240 research outputs found
Study of the Permeability of Foam Conditioned Soils with Laboratory Tests
No full textEPB tunneling requires that the excavated soil has a plastic and pulpy behavior to be able to apply a stabilizing pressure to the face, but it should also be impervious to counteract filtration forces that could develop ahead of the face. The evaluation of this parameter in granular soil, before and after conditioning, is therefore of key importance for a correct conditioning agents choice. Approach: A new laboratory procedure for testing the permeability of conditioned soil with foam has been proposed. The tests have been carried out at different hydraulic loads, chosen to be 0.1 bars and 1 bar. Results: The proposed procedure has been applied to determine the behavior of differently conditioned granular soils: a fluvial sand and a pozzolanic soil and has shown that an increasing of the FIR induces a relative increase in the time required by water to pass through a standard sample, emphasizing, in this way, the effectiveness of the conditioning on impermeability of the soil. Conclusion: The tests have shown the laboratory procedure adequately captures the behavior of the conditioned soil. Further, the proposed test may also be used as an index for the preliminary definition of the quality of the soil conditioning and suitability for EPB tunnelin
Influence of the Tunnel Shape on Shotcrete Lining Stresses
No full textTunnel excavation is frequently carried out in rock masses by the drill and blast method and the final shape of the tunnel boundary can be irregular due to overbreaks. In order to investigate the effects of overbreaks a study of the effect of tunnel boundary irregularity has been carried out. This is done developing a computational tool able to take into account fuzzy variables (i.e., thickness of the beams of the bedded spring approach used for the model). The obtained results show that irregularity effects should be considered when a shotcrete lining is used as the final tunnel lining (for the case where the tunneling procedure does not permit a smooth surface to be obtained). This is crucial to obtain a durable linin
Improvment of safety conditions of unstable rock slopes through the use of explosives
No full textThe paper discusses operations aimed at creating a safer natural or man made rock slope by artificially inducing the displacement of unstable elements by blasting. A detailed analysis of the problems with the use of explosives present when conducting these activities is carried out focusing on the advantages and disadvantages of this technology. The results of two examples of demolition of instable rock elements are presented and discussed thus providing suggestions for future blasting design
The behaviour of a two-component backfilling grout used in a Tunnel-Boring Machine
No full textThe instantaneous filling of the annulus that is created behind the segment lining at the end of the tail during the TBM advance is an operation of paramount importance. Its main goal is to minimize the surface settlements due to any over-excavation generated by the passage of the TBM. To correctly achieve the goals, a simultaneous backfilling system and the injected material should satisfy the technical, operational and performance characteristics. A two-component system injection for the back-filling is progressively substituting the use of traditional mortars. In this paper different systems of back-filling grout and in particular the two-component system are analyzed and the results of laboratory tests are presented and discusse
Risk management in tunnelling
No full textIn this chapter, the three phases of tunnelling process (planning/feasibility, engineering and construction) are described, by identifying the actions to be implemented for obtaining a fully serviceable tunnel during its assigned lifetime. The process has to deal with a series of unavoidable uncertainties and unknowns. Consequently, suitable risk management strategies should be defined and continuously adapted during the whole tunnelling process, considering the updated data derived from constant environment surveys and system monitorin
Use of Reinforcement and forepoling in TBM tunnelling
No full textTraining Course: Rock Support in Medium to poor rock condition
Steel pipe umbrella - design procedure
No full textTraining Course: Rock Support in Medium to poor rock condition
Innovative techniques and technologies for underground construction and implications of OS&H
No full textA global overview of the technologies that can be applied for modern tunnelling construction taking into account the OS&H aspects is shortly presented in the paper
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