岩土体灾变过程多尺度数值分析方法研究

发布时间：2018-06-23 01:39

本文选题：岩土体灾变 + 多尺度方法　；参考：《浙江大学》2014年博士论文

【摘要】：土体由大量土颗粒构成,其灾变过程是由微观颗粒、细观材料到宏观场地多尺度级联耦合渐进演化的结果。传统土力学基于连续介质假定,不能反映岩土体灾变破坏过程中颗粒间接触脱开、颗粒剧烈转动和颗粒破碎等微观尺度行为,多尺度数值模拟是再现岩土体灾变过程的有效手段。论文针对两种典型灾变破坏现象,即应变局部化灾变破坏和非应变局部化灾变破坏,开展多尺度数值模拟方法研究,取得如下研究成果： (1)针对应变局部化岩土体灾变问题,将剪切带等局部化带的弱非连续变形等效为无厚度的强非连续变形带,采用黏聚区域模型刻画剪切带的变形特性和能量耗散机制,基于增强有限单元法构造出无厚度剪切带单元,提出了基于黏聚区域模型的增强有限元分析方法。边坡渐进失稳破坏过程的分析表明,基于黏聚区域模型的增强有限元分析方法能够很好地再现剪切带的扩展过程,不存在网格敏感性等问题；剪切带的应变软化特性对滑裂面形状的影响不大,但极大地降低了边坡的极限承载能力。 (2)针对非应变局部化灾变问题,采用基于位移／速度协调和基于力协调的两种界面耦合方法实现有限元与离散元的多尺度耦合。算例表明,基于位移／速度协调的界面耦合方法不可避免地引起耦合系统的模糊反射；基于力协调的界面耦合方法允许离散元颗粒与有限元单元边界的接触分离,能够有效地再现离散元模型和有限元模型的接触作用及动量和能量交换过程。 (3)基于给定不同的加权函数分别引入不同尺度模型的截断边界和耦合区域,通过耦合区域内位移／速度、力协调条件,提出有限元与离散元耦合的广义桥域法。根据加权函数的不同取法,广义桥域法可以退化得到传统的桥域法和边-边界面耦合方法：适当选取加权函数可实现有限元-离散元耦合和离散元-有限元耦合区域分离,得到协调条件相互独立的分离区域耦合方法和分离界面耦合方法。本文还构造了有限元单时步对离散元多时步的时间积分算法。数值算例表明,分离区域耦合方法和分离界面耦合方法能够有效地避免模糊反射。桥域法和边-边耦合方法通过将高频波转化为低频波实现能量守恒；而分离区域耦合方法和分离界面耦合方法则将有限元模型不能描述的高频部分截断,耦合系统存在能量损失,随有限单元的细划和高频响应分量的减少而降低。有限元单时步对离散元多时步时间积分算法极大地提高了计算效率。 (4)在离散元开源软件Yade中实现了有限元与离散元的广义桥域耦合,编制了岩土体灾变过程的多尺度数值分析平台。多尺度模型的模拟结果与离散元模型的模拟结果相当,但计算效率有了很大的提高。 (5)采用广义桥域法模拟静力触探过程,再现了探头附近土颗粒流动现象,揭示了不同锥尖角度、不同深度时锥尖土体的破坏机理。分析结果表明,比贯入阻力和锥尖阻力大小随锥尖角度、重力场及刺入速度增大而增加,而侧壁摩阻力主要受重力场和刺入速度影响,与锥尖角度几乎无关。
[Abstract]:Based on the assumption of continuum media , the multi - scale numerical simulation is an effective means to reconstruct the catastrophe process of rock and soil .

( 1 ) According to the problem of strain localization , the weak non - continuous deformation equivalent of shear band is equivalent to the non - continuous deformation zone with no thickness , and the deformation characteristic and energy dissipation mechanism of shear band are characterized by using the finite element method . The reinforcement finite element analysis method based on the reinforcement finite element method is presented . The analysis of the failure process of the slope progressive instability analysis shows that the enhanced finite element analysis method based on the viscoelastic region model can better reproduce the expansion process of the shear band without the problems of grid sensitivity and the like .
The strain softening characteristics of the shear band have little influence on the shape of the sliding surface , but the ultimate bearing capacity of the slope is greatly reduced .

( 2 ) The multi - scale coupling of finite element and discrete element is realized by using two kinds of interface coupling methods based on displacement / velocity coordination and force coordination for non - strain localized catastrophic problems . The example shows that the interface coupling method based on displacement / velocity coordination inevitably causes the fuzzy reflection of the coupling system ;
The interface coupling method based on force coordination allows the contact separation between the discrete element particles and the finite element unit boundary to effectively reproduce the contact effect and the momentum and energy exchange process of the discrete element model and the finite element model .

( 3 ) The generalized bridge domain method of finite element and discrete element coupling is proposed based on a given different weighting function . The generalized bridge domain method of finite element and discrete element coupling is proposed based on the displacement / velocity and force coordination conditions in the coupling region .
The separation area coupling method and the separation interface coupling method can cut off the high frequency part which cannot be described by the finite element model , and the coupling system has energy loss , and decreases with the reduction of the fine and high frequency response components of the finite element .

( 4 ) The generalized bridge domain coupling of finite element and discrete element is realized in the discrete element open source software Yade , and the multi - scale numerical analysis platform of rock - soil body catastrophe process is compiled . The simulation results of the multi - scale model are equivalent to the simulation results of the discrete element model , but the calculation efficiency is greatly improved .

( 5 ) Using the generalized bridge domain method to simulate the static sounding process , the phenomenon of soil particle flow near the probe is reproduced , and the damage mechanism of the cone - tip soil at different cone - tip angles and different depths is revealed . The results show that the resistance of the cone - tip increases with increasing the angle of the cone , the gravity field and the penetration velocity , and the friction resistance of the side wall is mainly influenced by the gravity field and the penetration velocity , which is almost independent of the cone - tip angle .
【学位授予单位】：浙江大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TU43

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