波浪作用下斜坡上护面块体应力分布数值模拟

发布时间：2018-06-25 09:44

本文选题：斜坡堤 + 应力　；参考：《大连理工大学》2014年硕士论文

【摘要】：斜坡式防波堤是近海沿岸工程中常用的防浪结构物,其护面层既要起到消浪的效果,又要保持自身的稳定。然而在极端海况下,护面层易发生水力失稳和由于块体断裂破坏而引起的结构失稳。目前关于斜坡堤稳定性的研究工作多基于物模试验,由于比尺效应影响,物模试验结果往往不能正确反映原型结构的强度。因此以原型尺度开展波浪作用下斜坡式防波堤护面块体强度破坏的数值模拟研究工作具有十分重要的学术意义和工程应用价值。本文基于FEM/DEM方法建立二维原型尺度数值模型,模拟波浪荷载作用下斜坡上护面块体内部的应力分布和断裂破坏过程。其中结构物的水动力荷载采用微幅波理论模拟,块体的运动和变形采用FEM/DEM方法模拟。采用基于势函数的罚函数法计算分布式接触力,混凝土块体开裂采用Single/Smeared破坏模型模拟,并采用中心差分法的显式积分算法进行数值求解计算。模拟了块体的自重应力分布和块体碰撞破坏的两种类型,验证了数值模型应力和变形的计算精度。通过数值模拟给出了不同波浪荷载下斜坡上护面块体的运动特性、内部应力分布、裂缝形成和断裂破坏过程,并给出了不同点的应力历时曲线,分析了不同波浪荷载作用下块体内部应力变化规律,讨论了极端海况作用下块体的运动变化趋势和断裂破坏特性。在二维模型的基础上,基于3D FEMDEM方法建立三维原型尺度数值模型,模拟波浪荷载作用下斜坡上护面块体内部的应力分布。有限元计算采用高精度的有限应变有限旋转的二次四面体单元。比较分析了三维数值模型与ANSYS模型对自重作用下混凝土扭王字块的内部应力分布,并模拟了块体下落碰撞过程的动应力变化,验证了三维数值模型的应力计算精度。应用所建立的数值模型对线性波作用下斜坡上规则摆放的护面块体内部的应力分布及其变化特性进行了模拟分析,给出了不同点的应力历时曲线,并给出不同时刻的应力分布图和块体运动趋势图,深讨了块体内部应力的变化特性。数值模拟结果表明：波浪作用下,块体之间相互碰撞,接触点应力最大,其次为块体肢体的连接部分,块体表面各点应力成周期性变化。扭王字块整体稳定性较好,不易发生局部失稳或整体失稳,单个块体的运动趋势多以平移和翻滚为主。而在极端海况下,个别混凝土块体可能在两个肢体的连接部位发生断裂破坏,工程上应做加强处理。本论文的研究工作将为防波堤护面块体的设计提供参考依据。
[Abstract]:Slope breakwater is a commonly used anti-wave structure in offshore coastal engineering. Its protective layer not only has the effect of wave elimination, but also maintains its own stability. However, under extreme sea conditions, hydraulic instability and structural instability caused by block fracture are easy to occur. At present, the research work on stability of slope embankment is mostly based on physical model test. Because of the influence of scale effect, the results of physical model test often can not reflect the strength of prototype structure correctly. Therefore, it is of great academic significance and engineering value to simulate the strength failure of slope breakwater block with the prototype scale. Based on the FEM-Dem method, a 2-D prototype numerical model is established to simulate the stress distribution and fracture failure process of the slope surface block under wave loads. The hydrodynamic loads of structures are simulated by micro-wave theory, and the motion and deformation of blocks are simulated by FEM-Dem method. The penalty function method based on potential function is used to calculate the distributed contact force, and the single / Smeared failure model is used to simulate the crack of concrete block, and the explicit integral algorithm of the central difference method is used to solve the problem numerically. The distribution of gravity stress and the two types of block collision failure are simulated, and the calculation accuracy of the numerical model is verified. Through numerical simulation, the motion characteristics, internal stress distribution, crack formation and fracture failure process of the protection block on the slope under different wave loads are given, and the stress duration curves at different points are given. The variation law of internal stress in blocks under different wave loads is analyzed, and the variation trend of block motion and fracture failure characteristics under extreme sea conditions are discussed. On the basis of two-dimensional model, a three-dimensional prototype numerical model was established based on 3D FEMDEM method to simulate the stress distribution of the block on the slope under wave loads. High precision finite strain finite rotation quadratic tetrahedron element is used in finite element analysis. In this paper, the internal stress distribution of the concrete wrist-wangzhuang block under the self-gravity action of the three-dimensional numerical model and the ANSYS model is compared and analyzed, and the dynamic stress changes during the falling collision of the block are simulated, and the accuracy of the three-dimensional numerical model is verified. The numerical model is used to simulate and analyze the stress distribution and its variation characteristics of the regularly laid block on the slope under the action of linear wave, and the stress duration curves at different points are given. The stress distribution at different times and the trend map of block movement are given, and the variation characteristics of stress inside the block are discussed. The numerical simulation results show that under the action of wave, the stress of contact point is the largest, and the joint part of the block limb is the second, and the stress of each point on the surface of the block changes periodically. The whole stability of the writhing block is good, it is not easy to occur local instability or global instability, and the movement trend of single block is mainly translation and roll. However, under extreme sea conditions, individual concrete blocks may be broken and destroyed in the joint of two limbs, which should be strengthened in engineering. The research work in this paper will provide reference for the design of breakwater surface block.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：U656.2

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