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Detailed Example: Cut In London Clay

Potts et al. (1997) used a finite element analysis to explore a link between strain softening and delayed failures of old railway slopes cut into stiff plastic clays. Strain softening causes a soil’s strength to reduce from a peak to residual state. The strength loss does not occur simultaneously along a potential rupture zone because the rate of softening is linked with the magnitude of shear straining. As a result, the failure is progressive in the sense that the rupture surface propagates through the soil profile over time. Potts et al. (1997) simulated the progressive failure by using an elastic-plastic model in which strain softening was accommodated by allowing the effective strength properties to vary with deviatoric plastic strain.

The primary objective of this example is to demonstrate how the coupled formulation in SIGMA/W can be used to simulate the excavation process and associated time-dependent pore-water pressure response and deformations (i.e. swelling). The excavation and swelling analyses are representative of a non-strain softening soil. A secondary objective of this example file is to demonstrate how the strength reduction technique implemented within SIGMA/W can be used to capture the essence of a progressive failure. SIGMA/W does not have a strain-softening model; consequently, a progressive failure cannot be modeled in the truest sense. Specifically, the strength reduction technique cannot be used to simulate the time-dependency of a progressive failure, which occurs simultaneously, or as a result of the swelling phase. Rather, the strength reduction technique is applied after the swelling phase to determine the possibility of a progressive failure and explore the location and shape of the critical slip surface.

Read the Detailed Example, and then download the free GeoStudio 2007 Viewer License and follow along using the data file.

Cut In London Clay (11.5 MB)

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Banff 2010 Workshop

Anticipation is growing for our fall Geotechnical Modeling workshop in Banff, Alberta, Canada. This is a great hands-on opportunity for both beginning and experienced software users to receive training and sharpen modeling skills. We encourage you to join us if you would like to get more out of your use of GeoStudio.

The focus of the first three days are SLOPE/W, SEEP/W and SIGMA/W, along with a review of fundamental theory. The optional fourth day allows participants to take part in QUAKE/W, TEMP/W and VADOSE/W sessions or work on models in a Study Hall context.

Registration is open. Full details are available on the Banff Workshop page.

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