Mechanism of underexcavation and practical design method for building rectification

Abstract

Article Highlights The finite element simulation reveals the details of stress field and displacement field around the underexcavation hole, which is difficult to capture in site observation or in model test; The soil failure takes the underexcavation hole as the defect center and develops in the shape of “X”, which is very different from the previous study but agrees with the laboratory tests. The multi-hole finite element simulation shows that the deformation caused by stress redistribution is negligible compared to the anticipated forced settlement, which indicates that the forced settlement is from the hole closure. This simulation provides a basis for derivation of key parameters of rectification design. According to the total vertical force balance between the bottom of the base and the horizontal plane at hole centre line, the formula for the preferred hole spacing is obtained; According to that the amount of base settlement is equal to the volume of soil excavation, the formula for the hole diameter is obtained. The two formulas can assist geotechnical engineers with the rapid design scheme for building rectification.

Keywords

• Underexcavation
• Building rectification
• Numerical modelling
• Plastic failure
• Design method