SUMMARYThe discontinuous deformation analysis (DDA) with second-order displacement functions was derived based on six-node triangular mesh in order to satisfy the requirement for the accurate calculations in practical applications. The matrices of equilibrium equations for the second-order DDA were given in detail for program coding. By close comparison with widely used finite element method and closed form solutions, the advantages of the modified DDA were illustrated. The program coding was carried out in C+ + environment and the new code applied to three examples with known analytical solutions. A very good agreement was achieved between the analytical and numerical results produced by the modified DDA code.
SUMMARYA modified three-dimensional discontinuous deformation analysis (3D-DDA) method is derived using four-noded tetrahedral elements to improve the accuracy of current 3D-DDA algorithm in practical applications. The analysis program for the modified 3D-DDA method is developed in a C++ environment and its accuracy is illustrated through comparisons with several analytical solutions that are available for selected problems. The predicted solutions for these problems using the modified 3D-DDA approach all show satisfactory agreement with the corresponding analytical results. Results presented in this paper demonstrate that the modified 3D-DDA method with discontinuous modeling capabilities offers a useful computational tool to determine stresses and deformations in practical problems involving fissured elastic media with reasonable accuracy.
The present study reports the application of a neural network for the prediction of the axial load distribution along fully grouted cable bolts based on a database of laboratory pullout tests on short samples. At first, the network was trained to predict the axial force of a series of short cables grouted with Portland cement at a specific w/c ratio that are then confined radially with a constant pressure. Another database which was used for the training is the pullout force of the cables confined within a confining medium (for example, a borehole in a rock mass or another material). This is classified as constant radial stiffness boundary condition. The back propagation training algorithm was used in the present study for the load calculation. Subsequently, a finite element model was used to model the axial load along long cable bolts based on the integration of the behaviour of short elements. This approach simplifies the determination of load along long cable bolts which are often installed in rock masses with different Young's modulus, rock mass displacement profiles and stress change histories.
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