Two-dimensional displacement discontinuity method for transversely isotropic materials

Two-dimensional radial integration displacement discontinuity method with high-order isoparametric elements

Extended displacement discontinuity method for analysis of cracks in 2D piezoelectric semiconductors

Applications of the fast multipole fully coupled poroelastic displacement discontinuity method to hydraulic fracturing problems

Analysis of an interfacial crack in a piezoelectric bi-material via the extended Green’s functions and displacement discontinuity method

Revisit of the equivalence of the displacement discontinuity method and boundary element method for solving crack problems

3D mixed boundary elements for elastostatic deformation field analysis

Displacement discontinuity analysis of a nonlinear interfacial crack in three-dimensional transversely isotropic magneto-electro-elastic bi-materials

The displacement discontinuity method is extended on the plane thermoelasticity problems for bodies with cracks. The analytical solution for elementary discontinuities is obtained. The test and illustrated problems are solved.

Fracturing-hydraulic coupling in transversely isotropic rocks and a case study on CO2 sequestration

Analysis of incidents in underground mining reveals that ground falls, including roof and rib falls, is one of the major sources of injuries and fatalities, however the number of accidents has reduced significantly during recent years (MSHA 2015). For instance, in 2005, around 60% of total fatalities in underground mining were associated with ground falls. This percentage has dropped to 37% in 2015 (MSHA 2015). This significant reduction in underground incidents may be caused by several reasons such as: using advanced technology, advance in computer science, new policies on safety, etc. Development of mathematical methods such as finite element and boundary element methods can be classified under new advanced in computer science provided new computer programs for using in the mining industry. In general, these programs are used as a powerful tools to enhance the safety of mine designs. There are several programs have been developed and each program provides specific features and strengths as well as some specific limitations. The LaModel program was developed based on the displacement discontinuity method and has been successfully used over several years in mining industry.;During the last few years, several features have been added to the LaModel program to increase the ability of the program to analyze the underground coal mines. The new efforts lead to implementation of several new options into the program such as: gob modulus calibration, a local mine stiffness calculation for evaluating the potential of bump, and adding a subsidence calibration technique, and the energy release rate calculation as well as calibration of the model These components increase the analysis ability of the program for several specific conditions.;Enhancing the main algorithm of solution for mines with multiple seams is necessary to help mine design easily. Presently in the LaModel program, the fundamental elliptical, partial-differential equation of the laminated overburden is solved using a finite-difference approach. This finite-difference solution has proven to be fast when solving single seam problems. However, when solving multiple-seam problems, the solution time increases by several orders of magnitude. The multiple-seams model in LaModel are solved by first calculating the seam convergence distribution seam by seam and then calculating the multiple-seam stress between the seams. Calculating and projecting stresses between the seams is the most time consuming process in a Multiple-seam model. In this dissertation, three algorithms have been developed and implemented to improve the efficiency of the multiple-seam calculation in the program. These algorithms include:

A simultaneous experimental and numerical study on crack propagation in the pre-cracked beams specimens (concrete-like materials) is carried out using three-point bending flexural test. The crack propagation and coalescence paths of internal cracks in side beam specimens are experimentally studied by inserting double internal cracks. The effects of crack positions on the fracturing path in the bridge areas of the double cracked beam specimens are also studied. It has been observed that the breaking of concrete-like cracked beams specimens occurs mainly by the propagation of wing cracks emanating from the tips of the pre-existing cracks in the numerical and experimental analyses, respectively. The same specimens are numerically simulated by an indirect boundary element method (IBEM) known as displacement discontinuity method (DDM) using higher displacement discontinuity. These numerical results are compared with the existing experimental results. This comparison illustrates the higher accuracy of the results obtained by the indirect boundary element method by using only a small number of elements compared with the discrete element method (PFC2D code).

Sand production mechanisms were numerically studied by means of a displacement discontinuity boundary-element method. The method allows an explicit modelling of fracture growth in rocks in 2D. Rock fracture in hollow cylinder sand production tests was simulated. Different types of fracture growth typically observed in hollow cylinder tests were investigated, i.e. breakout formation, slit propagation and uniform collapse of the cavity. Changing the mechanical behavior of the rock, represented by the properties and constitutive behavior of the displacement discontinuity elements, from brittle to ductile resulted in a change of the failure pattern from breakouts to uniform collapse, reproducing thus the laboratory tests. A clear effect of the specimen size (external diameter) on the results was demonstrated numerically. The increase of the external diameter of the hollow cylinder results in a virtually linear increase of the hollow cylinder strength, at least in the range of diameter values investigated.

Influence of boundary curvature on tangential stresses for the displacement discontinuity method

The coupled diffusion and deformation phenomena induced by the opening of a hydraulic fracture in a poroelastic medium are modelled using an extension of the displacement discontinuity method. This method consists in distributing fluid source and poroelastic displacement discontinuity singularities along the locus of the fracture, and over time. As an illustration, the problem of a suddenly pressurized crack in an infinite formation is examined.

With the rapid economic and social development in China, using the full-face rock tunnel boring machine (TBM) in construction is becoming increasingly common. As the principal tool for rock breaking, the efficiency and service life of disk cutters used by the TBM will affect project progress and cost. The failure mechanism of disk cutters is still unclear. The specific impact of the changing temperature during rock breaking on tool failure behavior remains unclear. Therefore, this paper studies the temperature characteristics of disk cutters using the theoretical solution and finite element method (FEM) simulation. The finite difference method discretized the heat conduction equation and boundary conditions. The temperature distribution and variation are solved using coding in MATLAB. FEM simulation using ABAQUS is established to characterize the heat transfer process and analyze the temperature field. Several experiments are conducted for verification. The simulated results correlate well with analytical ones, proving the correctness and accuracy of the proposed method.