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A platform for research: civil engineering, architecture and urbanism
Influences of EDZ and Cross-Section Shapes on Spalling Failure Depth of Non-circular Tunnels in Gneissic Granite
Abstract Spalling has been recognized as a stress-induced brittle fracture adjacent to the underground openings when tunneling or mining deeply in a hard massive rock mass. Using a database consisting of 29 spalling cases of gneissic granite during the excavation of Qirehataer tunnels, a comprehensive evaluation of rock mass spalling strength, spalling failure depth and the influence of excavation damaged zone (EDZ) and the cross-section shapes is performed and presented. Relationships between the spalling failure depth and the rock mass damage index for D-shape and Horse-shoe shape cross-sections of non-circular tunnels with and without consideration of EDZ are analyzed and discussed. The study found that EDZ has a significant influence on the maximum tangential stress adjacent to the boundary of tunnels that the EDZ has a trend to result in a deeper failure depth than not taking the EDZ into account. The influence degree of EDZ on spalling failure depth could be 1.85 and 2.18 times higher than that without considering EDZ, for the D-shape and Horse-shoe shape tunnels, respectively. Through comparisons with the analysis based on in-situ geophysical testing data, it is found Martin and Christiansson’s method may have a trend to overestimate the spalling failure depth, the overestimation ratio of influence degree may be up to 1.35, and the overestimation becomes more significant with the increase of the rock mass damage index. Based on the analysis and comparisons with different shapes of tunnel cross-sections, it is also found that the D-shape geometry of tunnels has the advantage of avoiding spalling failure over than Horseshoe-shape in the hard and brittle rock mass.
Influences of EDZ and Cross-Section Shapes on Spalling Failure Depth of Non-circular Tunnels in Gneissic Granite
Abstract Spalling has been recognized as a stress-induced brittle fracture adjacent to the underground openings when tunneling or mining deeply in a hard massive rock mass. Using a database consisting of 29 spalling cases of gneissic granite during the excavation of Qirehataer tunnels, a comprehensive evaluation of rock mass spalling strength, spalling failure depth and the influence of excavation damaged zone (EDZ) and the cross-section shapes is performed and presented. Relationships between the spalling failure depth and the rock mass damage index for D-shape and Horse-shoe shape cross-sections of non-circular tunnels with and without consideration of EDZ are analyzed and discussed. The study found that EDZ has a significant influence on the maximum tangential stress adjacent to the boundary of tunnels that the EDZ has a trend to result in a deeper failure depth than not taking the EDZ into account. The influence degree of EDZ on spalling failure depth could be 1.85 and 2.18 times higher than that without considering EDZ, for the D-shape and Horse-shoe shape tunnels, respectively. Through comparisons with the analysis based on in-situ geophysical testing data, it is found Martin and Christiansson’s method may have a trend to overestimate the spalling failure depth, the overestimation ratio of influence degree may be up to 1.35, and the overestimation becomes more significant with the increase of the rock mass damage index. Based on the analysis and comparisons with different shapes of tunnel cross-sections, it is also found that the D-shape geometry of tunnels has the advantage of avoiding spalling failure over than Horseshoe-shape in the hard and brittle rock mass.
Influences of EDZ and Cross-Section Shapes on Spalling Failure Depth of Non-circular Tunnels in Gneissic Granite
Zhao, Guobin (author) / Wang, Dongyuan (author) / Shi, Long (author) / Wang, Sijing (author)
2022
Article (Journal)
Electronic Resource
English
BKL:
57.00$jBergbau: Allgemeines
/
38.58
Geomechanik
/
57.00
Bergbau: Allgemeines
/
56.20
Ingenieurgeologie, Bodenmechanik
/
38.58$jGeomechanik
/
56.20$jIngenieurgeologie$jBodenmechanik
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