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Structural Rehabilation & Retrofitting
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INNOVATIVE WAY OF DISMANTLING RETAINING WALL BY USE OF POST TENSIONING TECHNIQUE
   
Fig. 1. View of wall before removal

At one of the sites on the Hilly terrain of Jubilee hills, the owner of a property developing a residential property decided to remove the rear retaining wall which measures about 25 m in length and 15 m in height.  Of which the owner decided to cut off  and reduce the level of the retaining wall by about 6.0 m. 

 

The view of the site can be seen in Fig. 1.  The back side retaining wall to be lowered by about 6.0  m.  The wall is supported by  strut type columns and beam network at 7 locations which can also be seen in photo in Fig. 1.

The job had to be executed with utmost safety precautions and at the same time economizing the cost of demolition.

 

Normally the following two options are adopted:

  • Breaking using Pneumatic Breakers/electrical breakers
  • Cutting the wall using diamond cutting method and removing the cut pieces using Hydra.

In case of the first option, the time required for the job would be very high and further it would be very difficult for the workers to strand on 300 mm thick wall and chip the concrete.  The method  is high unsafe with high noise and dust pollution.

 

In case of the 2nd option of Diamond cutting in small pieces, though the method is relatively safe the cost of cutting would be very high and uneconomical.


To meet the above requirements of both safety and economy the innovative method of use of Post Tensioning was adopted to bring down the wall after diamond cutting.  By This method the complete wall was cut in single piece  and pulled  down.  The following step by step methodology was adopted to execute the work

 

As a first step the excavation was carried out to the required level exposing the complete wall and the strut supports of columns and beams.  This also effectively reduces the load on the wall and is now safe to cut off the struts.

The columns and beams are cut off  using stitch core cutting method in manageable pieces and removed using excavator and disposed off.

Fig 3. Shows the view of wall after removal of the strut columns and beams

Step 3:

Ground anchors are provided in the rock in front of the wall at suitable location by drilling a 25 mm dia hole to a depth of 1.0 m and fixing of 12.7 mm H T strand using polyester resin grout as shown in  Fig. 4.  

 

Step 4  :
H T Strand connection arrangement is carried out as shown in the following Fig No. 5.

 

Step 5  :
Once the connections are complete and after taking all precautionary arrangement, the wall us cut on three sides  (bottom and sides) using diamond cutting Wall  Saw/Wire saw.  It is ensured that a small portion of the bottom cut is left out so as to avoid any accidental fall of the cut wall.  Once the cutting is complete the Wall is pulled down by stressing the central strand.  The video below shows the final pulling down of the wall by stressing.

 


 
The complete job was completed in less than a week  safely and without any incident to the satisfaction of all concerned.
 
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Structural Rehabilation & Retrofitting
 
1. Innovative way of dismantling retaining wall by use of Post Tensioning Technique
2. Restoration of a Failed Bridge
3. Jaw Crusher Demolition of Towers
4. High Reach Demolition 4th Floor P T Slab Demolished
5. Stabilization of Vertical Pit Faces Using P T Technique
6. Removal of Columns by External Post Tensioning Technique to Increase Spans
7. Structural Rehabilation & Retrofitting
8. Removal and Recasting columns in a under construction building
9. Restoration of a National Highway Bridge under distress
10. Restoration of Bridge damaged by poor expansion joint maintenance
11. Restoration of a Heritage building at Hyderabad Public School
12. Restoration of Bridge damaged by Earth Quake at Andaman
13. Restoration of Fire Damaged Building, Hyderabad
Concrete Sawing & Core Driling
Bearing Replacement & Bridge Lifting