共查询到20条相似文献，搜索用时 140 毫秒
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堆石料三维边界面模型在FLAC3D中的开发与验证 总被引：1，自引：0，他引：1
堆石料三维边界面模型结合了统一非线性强度准则,可以反映三维应力空间堆石料的应变硬化、软化以及体积收缩和剪胀等传统本构模型难以反映的力学特性。基于三维边界面模型的基本理论,通过FLAC3D提供的二次开发平台,在VC++环境下实现了三维边界面本构模型的二次开发,并给出基于FLAC3D程序的边界面本构模型开发的关键步骤、编程要点和调试方法。利用开发的本构模型,开展了三轴压缩试验的数值模拟计算,并与理论值进行了对比分析。结果表明,嵌入在FLAC3D中的三维边界面本构模型能够较好地反映设定试验条件下的材料性能,而且三维边界面本构模型模型参数简单,都可从常规三轴试验获得,从而验证了三维边界面模型二次开发程序的优越性与合理性。 相似文献
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循环荷载作用下黏土改进边界面模型 总被引：1，自引：0，他引：1
为克服边界面模型应用不便、不能反映卸载过程中土体的弹塑性性质的缺陷,提出了一个循环荷载作用下可考虑弹塑性加、卸载过程的重塑黏土改进边界面模型。模型采用了简单的边界面形式,可大大简化该模型理论的推导与计算;采取了不预先定义边界面大小的方式,有效地降低了改进边界面模型在应用过程中的经验性;加入边界面胀缩规则,使模型可考虑土样卸载过程中的弹塑性性质,进而可反映土样的滞回特性。通过对重塑黏土进行循环三轴数值模拟试验,并与真实试验结果进行对比分析,验证了改进边界面模型的合理性和有效性。数值验证结果表明,改进边界面模型具有物理意义明确、参数易于确定、形式相对简单的特点,且该模型计算精度较高,计算结果与试验结果吻合得较好。 相似文献
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本文对高等级公路占地边桩的测设精度及放样方法进行了分析讨论，给出了线路中桩和边桩坐标的通用计算模型，还对特殊地段的边桩测设进行了探讨。文中所述的坐标放样法可广泛用于民线路测设工作。 相似文献
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坡积土隧道洞口边、仰坡在开挖后自稳能力差,且受隧道开挖影响,易发生破坏,导致隧道工程无法正常施工,并带来经济损失、危害施工人员安全。本文以香山隧道为工程背景,依据隧址地形地质,建立了隧道洞口边、仰坡的三维仿真模型,结合隧道进洞开挖,分析了洞口边、仰坡的位移和应力变化过程,研究了隧道开挖对边、仰坡的影响,优化了隧道进洞方案。研究结果表明,边、仰坡开挖坡度与原始坡度突变处会产生应力集中并形成贯通的潜在滑移面,隧道开挖对仰坡变形影响较大,坡形坡度对隧道洞口边、仰坡稳定性具有显著影响,放缓坡度和采用分步台阶开挖可有效改善边坡应力应变状态。 相似文献
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磁（重力）异常局部场与区域场分离处理中的扩边方法研究 总被引：6，自引：0，他引：6
本文针对局部场与区域场分离处理的特点，提出了区域场扩边的思想，并给出了一种区域场扩边方法。与其它两种数据处理中常用的扩边方法进行了对比研究。模型和实测资料的处理结果表明，区域场扩边方法效果最好，对折扩边方法次之，余弦衰减至零的方法效果最差。 相似文献
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给出了一种求解多块体接触的有限元解法,即将接触面条件精确引入并以节点接触力为基本未知量,把高度接触非线性问题凝缩在可能接触面上进行。首先从两块体三维接触力学模型着手,从整体有限元方程导出增量形式的协调方程,在此基础上详细讨论了多块体接触协调方程的建立方法。随后以广义Mohr-Coulomb准则为摩擦力条件,给出了增量形式的定解和判定条件。程序实施时,针对三维接触问题滑动方向无穷的问题,同时对接触状态及滑动摩擦力分量进行判定,使得迭代收敛快速准确;对于多块体常见的非光滑接触,即角点问题,将角点分类,并根据角点实际的接触状态分情况给出了更为合理的处理方法。通过算例验证后的程序应用于不连续面地下洞室开挖模拟,取得了满意的结果。 相似文献
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利用FLAC3D程序提供的二次开发平台UDM在VC++编译环境下实现了一基于修正剑桥模型的简化边界面模型的开发。介绍了边界面模型的基本原理,并给出了开发关键技术和具体实施方法。通过三轴加卸载试验、不排水静三轴试验、不排水动三轴试验等几种数值试验与修正剑桥模型进行了对比研究。计算结果验证了所开发的边界面模型的正确性及相对修正剑桥模型的优越性。 相似文献
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A robust contact theory can be regarded as key to three dimensional discontinuous deformation analyses (3D-DDA). Not only must this theory provide an efficient algorithm to judge the type and location of contacts but also it must be able to present comprehensive formulations for every kind of contact (open, sliding and locked contact). There are six types of contact in three dimensional discontinuous deformation analyses (vertex-to-vertex, vertex-to-edge, vertex-to-face, edge-to-edge, edge-to-face and face-to-face) that can be converted to vertex-to-face and edge-to-edge contacts. This paper presents a new model of edge-to-edge contact to three dimensional discontinuous deformation analyses (3D-DDA). This new model considers both kinds of edge-to-edge contact (cross-over and parallel edge-to-edge contact) and presents a criterion for inter-penetration. Sub matrices of normal and shear spring and friction force are derived by geometrical analysis and penalty method. This new model is implemented in a 3D-DDA computer programme, and the example results demonstrate the validity of the model. 相似文献
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S. Amir Reza Beyabanaki Roozbeh Geraili Mikola Kianoosh Hatami 《Computers and Geotechnics》2008,35(3):346-356
This paper presents a new contact calculating algorithm for contacts between two polyhedra with planar boundaries in the three-dimensional discontinuous deformation analysis (3-D DDA). In this algorithm, all six type contacts in 3-D (vertex-to-face, vertex-to-edge, vertex-to-vertex, face-to-face, edge-to-edge, and edge-to-face) are simply transformed into the form of point-to-face contacts. The presented algorithm is a simple and efficient method and it can be easily coded into a computer program. In this paper, formulations of normal contact, shear contact and frictional force submatrices based on the new method are derived and the algorithm has been programmed in VC++. Examples are provided to demonstrate the new contact rule between two blocks. 相似文献
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巨石作为一种大体积、大质量的滚石,其崩塌失稳及高速、高能远程运动往往导致沿途建筑物和交通线路的毁灭性灾难。以西藏自治区G318国道K4580典型滑坡为工程背景,基于三维非连续变形分析（three-dimensional discontinuous deformation analysis,简称3D-DDA）方法研究巨石崩塌失稳及运动全过程的特征与现象。分别建立该边坡未滑坡、浅层滑坡后和深层滑坡后3种坡形的巨石崩塌3D-DDA数值模型。采用滚石运动横向偏移经验模型,验证3D-DDA巨石运动模拟的准确性。在此基础上,分析巨石崩塌失稳机制及破坏后沿3种不同坡形边坡的运动轨迹和动能演进等运动特征。结果表明,3D-DDA能够有效模拟巨石崩塌失稳、运动发展、剧烈冲击碰撞直至最终静止等整个动力学过程。巨石崩塌表现为滑动→倾倒?滑动→倾倒→翻转?下落的失稳模式转换;巨石运动表现为碰撞、弹跳、飞跃、滚动、滑动等多种运动形式以及横向偏移、侧向偏转等三维空间运动特征,经过道路并与高架桥发生碰撞,引发巨石灾害。不同坡面几何特征下的巨石运动偏移量、弹跳高度、运动至坡底碰撞时间、最终稳定时间等均随着未滑坡、浅层滑坡后、深层滑坡后3种坡形变化而减小。通过3D-DDA巨石崩塌运动分析,预测巨石运动全过程、影响范围、冲击能量、停积位置等,可为巨石防灾减灾对策或措施制定提供依据。 相似文献
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A Model of Point-to-Face Contact for Three-Dimensional Discontinuous Deformation Analysis 总被引：15，自引：0，他引：15
Summary The key to three-dimensional discontinuous deformation analysis (3D DDA) is a rigorous contact theory that governs the interaction of many three-dimensional blocks. This theory must provide algorithms to judge contact types and locations and the appropriate state of each contact, which can be open, sliding or locked. This paper presents a point-to-face contact model, which forms a part of the contact theory, to be used in 3D DDA. Normal spring, shear spring and frictional force submatrices are derived by vector analysis and the penalty method. Also given are the open-close iteration criteria and operations performed for different changes in contact state. Sliding at a contact can occur in any direction parallel to the contact face, as opposed to one of two directions in two-dimensional DDA. This point-to-face contact model has been implemented into a 3D DDA computer program, and numerical results from several test cases demonstrate the validity of the model and the capability of the program. 相似文献
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非连续子母块体理论模型研究(Ⅰ):基本理论 总被引：1，自引：1，他引：0
对节理岩体的非连续变形与破坏失稳的数值模拟分析是目前岩土力学与工程领域中的前沿课题之一,岩体由节理裂隙以及由其切割而成岩石块体组成,介于连续与非连续之间,由于其内部结构的不确定性造成了其宏观力学行为的复杂性。在讨论了岩体破坏失稳的研究尺度的基础上,从多尺度耦合的角度出发,同时考虑连续问题、非连续问题以及连续问题向非连续问题转化,提出了非连续子母块体理论模型。在非连续子母块体理论模型中,假定岩体与岩体内部被层理、节理等结构面所切割而成的岩石块体均属于宏观尺度,把宏观的岩石块体定义为母块体,用假想的人工节理将其继续分为若干更小的块体,更小的块体称为子块体,子块体为各向同性的均质体,并且在计算中不再发生破坏分解为更小的块体,作为计算分析的基本单元,子块体的研究尺度属于细观尺度。模型也重新定义了子块体间的接触,并将其划分为连续接触与非连续接触两种类型,连续接触在一定条件下发生破坏转化为非连续接触;采用增广拉格朗日乘子法对子块体间的接触进行处理,能够计算出准确的弹簧接触力。 相似文献
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Yuzo Ohnishi Tomofumi Koyama Ikuo Hagiwara Shigeru Miki Testuya Shimauchi 《Geomechanics and Geoengineering》2014,9(2):97-112
This paper discussed the analytical precision on equations of motion in some practical studies that use 2-D DDA, 2D-Coupled analysis of NMM & DDA, and 3D-DDA. We point out the main reason for numerical instability in DDA is loss of the effective digits when superposing the global stiffness matrix under the variable conditions of large and the small blocks. Categories of analyses are distributed in 2D-DDA static masonry structures such as the Great Pyramid and the Pont du Gard, 2D-DDA dynamic rock fall problems and the sensitivity of its analysis on the velocity ratio and the penalty, earthquake response analysis of rock slopes, 2D-NMM, 2D-coupled analysis of DDA and NMM and 3D-DDA rock fall problem. The selected examples on the Great Pyramid, Pont du Gard and Bayon Temple at Angkor Thom are located in Egypt, France and Cambodia respectively as UNESCO world heritages sites. The authors evaluated the applicability of the methods and the reliability of the results by comparing different methods and site observations from the practical problems. 相似文献
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非连续变形分析(DDA)方法是一种新的用来分析块体系统运动和变形的非连续介质数值计算方法。研究的核心工作是致力于对现有DDA接触问题处理方法的改进。DDA主要采用罚函数法和Lagrange乘子法处理接触问题,合理设定罚参数很困难,此外,因开闭迭代而引起的刚度矩阵的不连续变化也会导致收敛方面的困难。为避免引入罚参数及传统意义上的开闭迭代,用混合线性互补模型(LCDDA)对DDA方法进行了重新描述。在此基础上,综合基于非光滑分析的Newton法的局部平方收敛和最速下降法的全局线性收敛的优势,提出求解LCDDA模型的有效算法。根据上述思想及理论研究成果编制了完整的计算程序,算例计算结果证明了方法的精度及可行性。 相似文献
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《Geomechanics and Geoengineering》2013,8(3):221-236
This paper presents a new point-to-face contact algorithm for contacts between two polyhedrons with planar boundaries. A new discrete numerical method called three-dimensional discontinuous deformation analysis (3-D DDA) is used and formulations of normal contact submatrices based on the proposed algorithm are derived. The presented algorithm is a simple and efficient method and it can be easily coded into a computer program. This approach does not need to use an iterative algorithm in each time step to obtain the contact plane, unlike the ‘Common-Plane’ method applied in the existing 3-D DDA. In the present 3-D DDA method, block contact constraints are enforced using the penalty method. This approach is quite simple, but may lead to inaccuracies that may be large for small values of the penalty number. The penalty method also creates block contact overlap, which violates the physical constraints of the problem. These limitations are overcome by using the augmented Lagrangian method that is used for normal contacts in this research. This point-to-face contact model has been programmed and some illustrative examples are provided to demonstrate the new contact rule between two blocks. A comparison between results obtained by using the augmented Lagrangian method and the penalty method is presented as well. 相似文献