Vacuum preloading and PVDs in soft soils beneath embankments: 3D coupled analysis incorporating overall stability study

Abstract

Although embankments on soft soils with prefabricated vertical drains (PVDs) under vacuum preloading have been widely studied, there is a lack of studies in the literature in which overall stability is analysed through three-dimensional (3D) mechanical-hydraulic coupled modelling. In order to contribute to overcome such deficiency, this paper presents 3D numerical analyses of an embankment on soft soils incorporating PVDs and vacuum preloading. A finite element code, which includes 3D fully coupled analysis, is used and a method for overall stability study – which uses the 3D numerical results obtained with the finite element code – is presented and applied. A parametric study is performed in order to analyse the influence of the magnitude of the vacuum preload and the staged construction of the embankment (time of vacuum application before completion of the embankment). Overall stability, excess pore pressures, settlements, horizontal displacements and stress levels are analysed.

Variation of negative vacuum pressure in vertical drains with time and depth under variable well resistance

“…1,2 With the development of technology as well as equipment in recent years, the reinforcement method of vacuum preloading to accelerate consolidation of soils with vertical drains is widely used in practical projects. [3][4][5] The vacuum preloading has caused a great deal of concern since it was proposed by Kjellman in 1952. 6 Subsequently, the vacuum preloading technique was successfully used to strengthen soft soils in the airport expansion project in Philadelphia, USA, which further demonstrated the feasibility of the vacuum preloading reinforcement method.…”

“…The vacuum preloading can effectively accelerate soil settlement and control soil lateral displacement, which is a more economical, stable and rapid method comparing with the surcharge preloading 1,2 . With the development of technology as well as equipment in recent years, the reinforcement method of vacuum preloading to accelerate consolidation of soils with vertical drains is widely used in practical projects 3–5 …”