Packer injection is a geotechnical engineering ground improvement method in which grout, cementitious slurry, or chemical agents are injected under pressure into soil or rock through a specialized device called a packer. A packer is placed within a drilled borehole to create a sealed zone that directs the injected material into targeted voids, fractures, or weak soil layers. This process enhances load-bearing capacity, reduces permeability, and improves overall subsurface stability.