PURPOSE: To adjust slime suction to prevent the excess slime and open or close a clearance packing in the injection rod, in the slime suction in an injection rod injecting a ground-curing agent with a high pressure from the inner pipe fitted by the outer pipe to an objective ground.

CONSTITUTION: An elastic bag 8 provided with an inner pressure-adjusting mechanism, expanding or contracting by the inner pressure at specified positions near the slime suction hole 5 of the slime suction clearance composed of the inner pipe 12 and the outer pipe 11 and other required clearance, is arranged to have a valve function and a packing function. And a slime suction guide groove 7 is provided at the nearby position of the slime suction hole 5. Accordingly, the inner pressure of the bag is increased in accordance with the inner pressure of the objective ground and the bag is swollen to inhibit the inflow of slime into the suction hole. In this way, slime suction is adjusted to prevent the curing agent from thinning in the injected layer and also the clearance in the injection rod can be plugged to freely open or close.