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The use of electrical conductivity measurements from a non-invasive hand held electromagnetic probe is showcased to monitor the water content of earthen embankments at routine inspections. A methodology to convert the electrical conductivity measurements from the electromagnetic device into water content values is illustrated. The methodology is based on measuring the soil electrical conductivity variation with respect to a baseline reference condition and calibrating a water content – electrical conductivity relationship by comparing electrical conductivity readings from the electromagnetic probes with water content readings taken from geotechnical probes installed in a few sections of the embankment. The values of water content converted from the conductivity measurements according to the proposed procedure were found to be in very good agreement with independent measures of water content taken at times well beyond the calibration period. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this paper is to describe a solution strategy to model the transport of a dilute solute into a porous material, the subsequent reactions, the evolution of material degradation and the mechanical response of the solid in terms of inelastic strains. The convection-diffusion reactive equation is split in a pure advection system of PDEs solved using a Taylor–Galerkin discretization technique and a system of ordinary differential equations solved with a fourth-order Runge–Kutta algorithm. The constants defining the rate of the chemical reaction, in this case, the dissolution of calcite under acid action, are determined with experimental tests. The constitutive model used to represent the debonding process has been developed by Nova and co-workers and implemented in the Finite Element computer code GeHoMadrid. The experimental response obtained in carbonatic soft rock specimens using a “weathering test device” is reproduced by means of the proposed strategy. Finally, a time dependent geotechnical application concerning the weathering induced subsidence of a shallow foundation is presented by comparing experimental results and numerical simulations. [Copyright &y& Elsevier]

Abstract: A 3D numerical model for mechanised excavations is presented, which is capable of simulating the overall process of excavation and construction of a tunnel when a TBM EPB (Tunnel Boring Machine–Earth Pressure Balance) is used. The main construction aspects of a mechanised excavation are modelled. Their influence on calculated ground displacements are investigated by means of a series of parametric analyses. With the aim of testing the performance of the proposed 3D numerical model, a series of 25 Class C predictions has been carried out. Case Histories related to the construction of the 1995–2003 Madrid Metro Extension Project were considered for this purpose. As a general rule, the results obtained with the Modified Cam–Clay model closely fit in situ measurements. When the Linear-Elastic or the Mohr–Coulomb models are used, it is not as easy to summarise the results obtained, as higher fluctuations are observed around in situ measured data. A good agreement is also shown when the distribution of horizontal displacements along depth is considered. For some sections, the mechanised excavation model is not capable of reproducing the high values of the surface settlements measured in situ. A closer look at the results shows that mixed face conditions are found for these cases, with the TBM excavating through layered soil formations having sharply different mechanical behaviour. [Copyright &y& Elsevier]