Bored Pile Foundation (Rebar cage fabrication & Installation)
Bored Pile Foundation (Rebar cage fabrication & Installation)
πRebar cage fabrication
Approved rebar drawing α‘αိုα်း Design length, rebar size & number, spacing, lapping, spacer and cover block α ααြα့် αီαာαဲ့ αျα်αှာαြα်αှာ Fabrication αြုαုα်ααα်။ Steel cage αို fabrication and handling αုα်α α₯်αှာ αွေး/αိα်αွားαာαွေααြα ်α ေαို့ ααုα ိုα်ααα်။ Consultant inspector αဲ့ α α ်αေးαှုαြိုαα်αံαူαြီး approval αူαားααα်။ Bored hole drilling αုα်αα်းα α₯်αြီးαာαဲ့ rebar cage αျαိုα်α‘ောα် α‘αα်αα့် αြα်αα်αားααα်။ Rebar cage αို αြေαြီးαဲ αှာ Concrete cover α‘αှα်αα ေαို့ α‘αွα် α‘αေးαြီးαါαα်။ 75mm concrete cover αα‘ောα် spacer αျားαုံαောα်α ွာ αα်αα်ααα်။ Plastic spacer , metal spacer αျားα‘αုံးαြုαြαြီး metal spacer αျားαိုαျα် αံαျေးααα်α‘ောα် Anti-rust paint αျားαြိုαα်αုα်αိα်းαားααα်။
πRebar Cage Installation
Rebar cage αျားαို Bored hole α‘αီးαုံးαေαာαို αွှေ့αားαြီး Crane αြα့် Vertical position αα‘ောα် αααα်။ αွα်းαဲαို α‘αα်ααို αα့်αα်α ွာ αြα်းαြα်းαျα်းαျααα်။ Rebar cage Lapping αေαာαို Binding wire (or) U-Bolt αျားαြα့်αေαျာαုα်αှောα်ααα်။ Lapping αေαာαှာ αα်αှα် Spiral tie αွα်းα‘αေα‘αွα်αို Spacing αှα်α‘ောα်αα်αα်ααα်။ (Cross-hole sonic logging test α‘αွα် Steel pipe αျားαα်αα်ααα်αိုαျα် Steel pipe α‘αα်αေαာ αေαုံα ေαို့ Welding αေαျာαော်ααα်။ Pile α‘ောα်αြေαှα့် α‘αေါ်αိα်αွα် Pipe cap αျား αα်αα်ααα်။ Steel pipe αျားαေαာααွှေ့α ေαို့ position α‘αှα်αα‘ောα် rebar cage αြα့်αွဲαα် αျα်αှောα်ααα်။) α‘ားαုံးαေαျာα ွာ α α ်αေးαြီးαြီαိုαှ Steel cage αို Pile αα ်αျောα်းαုံးα ာ ααα်αြီး ααα် αြေးαြေးαျα်း αျαွားααါαα်။
πPile cut-off level under N.G.L
α‘αျို့ Pile αျားαာ Natural ground level αα်αိα့်αေαα်αα်။ Drilling operation αိုαα်း N.G.L αှာ αာ αြုαုα်αျα် Rebar cage αို α‘ောα်αဲ Pile cut off level αောα်α‘ောα် αှိα့်αျαို့ αိုα‘α်αါαα်။ α‘αိုαါα‘αြေα‘αေαှာ Level drop of rebar cage αို Sounding αိုα်းαာαွα်αျα်αြီး α‘αူαံαျောα်းαုံးαျား (Hanging bars) αြိုαα် αြα်αာ Rebar cage αို αျိα်αွဲ αြီး αှိα့်αျααါαα်။ Hanging bar αို αိα်αှာ αွα်းαွေးαားαြီး αံαိုα်αျားαျှိုαာ Casing αောα်αှာαα်αားααα်။ Concreting αုα်αα်းαြီးα ီးαဲ့ α‘αါαှ Hanging bar αွေαို αြα်αα်αြα်αောα်αါαα်။
Rebar cage αျαြီးαျα် Casing level αို survey αြα်αα်α α ်αေးαြီး Level αှα်ααှα် αြα်αα်α α ်αေးααါαα်။
(αα်αα်)
αွေαှိုα်α¦း (αြို့αြ αααα)
Bored Pile Foundation (Rebar cage fabrication & Installation)
Rebar Cage Fabrication
Fabrication must be carried out on a level surface, strictly according to the approved rebar drawing, covering design length, rebar size and number, spacing, lapping, spacers, and cover blocks. Care must be taken during fabrication and handling to prevent the steel cage from bending or twisting. It must be pre-inspected and approved by the consultant inspector. The rebar cage must be prepared and ready for installation immediately after the bored hole drilling is completed. Achieving the correct concrete cover for the rebar cage in the ground is extremely important. A sufficient number of spacers must be installed to ensure a 75mm concrete cover. Plastic or metal spacers are commonly used; if metal spacers are used, they must be pre-coated with anti-rust paint to prevent corrosion.
Rebar Cage Installation
Rebar cages should be moved to the closest possible location near the bored hole and lifted by a crane into a vertical position. They must be lowered slowly and carefully into the hole, ensuring they are centered and straight. Lapping points on the rebar cage must be securely fastened with binding wire or U-bolts. The specified number of spiral ties must be installed at the lapping zones with the correct spacing. (If steel pipes are to be installed for a cross-hole sonic logging test, the pipe connections must be properly welded to be watertight. Pipe caps must be installed at the top and bottom of the pile. The steel pipes must be tied securely to the rebar cage to hold them in the correct position and prevent movement.) Only after everything has been thoroughly checked should the entire steel cage be lowered into the pile section by section, slowly and continuously.
Pile Cut-Off Level Under Natural Ground Level (N.G.L)
Some piles are located below the natural ground level. If the drilling operation is conducted from the N.G.L, the rebar cage must be lowered to reach the pile cut-off level deep below. In this situation, the required level drop for the rebar cage is calculated by sounding measurement, and auxiliary steel bars (hanging bars) are pre-cut and used to suspend and lower the cage. The top of the hanging bar is bent into a hook, placed over a steel pipe, which is then rested on the casing frame. After the concreting work is completed, these hanging bars are cut off.
After the rebar cage is installed, the casing level must be re-checked by survey to verify its level is correct.
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