To have the flow properties of excavation muddy soil and sludge, etc., having a high moisture content lost in a short period of time and to convert the muddy soil, etc., to the treated soil which has high strength and is easily reusable by adding coconut scrap to the muddy soil and mixing both by using an excavating machine having a mixer in a bucket.

The front end of the bucket 1 is provided with blades 2 for excavation and the bucket 1 is internally provided with mixing blades 3 of a rotary type. These mixing blades 3 are driven by chains 4 and mix the muddy soil and the additives by the rotational motion thereof. At the time of use, the muddy soil added with the coconut scrap is excavated by the bucket 1 and the mixing blades 3 are rotated in the state that the bucket 1 is kept filled full with the muddy soil. The mixed muddy soil is discharged after the bucket 1 is pulled up and the muddy soil and the coconut scrap are mixed. The muddy soil and the coconut scrap are rapidly and uniformly mixed by such rotation of the mixing blades 3 and, therefore, the added coconut scrap is effectively acted. The solidified and treated mud which has the high strength and is easy to handle is thus obtd.