Settlement during vibratory sheet piling

Abstract

During vibratory sheet piling quite often the soil near the sheet pile wall will settle. In many cases this is not a problem. For situations with houses, pipelines, roads or railroads at relative short distance these settlements may not be acceptable. The purpose of the research described in this thesis is to develop a model that is capable of predicting the settlement due to vibratory sheet piling with reasonable accuracy. The research is limited to sheet piling in sand. First a description is given of the processes during vibratory sheet piling. From this description the main mechanisms that are responsible for the settlement during vibratory sheet piling are identified. These are the densification of the soil and the displacement of a soil volume due to the volume of the sheet pile. Presently available models to predict the settlement are described and commented. It is concluded that all models possess some shortcomings. As densification is one of the main causes for the settlement much attention is paid to the behaviour of sand during cyclic loading. Available models to predict the densification for large numbers of loading cycles are described. Attention is paid to the combined effect of generation and dissipation of excess pore pressure. To supplement the findings from the literature a series of cyclic triaxial tests is performed to clarify some aspects. These tests show that the history of the sand greatly influences the behaviour during cyclic loading. A numerical model is developed that takes into account the different sub processes during vibratory sheet piling (interface behaviour sheet pile - soil, propagation of vibrations, densification, dissipation excess pore pressure and summation of the local volume strains). For the propagation and the densification different options are considered and implemented. The selected constitutive models are extended to handle both undrained and drained soil behaviour. To validate the developed model a well instrumented field test is designed and executed. This test is performed at Raamsdonksveer, The Netherlands. Measured data are the vibrations near the sheet pile, the pore pressure, the local densification, the settlement at surface and at two depths and the change in cone resistance. The measured data are processed and interpreted. In addition to the results of this test, measured surface settlements from a number of projects are used as well to compare predictions with the developed model with actual behaviour. A reasonable agreement between measured and predicted settlement is found.