NUMERICAL MODELLING OF SETTLEMENT COMPENSATION BY MEANS OF FRACTURE GROUTING

摘要

Displacement grouting is increasingly used as a corrective measure to control settlements of buildings induced by near surface excavations such as tunnelling (compensation grouting) or when structures have to be re-levelled because unacceptable (differential) settlements have occurred (corrective grouting). Design of displacement grouting works is still mainly based on empirical considerations and experiences from past projects. In this paper, the finite element method is utilized to describe the general effects of fracture grouting. In the proposed finite element model the soil displacement caused by opening fractures is simulated by volumetric expansion of elements representing the grouted area. It also accounts for the stiffness increase of both the grouted zone and the surrounding soil. The model presented is validated against analytical solutions, available for undrained conditions assuming linear elastic soil behaviour. More advanced elasto-plastic constitutive models have been utilised for solving practical boundary value problems, so far only for situations where drained conditions have been prevailing. The potential of the proposed framework is shown by back-analysing the effects of the compensation grouting operations at the Central Station in Antwerp (Belgium) and by a case history where fracture grouting was utilised to re-level a storage tank, which experienced significant differential settlements.