SUPERTOP foundation techniqueSUPERTOP foundation technique

NIPPON SHARYO

In quest of the removal technique of existing concrete foundation in the ground to cope with the demand increasing of “Building renewal projects”the construction volume of the SUPERTOP casing rotator is increasing remarkably in Japan and in Hong Kong. This chapter instructs varioustechniques in removing underground obstacles.

UNDERGROUND-UNDERGROUND-OBSTACLE REMOVALOBSTACLE REMOVAL

Covering the whole obstacle with a casing

Cleaning bywater jet

Extracting bycrane

Hammergrab

Steel pile

H-shaped beam

Casing

掘　　　削掘　　　削掘　　　削掘　　　削　　　　 Grabbing

The obstacles as steel pipes and H-shape beam (which are not possible to break them into small pieces by a chisel) can beremoved by covering whole obstacle with a casing and excavating soil around the obstacle with a hammer grab, andcleaning the remained soil in the casing with a water jet, and extract it by a crane.

Cut and break a steel pipe with casing bits

Breaking bychisel

Excavating by hammergrab

Steel pipeH-shaped beam casing

Cutting by casingbits

Steel pipes and H-shape beams can be easily removed after cutting them into two pieces by casing bits. Sometimes, ahammer grab is dropped into between the casing and the cut pieces of the steel pipe. Then, remove the cut pieces byrotating the casing together with hammer grab, resulting the cut pieces to be twisted and broken.

Cutpiece

(Cuttng by casing + removing by multi-gripper)Vibration/noise pollution free technique

Steelbeam

Multi-gripperMulti-gripper

Multi-gripperMulti-gripper

Steel pipe

( (Low sound/vibration level)Low sound/vibration level)When a high level of vibration or noise generation is prohibited, this multi-gripper is the most effective tool for removingunderground obstacles. The multi-gripper is a drilling tool through out the obstacle inside of the casing, not only ironreinforced concrete bases, PC-piles, steel pipes caissons, bored piles , etc.

Covering whole bored pile by casing

Bored pileCasing

Keep a gap [C] between bored pile and casing: 200~300 orKeep a gap [C] between bored pile and casing: 200~300 ormoremore

C

A sufficient space [gap:C 200 to 300mm and more] between the casing and the bored pile is required for easier breakingthe pile into small pieces and for smooth covering with the casing through out the pile . After chiseling the pile head in thecasing, excavate the broken pieces with a hammer grab.

Low vibration level with multi-gripper

Bored pileCasing

Keep a gap [C] between bored pile and casing: 200~300 orKeep a gap [C] between bored pile and casing: 200~300 ormoremore

C

A sufficient space [gap:C 200 to 300mm and more] between the casing and the bored pile is required for easier breakingthe pile into small pieces and for smooth covering with the casing through out the pile . In case high level of vibration isprohibited, excavate the broken pieces with a hammer grab after breaking the pile head in the casing with a multi-gripper .

Multi-gripper

(Cut and break a bored pipe with casing bits)

Casing

Bored pile

It is important to know “How many per cent of the casing is contacting with the bored pile” during driving the casingthrough out the pile. If it is hard to drive the casing into soil with a certain vertical accuracy, the cutting bits of the casingmay be slipped out from the bored pile.

(Cut and break a bored pipe with casing bits)

Pile

Casing

Covering ½ or more:Going straight ahead

Covering 1/2~1/3:Going into pilecenter

Covering 1/3 or less:Escaping from pilecenter

Pay special attentions to the casing. If the casing covers over 50% of the pile sectional area, it will go down straight ahead.If it covers1/2~1/3, then the casing will be inclined toward the pile center. If it cover less than 1/3, then it will be slipped andescaped from the pile center.

((Boring through out concrete base)Boring through out concrete base)

Concrete baseConcrete base

Cut by casingExtracting casing

Grabbing

C

To cut concrete base, even if it contains iron-reinforcements, is not so difficult by the cutting bits provided on the bottomend of the casing. But the concrete core remaining in the casing must be broken into small pieces by chiseling prior toexcavation them. The gap [C] must be kept by lifting the casing for better chiseling performance.

Under ground obstacles removalby MULTI-GRIPPER

Under ground obstacles removalUnder ground obstacles removalby by MULTI-GRIPPERMULTI-GRIPPER

Multi-gripper, specially invented drilling tool used together with SUPERTOP for underground obstacle removals. Its mosteffective application is [At the site where a high vibration level generated by chiseling is prohibited, or thick ironreinforcement bars, steel pipes and H-beams are existed in the obstacles to be removed.

Structure / functions of multi-gripperStructure / functions of multi-gripper

DrillingDrillingInsertion/removalInsertion/removal

Casing

Weight

shoe

Screw head

Link

When multi-gripper is suspended its shoe is retracted. The shoe is expanded and griped surely in the casing when thescrew head reaches to the bottom by the weight. Rotate and lower the casing and the screw head starts to crash thebottom. A drilling-reaction force from the bottom pushed up the screw head which results shoe to be expanded strongly.