摘要
为克服材料软化导致的有限元网格敏感性难题,提出了一个压力相关隐式梯度塑性模型来模拟土体软化条件下条形基础地基承载力。通过引入微应变作为附加运动学变量,推导了包含高阶广义应力的微力平衡和经典动量方程,并基于热力学第二定律,将附加的微力平衡转化为宏观等效塑性应变与微应变耦合的Helmholtz方程。进一步建立能耦合位移和微变量的有限元算法,并通过软化材料双轴压缩试验模拟,验证了该算法在应变局部化数值模拟中的适用性。将建立的方法用于条形基础地基承载力特性模拟,并通过与理想弹塑性模型计算结果对比表明,土体软化将导致地基承载能力降低,破坏模式表现为失稳区域变小且塑性应变幅值增大。
To overcome the mesh sensitivity induced by strain softening,an implicit gradient plasticity model is put forward to simulate the bearing capacity of a rigid strip foundation on strain-softening soil.A micro-variable is introduced to serve as the additional kinematic variable,and a micro-force balance containing higher-order generalized stresses together and the classical balance of momentum equation are derived.Based on the second law of thermodynamics,the additional micro-force balance is converted into a Helmholtz equation that couples the effective plastic strain and micro-strain.Furthermore,a finite element procedure coupling both displacements and micro-strain is implemented.The applicability of the proposed methodology to capture strain localization is verified by the plane strain compression tests.Finally,the established methodology is used to simulate the bearing capacity of a rigid strip foundation on strain-softening soil,and compared to the calculations from perfectly plasticity model.The simulations show that the strain softening induces a decreasing bearing capacity.The resulted failure mode shows a smaller instability range and a larger maximum deformation magnitude.
作者
吕玺琳
薛大为
LüXi-lin;XUE Da-wei(Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education,Tongji University,Shanghai 200092,China;Department of Geotechnical Engineering,Tongji University,Shanghai 200092,China)
出处
《岩土工程学报》
EI
CAS
CSCD
北大核心
2019年第A02期9-12,共4页
Chinese Journal of Geotechnical Engineering
基金
国家重点研发计划项目(2016YFC0800200)
国家自然科学基金面上项目(41672270)
关键词
隐式梯度模型
应变软化
剪切带
地基承载力
网格敏感性
implicit gradient plasticity
strain softening
shear band
bearing capacity of foundation
mesh sensitivity
