Modelling excavations in discontinuous rock using the distinct element method

Bao, Weiyu (2005) Modelling excavations in discontinuous rock using the distinct element method. University of Southampton, Doctoral Thesis.

Record type: Thesis (Doctoral)

Abstract

This investigation is carried out using a case study of the deep excavation of the permanent shiplock of the Three Gorges Project in China. A three-dimensional model (using the 3-Dimensional Distinct Element Code, 3DEC) is developed to simulate the construction of the shiplock by multi-staged excavation. The model is validated using available field data. The significance of modelling individual discontinuities and the excavation damaged/disturbed zone (EDZ) is demonstrated. A parametric study is carried out to investigate the sensitivity of the model to the properties and constitutive models of discontinuities, rock blocks and the EDZ. The sensitive parameters identified include discontinuity stiffness, rock modulus and simulation of EDZ. The model may be sensitive to joint friction angle depending on the overall discontinuity orientation relative to excavation, while it is generally insensitive to the other strength parameters of the discontinuities and rock blocks. The elastoplastic model (Mohr-Coulomb model) simulates the behaviors of both discontinuities and rock blocks better than the elastic model when material failure is present.

To assess the importance of using a three-dimensional model rather than the two-dimensional models usually employed in practice, a two-dimensional model (using the Universal Distinct Element Code, UDEC) is also developed. Its results are compared with field data and the results of the three-dimensional model. The three-dimensional model is found to reproduce the behaviour of rock mass better because of the more realistic assumptions made on stress conditions and discontinuity representation.

Text

1020598.pdf - Version of Record

Available under License University of Southampton Thesis Licence.

Download (4MB)