Control of jet grouting process induced ground displacement in clayey soil

Abstract

The plasticity and low flowability of spoil discharge from clay soil often result in the clogging of boreholes during jet grouting, thereby causing harmful ground displacement, which damages the normal function and safety of nearby underground infrastructures, pipelines, or overlying structures. This study proposed some control measures for jet grouting in clayey soil which combined with: (a) expanding the cross-section of the spoil exit (or borehole), (b) pre-cutting the surrounding soil with a water jet synchronized with jet grouting, and (c) placing additional guided holes for spoil discharge into the ground surface smoothly. The in-situ grouting test demonstrated that combining the abovementioned measures with the typical jet grouting process could mitigate the borehole clogging issue and minimizes excessive lateral displacement induced by jet grouting in clay layers. More importantly, a series of inspections, measurements, and monitoring results indicated that the proposed measures provide no adverse effects on the effective diameter, strength, and waterproofing of the jet-grouted columns. While the incorporation of the proposed measures into standard jet grouting procedures may result in additional time and construction expenses, it is recommended to implement them in areas where there is a high risk of borehole clogging.