Numerical modelling of water jet induced erosion

This research project that is carried out in the wider research context of experimental and numerical geotechnics deals with the investigation of jet grouting. This ground injection method is frequently used in geotechnical engineering for the production of underpinnings and piles, reducing settlements of new and existing foundations, supporting open and underground excavations, and creating water cut-offs for dams. Using a high-pressure pump, a cutting jet of water or binder suspension is used at a pressure of approx. 500 bar to cut or erode the soil. Water or grout mixture are injected through a nozzle in the grout pipe, which is rotated continuously, and the radially propagating jet from the borehole axis erodes subsurface soil. A large number of factors influences the jet grouting process and its efficiency: on the one hand, soli properties play an important role, on the other hand, factors such as the used jet material, the geometry, distance and arrangement of the nozzles, the pressure of the jet as well as the speed of rotation and pulling rate of the nozzle have a big impact. Even though jet grouting is a ground improvement technique which nowadays contributes to the solution of several geotechnical problems, large uncertainties still exist in the prediction of the diameter of jet columns. In the course of the project, we use a combination of experiments and numerical simulations to investigate on the details of the process. The main challenge is that effects that take place on very small scales affect the overall behaviour of the entire process. It is thus necessary to resolve small details with the simulations while at the same time also the entire, large setup must be captured. For being able to depict the presence of both fluids and solids (bulk materials such as soil), two different, established CFD-DEM (coupling between fluid dynamics method and particle simulation method) methods are combined. Particularly the treatment of the interface between the two methods is challenging and must be developed in the course of this project. The experiments are conducted by the research partner at the Institute of Geotechnical Engineering and Construction Management at the Hamburg University of Technology.

No additional funding sources recorded.