Estimation of Axial Pile Bearing Capacity According to Shear Strength Parameters of Soil     

Yu Xiaodong  Yan Shuwang Sun Wanhe Postgraduate Student  Tianjin University  Tianjin Professor  Tianjin University  Tianjin Senior Engineer  Tianjin Port Engineering Institute  Tianjin 《中国海洋工程》1997,(2)

At pesent,it is very popular to estimate pile bearing capacity by use of empirical formula andphysical indexes of soil provided in the design codes for civil construction in China.This paper attempts toapply mechanical indexes of soil and semi-empirical formulas,which are based on soil mechanical theoriesand were summarized and presented by Meyerhof in 1976,to calculate the axial pile bearing capacity.Lo-ading test results of 24 single piles in Tianjin area have been collected and compared with the proposed cal-ulation approach.  相似文献   

Shear Failure of a Clamped Dented Tubular Beam Under Lateral Impact   总被引：1，自引：0，他引：1  

Wang Deyu  Zhang Shanyuan Associate Prof.  Depart  of Naval Archi.  Ocean Engineering  Shanghai Jiaotong University  Shanghai Prof.  Research Institute of Applied Mechanics  Taiyuan University of Technology  Taiyuan 《中国海洋工程》1996,(2)

- The shear failure of a rigid-plastic dented clamped tubular beam under the lateral impact of a mass is investigated. Both the denting and the impact point are in the middle span of the beam. It is assumed that denting does not spread during the shear sliding. Numerical results show that the axial force and lateral deflection of the beam are very small at the moment of the occurence of shear failure, which means that the finite deformation effect can be neglected in the shear failure analysis. Also, some aspects of the initial impact energy are investigated.  相似文献   

华南三水盆地白垩纪—早第三纪古纬度漂移与南海演化   总被引：1，自引：0，他引：1  

袁友仁  王保贵  汤贤赞  赖小嘉  范时清  柳枞阳 《热带海洋学报》1992,(1)

本文主要依据三水盆地古地磁数据所反映的华南地块的古纬度漂移讨论南海的演化模式。结果认为,华南在南海的形成演化中居主导地位,南海基本上是晚白垩世至中新世期间通过华南的南漂及其后的北向回漂过程中,华南大陆南部的拉张、断裂、解体并自东向西扩展的方式形成的,而南海中散布的微大陆碎块则是在华南回漂时被滞留下来的。演化过程中,其周缘菲律宾岛弧自南向北漂,直到上新世后才构成南海的东界;印支地块则仅起转换边界作用;加里曼丹则基本土没有明显的漂移。  相似文献   

东海南海交接带重磁场特征及新生代盆地成因     

吴时国  郭军华  刘展 《海洋地质与第四纪地质》2004,24(3):49-55

东海南海构造交接带及其邻近海区(简称交接带)位于中国东部大陆边缘,东邻俯冲板块边界。台湾以北是琉球海沟俯冲带,台湾以南为马尼拉海沟俯冲构造带。区域重磁资料分析结果表明,该东海陆架区存在3条重力高和2条重力低,重力高分别对应于闽浙隆起带、渔山低凸起和陆架外缘隆起,最大值高达50×10-5m·s-2;重力低对应于沉积盆地,最低值在台西南盆地,约为-20×10-5m·s-2。重磁特征表明东海盆地外缘台湾 钓鱼岛构造带具有明显的自由空间异常,磁场为平缓负异常,由古近系、白垩系或更老的变质岩及中新世的侵入岩组成,向南延伸至澎湖隆起。因为澎湖隆起具有高重力异常,放射性年龄表明这些碱性玄武岩形成于17 8～8MaBP,其特征同现在的琉球岛弧一样,可能是残留的古琉球岛弧。台西南盆地南侧(上陆坡)的凸起具有类似的幅度异常,呈ENE—WSW向,并消失在台西南盆地南段。新生代以来,盆地张裂活动具有不同时性,并向陆架边缘变得年轻。东海大陆边缘盆地属弧后残留盆地成因,多因岛弧的迁移而新生,但珠江口盆地则是被动大陆边缘裂陷作用所致。  相似文献   

莺歌海盆地形成与演化的动力学机制   总被引：4，自引：0，他引：4  

孙向阳  任建业 《海洋地质与第四纪地质》2003,23(4):45-50

莺歌海盆地位于印支半岛与南海北部大陆边缘交接区,复杂的地质构造背景使其形成演化的动力学机制成为国内外的研究焦点。从区域动力学演化的角度,系统分析了影响莺歌海盆地发育的印支地块构造演化特征,认为莺歌海盆地构造演化主要受印支半岛早期的逃逸挤出构造和晚期的挤压-伸展构造系统影响(或控制),在此动力学驱动机制下,莺歌海盆地新生代以来的构造演化经历了3个阶段,即左旋走滑-伸展裂陷阶段、中下地壳韧性伸展-热沉降阶段和加速沉降阶段。  相似文献   

Bathymetry of the Tonga Trench and Forearc: a map series   总被引：1，自引：0，他引：1  

Wright  Dawn J.  Bloomer  Sherman H.  MacLeod  Christopher J.  Taylor  Brian  Goodlife  Andrew M. 《Marine Geophysical Researches》2000,21(5):489-512

Four new bathymetric maps of the Tonga Trench and forearc between 14 °S and 27 °S display the important morphologic and structural features of this dynamic convergent margin. The maps document a number of important geologic features of the margin. Major normal faults and fault lineaments on the Tonga platform can be traced along and across the upper trench slope. Numerous submarine canyons incised in the landward slope of the trench mark the pathways of sediment transport from the platform to mid- and lower-slope basins. Discontinuities in the trench axis and changes in the morphology of the landward slope can be clearly documented and may be associated with the passage and subduction of the Louisville Ridge and other structures on the subducting Pacific Plate. Changes in the morphology of the forearc as convergence changes from normal in the south to highly-oblique in the north are clearly documented. The bathymetric compilations, gridded at 500- and 200-m resolutions and extending along 500 km of the landward trench slope and axis, provide complete coverage of the outer forearc from the latitude of the Louisville Ridge-Tonga Trench collision to the northern terminus of the Tonga Ridge. These maps should serve as a valuable reference for other sea-going programs in the region, particularly the Ocean Drilling Program (ODP) and the National Science Foundation MARGINS initiative.  相似文献   

Comparison of Strain-rate Dependent Stress-Strain Behavior from Ko-consolidated Compression and Extension Tests on Natural Hong Kong Marine Deposits     

Jian-Hua Yin  Chun-Man Cheng 《Marine Georesources & Geotechnology》2006,24(2):119-147

This article presents results from a series of K_o-consolidated compression and extension triaxial tests on specimens from undisturbed samples of Hong Kong Marine Deposits (HKMD). To investigate the strain-rate effects, a total of seven K_o-consolidated triaxial tests were conducted including four compression tests and three extension tests. After K_o-consolidation, the triaxial test specimens were sheared at step-changed axial strain rates under three different confining pressures of 50 kPa, 150 kPa, and 400 kPa, respectively. The step-changed strain rates were applied in the following order: +2%/h, +0.2%/h, +20%/h, -2%/h (unloading) and +2%/h (reloading) for the four compression tests and -2%/h, -0.2%/h, -20%/h, +2%/h (unloading) and -2%/h (reloading) for the three extension tests. The results are reported and analyzed in the paper. The results show that the strain rate effects, the stress-strain characteristics, and the effective stress paths of the specimens for tests in a compression state are different from those for tests in an extension stage. One order of magnitude increase in axial strain rate causes an average 8.6% increase in undrained shear strength for compression tests and a 12.1% increase for extension tests. It is also found that the failure mode of the specimens in compression is different from that in extension. The stress-strain behavior of specimens shows strain-softening and a clear shear band in compression tests, but strain-hardening without any clear shear band in extension tests for the same absolute value of axial strain.  相似文献   

Numerical study of enhanced energy dissipation near a seamount     

Nobuyuki Iwamae  Toshiyuki Hibiya  Yoshihiro Niwa 《Journal of Oceanography》2006,62(6):851-858

Using a two-dimensional primitive equation model, we examine nonlinear responses of a semidiurnal tidal flow impinging on a seamount with a background Garrett-Munk-like (GM-like) internal wavefield. It is found that horizontally elongated pancake-like structures of high vertical wavenumber near-inertial current shear are created both in the near-field (the region over the slope of the seamount) and far-field (the region over the flat bottom of the ocean). An important distinction is that the high vertical wavenumber near-inertial current shear is amplified only at mid-latitudes in the far-field (owing to a parametric subharmonic instability (PSI)), whereas it is amplified both at mid-and high-latitudes (above the latitude where PSI can occur) in the near-field. In order to clarify the generating mechanism for the strong shear in the near-field, additional numerical experiments are carried out with the GM-like background internal waves removed. The experiments show that the strong shear is also created, indicating that it is not caused by the interaction between the background GM-like internal waves and the semidiurnal internal tides. One possible explanation is proposed for the amplification of high vertical wavenumber near-inertial current shear in the near-field where tide residual flow resulting from tide-topography interaction plays an important role in transferring energy from high-mode internal tides to near-inertial internal waves.  相似文献   

辽东湾S2冰侧限剪切强度的试验研究   总被引：3，自引：0，他引：3  

李志军孟广琳  高树刚刘培林 《海洋工程》2002,20(1):20-23

利用试验方法系统地研究了辽东湾S2型海冰侧限剪切强度随剪切应变速率、加载方向、法向应力、温度和冰内孔隙率的变化规律。介绍了S2型海冰各向异性特点及剪切应变速率对剪切破坏方式的效应和韧脆破坏转变的条件。分析了不同加载方向海冰峰值剪切强度的差异 ,获得 - 6 2℃温度下S2冰内摩擦角和内聚力分别为 42°和 70 0kPa。利用统计分析给出峰值剪切强度与冰温和孔隙率的试验关系  相似文献   

Gradation affects basic mechanical characteristics of Chinese calcareous sand as airport subgrade of reefs     

Shen Yang  Xue Shen  Hanlong Liu  Huayang Ge  Xiaoxi Rui 《Marine Georesources & Geotechnology》2020,38(6):706-715

Abstract

Construction of the reefs in the South China Sea is a significant foundation to the secure stability and economic development of China. The construction of an airport runway is necessary for this realization. The calcareous sand is the main primary material in the runway construction. A certain type of calcareous sand near a certain reef of the South China Sea was studied in this paper. To investigate this specific calcareous sand, quartz sand was used as a reference for comparison. Microscopic 3-D imaging, compression and triaxial tests were conducted to test the micro, squeezing and shear properties. The effect mechanism of gradation on the calcareous sand’s compressibility and shear characteristics are discussed from a mesoscopic viewpoint using 3-D morphology. Calcareous sand particles are multiangular and flatter in comparison with quartz sand. The larger the particle sizes are, the more different the two sands’ morphologies are. The compressibility of calcareous sand is greater, and the effect of the coarse fraction (5–1?mm) content in the gradation plays the most significant role in this feature. When the coarse particles’ content is less than 25% and the mass ratio of the middle and fine particles (M) is constant, there is the worst coarse fraction content causing the calcareous sand to be most likely compressed. The worst coarse fraction content decreases with the increase in M, and an empirical formula is proposed. When the gradation, relative density and confining pressure are the same, the peak shear stress and strain of calcareous sand are all at a high level. The effect of confining pressure is manifested in calcareous sand. The shear strength and dilation of calcareous sand are also most affected by the medium coarse fraction (5–0.25?mm) content.  相似文献