Study of the Permeability of Foam Conditioned Soils with Laboratory Tests

EPB 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

Laboratory test for EPB tunnelling assessment:results of test campaign on two different granular soils

Earth Pressure Balanced shields are currently the most utilized tunnelling machines throughout around the world. The possibility of using conditioning agents that change the mechanical and hydraulic behaviour of a soil, changing it into a plastic paste and thus permitting soil pressure applications at the tunnel face, is the key point to explain the increasing utilization of this technology. Despite its great importance, not much laboratory researches can be registered on soil conditioning, particularly for cohesionless soils. The conditioning criterion is usually defined on the basis of a trial-and-error procedure developed directly at the job sites. A test that is able to simulate the extraction of soil from the bulk chamber with the screw conveyor inclined upwards, as in real machines, can offer a quantitative indication of the conditioned soil behavior for EPB use. The characteristics of the device and the results obtained on many different types of soil are discussed in order to point out the great importance and quality of results that can be achieved using the proposed test devic

Improvment of safety conditions of unstable rock slopes through the use of explosives

The 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

Numerical modelling of ground-tunnel support interaction using bedded-beam-spring model with fuzzy parameters

The study of the ground-tunnel interaction by introducing a predetermined degree of variation (fuzziness) in some parameters of the chosen model is presented and discussed. This research comes from the consideration that tunnel model parameters and geometry are usually affected by a degree of uncertainty, mainly due to construction imprecision and the great variability of rock mass properties. The research has been developed by using the fuzzy set theory assuming that three model parameters are affected by a certain amount of uncertainty (defined by the so-called membership functions). The response of the numerical model is calculated by solving the fuzzy equations for different shapes of the membership functions. In order to investigate the effects of some model parameters, and to provide a simple procedure and tool for the designers, a study on the effect of tunnel boundary conditions, based on a fuzzy model, has been carried out using a simple but well known and widely used design method such as the bedded-beam-spring mode

The behaviour of a two-component backfilling grout used in a Tunnel-Boring Machine

The 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

QuaRRi: a new methodology for rock-fall risk analysis and management in quarry exploitation

Rockfall is one of the most critical geological events that can affect quarrying activities. Nevertheless, few tools are currently available to help designers and managers correctly define the risk conditions and quantify the advantages, in terms of workers' safety and quarry management, that can be obtained using suitable prevention devices. For this reason it is necessary to evaluate the various parameters that are involved, and to define the most important and which have the greatest influence on rock-fall phenomena, taking into account the Prevention through Design approach. A risk evaluation systemwhich is able to support decision makers in the critical rockfall risk assessment phase, and offer decision makers the updated information that is necessary for a continuous and dynamic operation design during exploitation activities is here presented and discusse

INDAGINI PRELIMINARI NELLA COSTRUZIONE DI GALLERIE: ANALISI DELLA LETTERATURA TECNICA

L'articolo illustra e discute l'importanza delle indagini preliminari nella progettazione delle gallerie tenendo conto della necessità ormai imprescindibile nella pratica progettuale moderna di sviluppare una corretta risk analysis del progetto, sulla base delle indicazioni proposte e presentate nella letteratura tecnica. Il confronto delle indicazioni fornite dalle più aggiornate linee guida internazionali e un'ampia disanima di casi applicativi permettono di mettere in luce gli aspetti chiave per la pianificazione delle indagine preliminari sia nel caso di scavo convenzionale sia meccanizzato

Whole Child Philosophy

Whole child philosophy in physical educatio

Supporting student transitions: Integrating life design, career construction, happenstance, and hope

No asbstract needed