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CS CONSTRUCTION & GEOTECHNIC PTE LTD

No. 2 TG PENJURU CRESCENT (S) 608968

TEL 6362 6866 FAX 6362 6877

Method Statement for Micropiling Works

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1 Method Statement For Single-Debonded Micropile Installation .......................... 2

2 Material Specification .............................................................................................. 4

2.1 Structural Load – Bearing Component .............................................................. 4

2.2 Grouting Materials ................................................................................................... 4

2.3 Grout Mix .................................................................................................................... 4

3 Micropile Details ...................................................................................................... 6

3.1 Micropile Details ....................................................................................................... 6

3.2 Brochure for Bithuthene 3000 .............................................................................. 7

3.3 Couplers For Steel Bars .............................................................................................. 8

3.4 Sample Installation Record Form………………………………………………9

3.5 Sludge Disposal Arrangement ............................................................................ 10

3.6 Drilling Machinery Catalogues ........................................................................... 11

4 Pile Load Tests ....................................................................................................... 12

4.1 Kentledge Assembly .................................................................................................. 12

4.2 Anchor Reaction Assembly ................................................................................. 16

4.3 Pile Test Schedule (For Static Load Test - ULTIMATE AND STANDARD) ........ 16

4.4 Test Pile Record Form (For Static Load Test) ................................................ 17

4.5 PDA Test .................................................................................................................. 18



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1 METHOD STATEMENT FOR SINGLE-DEBONDED MICROPILE INSTALLATION

Following is the proposed installation sequence for the typical micropiles:

1. Set-up the micropile position;

2. Offset pile setting up point to a location that is safe from disturbance;

3. A short length of temporary steel casing shall be set-up at the location of micropile as a

guide for the drill rods. Water shall be used as lubricating medium, Boring shall then be

advanced up to toe to debonding using drilling tools in wet or dry method which

depends on the ground condition and water table level. Withdraw the drill rods and drill

bit;

4 Lowering of permanent steel casing pre-wrapped with 1 layer of Bithuthen 300 (full

length) shall be done using the drilling machine. The casing sections will be joined by

fillet welding all around;

5. Rotary drilling will be proceeded using API drill-rods combined with Drag-Bit or Ken-

claw or Roller-Bit or just using Continuous Flight Auger. Auger-bullet bits will be used

to core through weathered rock. Down the hole-hammer to be used if the strata are

impenetrable to normal bits or if very hard rock is encountered. Casing is to be

extended to rock head, if DTH method is used. Air will be used to operate the hammer

and for flushing;

6. Upon completion of the drilling, the hole will be flushed using drill rods/machine with

water so as to remove any loose soil chippings. Subsequently, the drill rods are to be

withdrawn any sounding, will be carried out to verify the drilled depth;

7. The prefabricated reinforcement bar cage, together with the grouting hose, shall then be

lowered into the bored hole in required sections using the drilling machine. The

grouting hose is loosely tied to reinforcement bar using GI wire subsequent bar cages

will be joined using mechanical couplers;

8. Placement of grout onto hole shall be carried out by tremie method using the hose tied

to the bars. The grouting is considered complete when good grout (i.e. grout of same

texture and consistency as the original grout) appears at the top of casing. The grout



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hose shall be progressively pulled up, keeping the tie of the hose under the grout level

during the grouting operation;

9. Withdraw grout hose completely and top up the grout ,if there is a drop in grout level;

10. Proceed to the next pile and follow the same procedure. Alternatively, debonding may

be done for a few pile first. Subsequently, drilling and pile installation may be followed

thereafter.



TEL 6362 6866 FAX 6362 6877


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2 MATERIAL SPECIFICATION

2.1 STRUCTURAL LOAD – BEARING COMPONENT

1. The micropile shall be designed to support the applied load to be transmitted to the load

bearing stratum through shaft friction and end bearing and shall also consist of a top

anchorage of the pile steel reinforcement in the pilecap.

2. Top anchorage shall consist of 750 mm projection of the main steel bars of the pile into

pile cap.

3. High tension steel (fy = 460 N/mm2) shall be used:

Different Sizes of Micropiles

Pile Diameter (mm) Reinforcement Pile Capacity (kN)

φ = 300 4 T 40 955

4. The reinforcement bars will be spliced at joints using threading and mechanical couplers..

The splicing shall be done using M-Tech mechanical couplers supplied by MCC Rebar

splicing Technology P/L. or Dextra Mechanical splicing system supplied by Natsteel

Holdings Pte Ltd.

5. The fabrication of rebar cage shall be done on site. Centralizers spaced at 3 m c/c shall

be used to hold the bars and ensure their verticality. Lantern plastic spacers are fixed to

the bar at 3m c/c to ensure sufficient cover between steel bar and sidewall of the

borehole.

6. R6 bars shall be used as spiral links and tied with GI wire to the reinforcement bars at

pitch of 100-mm c/c.

2.2 GROUTING MATERIALS

The grout shall be mixed on site using OPC (Ordinary Portland Cement) complied with

Singapore Standard. Clean water supplies obtained from water mains will be used in mixing.



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2.3 GROUT MIX

The proportion of grout and the minimum strength of work cubes shall comply with the

following requirement:

• The water-cement ratio used in the preparation of cement grout shall range from 0.40-

0.45.

• Minimum characteristic cube strength: 28 N/mm2 on 7 days

40 N/mm2 on 28 days

Grout shall be mixed on site and pumped for placement immediately.

Placement of grout shall be using tremie method with PVC/HDPE hose or galvanized iron pipe.

Two sets of two test cubes each shall be taken from the grout mix for each pile to a 100 x 100 x

100 mould. First set of test cubes shall be tested at 7 days and the other set of cubes shall be

tested at 28 days.

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