Investigation of the technological effects of jet grouting diaphragm on the pit enclosure

Abstract

The article considers the features of the technological impact on the “wall in the soil” of jet grouting diaphragm, arranged during the excavation of the pit at the reconstruction object in the conditions of dense historical buildings in the central part of St. Petersburg. It is established that under the influence of the pressure arising from the device of the spacer Jet diaphragm, the "wall in the ground" before the start of the main stages of the "zero" cycle receives a preliminary stress and an initial bend in the opposite direction to the pit. The maximum values of the initial displacements and forces are observed at the level of the Jet diaphragm and are comparable in magnitude with the calculated effect on the fencing of the "zero" cycle works (excavation of the pit, installation of the spacer system and the foundation plate). A series of numerical calculations has been implemented using the Plaxis 2D and 3D software package for modeling a single Jet well, a number of wells, an array of well belts and assessing the impact of their device on the surrounding soil and excavation. The results of numerical modeling of the operation of the pit enclosure and the stress-strain state of the soil mass when the Jet-diaphragm is installed on the reconstruction object are presented. The results obtained were compared with the data of full-scale geotechnical monitoring of the state of the "wall in the ground". The proposed method of numerical modeling of the Jet-diaphragm device process has shown sufficient convergence with the results of field studies.