(2)

Compared to the shallow-layer vacuum preloading and in situ solidification techniques, the large shell cushion fully utilizes Type III natural sand, which is often considered waste in dredging projects. This makes it an environment-friendly and low-carbon technology, more suitable as a working cushion for equipment in foundation treatment projects in rivers, lakes, seas, and coastal areas with suspended and fluid mud. However, the mechanical behavior during construction and the working mechanism of this type of shell cushion is still unclear, thus hindering its further application. In light of this, based on the strength properties of soils characterized by suspended and fluid mud, this paper starts using numerical simulation to study the mechanical behavior during construction and the bearing deformation characteristics of this shell cushion in depth. Then on this basis, a semi-empirical calculation method for the bearing capacity of this shell cushion is derived using one-dimensional consolidation theory and soil strength theory. Finally, the method is validated by applying it to engineering projects. The results indicate that: (1) the formation of a composite flexible structure in large shell cushions can fully utilize the lateral confinement effect, and the formation of a flat structure can effectively maximize the surface closure effect. The drainage consolidation effect mainly benefits from the drainage function of bagged sand drains. (2) When the underlying layer is suspended mud (water content over 150%), the bearing failure of the soft foundation under the working load of the equipment presents a characteristic of overall shear failure. When the underlying stratum is fluid mud (water content between 85 and 150%), the bearing failure of the soft foundation under the working load of the equipment presents a characteristic of punching shear failure. (3) The formula to calculate the bearing capacity for the shell cushion proposed includes three key technical indicators: stress diffusion coefficient, additional cohesion, and tension. This formula can predict the bearing capacity of the shell cushion effectively, with a calculation error of less than 14% compared to finite element simulation.

来源平台：JOURNAL OF OCEAN ENGINEERING AND MARINE ENERGY