Arresting settlement of clay using low-pressure grouting

In Singapore, ground settlement is one of the major problems encountered in built-up areas such as housing and industrial estates. While structures themselves are not affected by settlement, as they are supported by piles, a large amount of ground settlement occurs due to the presence of a thick layer of soft clay beneath service roads and car-parking areas. In built-up areas it may not be appropriate to us the conventional high-pressure jet grouting method as it has a potential of causing soil and foundation movement. In the present study a modified version of the jet grouting method, called ‘low-pressure grouting’, was developed to arrest the settlement of a soft clay layer in a built-up area. A laboratory grouting model apparatus was developed to simulate in situ low-pressure grouting, and the performance of the grouting was evaluated. The experimental data obtained were used to develop a predictive model, and the model was used to evaluate a grouted column. It was found that the diameter of the grouted column during low-pressure grouting fell within the lower range of that seen when using conventional high-pressure jet grouting. It was concluded that the proposed low-pressure grouting method can be used to treat a soft clay layer in a built-up area.