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Perforating the masonry walls in rehabilitation of masonry Buildings using center core method. Alireza Mahdizadeh - Jamaledin Borzouie. Center core method is the good suggestion for retrofitting of Historical masonry buildings due to non-destructive construction.
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Perforating the masonry walls in rehabilitation of masonry Buildings using center core method AlirezaMahdizadeh - JamaledinBorzouie
Center core method is the good suggestion for retrofitting of Historical masonry buildings due to non-destructive construction.
Importance of Historical Buildings Cultural Importance Economy of tourists Economic Impacts Large cost of renovation after earthquake Life loss ( Historical schools)
Arg-e-Bam and Bam earthquake,2003 The largest adobe building in the world The origins of Bam : 6th to 4th centuries BC
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 $ Before Bam Earthquake,2003 After Bam Earthquake,2003
Solution Why Center core? • Large number of • masonry buildings Non-destructive method • Without Evacuation
Steps Problems
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
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
Parts of Drilling systems Drilling Machine Rod Stabilizer Stabilizer reduces the lateral movements and bit shaking along the drilling path
Parts of Drilling systems Drilling Machine Rod Stabilizer Bits Bit penetrates through the depth and determines the drilling path
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 step 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
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
Step 2: Designing new bits and stabilizers by result of past drillings TC Non coring D: 76 mm TC 6 mm×6mm 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
To prevent spiral motion and lateral motion Special stabilization was designed 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
……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 Non-Coring part Main Drilling part Coring part of bit guide the bit way
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
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.
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.
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.
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.
