- Title
- A numerical investigation of the mechanisms of post-mining subsidence
- Creator
- Fathi Salmi, Ebrahim
- Relation
- University of Newcastle Research Higher Degree Thesis
- Resource Type
- thesis
- Date
- 2016
- Description
- Research Doctorate - Doctor of Philosophy (PhD)
- Description
- Subsidence is one of the most challenging and controversial problems in rock mechanics and geotechnical engineering. In particular, the expansion of urbanised areas over abandoned mining excavations has brought about several questions concerning the long term stability of such excavations and the duration of the subsidence development. This study, therefore, aims to investigate the mechanisms of post mining subsidence. The role of the effective factors on the mechanisms of excavation induced ground movements are assessed through some case studies of actual subsidence incidents. Clearly, one of the fundamental stages of conducting numerical or theoretical analyses for calculating the magnitudes of subsidence is to reliably estimate the mechanical parameters of rock masses. A simple and practical approach is developed in this study, based on the concept of rock mass classification methods to approximate the rock mass parameters. Additionally, the mechanisms of mining induced subsidence in sloping terrain are investigated through numerical modelling. An interesting example of mining beneath escarpments in New South Wales, Australia, is investigated to capture the effects of the surface topography on the mechanisms of subsidence. Furthermore, the role of the gradual deterioration of a rock mass on the duration of the subsidence development in shallow abandoned coal mines is investigated. The conventional Tributary Area Method (TAM) is augmented to incorporate the effects of the gradual deterioration on the loads of pillars. Moreover, the conventional pillar strength methods are modified to take into account the effects of the gradual deterioration. The combination of these two approaches provides a suitable ground for assessing the life times of pillars. Furthermore, a simple and practical approach is proposed to take into account the role of gradual deterioration in the numerical modelling. The proposed approach is then employed for assessing the formation of subsidence over an abandoned shallow coal mine around the village of Dolphingstone, UK. The outcomes of the numerical modelling are then verified against the results of the empirical methods for estimating the stand up time of room and pillar mining excavations. Creep is the other time dependent behaviour of rocks, controlling the long term stability of excavations. The role of this factor on the mechanisms of post mining subsidence is also investigated in this study. The theories of visco elasticity and visco plasticity are employed in the frameworks of the analytical and numerical modelling to study the effects of creep on the gradual development of subsidence over abandoned room and pillar mines. The outcomes of the study show that creep plays a pronounced role on the values of the time dependent displacements over mining excavations. Moreover, a procedure is developed to take into account the effects of gradual weakening due to mechanical factors (e.g., creep) or environmental factors (e.g., weathering and moisture softening) on the formation of sinkholes. The proposed approaches are then employed for investigating the mechanisms of the subsidence over an abandoned limestone mine in the West Midlands, UK.
- Subject
- mining subsidence; time-dependent behaviour; numerical modelling; gradual deterioration
- Identifier
- http://hdl.handle.net/1959.13/1335396
- Identifier
- uon:27428
- Rights
- Copyright 2016 Ebrahim Fathi Salmi
- Language
- eng
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| Thumbnail | File | Description | Size | Format | |||
|---|---|---|---|---|---|---|---|
| View Details Download | ATTACHMENT01 | Thesis | 11 MB | Adobe Acrobat PDF | View Details Download | ||
| View Details Download | ATTACHMENT02 | Abstract | 188 KB | Adobe Acrobat PDF | View Details Download |