Alireza Mahdizadeh - Jamaledin Borzouie
Perforating the masonry walls in rehabilitation of masonry
Buildings using center core method
Center core method is the good suggestion for retrofitting of
Historical masonry buildings due to non-destructive
construction.
Importance of Historical Buildings
Cultural Importance
Economic Impacts
Life loss ( Historical schools)
Economy of tourists
Large cost of renovation after earthquake
Arg-e-Bam and Bam earthquake,2003
The largest adobe building in the worldThe origins of Bam : 6th to 4th centuries BC
Before Bam Earthquake,2003 After Bam Earthquake,2003
Before Bam Earthquake,2003 After Bam Earthquake,2003
Time needed for rebuild of this structure after damage of Bam earthquake :12 years
Total cost for rebuild : 120 million $
others1% concrete
2%
steel8%
Masonry89%
Solution
Retrofitting of these buildings
Center core
....
....
Why Center core?
Large number of masonry buildings
Non-destructive method
Without Evacuation
Perforating the
masonry walls
Placing bars in holes
Placing grout in holes
Steps Problems
How to perforate masonry walls without any cracks
on wall surface
Area, Distance, Number of bars
Properties of grout
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 building has 3 stories
The selected school: Do ShahidAged about 50 years
Drilling Machine
Parts of Drilling systems
Rotary
Hydraulic
Rod
Drilling machine produces the energy for rotation of the bit
Rod transmits the rotating force to the stabilizer and bit
Drilling Machine
Parts of Drilling systems
Rod
Stabilizer
Stabilizer reduces the lateral movements and bit shaking along the drilling path
Drilling Machine
Parts of Drilling systems
Rod
Stabilizer
Bit penetrates through the depth and determines the drilling path
Bits
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.
Step 1: changing available Bits and Stabilizers in drilling to obtain general vision for next stepBit
propertiespicture Damage
DiamondNon coringD: 76 mm
Bit deviation due to large contact surface with cement
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.
DiamondCoringD: 76 mm
TCCoringD: 93mm
How we deal with this new problem?
Bit properties
picture Damage
TCNon coringD: 93 mm
Cracks appear due to weak bricking
Finishing remains unhurt
TCNon coringD: 66mm
Good Suggestion for next step
TC Non coringD: 76 mmTC 6 mm×6mm
Step 2: Designing new bits and stabilizers by result of past drillings
New changes:
Increaseof TC dimension: 6 mm×6mm
New ways for exist of cuttings
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
To prevent spiral motion and lateral motion Special stabilization was
designed
Adding this type of stabilization decrease lateral movement; however, these holes do not supply enough area for escape of cuttings
These holes were considered for escape of cuttings
……Other bits and a stabilizer were designed and cracks that appeared in each step led to development of final drilling system and technical drilling….
Final Bit
Final Bit
Final Bit
Final Bit
Coring part of bitguide the bit way
Non-Coring partMain Drilling part
How the new designed bit act?
Masonry Wall
Masonry Wall
Rod
Coring part of bitguide the bit way
Non-Coring partMain Drilling part
Escape lineOf cuttings
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.
Conclusion3. 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.
Conclusion5. 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.
Conclusion8. 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.
Thanks for your kind Attention
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