6Total cost for rebuild : 120 million $ Time needed for rebuild of this structure after damage of Bam earthquake :12 yearsTotal cost for rebuild : 120 million $Before Bam Earthquake,2003After Bam Earthquake,2003
7Center core .... Solution Why Center core? Retrofitting of these buildingsCenter core....Large number ofmasonry buildingsNon-destructive methodWithout Evacuation
8Steps Problems Perforating the masonry walls Placing bars in holes Placing grout in holesHow to perforate masonry walls without any cracks on wall surfaceArea, Distance, Number of barsProperties of grout
9the building was studied under the critical conditions Very weak mortarStrong bricksLoose finishing of the wallWall thickness is at most 30 centimetresThe selected school: Do ShahidAged about 50 yearsThe building has 3 stories
10Parts of Drilling systems Drilling MachineRodRotaryHydraulicDrilling machine produces the energy for rotation of the bitRod transmits the rotating force to the stabilizer and bit
11Parts of Drilling systems Drilling MachineRodStabilizerStabilizer reduces the lateral movements and bit shaking along the drilling path
12Parts of Drilling systems Drilling MachineRodStabilizerBitsBit penetrates through the depth and determines the drilling path
13Principle of design4 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.
14How we deal with this new problem? Step 1: changing available Bits and Stabilizers in drilling to obtain general vision for next stepBit propertiespictureDamageHow we deal with this new problem?DiamondNon coringD: 76 mmBit deviation due to large contact surface with cementDiamondCoringD: 76 mmCracks 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.TCCoringD: 93mm
15Good Suggestion for next step Bit propertiespictureDamageTCNon coringD: 93 mmCracks appear due to weak brickingGood Suggestion for next stepTCNon coringD: 66mmFinishing remains unhurt
16Step 2: Designing new bits and stabilizers by result of past drillings TCNon coringD: 76 mmTC 6 mm×6mmزائدههاي TC چهارگوش به ابعاد 6×6 ميليمترNew changes:Increaseof TC dimension: 6 mm×6mmNew ways for exist of cuttings
17Step 2: Designing new bits and stabilizers by result of past drillings Increase dimension of cuttingsA Cutting act as a baseSpiral motion of drilling systemCrack in wall surfaceزائدههاي TC چهارگوش به ابعاد 6×6 ميليمتر
18To prevent spiral motion and lateral motion Special stabilization was designed زائدههاي TC چهارگوش به ابعاد 6×6 ميليمترThese holes were considered for escape of cuttingsAdding 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
23Final Bit Non-Coring part Main Drilling part Coring part of bit guide the bit way
24How the new designed bit act? Escape lineOf cuttingsRodMasonry WallMasonry WallNon-Coring partMain Drilling partCoring part of bitguide the bit way
25Conclusion1. 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.
26Conclusion3. 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.
27Conclusion5. 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.
28Conclusion8. 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.