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ABSTRACT ABSTRACT: This paper presents a case study on the optimum design of excavation and support system of a shallow tunnel which is faced with the unexpected bad geological condition during excavation, The detailed geological investigation shows that the rock mass in the region of concerns is heavily weathered and fractured with RMR value less than 20. Considering this, the concept of the new design is focused on the reinforcement of the ground preceding the excavation and two design patterns are suggested. One is L W -grouting & fore-poling with pilot tunnelling and the other is the steel pipe reinforced grouting. Numerical analysis by FLAC shows that these two patterns maintain the roof ground stable during the whole excavation process while the original pattern causes tensile failure around the tunnel and the severe floor heaving. This process of the design assessment can be a good guide in the construction of the tunnels in heavily fractured rock mass.
ABSTRACT ABSTRACT: In tunnel excavation by blast beneath the surface structures in urban area, the characteristics of ground vibration induced by blast and its influence on surface structures are analyzed by the field test and the numerical analysis on dynamic behaviors of the structure. According to the field test on the propagating characteristics of blast vibration through the rock mass and the concrete foundation pile, the attenuation index of peak particle velocity with distance shows the range of 1.7-2.0 for the rock mass and the range of 2.0-2.3 for the concrete pile. This shows that the blast vibration reduces more rapidly in the concrete pile. It is known from the numerical analysis on dynamic behavior of the structure that the coefficient of response, velocity ratio of structure response to input wave, is different according to the story of the structure. It can be said from this research that the characteristics of the ground vibration and the dynamic behavior of the structure should be well evaluated and be considered as important factors for safe blasting design especially in underground excavation at shallow depth in urban area.
- Energy > Oil & Gas > Upstream (0.51)
- Construction & Engineering (0.47)