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1.
隧道工程地质评价的内容和方法 总被引:2,自引:0,他引:2
结合工程隧道实际,首先阐述了隧道工程的基本地质环境和工程地质条件,然后针对隧道工程可能出现的不良地质现象和可采取的工程措施,从大气降水、围岩稳定、围岩压力、洞口稳定、隧道比选等角度探讨隧道工程地质评价的主要方法和一般内容,进行隧道工程地质评价,为隧道施工、支护提供了依据. 相似文献
2.
The FAST/SKA site selection in Guizhou province 总被引:1,自引:0,他引:1
Many karst depressions with diameters of 300 m to 500 m, suitable for constructing Arecibo-style radio telescopes, were identified
in the south of Guizhou Province by Remote Sensing (RS) and Geographic Information System (GIS) technologies together with
field investigations. Fundamental topography and landform databases were established for 391candidate depressions, and using
GIS the3-dimensional images of depressions, at a scale of 1:10000, were then simulated to fit a spherical antenna.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
3.
吴泽忠 《成都信息工程学院学报》2004,19(2):258-262
在序线性拓扑空间里研究了含有集约束向量极值问题的最优性条件,并建立了充分性和必要性条件. 相似文献
4.
对广西岩溶区三个铅锌硫化物矿床风化带观测结果表明,中低山岩溶区硫化物矿床具有更强烈的风化淋滤作用,但次生晕面积较小;岩溶平原区硫化物矿床风化与元素表生迁移特征较相似于非岩溶区的情况,表现在可产生较宽的pH偏低带和较大面积的次生晕 相似文献
5.
A. P. M. Vaughan L. A. Dowling F. J. G. Mitchell S.‐E. Lauritzen A. M. McCabe P. Coxon 《第四纪科学杂志》2004,19(6):577-590
Organic‐rich deposits, uncovered during overburden removal from mantled gypsum karst at Knocknacran opencast gypsum mine, Co. Monaghan, are the best candidate to date for a last interglacial record in Ireland. The two till and organic‐rich deposits (preserved at different quarry elevations) were emplaced on to a Tertiary dolerite surface during high‐energy flood events and subsequently folded and faulted by movement towards sinkholes in underlying gypsum. Uranium–thorium disequilibrium dating suggests that the organic‐rich deposits in the upper section were hydrologically isolated at ca. 41 ka and those in the lower section at ca. 86 ka. Interpretation of the pollen content, although tentative because of the depositional and post‐depositional history of the material, suggests that the organic material originated in a warm stage possibly warmer than the post‐Eemian interstadials. The unusual setting of preservation may indicate that in situ, last interglacial deposits have generally been removed by erosion in Ireland. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
6.
本矿床是我国金红石矿床重要的成因及工业类型,为具有特定化学成分的岩石在特定变质条件下形成的。本文通过对大量数据的处理,查明了化学成分与成矿的关系:高Al2O3、MgO、Fe2O3+FeO、K2O、P2O5、H2O+、MnO,低SiO2、CaO、Na2O、CO2、S等,利于钛富集;高TiO2、MgO、P2O5、S,低SiO2、CaO、K2O、Al2O3、Fe2O3/FeO,利于金红石形成;高Sc、Zr、Ni、Zn及La/Yb,低Y、Nb、Th、Cd、Ba、Be、ΣREE,利于金红石纯度提高。对研究矿床成因及寻找新的同类矿床等有重要意义 相似文献
7.
8.
In this paper the second order characteristic (discontinuous bifurcation) condition is derived for the granular flow (fully plastic) equations. This second order bifurcation equation is shown to be formally identical to the first order localization requirement during steady elastoplastic deformation provided the elastic compliance tensor is substituted for the product of the plastic multiplier with the flow Hessian. For isotropic yield and flow functions the invariant form of the characteristic condition is given in detail, as well as an alternative expression in adapted co‐ordinates. The characteristic condition can be regarded as defining a hardening function which is maximized to identify the critical angles. When the method is applied to 3D Coulomb flow, Mohr's 3D fracture plane conditions are obtained uniquely. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
9.
Nonstationary hydrodynamic models of a viscous accretion disk around a central compact object were constructed. Two different numerical methods (TVD and SPH) are used to study the dynamics of dissipatively unstable acoustic perturbations at the nonlinear stage in terms of the standard α-disk model. The standard disk accretion in the Shakura-Sunyaev model is unstable against acoustic waves for various parameters of the system. If the α parameter, which specifies the level of turbulent viscosity, exceeds α?0.03, then a complex nonstationary system of small-scale weak shock waves is formed. The growth rate of the perturbations is higher in the central disk region. For α?0.2, the relative shock amplitude can exceed 50% of the equilibrium disk parameters. The reflection of waves from the disk boundaries and their nonlinear interaction are important factors that can produce unsteady accretion. The luminosity of such a disk undergoes quasi-periodic oscillations at a level of several percent (?5%) of the equilibrium level. 相似文献
10.
In view of rapid developments in iterative solvers, it is timely to re‐examine the merits of using mixed formulation for incompressible problems. This paper presents extensive numerical studies to compare the accuracy of undrained solutions resulting from the standard displacement formulation with a penalty term and the two‐field mixed formulation. The standard displacement and two‐field mixed formulations are solved using both direct and iterative approaches to assess if it is cost‐effective to achieve more accurate solutions. Numerical studies of a simple footing problem show that the mixed formulation is able to solve the incompressible problem ‘exactly’, does not create pressure and stress instabilities, and obviate the need for an ad hoc penalty number. In addition, for large‐scale problems where it is not possible to perform direct solutions entirely within available random access memory, it turns out that the larger system of equations from mixed formulation also can be solved much more efficiently than the smaller system of equations arising from standard formulation by using the symmetric quasi‐minimal residual (SQMR) method with the generalized Jacobi (GJ) preconditioner. Iterative solution by SQMR with GJ preconditioning also is more elegant, faster, and more accurate than the popular Uzawa method. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献