Three-dimensional numerical analysis of the keying of vertically installed plate anchors in clay     

Long Yu  Jun Liu  Xian-jing Kong  Yuxia Hu 《Computers and Geotechnics》2009

Plate anchors, such as suction embedded plate anchors and vertically driven plate anchors, offer economically attractive anchoring solutions for deep/ultra-deep water offshore developments. The rotation/keying processes of plate anchors will cause embedment losses, which lead to decreases of the uplift resistances of the anchors in normally consolidated soil. In the present paper, the keying processes of vertically installed strip and square plate anchors are simulated using the 3-D large deformation finite element method. The effects of loading eccentricity and pullout angle on the embedment loss during keying are investigated. Both the development of the uplift resistance and the soil flow mechanisms are presented. The numerical results show that the loading eccentricity e/B has a much larger effect on the embedment loss than the pullout angle does. The anchor shape has a minimal effect on the loss in anchor embedment. The shape factors (square/strip) are 1.05–1.09 for loss of embedment and 1.10–1.19 for capacity.  相似文献   

Buckling analysis of 3D layered structures using a Cosserat continuum approach     

A. Riahi  J.H. Curran  H. Bidhendi 《Computers and Geotechnics》2009

This paper concerns the buckling analysis of three-dimensional (3D) layered continua using the Cosserat approach. The finite element method (FEM) is used to implement the adopted Cosserat formulation. As a result, the interfaces between the layers need not be explicitly modelled. Instead, the internal characteristic length, i.e., the layer thickness and also the interaction conditions between the layers are incorporated into the governing equations of the solution. This paper introduces a new 3D geometric stiffness matrix based on the principle of virtual work. The proposed geometric stiffness matrix is applied to the linear buckling analysis of a number of benchmark problems with various geometries, boundary conditions, and interaction conditions between the layers. In all cases, the FEM Cosserat solution exhibits a high level of consistency with the analytical solution.  相似文献   

Arbitrary Lagrangian Eulerian based finite element analysis of cone penetration in soft clay   总被引：1，自引：0，他引：1  

D.S. Liyanapathirana 《Computers and Geotechnics》2009

This paper presents a numerical model for the analysis of cone penetration in soft clay based on the finite element method. The constitutive behaviour of the soil is modelled by modifying an elastic, perfectly-plastic soil model obeying Von-Mises yield criterion to take into account the strain-softening, rate dependent behaviour of soft clay. Since this is a problem involving large soil deformations, the analysis is carried out using an Arbitrary Lagrangian Eulerian method where the quality of the mesh is preserved during penetration. The variation of cone resistance is examined with various parameters such as rigidity index of the soil, in situ stress anisotropy and roughness at the cone–soil interface, which influence the penetration resistance of the cone. A theoretical correlation has been developed incorporating these parameters and the results have been compared with previous correlations based on the cavity expansion theory, finite element method and strain path method. With the increase in strain-softening, relative brittleness of the soil increases and the penetration resistance is significantly reduced. With the rising strain-rate dependency, penetration resistance increases but this increase is independent of the degree of brittleness of the soil.  相似文献   

Effects of tunnelling on existing support systems of perpendicularly crossing tunnels     

H.Y. Liu  J.C. Small  J.P. Carter  D.J. Williams 《Computers and Geotechnics》2009

The interactions between perpendicularly crossing tunnels in the Sydney region are investigated using a full three-dimensional (3D) finite element analysis coupled with elasto-plastic material models. Special attention is paid to the effect of subsequent tunnelling on the support system, i.e. the shotcrete lining and rock bolts, of the existing tunnel. The results of the analysis show that in a region such as Sydney, with relatively high horizontal stresses, installation of the new tunnel causes the shotcrete lining of the existing tunnel to be in tension in the side facing towards the tunnel opening and in compression at the crown and invert. The pre-stressed rock bolts are usually tensioned more in the sections closest to the tunnel opening. For this particular study, if a new tunnel is driven perpendicularly beneath an existing tunnel, significant increases are induced in the bending moments in the shotcrete lining at the lateral sides of the existing tunnel and in the axial forces at its crown and invert. The increase in side bending moments causes further tensile cracking but the crown and invert stresses remain within the thresholds for both compressive failure and tensile cracking for shotcrete lining of typical concrete quality. Moreover, the driving of the new tunnel causes the tensile forces in the existing side rock bolts to increase and those in the existing crown rock bolts to decrease. In contrast, if the new tunnel is driven perpendicularly above the existing tunnel, compressive failure of the existing shotcrete lining is induced at the crown of the deeper tunnel for concrete of typical capacity and a significant tensile force increase of the existing rock bolts around the crown. It is concluded that in order to ensure the stability of the existing tunnel, local thickening is needed at the sides of the existing shotcrete lining if the shallow tunnel is installed first and local thickening is needed at the crown if the deep tunnel is installed first.  相似文献   

Load transfer analysis of rock-socketed drilled shafts by coupled soil resistance     

Hoonil Seol  Sangseom Jeong  Yongmin Kim 《Computers and Geotechnics》2009

The load distribution and deformation of rock-socketed drilled shafts subjected to axial loads are evaluated by a load transfer method. The emphasis is on quantifying the effect of coupled soil resistance in rock-socketed drilled shafts using 2D elasto-plastic finite element analysis. Slippage and shear-load transfer behavior at the pile–soil interface are investigated by using a user-subroutine interface model (FRIC). It is shown that the coupled soil resistance acts as pile-toe settlement as the shaft resistance is increased to its ultimate limit state. Based on the results obtained, the coupling effect is closely related to the ratio of the pile diameter to soil modulus (D/E_s) and the ratio of total shaft resistance against total applied load (R_s/Q). Through comparison with field case studies, the 2D numerical analysis reasonably estimated load transfer of pile and coupling effect, and thus represents a significant improvement in the prediction of load deflections of drilled shafts.  相似文献   

A stabilized finite element formulation for finite deformation elastoplasticity in geomechanics     

Kaiming Xia  Arif Masud 《Computers and Geotechnics》2009

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Parametric studies of DDC-induced deflections of sheet pile walls in soft soils     

Yong Tan  Ye Lu 《Computers and Geotechnics》2009

This paper presents a thorough finite element (FE) parametric study of sheet pile wall deflections caused by deep dynamic compaction (DDC). In this study, the effects of several parameters which may affect the wall deflections were investigated. These parameters are (1) wall embedment length; (2) tamping distance; (3) impact energy per blow; (4) blow counts; (5) soil types on the supporting side of sheet pile walls; and (6) wall stiffness. The effects of these parameters were quantified and discussed, and the factors that help to reduce wall deflections were identified. A series of figures which depict the effects of these parameters were generated. Finally, some suggestions and recommendations for design and construction were reached.  相似文献   

一个新的东亚冬季风强度指数及其强弱变化之大气环流场差异   总被引：38，自引：3，他引：35  

王会军  姜大膀 《第四纪研究》2004,24(1):19-27

文章提出了一个新的东亚冬季风强度指数,并以此为依据从1948～1999年中挑选出两组强弱冬季风年份,通过合成分析对大气环流场和海表温度场在强弱东亚冬季风年的差异进行了对比分析。结果表明:东亚冬季风强度变化不单纯受局地气候系统影响,而与北半球半球尺度上的大气环流异常紧密相连。相对于弱的情形,强东亚冬季风年份中国大陆中东部及其东部大部分海域在整个对流层盛行偏北风距平、乌拉尔阻高显著加强、欧洲大陆西部维持一个深厚的气旋性异常环流系统、西风带环流偏弱、200hPa层南亚高压偏弱;中国大陆、北极地区、蒙古国大部分地区、欧洲大陆西北部表面温度降低;我国大陆与北太平洋海平面气压差加大;东亚大槽加强。研究还揭示,强东亚冬季风年份对应于北大西洋涛动弱指数,北大西洋和北太平洋海温状况对同期东亚冬季风强弱有着显著的影响  相似文献   

Analysis of the Variability of a Two-Dimensional Finite Strain Estimate     

Kingshuk Roy Choudhury 《Mathematical Geosciences》2009,41(5):535-553

Finite strain estimation is a widely used technique for the study of rock deformation in structural geology. One particular algorithm proposed by Shimamoto and Ikeda uses the ‘average shape matrix’ of deformed markers. This paper provides a detailed error analysis for resulting strain estimates in two dimensions. When the number of markers exceeds 100, estimators of components of the strain tensor are shown to have an approximately Gaussian distribution with variances that increase with their mean. Equal variance estimators are obtained by applying a log transform for the elongation and an arcsin transformation for the orientation estimates. Confidence interval formulae for strain tensor components are proposed. Lithology specific constants arising in these formulae are estimated from undeformed samples. The results are validated by application to simulated data as well as observational data from thin sections of sandstone sampled from SE Ireland.  相似文献   

金坪引水隧洞围岩变形稳定性评价     

张勇  聂德新 《工程地质学报》2005,13(4):461-464

金坪引水隧洞埋深较大,部分洞段岩体强度较低,洞室开挖后由于二次应力的作用围岩有可能产生变形,因此合理的评价隧洞围岩变形稳定性问题具有重要的工程意义。鉴于此,文章针对金坪引水隧洞围岩变形稳定性问题,对隧洞在大埋深环境下的围岩应力分布特征进行了数值模拟分析,利用与围岩的应变率和岩体抗压强度相关的两种评价方法,分析了可能发生围岩变形的部位和洞段,对引水隧洞围岩变形稳定性做出了综合评价。  相似文献