An improved version of the observational method is developed and proposed. The method uses field measurements as the direct inputs to the framework of the constitutive behaviour and analyses the behaviour synchronously as measurements are recorded. The method is developed for the specific case of embankments on soft clays, and its effectiveness is tested on a well-documented case history. The framework provided for the application of the method is basically the idealized stress space of the critical state theory, but the constitutive anisotropic elastoplastic soil model is added to this framework to analyse the behaviour and provide direct links between measurements and design parameters. Strain-rate dependency of the soft soils is also incorporated in the interpretation of the behaviour. To consider the variation in the behaviour of foundation soils, a zonation system is applied. Stress axis rotation is considered for active and passive regions effectively. Substantial savings can be achieved using the method in terms of time and cost, and the method is reliable. In addition, such an application improves the understanding of the real behaviour of soils.