Design of Underground Structures and Analysis of Self-Support Capacity
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Design of underground structures and.... Available from: https://www.researchgate.net/publication/327036255_Design_of_underground_structures_and_analysis_of_self-support_capacity
The complicated rock structures and the stability of surrounding rocks of the underground powerhouse are key ground mechanical challenges for hydropower projects. In this paper, an example of contributing self-support capacity of rock mass to evaluate optimised support for long-term usage of structure is given. It describes importance of investigations in the initial in situ stress distribution, rock mechanical and geological proper- ties, engineering rock mass classifications by different methods, numerical modelling, comparison of tools for stability and support analysis and proper stability control for rock excavation and support.
The results show that after underground excavations in hard rock, detailed analysis of measures to investigate deformation and self-supporting capacity creation is useful and a cost-saving procedure. Hard rock mass itself around underground openings has a certain self-support capacity. After tunnelling or larger underground excavation, surrounding rock goes in deformation along the unloading direction, and in the tangential direction, there occurs squeezing of material under the load forces. The inner surrounding rock mass starts to interconnect, and rock mass structure begins to degenerate after an unloading zone is created in the surrounding rock. In the unloaded zone, a self-supporting zone is formed because rock blocks occlude. After displacements, it takes all the load from itself and the above rock mass is integrated with structure. The created zone with new mechanical properties allows the surrounding rock to stabilise in short time. The creation of self-supporting zone is a phenomenon of self-regulation of stress that keep sresistance of deformation in rock mass. Before installation of support systems, it is useful and considerable to control the estimated decompression period correlated with the pre-deformation.
The boundary of self-supporting zone can be determined according to the stress path analysis procedure. Complex ground conditions and limit state may affect the stability of caverns and tunnels by the geometry of joints and density of fractures in the surrounded rock mass. With the development of technology and research in numerical analysis of material deformability, comparisons of the calculation obtained by different numerical methods such as finite element method, discrete element method and indirect boundary element method and in case of fractured rock mass also by PFC for better understanding of stress distribution and deformation effects on joins around excavations are numerically studied. In practice, comparisons that indicatethe validity of the stress analyses around excavation openings have already been performed. The influence of model geometry on each numerical method has to be analysed. Groundwater is one of main issues in underground excavations, where numerical simulation is necessary to estimate the amount of water inflow. A proper scale has high importance for correct analysis in such models.
Full article is available on:
Design of underground structures and.... Available from: https://www.researchgate.net/publication/327036255_Design_of_underground_structures_and_analysis_of_self-support_capacity
2nd wont argue but 3rd is true. 2D analysis for clear 3D problem??? Isotropic models...cant win.
A little review of the article: 1st - rock mass should be modeled as anisotropic and not isotropic 2nd - it’s self bearing capacity not self support cos rock cannot support itself. 3rd - we are able to consider pre-deformation phenomenon in tunnels, not caverns since steess re-destribution in caverns is totally different...