Prediction of Foundation Deformations in Edmonton Using an In Situ Pressure Probe

Abstract

For overconsolidated soils and soft rocks the instantaneous component of foundation settlement or heave is a substantial part of the total deformation. Hence, for such cases large portions of the total deformation can be estimated using the theory of elasticity if representative moduli can be determined. However, deformation moduli, especially in overconsolidated soils, are susceptible to sample disturbance and this severely restricts the accuracy of predicting foundation deformation based on laboratory test results. In Edmonton, settlements of large buildings are overestimated 10–30 times if oedometer results are used. Therefore an in situ pressure probe technique has been used to measure moduli of instantaneous deformation in boreholes penetrating foundation strata near two multi-storey buildings in Edmonton — the C.N. and A.G.T. Towers. For these structures records of either settlements (C.N. Tower) or excavation heave (A.G.T. Tower) were available. The moduli obtained from in situ pressuremeter tests were used in the finite element analysis. The results agree remarkably well with field observations and demonstrate the applicability of this method in practice. The economics of the pressure probe investigation technique is competitive with existing methods.