Abstract: Measurement of the skin friction of piles, according to which a skin-friction measuring device having a cylindrical testing part which is rotatable relative to a main body of the device is introduced into a bored hole in a ground and is rotated by a boring rod, and by rotating the boring rod, the friction force then generated between the cylindrical testing part and the wall of the bored hole is determined in terms of the torque required for rotating the cylindrical testing part.

Abstract: The present invention provides a method of improving soft ground.In this method, slurry formed by a mixture of cement-based hardener and water is supplied to the soft ground under pressure and is mixed with soft soil thereby to harden the same. Then, at least when a ground improvement machine having mixing propellers is penetrated into the above-mentioned soft soil, the cement-based hardening slurry is discharged from the mixing propellers.Further, in another method of improving soft ground according to the present invention, slurry formed by a mixture of cement-based hardener and water is supplied to the soft ground under pressure and is mixed with soft soil. Then, when deep and short walls, both consisting of mixed layer of the cement-based hardening slurry and the soft soil are formed one after the other, a plurality of deep walls are formed at a distance therebetween and then the short walls are jointly formed between a plurality of these deep walls.

Abstract: An improved pile driving method is disclosed, which is particularly applicable in piling into a hard rock bed widely in the construction of buildings, bridges, harbor facilities, piers and so forth, and in which a high-pressure water guide pipe is attached to a pile to be driven, in a manner of being movable within a certain limit, and while effecting a removal of rock pieces produced by crushing by the pile driving, through jetting a water supplied under pressure through the guide pipe, driving of the pile is worked by a vibration pile driver. This method employs a reduced amount and suppressed pressure of water to be jetted in comparison to conventional methods.

Abstract: An improved pump-type sludge dredging apparatus including a pump dredger having a first ladder, a sludge suction pump acting in cooperation with the ladder and pump dredger, a suction pipe, a second ladder, a suction device suspended from the second ladder and connected to the pump through a suction pipe, a rotator, a half-cylindrical sludge collector plate, a substantially inverted U-shaped body structure, a grating, movable vanes disposed outside the grating and gas collecting chambers.