Abstract
Grouting has been deemed as one of the most effective measures for mitigation of ground movements during tunnel construction in soft soil. Notwithstanding that, a reliable measure to quantitatively evaluate the grouting-induced ground movements during shield tunnelling in soft soil has not yet been developed. This paper presents a simple method capable of quantitatively estimating the ground movements associated with grouting for tunnel-boring operations where the grouting parameters and soil properties are taken into consideration. The grouting process is simplified as the expansion of a cylindrical cavity with a uniform radial stress applied at soil-grout interface in a half plane, and the analytical solution proposed by Verruijt is introduced for determining the ground movements by the expansion of the cylindrical cavity. The proposed method is verified with a case history undertaken in London Clay. The results obtained suggest that this procedure would be helpful in managing the grouting parameters adopted in upcoming soft ground tunnelling project and mitigating the environmental impacts on nearby properties.
Highlights
Grouting has been deemed as one of the most effective measures for mitigation of ground movements during tunnel construction in soft soil
In the grouting process, due to the injection of pressurized grout, it will bring the additional loads on the surroundings and be likely to cause the ground displacements, which can lead to adverse effects on existing building foundations or utilities [29,30,31,32]. erefore, it is of great concern to estimate the magnitude of expected ground displacements before tunnel construction [33]
E objective of this paper is to develop an approach that is capable of estimating the ground movements induced by grouting during tunnel construction in soft soil by taking into account the grouting parameters and soil properties, based upon the expansion theory of a cylindrical cavity in a half plane. e proposed method was applied to analyse a case history undertaken in London Clay for demonstrating its applicability
Summary
The annular gap can generally be formed between the erected tunnel lining and the excavated ground due to the smaller extrados of tunnel lining than the shield. e annular gap needs to be soon backfilled with grout to stabilize the tunnel linings and to mitigate the movements of surrounding soil. Verruijt [39] developed an analytical solution for calculating the deformations by expansion of a circular cavity with uniform radial stress in a half plane, and in this study, Verruijt’s solution was adopted to determine the ground movements caused by grouting during shield tunneling in soft soil. e physical meaning of the radius of circular cavity and the uniform radial stress can be interpreted as the radius of the soil-grout interface (rsg is related to the diameter of tunnel lining and grout volume) and the uniform pressure at the soil-grout interface (pum is related to the grout pressure), respectively
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