10.4.1 Compaction grouting
Although the compaction grouting method is widely applied in geotechnical engineering，in most cases，it is used to uplift the settled buildings.
Theoretically，the compaction grouting method is limited in its application to buildings under a certain weight.No related studies in the literature indicate the maximum building weight the compaction grouting method is capable of uplifting.Graf（1992）once lifted up a 4.5 m×4.5 m square footing by 5 cm using compaction grouting.The footing was 1.2 m deep and bore a dead load of 500 tons and a live load of six driveways.The grouting bulb was 5.75 m deep below the ground surface.Wong et al.（1996）uplifted one of the footings of a four floor building by 24 mm，which was about 1 m below the ground surface.Grouting was implemented from the bottom up，starting at the depth of 8 m below the ground surface up to 3 m below the ground surface.When the grouting depth grew higher than 4.5 m，the foundation could be observed uplifted apparently.
A detailed plan of the grouting pressure，grouting rate，grouting depth，arrangement of the grouting points，and the implementation method is required before the building rectification operation.Besides，the building should be equipped with complete monitoring instruments for immediate adjustment of the operation.
To uplift a building，the ways of grouting are two：either bore through the floor of the building and grout vertically or grout slantingly from the building side，as shown in Figure 10.13.The former has better effects since it is more direct.Nevertheless，it will affect the use of the building.The latter is less effective but has the benefit of not disturbing the use of the building.
Basically，the arrangement of the grouting points should be aimed at the place where settlement is the largest.The major grouting point should be arranged at a larger depth.The places where settlements are smaller can be arranged as the minor grouting points where the depths are slightly shallower than the major one，as shown in Figure 10.14（Nonveiller，1989）.The sequence of grouting should follow the degrees of settlement，beginning with the place where settlement is the largest and then proceeding to the minor points next to it.The operation is to be repeated till the desired amount of lifting is achieved.If the lifting amount is too large，the operation can be carried out in stages.
Figure 10.13 Grouting positions of the compaction grouting method
Figure 10.14 Arrangement of the injection points with the compaction grouting method for the rectification of buildings