Geology tunnel excavation

Furthermore, the site visit and the information obtained therein can be employed as a basis for a design-project in which the students can put in practice what they have learned in the module. The work can include, for instance, a description of the proposed project (that can be the same as or different from the real one), a description and characterization of the geological materials in one specific formation (for instance, the Black Schist formation presented in Fig. 2), and a selection ofthe tunnel excavation method and design of the support system for the tunnel length located within such formation. 

Based on the available geological, hydraulic and mechanical characterizations of the Site as well as on results of hydraulic tests performed on boreholes, a hydro-mechanical model for the zone around the FEBEX tunnel was to be prepared. Using this model, changes in water pressure induced by the boring of the FEBEX tunnel in the near vicinity, as well as the total water flow rate to the excavated tunnel was required. 

Backblom, G., Martin, C.D. 1999 Recent experiments in hard rocks to study the excavation response Implications for the performance of a nuclear waste geological repository. Tunnelling and underground space technology 14 377-394. 

Tan, B.K. 1983b. Engineering geological case studies of tunnelling and deep excavations in Malaysia. Proc. 

A pilot tunnel is probably the best method of exploring tunnel locations and should be used if a major-sized tunnel is to be constructed in ground that is known to have critical geological conditions. It also drains the rock ahead of the main excavation. If the inflow of water is excessive, the rock can be grouted from the pilot tunnel before the main excavation reaches the water-bearing zone. 

ABSTRACT To reduce the risk related to water seepage during tunnel/cavern excavation, some analytical solutions for water inflow prediction corresponding to specific geological conditions have been established over the last decades. Unfortunately, these analytical solutions are only applicable for tunnels/ caverns with regular cross-sections, such as circular, elliptical or square. In reality, the cross-sections for most of real tunnels/cavems are always asymmetric, such as in a horseshoe shape. Therefore, the existing analytical solutions are not very suitable for water inflow prediction. 

Geological and Geotechnical properties of tunnel route have discussed previously. In this part, an investigation on the soil behavior against TBM excavation is presented. 

Important and hazardous statement of soil layering is arisen when various types of soil layers outcrop in the face and crown of the tunnel. In this case, despite of similar performance of TBM, the soil layers will behave differ from together because of differences in soil engineering geological properties. During the excavation process, the materials of the looser and softer layers are excavated more than other layers and consequently large cavities are created in tunnel face. This statement takes place especially when loose sand layers are seen in beside of stiff clay layers (Fig. 1). This phenomenon can cause to collapse of sandy materials, cavitation and undesired ground settlement. 

Engineering geological properties of the Tabriz urban railway line 2 (TURL2) tunnel were discussed in this study. The materials of the tunnel route mostly consist of quaternary alluvium and Miocene formations that lithologically composed of sandstone, siltstone, claystone and marl. The status of these geological units is similar to soil (stiff soil at lower depths) layers that have different Geotechnical characteristics so it is expected that each of layers show a specific behavior during excavation. 

The Underground Construction module covers several aspeets related to tunnel design, such as engineering geology of underground excavations (see e.g., Goodman, 1993) construction methods (e.g., TBM vs. NATM) and methods for tunnel design (see e.g., Hoek and Brown, 1980 Panet, 1995). 

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