Discrete element method for modelling a fracture evolution of a roadway surrounding rock

Patent metadata

Field	Value
Publication number	US-11209415-B2
Application number	US-201917043707-A
Country	US
Kind code	B2
Filing date	Oct 8, 2019
Priority date	Jul 15, 2019
Publication date	Dec 28, 2021
Grant date	Dec 28, 2021

Abstract

A discrete element method for modelling fracture evolution of roadway surrounding rock is provided, which includes: taking rock cores from a coal seam in the field and recording RQD values, observing roadway deformation, and making a statistical analysis on distribution characteristics of fractures in the coal seam; testing mechanical parameters of coal-rock samples indoors, and calculating strength of a rock mass according to the RQD values; creating a numerical model by using a UDEC-Trigon module to adjust the parameters to match the strength of the rock mass, and correcting model parameters; and creating a numerical model of an engineering scale to adjust the parameters to match field deformation characteristics, and finally simulating fracture evolution of the roadway surrounding rock. The present invention provides accurate and basic mechanical parameters for discrete-element numerical simulation of roadway deformation, guaranteeing realistic and reliable simulation results.

First claim

What is claimed is:

1. A discrete element method for modelling a fracture evolution of a roadway surrounding rock, comprising following steps:
S 1 : in a test roadway, observing deformation characteristics of the roadway and taking rock cores from coal seam and rock mass; recording deformation characteristics of the roadway surrounding rock, and monitoring distribution characteristics of fractures in roof and two ribs of the roadway; and taking rock cores from the roof and the coal seam, and recording RQD values of the roof rock cores and the coal seam rock cores;
S 2 : separately making the obtained roof rock cores and the coal seam rock cores into standard intact rock, and carrying out experiments in mechanics to test an uniaxial compressive strength, a tensile strength, and an elastic modulus of the intact rock; and according to a functional relationship between a ratio of an elastic modulus of a rock mass to that of the intact rock and the RQD, and a functional relationship between an uniaxial compressive strength of the rock mass and that of the intact rock, determining the uniaxial compressive strength and the elastic modulus of the rock mass, wherein a tensile strength of the rock mass is 0.1 of its uniaxial compressive strength;
S 3 : creating a calibration model by using a Trigon module in UDEC, wherein an average value of side lengths of triangular blocks in the calibration model is determined according to the distribution characteristics of fractures statistically analyzed in step S 1 ; by using the uniaxial compressive strength, the tensile strength, and the elastic modulus of the rock mass calculated in step S 2 as known characteristic values, performing an inversion with the calibration model to obtain parameters for a triangular block and parameters for a joint in the calibration model; and
S 4 : creating a large-size numerical model with a field scale by using the UDEC, defining an area of study, and dividing the area of study into triangular blocks by using the Trigon module, wherein an average value of side lengths of the triangular blocks and the triangular block parameters are identical with those in the calibration model in step S 3 ; forming rectangular blocks increasingly growing in length by division in areas outside the area of study; and based on the deformation characteristics of the roadway surrounding rock and the distribution characteristics of fractures that are observed in step S 1 , performing an inversion to obtain mechanical parameters of the rectangular blocks in the large-size numerical model.

2. The discrete element method for modelling the fracture evolution of the roadway surrounding rock according to claim 1 , wherein the parameters for the triangular block and the parameters for the joint in the calibration model that are obtained by the inversion in step S 3 respectively comprise a size and an elastic modulus of the triangular block, and a normal stiffness, a shear stiffness, a cohesion, a friction angle, and a tensile strength of the joint; and the inversion specifically comprises:
a) separately creating a rectangular calibration model of 2 m in width and 4 m in height and a circular calibration model with a diameter of 2 m, wherein an average value of the side lengths of the triangular blocks is guaranteed to be consistent with a fracture length obtained based on field statistics;
b) setting the elastic modulus of the triangular blocks in the calibration model to be equal to that of the rock mass calculated according to a formula (II);
c) deducing normal stiffness K n of the joint between the triangular blocks according to a formula (IV), a ratio of a shear stiffness K s to the normal stiffness K n being 0.2; and determining a Poisson's ratio μ according to a variation in K s /K n , wherein the formula (IV) is specifically as follows:

K
n

=

n
[

K
+

(

4
/
3

)

⁢
G

Δ
⁢

⁢

Z
min

]

⁢

(

1
≤
n
≤
10

)

(
IV
)

wherein K and G are respectively a volume modulus and a shear modulus of the triangular blocks, in GPa, and are calculated according to equations K=E/3(1−2μ) and G=E/2(1+μ), μ being the Poisson's ratio of the block, and E being an elastic modulus of the block, in GPa; ΔZ min is a minimum width of adjoining units in a vertical direction, in m; and n is equal to 10; and
d) carrying out a series of uniaxial compression test and Brazilian splitting test by using the calibration model, to obtain stress-strain curves; employing means of trial and error iteration to make simulated mechanical parameters match the uniaxial compressive strength, the tensile strength, and the elastic modulus of the rock mass calculated in step S 2 ; and finally performing an inversion to obtain a cohesion, an internal friction angle, and a tensile strength of the joint in the calibration model.

3. The discrete element method for modelling the fracture evolution of the roadway surrounding rock according to claim 2 , wherein in step S 1 , a roadway surface displacement measuring station is mounted by means of a crisscross layout, the deformation characteristics of the roadway surrounding rock are recorded with an explosion-proof camera, the distribution characteristics of fractures in the roof and the two ribs of the roadway are monitored with a drilling observation instrument, and a distribution rule of lengths of fractures in a surface of a drill hole is quantified by means of drilling tracing.

4. The discrete element method for modelling the fracture evolution of the roadway surrounding rock according to claim 1 , wherein in step S 1 , a roadway surface displacement measuring station is mounted by means of a crisscross layout, the deformation characteristics of the roadway surrounding rock are recorded with an explosion-proof camera, the distribution characteristics of fractures in the roof and the two ribs of the roadway are monitored with a drilling observation instrument, and a distribution rule of lengths of fractures in a surface of a drill hole is

Assignees

• Univ China Mining
• China Mining & Civil New Material Science And Tech Ltd
• Boxia Mining Tech Ltd

Inventors

• Wang Xiangyu
• Bai Jianbiao
• Xia Junwu
• Yan Shuai

Classifications

• G06F2119/06

  Power analysis or power optimisation · CPC title

• G06F30/20

  Design optimisation, verification or simulation (optimisation, verification or simulation of circuit designs G06F30/30) · CPC title

• G01N33/24 Primary

  Earth materials (G01N33/42 takes precedence) · CPC title

• G06F30/23

  using finite element methods [FEM] or finite difference methods [FDM] · CPC title

• G06F30/25

  using particle-based methods · CPC title