Abstract
For the stability and failure pattern analysis of bimslopes, a novel second-order cone programming optimized micropolar continuum finite element method (mpcFEM-SOCP) incorporating the micropolar Mohr-Coulomb (MC) model is developed. Based on two bimslopes, the effectiveness and superiority of the present method is examined. Numerical analyses disclose that the presence of rock blocks “intruding” the potential slip surface may increase the ultimate bearing capacity of the rigid footing and contribute to the stability of bimslopes. Compared to the second-order cone programming optimized classical continuum finite element method (FEM-SOCP), it is interesting to note that mpcFEM-SOCP may reveal different failure mechanisms evidently from those predicted by FEM-SOCP in some cases. For the bimslope with square-cluster rock blocks, it is observed by FEM-SOCP and mpcFEM-SOCP that the presence of scattered rock blocks complicates the failure patterns of bimslopes. Compared to the generalized limit equilibrium method in the Pybimstab package assuming a single slip surface, FEM-SOCP and mpcFEM-SOCP may produce finger-pattern slip surfaces, and particularly the width of slip surfaces in matrix soil may be adequately modeled by the internal characteristic length /c bridging the particle characteristics of matrix soil and the macroscopic strain localization behavior.
摘要
针对土石混合体边坡稳定性和破坏模式分析, 提出了一种基于微极Mohr-Coulomb(MC)模型 的二阶锥规划微极连续体有限元法(mpcFEM-SOCP)。以两个土石混合体边坡为例, 验证了所提方法的 有效性和优越性。数值分析表明, 块石“侵入”潜在滑面会增加刚性基础的极限承载力以及边坡的稳 定性。与二阶锥规划经典连续体有限元法(FEM-SOCP)相比, 在某些情况下mpcFEM-SOCP 可以揭示不 同的土石混合体边坡破坏机制。通过FEM-SOCP 和mpcFEM-SOCP 可以观察到, 对于方形簇块石土石 混合体边坡, 分散的块石会使土石混合体边坡破坏模式更为复杂; 与Pybimstab 程序包中(假设单滑移 面)的广义极限**衡方法相比, FEM-SOCP 和mpcFEM-SOCP 会提供手指分叉式滑移面; 通过关联基质 土颗粒特性和宏观应变局部化行为的内部特征长度l c 能够较好地模拟基质土滑移面的宽度。
Abbreviations
- DOF:
-
Degree of freedom
- FEM:
-
Finite element method
- FEM-SOCP:
-
Second-order cone programming optimized classical continuum finite element method
- FOS:
-
Factor of safety
- FOSf :
-
FOS corresponding to the static force equilibrium
- FOSm :
-
FOS corresponding to the moment equilibrium
- GLE:
-
Generalized limit equilibrium
- LAM:
-
Limit analysis method
- LEM:
-
Limit equilibrium method
- MC:
-
Mohr-coulomb
- mpcFEM-SOCP:
-
Second-order cone programming optimized micropolar continuum finite element method
- SSRFEM:
-
Shear strength reduction finite element method
- UCS:
-
Uniaxial compressive strength
- VBP:
-
Volumetric block proportion
- a :
-
Vector of linear equation
- A :
-
Coefficient matrix of linear equation
- b :
-
Vector of body force
- c :
-
Cohesion
- c :
-
Coefficient vector
- c 0 :
-
Initial cohesion
- ℂq :
-
Quadratic cone
- ℂr :
-
Rotated quadratic cone
- d b :
-
Rock block size
- d thr :
-
Threshold of rock block sizes
- D e :
-
Elastic stiffness matrix
- E :
-
Elastic modulus
- F mc :
-
Micropolar MC yield function with compression positive
- G :
-
Lamé constant (or shear modulus)
- G m :
-
Micropolar shear modulus
- h 1, h 2 and h 3 :
-
Constant coefficients
- h cp :
-
Negative softening modulus of cohesion
- I :
-
Index diagonal matrix
- I R :
-
Roundness index
- I SPH :
-
Sphericity index
- k 0 :
-
Parameter denoting the hardening exponent of the material
- l c :
-
Internal characteristic length
- l e :
-
Average mesh size
- l v :
-
Evolving internal characteristic length
- L f :
-
Length of engineering features or the slope dimensions
- m ij :
-
Couple stress components
- nels :
-
Total number of finite elements in mesh
- n o :
-
Total number of integration points in the whole solution domain
- N u :
-
Shape (or interpolation) function for displacement
- N o :
-
Shape (or interpolation) function for stress
- R o :
-
Mean surface roughness
- \({{{\boldsymbol{\hat r}}}_{k + 1}}\) :
-
Unknown nodal reaction force
- u :
-
Displacement vector
- u x, u y :
-
Translational displacement components in two plane coordinates Prescribed nodal displacement vector
- û :
-
Nodal displacement vector of each element
- v :
-
Poisson ratio
- x :
-
Solution vector
- σ :
-
Stress vector
- σ ij :
-
Stress components
- σ m :
-
Mean normal stress
- \({{\boldsymbol{\hat \sigma }}}\) :
-
Stress vector at stress integration points in each element
- τ*:
-
Generalized shear strength
- ε :
-
Strain vector
- ε ij :
-
Strain components
- \(\overline \varepsilon _{\rm{p}}^{{\rm{ip}}}\) :
-
Total accumulated equivalent plastic strain at each integration point
- κ ij :
-
Micro-curvature components
- α m :
-
Shear modulus ratio
- γ b :
-
Unit weight of rock blocks
- γ m :
-
Unit weight of matrix soil
- λ :
-
Lamé constant
- ∇:
-
Differential operator
- φ :
-
Internal friction angle
- ω z :
-
Micro-rotation component
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CHEN ** provided the concept and methodology and wrote the original draft; TANG Jian-bin provided the methodology and performed some numerical analysis; CUI Liu-sheng performed some investigations; LIU Zong-qi conducted data curation.
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CHEN **, TANG Jian-bin, CUI Liu-sheng and LIU Zong-qi declare that they have no conflict of interest.
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Foundation item: Project(52178309) supported by the National Natural Science Foundation of China; Project(2017YFC0804602) supported by the National Key R&D Program of China; Project(2019JBM092) supported by the Fundamental Research Funds for the Central Universities, China
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Chen, X., Tang, Jb., Cui, Ls. et al. Stability and failure pattern analysis of bimslope with Mohr-Coulomb matrix soil: From a perspective of micropolar continuum theory. J. Cent. South Univ. 30, 3450–3466 (2023). https://doi.org/10.1007/s11771-023-5452-z
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DOI: https://doi.org/10.1007/s11771-023-5452-z
Key words
- bimslope
- block-in-matrix structure
- micropolar continuum
- randomly distributed rocks
- tortuous slip surface
- volumetric block proportion