SOIL IMPROVING APPARATUS

PROBLEM TO BE SOLVED: To efficiently pump up underground water when soil is to be improved by application of an impact force to ambient soil under the ground. SOLUTION: This soil improving apparatus includes a vertically extending hollow rod having a helical blade 18 and a lower end provided with an opening 19, a compressed air supply pipe 13 inserted into the rod and having a closed lower end and an opening 34, a pipe member 14 attached to the supply pipe in such a way as to surround the periphery of a portion of the supply pipe at a position above the opening of the supply pipe, and a sheet member 15 attached to the supply pipe and the pipe member in such a way as to surround the periphery of a portion of the supply pipe and defining a closed space 36 communicated with the opening of the supply pipe and the inside of the pipe member.