*2.1. Principle of FCB*

FCB is a new technology for reducing embankment settlement while ensuring the normal operation of road transport, its schematic diagram is shown in Figure 1. First, the amount of FCB replacement needed is based on the amount of static load of embankment to be uninstalled, which is, in turn, used to design the transverse hole construction plan. Then, drilling horizontal holes on the embankment continuously, with the hole machinery along the embankment on one side or both sides, next, FCB is injected directly into the holes using perfusion enrichment after the hole formed. The unit weight of regular FCB filling is 5.5–6.0 kN/m3, which is 1/3 to 1/4 of the general soil bulk density (i.e., 20 kN/m3), to effectively reduce the embankment permanent load. The undisturbed foundation soil becomes super-solid, and the effect of the improvement is clear. The normal operation of the highway will not be affected during construction.

**Figure 1.** Embankment FCB replacement construction by citing transverse holes.
