Effects of the geometry of two‐dimensional fractures on their hydraulic aperture and on the validity of the local cubic law          下载免费PDF全文

Ahmad Hajjar  Luc Scholtès  Constantin Oltéan  Michel Antoine Buès 《水文研究》2018,32(16):2510-2525

Flow through rough fractures is investigated numerically in order to assess the validity of the local cubic law for different fracture geometries. Two‐dimensional channels with sinusoidal walls having different geometrical properties defined by the aperture, the amplitude, and the wavelength of the walls' corrugations, the corrugations asymmetry, and the phase shift between the two walls are considered to represent different fracture geometries. First, it is analytically shown that the hydraulic aperture clearly deviates from the mean aperture when the walls' roughness, the phase shift, and/or the asymmetry between the fracture walls are relatively high. The continuity and the Navier–Stokes equations are then solved by means of the finite element method and the numerical solutions compared to the theoretical predictions of the local cubic law. Reynolds numbers ranging from 0.066 to 66.66 are investigated so as to focus more particularly on the effect of flow inertial effects on the validity of the local cubic law. For low Reynolds number, typically less than 15, the local cubic law properly describes the fracture flow, especially when the fracture walls have small corrugation amplitudes. For Reynolds numbers higher than 15, the local cubic law is valid under the conditions that the fracture presents a low aspect ratio, small corrugation amplitudes, and a moderate phase lag between its walls.  相似文献   

Application of micropolar plasticity to post failure analysis in geomechanics     

Majid T. Manzari 《国际地质力学数值与分析法杂志》2004,28(10):1011-1032

A micropolar elastoplastic model for soils is formulated and a series of finite element analyses are employed to demonstrate the use of a micropolar continuum in overcoming the numerical difficulties encountered in application of finite element method in standard Cauchy–Boltzmann continuum. Three examples of failure analysis involving a deep excavation, shallow foundation, and a retaining wall are presented. In all these cases, it is observed that the length scale introduced in the polar continuum regularizes the incremental boundary value problem and allows the numerical simulation to be continued until a clear collapse mechanism is achieved. The issue of grain size effect is also discussed. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

Three-dimensional numerical simulation of obfique wave action on vertical walls     

LI Benxia YU Xiping YU Yuxiu 《海洋学报(英文版)》2006,25(1):147-153

A three-dimensional numerical model based on the potential theory was developed to study the oblique wave action on vertical walls. A source term inside the domain was used to generate incident waves and outgoing waves were dissipated by sponge layers and transmitted by radiation boundaries. The finite difference method was used to solve the governing equations and boundary conditions in the regular transformed domain in σ-coordinate. Satisfactory agreements between the numerical predictions and experimental results of wave force were obtained. It is concluded that the maximum wave force acting on the vertical walls is induced by the obliquely incident waves rather than the normally incident waves.  相似文献   

New Approach for Estimation of Static and Seismic Active Earth Pressure   总被引：1，自引：1，他引：1  

Deepankar Choudhury  Shailesh Singh 《Geotechnical and Geological Engineering》2006,24(1):117-127

To estimate static and seismic active earth pressure (P_ad) on a rigid retaining wall, numerical analyses using different step sizes have been carried out in this paper, based on the modified Culmann line method by considering Coulomb’s planar rupture surface. Equivalent pseudo-static seismic forces are considered in the analysis. A new concept of modified unit weight by considering ground surcharge is introduced under static and seismic conditions. By numerical analysis, area of soil (A) has been estimated to obtain the ratio of A/A₀ where A₀ is θh², θ is the angle between retaining structure and ground surface and h is the vertical height of the wall. This ratio remains constant for a particular type of soil and has been used to estimate the maximum active earth pressure using force diagram. Results are provided in tabular form for easy calculation of the coefficient of static and seismic active earth pressure. Present results by considering the new technique, compares well with the results obtained by earlier researchers.  相似文献   

薄钢板剪力墙抗震性能试验研究   总被引：15，自引：6，他引：15  

苏幼坡  刘英利  王绍杰 《地震工程与工程振动》2002,22(4):81-84

通过4个薄钢板剪力墙和1个钢筋混凝土框架的试验，研究了薄钢板剪力墙在低周往复荷载作用下的刚度、承载力、延性和耗能性能。试验表明，利用薄钢板剪力墙在低周往复荷载作用下的刚度、承载力、延性和耗能性能。试验表明，利用薄钢板剪力墙作为抗侧力构件是可行的。在钢筋混凝土框架中设置薄钢板可有效地增加刚度，承载力和耗能性能。  相似文献   

大开间小型混凝土砌块10层模型房屋抗震性能试验研究(Ⅰ)   总被引：8，自引：3，他引：8  

周抚生  郭迅  郑志华  毛国成 《地震工程与工程振动》2002,22(6):58-64

我国抗震设计规范（GB50011－2001）规定在6、7、8度区，混凝土小砌块结构分别可以建七、六、五层。由于混凝土小砌块结构的最大优势在于10－20层（与混凝土框架或框架剪力墙结构比）。本文按1／4比例制作了10层混凝土小砌块结构模型，按7度设防要求实施构造措施，通过振动台试验研究模型结构的抗震性能。结果表明，模型结构完全能够满足在7度区“小震不坏，大震不倒”的要求。圈梁、构造柱以及水平拉结筋构成的约束体系抗震作用是明显的。试验利用砌块的非注芯孔灌注铁砂来模拟墙体出平面动力效应。在本模型的构造措施下，平出面反应不对结构破坏起控制作用。  相似文献   

新型组合连梁控制结构体系   总被引：9，自引：0，他引：9  

邓志恒  潘峰  陶晓光  唐光暹 《世界地震工程》2003,19(3):6-11

分析了连梁在水平力作用下的破坏机制，对连梁结构体系的发展及结构抗震控制进行了评述，在此基础上提出一种新型组合连梁控制结构体系，并对其进行了概念分析，提出了有待研究的若干关键问题。  相似文献   

某中学教学楼的抗震鉴定与加固设计   总被引：1，自引：0，他引：1  

赵更歧  张冰华  张哲  王俊岭 《世界地震工程》2004,20(3):90-94

按老规范设计的砌体结构未考虑抗震，使用年代过长会出现承载力不足的问题，需对原结构按新规范进行全面检测和抗震鉴定，若鉴定结果表明该结构不符合抗震要求，则需进行加固，结合一实际工程对检测程序和加固方法做一全面论述，供工程实际中参考。  相似文献   

Seismic earth pressures on rigid and flexible retaining walls     

P.N. Psarropoulos  G. Klonaris  G. Gazetas 《Soil Dynamics and Earthquake Engineering》2005,25(7-10):795-809

While limiting-equilibrium Mononobe–Okabe type solutions are still widely used in designing rigid gravity and flexible cantilever retaining walls against earthquakes, elasticity-based solutions have been given a new impetus following the analytical work of Veletsos and Younan [23]. The present paper develops a more general finite-element method of solution, the results of which are shown to be in agreement with the available analytical results for the distribution of dynamic earth pressures on rigid and flexible walls. The method is then employed to further investigate parametrically the effects of flexural wall rigidity and the rocking base compliance. Both homogeneous and inhomogeneous retained soil is considered, while a second soil layer is introduced as the foundation of the retaining system. The results confirm the approximate convergence between Mononobe–Okabe and elasticity-based solutions for structurally or rotationally flexible walls. At the same time they show the beneficial effect of soil inhomogeneity and that wave propagation in the underlying foundation layer may have an effect that cannot be simply accounted for with an appropriate rocking spring at the base.  相似文献   

Pseudo‐dynamic seismic response of reinforced concrete frames infilled with non‐structural brick masonry     

F. Colangelo 《地震工程与结构动力学》2005,34(10):1219-1241

This paper presents pseudo‐dynamic test results on the in‐plane seismic behaviour of infilled frames. Thirteen single‐storey, single‐bay, half‐size‐scale, reinforced concrete‐frame specimens, most of which infilled with non‐structural masonry made of perforated bricks and cement mortar are tested. The infills are in contact with frames, without any connector; openings are not covered. The frames are different in their strength and details, reinforcement grade, and aspect ratio. Seismic input is the 1976 Tolmezzo (Friuli, Italy) ground acceleration, to which specimens are subjected two times: virgin and damaged by the previous test. The global seismic response of initially virgin infilled specimens considerably differs from that of bare specimens. This follows a dramatic change of properties: compared to a bare frame, the initial stiffness increases by one order of magnitude, and the peak strength more than doubles. The peak drift lessens; however, the displacement ductility demand does not. The energy demand is greater. Nevertheless, the influence of infill decreases as damage proceeds. Displacement time histories of damaged specimens are quite similar. At the local level, infill causes asymmetry and concentration of the frame deformation. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献