212 research outputs found
Stress dependent thermal pressurization of a fluid-saturated rock
Temperature increase in saturated porous materials under undrained conditions
leads to thermal pressurization of the pore fluid due to the discrepancy
between the thermal expansion coefficients of the pore fluid and of the solid
matrix. This increase in the pore fluid pressure induces a reduction of the
effective mean stress and can lead to shear failure or hydraulic fracturing.
The equations governing the phenomenon of thermal pressurization are presented
and this phenomenon is studied experimentally for a saturated granular rock in
an undrained heating test under constant isotropic stress. Careful analysis of
the effect of mechanical and thermal deformation of the drainage and pressure
measurement system is performed and a correction of the measured pore pressure
is introduced. The test results are modelled using a non-linear
thermo-poro-elastic constitutive model of the granular rock with emphasis on
the stress-dependent character of the rock compressibility. The effects of
stress and temperature on thermal pressurization observed in the tests are
correctly reproduced by the model
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Centrifuge model testing for pile foundation reuse
With continuous development in the urban environment the ground is becoming more and more congested with redundant foundations. The underground development of services and infrastructure already restricts the location of new building foundations and the redundant foundations only add to this problem. This paper describes how existing single pile foundations in overconsolidated clay are likely to behave when their loading conditions are changed by un-loading caused by demolition and subsequent re-loading from a new development. The influence of any new foundations on the existing foundations is also described. Experimental data were obtained from a series of centrifuge model tests undertaken at 60g in which a number of different geometries of novel pile groups were modelled. Model tests included comparison of the behaviour of bored piles when supplemented with mini-pile groups
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