Field and Laboratory Tests Investigating Settlements of Foundations on Weathered Keuper Marl

Abstract

Measured settlements of buildings on the weathered Keuper Marl appeared to be much smaller than calculated settlements, which were based on stiffness modulus from standard oedometer tests. Therefore, both special triaxial K ₀-tests and oedometer tests were carried out for an accurate determination of stiffness moduli. Modulus obtained in the triaxial K ₀-tests were at least two to three times the values obtained in the oedometer tests. To verify observations from the laboratory tests, the loads and the settlements of two single footings on weathered Keuper mudstone have been measured during construction of a building over 1 year. Also, a large scale footing load test with measurements of deformations were conducted on the weathered Keuper mudstone. The measured settlements of the two single footings and the tested foundation were compared with the settlements based on conventional calculations with moduli from oedometer tests and triaxial K ₀-tests. Up to a foundation pressure of σ_v = 500 kN/m² the calculated settlement based on E _S-modulus obtained from triaxial K ₀-tests was found to correspond well to the measured deformation. For foundation pressure beyond 500 kN/m², the foundation response was highly non-linear and it could not be described any more with the linear-elastic model. Therefore the footing load test was also simulated by FEM analyses.