Parametric study for optimal design of large piled raft foundations on sand     

《Computers and Geotechnics》2014

In designing piled raft foundations, controlling the total and differential settlements as well as the induced bending moments of the raft is crucial. The majority of piled raft foundations have been designed by placing piles uniformly. In such a design method, the settlements of the piled rafts are likely to be large, which leads to an increase of the pile length and/or number of piles required to reduce the settlements. However, this increase does not satisfy the requirement for economical design. On the basis of a parametric study, this paper contributes a framework for considering an economical design methodology in which piles are placed more densely beneath the column positions when the piled raft is subjected to column loads. The analysis uses PLAXIS 3D software, and the validity of the parametric study is examined through the results of centrifuge model tests conducted by the authors. The study shows that the concentrated pile arrangement method can help to considerably reduce the total and differential settlements as well as the induced bending moments of the raft. Moreover, the effects of parameters, such as pile length, pile number, raft thickness and load types, on the piled raft behavior are investigated. This study can help practicing engineers choose pile and raft parameters in combination with the concentrated pile arrangement method to produce an economical design.  相似文献   

Cosmological Constant, Minimal Mass and Electroweak Interaction     

Corrado Massa 《Astrophysics and Space Science》2006,306(3):175-176

A lower bound for the mass of a rotating body is derived in the general relativity theory with positive cosmological term Λ. The bound suggests a neutrino rest mass ∼1 meV and a neutrino magnetic moment of 10⁻⁴¹ erg/gauss ∼ Planck's magnetic moment. A connection between gravity and electroweak interaction is suggested.  相似文献   

Seismic source representation in orthogonal functions     

D. W. Vasco 《Geophysical Journal International》1990,102(3):531-535

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矩谱法求磁性体质心的若干问题     

王西文 《地球科学与环境学报》1989,(1)

B K Bhattachryya(1975)推导的求磁性体质心的矩谱公式理论严谨,计算速度快,并且有不需要预先知道磁性体磁化率的特点。在该公式的基础上,本文对求质心的各种影响因素作了细致讨论,推导出了提高求解质心精度的改正公式。  相似文献   

Eulerian spatial moments for solute transport in three-dimensional heterogeneous,dual-permeability media     

J.?Xu  B.X.?HuEmail author 《Stochastic Environmental Research and Risk Assessment (SERRA)》2004,18(2):47-60

A Eulerian analytical method is developed for nonreactive solute transport in heterogeneous, dual-permeability media where the hydraulic conductivities in fracture and matrix domains are both assumed to be stochastic processes. The analytical solution for the mean concentration is given explicitly in Fourier and Laplace transforms. Instead of using the fast fourier transform method to numerically invert the solution to real space (Hu et al., 2002), we apply the general relationship between spatial moments and concentration (Naff, 1990; Hu et al., 1997) to obtain the analytical solutions for the spatial moments up to the second for a pulse input of the solute. Owing to its accuracy and efficiency, the analytical method can be used to check the semi-analytical and Monte Carlo numerical methods before they are applied to more complicated studies. The analytical method can be also used during screening studies to identify the most significant transport parameters for further analysis. In this study, the analytical results have been compared with those obtained from the semi-analytical method (Hu et al., 2002) and the comparison shows that the semi-analytical method is robust. It is clearly shown from the analytical solution that the three factors, local dispersion, conductivity variation in each domain and velocity convection flow difference in the two domains, play different roles on the solute plume spreading in longitudinal and transverse directions. The calculation results also indicate that when the log-conductivity variance in matrix is 10 times less than its counterpart in fractures, it will hardly influence the solute transport, whether the conductivity field is matrix is treated as a homogeneous or random field.  相似文献   

滇西区域构造应力场分析     

林向东  赵亮  袁怀玉  吴朋  武敏捷  叶泵  赵桂儒  孙海霞  杨选  侯丽娟 《地震地磁观测与研究》2021,42(2):166-167

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用不完整的地震资料估计地震矩年变化率          下载免费PDF全文

邵辉成  杜兴信  金学申 《地震地质》1999,21(4):406-410

在充分考虑现有地震资料的不完备性和震级服从两端截去泊松分布的条件下,建立了用历史地震资料和现代地震资料及考古地震资料计算地震矩年变化率的方法。计算了西南地区几个地震带的地震矩年变化率,并与地质资料得到的结果进行了比较,结果表明该方法是切实可行的  相似文献   

Some aspects of head‐variance evaluation     

Daniel M. Tartakovsky  Igor Mitkov 《Computational Geosciences》1999,3(1):89-92

We compare two methods of evaluating head covariance for two‐dimensional steady‐state flow in mildly heterogeneous bounded rectangular aquifers. The quasi‐analytical approach, widely used in stochastic subsurface hydrology, is based on the Green's function representation, and involves numerical four‐fold integration. We compare this approach with a numerical solution of the two‐dimensional boundary‐value problem for head covariance. We show that the finite differences integration of this problem is computationally less expensive than numerical four‐fold integration of slowly‐convergent infinite series. This revised version was published online in July 2006 with corrections to the Cover Date.  相似文献   

武定地震序列的震源参数与频率特征   总被引：5，自引：0，他引：5  

秦嘉政  谢庆茵  钱晓东  张俊伟 《地震地磁观测与研究》1999,20(3):13-17

利用武定地震序列数字化记录地震图资料研究了直接用速度谱和位移谱测定地震矩的方法,结果给出前者的误差比后者小５０％,两者无系统差。对序列地震震源参数的研究结果给出,地震矩Ｍ０在１０１２～１０１６（Ｎ·ｍ）之间,震源破裂半径ａ在１００～３５０ｍ范围,震源距ｒ或震级ＭＬ与近场波谱拐角频率ｆ０相关性不明显,序列地震应力降Δσ多数在１０～８０ＭＰａ的范围,表明武定地震序列是在高应力背景下发生的爆发性地震群。  相似文献   

弹簧钢球式安全离合器在钻机中的应用          下载免费PDF全文

田树伟  张培丰 《探矿工程》1999,(6):23-24

分析了钻机在过程中经常发生机械事故的主要原因,提出了解决这一问题的方法,即在钻机内的传动轴上安装弹簧钢球式安全离合器在钻机中的经过反复试验论证辽一方法的可行性。  相似文献