1. Alireza Mahdizadeh - Jamaledin Borzouie
Perforating the masonry walls in rehabilitation of masonry Buildings using center core method
Alireza Mahdizadeh - Jamaledin Borzouie

2. Center core method is the good suggestion for retrofitting of Historical masonry buildings due to non-destructive construction.

3. Importance of Historical Buildings
Cultural Importance
Economy of tourists
Economic Impacts
Large cost of renovation after earthquake
Life loss ( Historical schools)

4. Arg-e-Bam and Bam earthquake,2003
The largest adobe building in the world
The origins of Bam : 6th to 4th centuries BC

5. Before Bam Earthquake,2003
After Bam Earthquake,2003

6. Total cost for rebuild : 120 million $
Time needed for rebuild of this structure after damage of Bam earthquake :12 years
Total cost for rebuild : 120 million $
Before Bam Earthquake,2003
After Bam Earthquake,2003

7. Center core .... Solution Why Center core?
Retrofitting of these buildings
Center core
....
Large number of
masonry buildings
Non-destructive method
Without Evacuation

8. Steps Problems Perforating the masonry walls Placing bars in holes
Placing grout in holes
How to perforate masonry walls without any cracks on wall surface
Area, Distance, Number of bars
Properties of grout

9. the building was studied under the critical conditions
Very weak mortar
Strong bricks
Loose finishing of the wall
Wall thickness is at most 30 centimetres
The selected school: Do Shahid
Aged about 50 years
The building has 3 stories

10. Parts of Drilling systems
Drilling Machine
Rod
Rotary
Hydraulic
Drilling machine produces the energy for rotation of the bit
Rod transmits the rotating force to the stabilizer and bit

11. Parts of Drilling systems
Drilling Machine
Rod
Stabilizer
Stabilizer reduces the lateral movements and bit shaking along the drilling path

12. Parts of Drilling systems
Drilling Machine
Rod
Stabilizer
Bits
Bit penetrates through the depth and determines the drilling path

13. Principle of design
4 boreholes (total 28 m height) were perforated in this project. In each borehole, drilling technique, equipments and bits were changed or design according to the damage in the wall surface . After observation of these cracks the wall surface was destructed; moreover, a new bit or stabilizer was designed according to movement of bit on surface of bricks and other observations ( air pressure, rotation of bit ...) to obtain the most suitable ones.

14. How we deal with this new problem?
Step 1: changing available Bits and Stabilizers in drilling to obtain general vision for next step
Bit properties
picture
Damage
How we deal with this new problem?
Diamond
Non coring
D: 76 mm
Bit deviation due to large contact surface with cement
Diamond
Coring
D: 76 mm
Cracks were observed In the weakest part of the wall due to high air pressure and lack of mortar in the gap between two bricks, the air flow pushes the finishing and damages it such that cuttings were dispersed. TC
Coring
D: 93mm

15. Good Suggestion for next step
Bit properties
picture
Damage TC
Non coring
D: 93 mm
Cracks appear due to weak bricking
Good Suggestion for next step TC
Non coring
D: 66mm
Finishing remains unhurt

16. Step 2: Designing new bits and stabilizers by result of past drillingsTC
Non coring
D: 76 mm
TC 6 mm×6mm
زائده­هاي TC چهارگوش به ابعاد 6×6 ميلي­متر
New changes:
Increaseof TC dimension: 6 mm×6mm
New ways for exist of cuttings

17. Step 2: Designing new bits and stabilizers by result of past drillings
Increase dimension of cuttings
A Cutting act as a base
Spiral motion of drilling system
Crack in wall surface
زائده­هاي TC چهارگوش به ابعاد 6×6 ميلي­متر

18. To prevent spiral motion and lateral motion Special stabilization was designed
زائده­هاي TC چهارگوش به ابعاد 6×6 ميلي­متر
These holes were considered for escape of cuttings
Adding this type of stabilization decrease lateral movement; however, these holes do not supply enough area for escape of cuttings

19. ……Other bits and a stabilizer were designed and cracks that appeared in each step led to development of final drilling system and technical drilling….
زائده­هاي TC چهارگوش به ابعاد 6×6 ميلي­متر

20. Final Bit

21. Final Bit

22. Final Bit

23. Final Bit Non-Coring part Main Drilling part Coring part of bit
guide the bit way

24. How the new designed bit act?
Escape line
Of cuttings
Rod
Masonry Wall
Masonry Wall
Non-Coring part
Main Drilling part
Coring part of bit
guide the bit way

25. Conclusion
1. Rate of penetration with non-coring bits is high. However, these bits are not as precise as coring bits. In spite of high precision coring bits are not so fast due to several pull out of the bits for emptying the cores.
2. If non-coring bits are used, as the size of TCs increases, the deviation of the hole will increase. Larger cuttings lead to asymmetric engagement of TC and cuttings and make a permanent change in the axis of rotation.

26. Conclusion
3. Stabilizers are used to increase the accuracy and decrease the deviation in drilling path. Although, it must be noted that they increase air pressure on the surface of the holes and crack the finishing.
4. The most important result of this study is the combination of coring and non-coring bits. To stabilize the drilling path and decrease the deviation, a guide is installed on the TC-Non-Coring bit instead of stabilizers. On the whole, this drilling bit contains a TC Coring bit which cores from the masonry walls. This bit penetrates through the wall as a guide and prevents the bit from deviation and out of axis rotation. In a short distance from the TC-Coring bit, TC Non-Coring bit is installed. This bit crushes the cores and makes the cuttings ready for being removed from the hole as dust. The smaller the cuttings are, the lower air pressure is needed to remove them.

27. Conclusion
5. This newly invented bit could use for mining, oil and other excavations as well.
6. Hydraulic drilling machines have a better performance compared to SGZ Rotary machine because they are larger.
7. The drilling technique must be such that the bit pressure would be minimum.

28. Conclusion
8. The brick type, mortar and the quality of bricking are determining factors for setting the drilling speed and air pressure. It seems that we can’t have exact quantities of such factors now; however, an expert drilling operator may achieve this.
9. During drilling operation, the speed of rotation and air pressure could be set by observing the size of cuttings. An expert can minimize the size of cuttings by paying attention to it.

29. Thanks for your kind Attention