Experimental and theoretical comparison between static and dynamic torsional soil tests

The dynamic properties of dry Leighton Buzzard sand have been investigated using a resonant column test apparatus. These data are compared with very low frequency cyclic tests on identical specimens of sand. The comparison indicates that the properties of dry sand are independent of frequency. A simple one-dimensional model of kinematic hardening plasticity is used to predict the dynamic behaviour of the sand. The input parameters for this model are based on the results of static tests. These may be conducted on standard laboratory equipment with only minor modifications. The predictions are in good agreement with the measured data.

The modelling of soil plasticity

The modeling of the soil plasticity was discussed and it was shown that the grain breakage is an important factor of the plastic soil behaviour. A reduction of internal coefficient of friction was observed when stress-level was increased. The yield paths of all stress path tests determined by curve fitting were presented.

Destruction-free parameter extraction for a physics-based circuit simulator IGCT model

This paper presents a practical destruction-free parameter extraction methodology for a new physics-based circuit simulator buffer-layer Integrated Gate Commutated Thyristor (IGCT) model. Most key parameters needed for this model can be extracted by one simple clamped inductive-load switching experiment. To validate this extraction method, a clamped inductive load switching experiment was performed, and corresponding simulations were carried out by employing the IGCT model with parameters extracted through the presented methodology. Good agreement has been obtained between the experimental data and simulation results.

Soil conditioning under London

The CTRL Contract 220 covered 7.5km twin-bore tunnels excavated between late 2002 and early 2004 from Stratford Box to St Pancras station in Central London. To ensure efficient machine operation as well as the transport and disposal of soil, soil conditioning treatments were applied. Specifically, the foam injection ratio (FIR) and the polymer injection ratio (PIR) (injected volume of foam and polymer solution expressed as a percentage of the excavated soil volume) were employed. It was found that carefully selected soil conditioning allowed chamber pressures of 200kPa or more to be accurately controlled in the stiff London Clay and to an extent, in the very stiff clays of the Lambeth Group. Average FIRs of 50% and PIRs of 7 and 9% were used in the Thanet Sand and in the Lambeth Group Clays. In contrast, much lower quantities of foam were used in the London Clay.