Study on the mechanism of ultra-high pressure jet grouting to improve the bearing capacity of foundation based on DEM and CFD method

Abstract

Ultra-high-pressure injection grouting is one of the main method to improve the bearing capacity of foundations, in order to investigate the diffusion mechanism of ultra-high-pressure injection grouting, the simulation method combining particle flow(DEM) and computational fluid dynamics(CFD) is used, and the macroscopic and microscopic parameters of the particles are determined by triaxial tests in the laboratory and numerical simulation tests, and the simulation method is verified by similar model tests. The validity of the simulation method was verified by similar model tests. Based on this, the numerical test of UHP injection grouting was carried out under different injection pressures of 20~60 MPa to monitor the changes of injection range, porosity and fluid pressure. The result show that the UHP jet grouting reinforcement process can be divided into three stages: cutting and wrapping, compression and tightening, and large-scale vortex cutting and replacement. With the increase of injection pressure, the injection distance increases approximately linearly, but the width of the cavity may be the same under different pressures; the peak value of the porosity of the soil around the cavity in the injection process is closely related to the shape of the cavity formed; in a very short period of time at the beginning of the injection(within 0.05) the soil body has appeared to have a multi-stage splitting phenomenon, and the fluid pressure is a significant change in the form of a stair-step; with the increase of the pressure, the vortex cutting and stirring of the soil body formed by the jetting will With the increase of pressure, the vortex cutting mixing soil formed by jetting will occur in advance, and there may be a critical pressure value(30 MPa), which can provide a certain reference for the actual project.

Keywords

ultrahigh-pressure jet flow / numerical simulation / fluid-solid coupling / particle flow / underground engineering