非连续变形分析（DDA）方法的开裂算法研究

发布时间：2018-01-01 02:04

本文关键词：非连续变形分析（DDA）方法的开裂算法研究　出处：《西南科技大学》2017年硕士论文　论文类型：学位论文

【摘要】：岩体破坏模拟是计算岩土力学领域的热点问题,其中连续岩石介质的开裂破坏是岩体破坏的重要形式。本文采用非连续变形分析(DDA)方法模拟连续岩石介质的开裂破坏,着重研究和发展了一种新型DDA开裂模拟算法。首先在DDA方法中引入岩石细观非均匀性模型,对非均匀岩石试件的开裂破坏进行模拟。发现在原有的DDA子块体节理面开裂算法中由于开裂只能沿虚拟节理面发生,开裂破坏的模拟结果受网格划分的影响较大,且计算效率较低。为此,本文发展了一种DDA子块体单元开裂算法,允许裂纹贯穿子块体单元。具体研究工作概括如下:(1)为真实再现岩石材料的开裂破坏,基于Weibull分布函数,在DDA方法中引入了考虑弹性和强度参数非均匀性的岩石细观非均匀性模型。采用DDA子块体节理面开裂算法对巴西圆盘劈裂实验和方件单轴压缩实验进行了计算,在细观线性本构下得到了岩石的宏观非线性力学响应。在此基础上,对含有不同倾角中心裂纹缺陷的圆盘及方件模型的破坏进行了计算,探讨了非均匀性对计算结果的影响。(2)通过以上模拟工作发现,由于裂纹只能沿预置虚拟节理面发生,真实开裂路径只能通过裂纹带逼近,因此需要采用足够小的子块体单元来减小网格划分对开裂路径的影响,计算效率低。为此,发展了DDA子块体单元开裂算法,即允许裂纹贯穿子块体。通过对初始模型加点,搜索不连续面回路以及定义裂纹尖端完成子块体开裂前的准备,然后基于修正的莫尔库仑准则,对子块体的开裂破坏进行判断,最终形成新的子块体,并对开裂后子块体的应力、应变、接触等信息进行传递更新。编写了相应的程序代码。(3)采用新的开裂算法对经典巴西圆盘劈裂和霍普金森杆层裂实验进行模拟,模拟结果与相应的理论结果和实验结果吻合较好,初步验证了DDA子块体单元开裂算法的可行性。与DDA子块体节理面开裂算法相比,新的开裂算法所得的开裂路径不再需要裂纹带来逼近,开裂方向受网格划分的影响减小,模拟对网格划分数目的需求降低,因此开裂路径更为准确,计算效率更高。(4)将DDA子块体单元开裂算法应用到岩石材料的开裂破坏问题当中,对三点弯曲梁断裂、方件的简单拉压破坏、岩质边坡失稳进行了模拟与分析,结果表明DDA子块体单元开裂算法可以较好地解决岩石材料中的裂纹发育扩展问题,从而为一些岩石破裂失稳工程问题的解决提供了数值手段。
[Abstract]:Rock mass failure simulation is a hot issue in the field of computing geotechnical mechanics. The cracking and failure of continuous rock medium is an important form of rock mass failure. In this paper, the method of discontinuous deformation analysis (DDA) is used to simulate the cracking and failure of continuous rock medium. A new DDA crack simulation algorithm is studied and developed. Firstly, the rock mesoscale nonuniformity model is introduced into the DDA method. The cracking failure of non-uniform rock specimen is simulated. It is found that in the original DDA sub-block joint cracking algorithm, the crack can only occur along the virtual joint surface. The simulation results of cracking and failure are greatly affected by mesh generation, and the computational efficiency is low. Therefore, a cracking algorithm of DDA sub-block element is developed in this paper. The concrete research work is summarized as follows: 1) it is a true representation of cracking and failure of rock materials based on Weibull distribution function. The rock meso inhomogeneity model considering the inhomogeneity of elastic and strength parameters is introduced into the DDA method. The splitting experiment of Brazilian disk and uniaxial compression experiment of square parts are carried out by using DDA subblock joint crack algorithm. Calculated. The macroscopic nonlinear mechanical response of rock is obtained under the meso-linear constitutive model. On the basis of this, the failure of disk and square model with crack defects at different dip angles are calculated. The influence of inhomogeneity on the calculation results is discussed. (2) through the simulation work above, it is found that because the crack can only occur along the prefabricated joint plane, the real crack path can only be approached by the crack band. Therefore, it is necessary to reduce the effect of mesh generation on the cracking path by using sub-block elements that are small enough, and the computational efficiency is low. Therefore, the cracking algorithm of DDA sub-block elements is developed. By adding points to the initial model, searching the discontinuous surface loop and defining the preparation before the crack tip completes the sub-block cracking, the modified Mohr Coulomb criterion is used. The cracking failure of sub-block is judged, and a new sub-block is formed, and the stress and strain of sub-block after cracking are analyzed. The new crack algorithm is used to simulate the classical Brazilian disk splitting and Hopkinson bar spallation experiments. The simulation results are in good agreement with the corresponding theoretical and experimental results, which preliminarily verify the feasibility of the DDA sub-block element cracking algorithm, compared with the DDA sub-block joint plane cracking algorithm. The crack path obtained by the new crack algorithm no longer needs to be approximated by the crack, and the crack direction is reduced by the mesh division, and the demand for the number of mesh division is reduced by the simulation, so the crack path is more accurate. The DDA sub-block element cracking algorithm is applied to the cracking and failure problem of rock material. The fracture of three-point bending beam and the simple tension-compression failure of square part are studied. The simulation and analysis of rock slope instability show that DDA subblock element cracking algorithm can solve the problem of crack growth and propagation in rock materials. This provides a numerical method for solving some problems of rock fracture instability engineering.
【学位授予单位】：西南科技大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TU45

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