3DEC数值模拟方法

Distinct Element Method
Specification of shapes in 2 and 3 dimensions
• 2 & 3 dimensions – PFC disks & spheres
• 2 dimensions – UDEC arbitrary polygons – convex and concave – with rounded corners
*Cundall,P.A., and R.D. Hart.”Numerical Modeling of Discontinua,” Engineering Computations, 9(2), 101-113 (1992)
Finite element codes for modeling “discontinua” are often modified continuum programs, which cannot handle general interaction geometry (e.g. many intersecting joints). Their efficiency may degenerate drastically when connections are broken repeatedly.
If we attempt to identify neighboring blocks by an exhaustive scan (i.e. each block tested against each other), then the search-time is proportional to N2 where N is the number of blocks.
Fractured rock volume loaded axially with 10 MPa confining stress
Fundamental Rock Mechanics
Grain structure
Displacements
Exaggerated deformation
Simulated unconfined compression test on crystalline r Support
N S
N S
What is 3DEC?
• 3DEC is best suited to modeling discontinuous materials (containing many intersecting discontinuities in 3D) that exhibit nonlinear behavior
and memory allocation scheme that can handle many hundreds or thousands of discontinuities or contacts.
The name “Distinct Element Method” is used for a DEM that uses an explicit dynamic solution to Newton’s laws of motion.
What is 3DEC?
• A Distinct Element code that allows the simulation of the interaction of blocks
– e.g. jointed rock mass, masonry wall
What is 3DEC?
• Discontinuities are regarded as distinct boundary interactions between blocks
1Koliji et al, 2001. Int. J. Hydropower & Dams, 18, 56-61
Toppling
Normal faulting in the upper part of the slope
S-shaped deformation of rock lamellae
Slope Stability
• Automatic Factor of Safety calculation for 3D slopes
• Uses Shear Strength Reduction method
Abutment stability assessment at Hongrich arch dam1
• Discontinuous Deformation Analysis
Assumes contacts are rigid bodies and bodies may be rigid or deformable. No-penetration is achieved by iteration
• Momentum Exchange Methods
Fractured reservoir model
Hydraulic Fracture
Fluid pressure in joints during injection
Top portion of reservoir hidden for ease of viewing
Microseismicity
What is 3DEC?
• 3DEC blocks are rigid or deformable
• Deformable blocks are automatically meshed with tetrahedra to simulate a nonlinear continuum
What is 3DEC? With Ground Support
• Modal Methods
Similar to distinct element method in the case of rigid blocks. For deformable bodies, modal superposition is used so non-linearity is difficult to implement
3DEC数值模拟方法
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提纲 3DEC(5.0)软件特点 3DEC(5.0)理论基础 3DEC(5.0)新功能 3DEC (5.0)算例分析
提纲 3DEC(5.0)软件特点 3DEC(5.0)理论基础 3DEC(5.0)新功能 3DEC (5.0)算例分析
Distinct Element Method
Three aspects ... 1. Geometry 2. Contact mechanics 3. Solid body mechanics
Distinct Element Method
Geometry 1) Specification of shapes in 2 and 3 dimensions 2) Interaction of pairs of contacting blocks or particles 3) Identification of contact character between 2 blocks
2. recognizes new interactions (contact) automatically as the calculation progresses
A discrete element code will embody an efficient algorithm for
detecting and classifying contacts. It will maintain a data structure
Types of Discrete Element Methods for Discontinuum Analysis
• Distinct Element
Use explicit time-marching scheme to solve equations of motion directly. Bodies may be rigid or deformable, contacts are deformable
Canister cover
Claystone Shotcrete
Localization in claystone at 6 months Concrete
Reproduced with permission of ANDRA
Hydraulic Fracture
Discrete Fracture Network
• 3 dimensions – 3DEC arbitrary polyhedra – concave bodies are constructed of several convex bodies attached together
Distinct Element Method
Interaction of pairs of contacting blocks or particles
• Contacts are automatically updated as calculation progresses – large displacements are allowed
• Non-linear force displacement behavior may be assigned to contacts (joints)
DEM Definitions
The name “Discrete Element Method” (DEM) should be applied to a method only if it*:
1. allows finite displacements and rotations of discrete bodies; including complete detachment
Normal faulting
S-shaped deformed rock lamellae
Flexural toppling
提纲 3DEC(5.0)软件特点 3DEC(5.0)理论基础 3DEC(5.0)新功能 3DEC (5.0)算例分析
离散元方法
离散元的理论基础是牛顿第二定律。离散元法是将所研究的区 域划分成一个个分立的多边形块体单元，单元与单元之间具有一定 的初始接触状态，随着单元的平移和转动，调整各个单元之间的接 触关系。最终，块体单元可能达到平衡状态,也可能一直运动下去。 因此，离散元法适用于研究节理系统或块体集合在准静力或动力条 件下的运动问题。离散元法以各种块体为研究对象，块体与块体之 间没有变形协调的约束，只需要满足力的平衡条件。构成单元的节 点可以分离。单元之间的相互作用力可以根据力和位移的关系求出 ，而单个单元的运动则完全根据该单元所受的不平衡力和不平衡力 矩的大小按牛顿运动定律确定。
• Solves the full dynamiDcispleaceqmenut ations of motion even Magnitude for quasi-static problems
• Allows for large displacements, rotations and dynamic analyses
矿山开采稳定性分析研究
矿层分布模型
当前开 采条件 下矿柱 几乎没 有屈服 断层影 响不大
开挖后对地表建筑物的影响
地质构造分布
屈服矿柱分布情况
矿岩崩落数值模拟
矿藏分布三维模型
对崩 落速 度和 规模 进行 预测
拉底后矿岩出露模型
拉底步骤
矿岩三维节理模型
崩落过程模拟
Nuclear Waste Disposal
Assume both the contacts and bodies to be rigid. Momentum is exchanged between two contacting bodies during collision. Can represent friction sliding.