Flat Cavity Expansion: Theoretical Model and Application to the Interpretation of the Flat Dilatometer Test

This paper presents a theoretical model for flat cavity expansion in elastic soil. By using the conformal mapping method, the nonaxisymmetric boundary value problem of flat cavity expansion is transformed from the original physical plane into the axisymmetric boundary value problem in the phase plane, which results in a series of closed-form solutions for the stress and displacement induced by the flat cavity expansion. These closed-form solutions are then validated by FEM and provide the basis for the interpretation of the list-off pressure of the flat dilatometer test. Subsequently, a closed-form solution for the list-off pressure in the flat dilatometer test is given. The suitability of the solution for the list-off pressure is validated by comparing the predictions with a series of field test data provided by previous scholars. Good agreement is achieved. The proposed theoretical model improves on the previous empirical method for the interpretation of the list-off pressure in the flat dilatometer test. It also provides a new method for analyzing the nonaxisymmetric cavity expansion problem, improves the theory framework of the conventional cavity expansion theory, and can be seen as an extension of the conventional cavity expansion theory.