湖盆三角洲储层内部构型及地质建模研究工作奠定了基础。  相似文献   

The mineralogy of the Gosse pile ultramafic intrusion,central Australia. II. Pyroxenes     

A. C. Moore 《Australian Journal of Earth Sciences》2013,60(3):243-258

The orthopyroxenes of Gosse Pile, a layered ultramafic sequence within the Giles Complex of central Australia, show unusual exsolution features such as the development of ‘hour‐glass’ shapes by clinopyroxene lamellae, and also the exsolution of spinel and rutile. Both orthopyroxene and clinopyroxene have high R2O3 contents and their distribution coefficients for Mg and Fe are high (average KD = 0.88). Some, if not all, of these features are considered to indicate that the Gosse Pile rocks crystallized under high pressure. This interpretation also explains the predominance of orthopyroxene over olivine as an early cumulus phase. Estimated conditions during crystallization are 10–14 kilobars and between 1,200‐l,400°C.  相似文献   

利用精密单点定位（PPP）方法在黑龙江省进行1∶10000像片控制测量的精度分析     

季朝亮  齐中华  张力仁  李宗聚 《测绘与空间地理信息》2014,(10):234-236

通过对黑龙江省某测区利用GPS静态网和精密单点定位（PPP）两种方法对1∶10 000像片控制测量成果进行对比分析,在利用CQG2000对大地高进行高程异常改算精度同传统GPS网拟合高程进行对比分析。通过对比分析得出结论：精密单点定位（PPP）方法施测的像控点平面精度能够满足1∶10 000地形图更新、山区1∶10 000地形图测绘中±1 m的精度要求。同时也验证了＂我国大陆重力大地水准面CQG2000绝对精度在东经120°以东高于±0.3 m的可靠性。  相似文献