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1.
Trees growing close to buildings in urban landscapes may change the soil moisture around foundations, producing shrinkage and swelling. This paper presents a numerical solver to estimate the movements resulting from these volumetric strains. This tool will be of assistance in both designing the footings of new buildings and in the analysis of damage associated with buildings that have already been constructed. The conceptual model used is based on current knowledge of the hydro-mechanical behaviour of unsaturated soils. Its numerical implementation is simple, making it easy for users to make changes as they see fit. The program has been verified, validated, and applied in a real stabilization problem. 相似文献
2.
Dual-continuum (DC) models can be tractable alternatives to explicit approaches for the numerical modelling of multiscale materials with multiphysics behaviours. This work concerns the conceptual and numerical modelling of poroelastically coupled dual-scale materials such as naturally fractured rock. Apart from a few exceptions, previous poroelastic DC models have assumed isotropy of the constituents and the dual-material. Additionally, it is common to assume that only one continuum has intrinsic stiffness properties. Finally, little has been done into validating whether the DC paradigm can capture the global poroelastic behaviours of explicit numerical representations at the DC modelling scale. We address the aforementioned knowledge gaps in two steps. First, we utilise a homogenisation approach based on Levin's theorem to develop a previously derived anisotropic poroelastic constitutive model. Our development incorporates anisotropic intrinsic stiffness properties of both continua. This addition is in analogy to anisotropic fractured rock masses with stiff fractures. Second, we perform numerical modelling to test the DC model against fine-scale explicit equivalents. In doing, we present our hybrid numerical framework, as well as the conditions required for interpretation of the numerical results. The tests themselves progress from materials with isotropic to anisotropic mechanical and flow properties. The fine-scale simulations show that anisotropy can have noticeable effects on deformation and flow behaviour. However, our numerical experiments show that the DC approach can capture the global poroelastic behaviours of both isotropic and anisotropic fine-scale representations. 相似文献
3.
Currently, numerical studies at the real scale of an entire engineering structure considering internal erosion are still rare. This paper presents a three-dimensional (3D) numerical simulation of the effects of internal erosion within a linear dike located on a foundation. A two-dimensional (2D) finite element code has been extended to 3D in order to analyze the impact of internal erosion under more realistic hydromechanical conditions. The saturated soil has been considered as a mixture of four interacting constituents: soil skeleton, erodible fines, fluidized fine particles, and fluid. The detachment and transport of the fine particles have been modeled with a mass exchange model between the solid and the fluid phases. An elastoplastic constitutive model for sand-silt mixtures has been developed to monitor the effect of the evolution of both the porosity and the fines content induced by internal erosion upon the behavior of the soil skeleton. An unsaturated flow condition has been implemented into this coupled hydromechanical model to describe more accurately the seepage within the dike and the foundation. A stabilized finite element method was used to eliminate spurious numerical oscillations in solving the convection-dominated transport of fluidized particles. This numerical tool was then applied to a specific dike-on-foundation case subjected to internal erosion induced by a leakage located at the bottom of the foundation. Different failure modes were observed and analyzed for different boundary conditions, including the significant influence of the leakage cavity size and the elevation of the water level at the upstream and downstream sides of the dike. 相似文献
4.
The grain/bed collision in sand transport by wind 总被引：6，自引：0，他引：6
In the last decade much progress has been made toward the development of a comprehensive model of aeolian sediment transport in which the grain/bed collision has been identified as having a significant role. The grain/bed collision has been studied by both physical experiments and numerical simulation. A principal objective of these studies has been to gather sufficient data to characterize the collision in order that it may be represented as an empirical function in numerical models of the sand transport system. Thus the study of the exact physical mechanism of the collision has to some extent been neglected. The transport of larger particles in saltation over a loose surface is known to promote the release of finer particles from that surface into suspension. Thus the precise physics of the grain/bed collision become highly significant with regard to the physics of dust release from a surface. This paper re-examines previous collision data and compares them with a simple collision model. This model proposed that the impinging grain strikes a single surface grain and rebounds: an alternative mechanism might be that the impinging grain ploughs through the surface striking a number of bed grains before rebounding. The collision data are shown to support the model: first, because the duration of the collisions observed on the high speed film supports a short contact time with the surface and, second, because the data fit well with the model. 相似文献
5.
《Geomechanics and Geoengineering》2013,8(2):129-138
Issues related to the numerical simulation of moisture migration patterns in the unsaturated zone and in the vicinity of mature trees are explored in this paper. The research is based on the use of Richard's equation for unsaturated moisture flow incorporating a sink term. A numerical solution has been achieved via the finite-element method for spatial discretization along with a finite-difference time-marching scheme. An axisymmetric solution is developed to represent water uptake near an established tree. The approach adopted utilizes radial symmetry and assumes a linear distribution of water extraction rates with both depth and radius. The model has been validated by direct comparison with field measurements recorded (by others) for a mature lime tree located on a boulder clay subsoil. Non-linear hydraulic properties have been obtained from independent published data. A good correlation between field data and simulated results has been achieved. The simulation covers a full annual cycle starting from field capacity in winter, extending through a full spring–summer drying period and subsequent autumn recharge. It is believed that this is the first attempt to simulate the behaviour of an established tree over such a time-scale. This relatively straightforward approach is thought to be suitable for development and application to a range of geo-engineering problems (e.g. slope stability, shrinkage/heave prediction, etc). 相似文献
6.
Numerical simulation of oil migration and accumulation is to describe the history of oil migration and accumulation in basin
evolution. It is of great value to the evaluation of oil resources and to the determination of the location and amount of
oil deposits. This thesis discusses the characteristics of petroleum geology and permeation fluid mechanics. For the three-dimensional
problems of Dongying hollow of Shengli Petroleum Oil Field, it puts forward a new model and a kind of modified method of upwind
finite difference fractional steps implicit interactive scheme. For the famous hydraulic experiment of secondary migration–accumulation,
the numerical simulation test has been done, and both the computational and experimental results are basically identical.
For the actual problem of Dongying hollow, the numerical simulation test and the actual conditions are basically coincident.
Thus, the well-known problem has been solved. 相似文献
7.
M Banerjee 《Journal of Earth System Science》1986,95(2):153-167
In the present study, the use of one of the recent dependent domain models of capillary hysteresis in the numerical analysis of intermittent infiltration and redistribution of water in two types of soils (a sand and Rubicon Sandy Loam) has been shown. The numerical results for both the soils have been presented in terms of pressure head depth, moisture content depth and the pressure head-moisture content relationships. The capillary hysteresis model has been found to be very useful for the prediction of both wetting and drying scanning curves of various orders. 相似文献
8.
The fluidization technique has been in use for particulate material processing operations for many years. It has been widely believed that the ratio of size and density of the particulate components controls the separation efficiency. In this paper, it is demonstrated that fluid velocity during fluidization could assume an overriding significance when an improvement in separation efficiency is required. This was at first experimentally established by analyzing simpler particulate systems, and later a simulation scheme was adopted to study a wider range of particulate systems. The numerical scheme known as the discrete element method (DEM), that incorporates both the solid- and hydro-dynamic components of the interactive forces, served as an important tool in understanding the separation behavior of binary particulate systems in fluidized beds. It has been established that mere fluidization does not necessarily guarantee an optimal separation, especially when the particles differ widely in density and size. 相似文献
9.
In this paper, steady-state conditions for ideal monodisperse dry granular materials are both theoretically and numerically analysed. A series of discrete element (DEM) numerical simulations have been performed on a periodic cell by imposing stress paths characterized by different Lode angles, pressures, and deviatoric strain rates. The dependence of the material response on both inertial number and loading path has been discussed in terms of void ratio, fabric, and granular temperature. DEM numerical results have been finally compared with the prediction of an already conceived model based on both kinetic and critical state theories, here suitably modified to account for three-dimensional conditions. 相似文献
10.
随着计算机科学和地质大数据技术的迅猛发展,数值模拟和机器学习已成为当今地学领域定量发展的重要前沿方向。数值模拟综合运用了研究区地质、构造、地球物理、地球化学等多源信息,将成矿条件与过程进行量化模拟分析,对研究成矿动力学演化过程及成矿响应有重要意义,可对已有成矿要素/信息在时空上进行扩展/外推,扩大了成矿预测信息的广度和深度,为解决深部成矿预测中获取深部信息难题提供了一种可能的有效途径。支持向量机是一种重要的机器学习分类算法,它具有简洁、方便、高效和计算结果较稳定等特点,在众多领域中得以成功应用,是成矿预测中多源信息提取与融合的一种可靠的技术手段。为了充分利用数值模拟与机器学习的优势,本文提出将计算机数值模拟方法和机器学习(即支持向量机算法)相结合来进行深部成矿预测的新方法。以粤北凡口超大型铅锌矿为例,首先,对凡口矿区勘探线剖面进行构造应力场模拟;进而,以已知钻孔数据作为训练集和测试集,运用支持向量机算法对模拟结果中的不同参量(也即模拟所得的成矿条件)进行训练学习;最后,建立相应的定量找矿预测模型对研究区(或剖面)外围和深部找矿进行预测评价。研究结果表明,本文所建立的预测模型精确度和召回率都较好,预测结果显示出了三个成矿可能较大的区域,说明数值模拟技术和机器学习算法结合应用的效果较好。这种新的成矿预测方法为深部找矿预测提供了一种可行的新思路和新途径,可以有效地拓展运用到其他矿区、其他类型矿床的深部找矿预测工作中。 相似文献
11.
水合物沉积物力学性质的三维离散元分析 总被引：1，自引：0，他引：1
水合物沉积物力学特性研究是天然气水合物开采领域中的热点问题。为深入了解水合物对沉积物力学特性的影响,在提出一个新的水合物沉积物离散元数值试样制备方法的基础上,模拟了不同水合物饱和度沉积物试样的三轴排水试验,并从其应力-应变关系、体变特性、弹性模量及峰值强度等方面对模拟结果及已有室内三轴试验结果进行了对比,然后利用该方法对具有不同微观胶结参数的水合物沉积物样进行了三轴离散元数值试验。研究结果表明：所提出的离散元模拟方法能较好地反映水合物沉积物的主要力学特性;天然气水合物与土颗粒间胶结性能的改变会对水合物沉积物的力学响应产生一定的影响;水合物沉积物强度和模量的增加是孔隙填充水合物和粒间胶结水合物共同作用的结果。 相似文献
12.
This paper deals with the propagation, reflection and transmission of shear waves in monoclinic media. The dispersion equation for a monoclinic layer overlying a monoclinic half-space has been obtained and curves are plotted. The amplitude ratios for both the reflected and transmitted waves due to reflection of shear waves at the interface of two monoclinic half-spaces have also been computed and the numerical results are presented graphically. The results are compared with the isotropic case. It has been observed that, in monoclinic media, the amplitude ratios for reflected and transmitted wave increases approximately by 25 and 50 per cent respectively, in comparison to the isotropic case. © 1997 John Wiley & Sons, Ltd. 相似文献
13.
This paper proposes a numerical approach to the hyperstatic reaction method (HRM) for the analysis of segmental tunnel linings. The influence of segmental joints has been considered directly using a fixity ratio that is determined on the basis of the rotational stiffness. The parameters necessary for the calculation are presented. A specific implementation has been developed using a FEM framework. This code is able to consider the three‐dimensional (3D) effect of segment joints in successive rings on the tunnel lining behaviour. The present HRM allows one to take an arbitrary distribution of segment joints along the tunnel boundary into consideration. In addition, the rotational stiffness of segment joints has been simulated using nonlinear behaviour, as it is closer to the true behaviour of a joint than linear or bilinear behaviour. The numerical results of three hypotheses on ring interaction, which allow the 3D effect of a segmental tunnel lining to be taken into account, have been compared with data obtained from the shield‐driven tunnel of the Bologna–Florence high‐speed railway line project. The numerical results presented in the paper show that the proposed HRM can be used to effectively estimate the behaviour of a segmental tunnel lining. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
14.
数值模拟是一种利用电子计算机,通过数值计算和图像显示的方法,研究工程问题、物理问题乃至自然界各类问题的方法。随着高性能计算的不断发展,数值模拟方法在沉积盆地构造变形研究中的应用不断扩大,学术界和工业界将数值模拟方法广泛应用于盆地构造变形特征与变形机制的定量研究,取得了丰硕的成果。本文在系统分析前人数值模拟成果的基础上,阐述了有限元、有限差分、边界元和离散元四种常用数值模拟实验方法的特征和应用。同时,本文对近年来数值模拟方法在沉积盆地褶皱冲断构造变形中的研究进展进行了分类总结,重点介绍这一方法在构造特征与变形机制研究中取得的成果,为数值模拟方法在盆地构造变形领域应用的不断扩大和深入提供参考。最后,本文对数值模拟技术在目前应用中面临的问题和未来的发展方向提出了一些看法和建议。 相似文献
15.
16.
L.J. Lorig 《Computers and Geotechnics》1985,1(2):79-97
Analysis of reinforced excavations in jointed rock requires that the functions of reinforcement be considered explicitly. This can be achieved in a computational model by calculating, for each reinforcement element, the forces generated by displacements across the discontinuity through which the element passes. Simple force-displacement relations are exploited to describe both shear and axial behaviour of a reinforcement element. Large shear displacements are assumed to be accompanied by simple geometric changes in an element where it crosses a discontinuity. The resultant numerical representation based on this model has been incorporated in a distinct element scheme for the analysis of blocky media. Illustrative examples are presented which compare the performance of the numerical model with results from laboratory scale physical experiments. 相似文献
17.
This is a summing-up report based on 48 papers on the applications of numerical method to soil mechanics. Recently, there is a new development of coupling of finite element with other numerical ones in soil mechanics. The dynamic numerical analyses have found further application to nonlinear stress-strain relationship, effective stress, and three dimensional problems. The suitable contact element or conjunct element could be used for contact conditions in finite element calculation. It is an important direction to combine usual numerical method with probabilistic method, which has been used in evaluations of consolidation effect, slope stability, dam, seepage, deformation calculation, interaction, and the performance analyses of pole and foundation. 相似文献
18.
数值计算方法在土力学中的应用 总被引：2，自引：0，他引：2
本文是对48篇有关数值方法在土力学方面应用的论文进行综述的报告。近年来,在土力学方面有限元和其它数值方法的耦合有了新的发展,动力分析在非线性应力应变关系、三维问题和有效应力分析中得到了进一步的应用,接触单元或连接单元可用来处理有限元计算时的接触条件。数值方法和概率方法的结合是一个值得重视的发展方向。这些方法可应用于估计固结效应、土坡稳定、土石坝、渗流、变形计算、共同作用、桩和地基性状分析等方面。 相似文献
19.
地质构造变形数值模拟研究的原理、方法及相关进展 总被引：4，自引：0，他引：4
地质构造变形数值模拟实验研究是遵循自然科学规律,依据数学、物理学、化学等学科中已为人们认识的规律为原理;依靠计算机先进的综合处理系统;以固体地球科学资料为基础所构建的地质模型为实验研究本体。因而,地质构造变形数值模拟是采用数学物理方法对相关地质学问题的科学描述,并采用理论分析和数值模拟实验方法,对所描述的相关地质学过程进行定量化求解。由于数值模拟可以综合利用其它学科的研究成果,建立和模拟不受时空限制的各种地质模型,为定量化地解决一些复杂的地质学问题,提供有效的分析工具,已经引起了国内外地学界的重视和深入研究。数值模拟实验研究方法的发展,将极大地促进我国地学界从采用了多年的传统的描述性研究方法向科学的定量化研究方法的转变。 相似文献
20.
Ali Parsa-Pajouh Behzad Fatahi Philippe Vincent Hadi Khabbaz 《Geotechnical and Geological Engineering》2014,32(5):1187-1210
In this study, FLAC finite difference software has been adopted to simulate the performance of the ground improved using prefabricated vertical drains assisted preloading, considering smear zone characteristics. The numerical code has been applied to predict smear zone properties employing a back calculation procedure using the results of several case studies. The construction of a trial embankment is proposed as a reliable method to predict the smear zone characteristics. The proposed back calculation method is applied to estimate the minimum required degree of consolidation and consequently the minimum required preloading time, resulting in a reliable estimation of the smear zone permeability and extent. Three preloading case studies considering both conventional preloading and vacuum assisted preloading have been simulated to verify the numerical code and to conduct the parametric study using the back calculation procedure. According to the results, the properties of the smear zone can be back-calculated reliably, when at least 33 % degree of consolidation due to trial embankment construction is achieved. 相似文献