Rock Excavation By Control Blasting Method |

Rock Excavation By Control Blasting Method


Controlled blasting is a technique of blasting, which is used to reduce the amount of over break and to control ground vibrations. The different types of controlled blasting techniques are pre-splitting, smooth blasting, line drilling, perimeter blasting, and cushion blasting.

1.00: Blast Monitoring:
1.10: Maximum Explosive Charge per Instant Or per detonation has been tabulated:
For PPV 4.00 mmps.

2.00: Proposed Blast Design:
We have limitations as regards to the maximum explosive charge to be used per
instant. So in order to get the optimum production rate with we have to depend upon
the initiations systems to be used and the special Controlled blasting methods to be
incorporated to reduce the blast induced ground vibrations.
2.10: Initiation systems that can be used:
· Instantaneous Electric Detonators.
· Electric Millisecond Delay Detonators
· Shock Tube System of initiation.

2.11: Of the three methods above the Instantaneous Electric Detonators will offer
minimum production with large size boulders and maximum vibrations. As a matter
of fact this is being presently used as cost wise it is the cheapest.
2.12: The Electric Millisecond Delay detonators though slightly expensive, can offer
us better production rate smaller size boulders and less vibrations as compared to
the previous one. Electric delays are available in 10 # & each one is numbered as
1,2,3…up to 10 no.. There are 25millisecond delays installed. Number 1 delay will
detonate 25 millisecond after no. “0”, no. 2 will detonate 25 millisecond after no. “1” &
so on. All the delays will detonate within 250 millisecond. So total explosive charge in
all the blast holes can be safely divided in to 11 parts. One part (delay) detonating at
one time. This will reduce the vibrations as explosive is divided. So with this system
instead of 10 # blast holes we can blast 22 holes per blast & that too with more depth
& increased explosive charge per hole offering increased production. 

2.13: The Shock Tube system, though expensive, will able to give us maximum
production with smaller size boulders and low vibrations values. Hence, it is the best
for optimum production. This is the most modern system in which we can control the
sequence of blasting with more accurate timing. Here we can blast each of the blast
hole at totally independent or different timing. This is one of the major advantages of
this initiation system as we can practically blast each hole at different timings and
thereby load the blast hole at maximum capacity mentioned in the tabular form. This,
no doubt, increases the production than previous two methods.

2.20: Special Methods Of Controlled Blasting To Be Incorporated:
Following are the two methods that can be used.
· Line Drilling and / or Presplitting
· Air Column Method.

2.21: Line Drilling has already being done all round the periphery of the blasting area
which can help in reducing intensity of transverse vector component of the blast
induced ground vibrations.
2.22: Air Column Method:
Air Column method for nullifying vertical vector component of Peak Particle Velocity
& finally reducing Peak Particle Velocity Value of the true vector sum. Kindly refer
figure no: 1. This method consists of leaving an air column at the bottom of the of
the explosive charge. The spacing used for leaving this air column can be a piece of
hard PVC pipe having diameter 25mm & length of 75mm. By creation of air column
at the bottom of the explosive charge there is convenient change in the media of
travel for the vertical vector component of the blast induced ground vibrations. This
change in media of travel in turn change status of the vertical vector from
compressive wave in to tensile wave form and hence no vibrations are transmitted to
the bottom of the blast hole. Further, due to this air column the centre of gravity of
whole explosive column is raised providing more strength to the transverse & radial
vector components by raising their level. This results in better fragmentation.

3.00: Blast Design:
3.10: Drilling Parameters:
Diameter & depth of the blast holes: 32mm & 2.00 mtrs.
Drilling Geometry: Holes are to be drilled vertical in 0.5 mtrs grid pattern.
Spacing & Burden Values: Spacing 1.00 mtrs & Burden 0.5 meters.
Production Per Blast Hole: 1 cubic meters insitution.

3.11:Number of blast holes per blast using millisecond electric delay detonators: 11#.
Production Per Blast: 11 cubic meters.
Number of blasts per day: Five #. (within one hour).
Total production per day: 55 cubic meters.
3.12: Number of blast holes per blast using shock tube system: 50#
Production per blast: 50 cubic meters. Number of Blasts per day: 5 # .
Total production per day: 250 cubic meters per day.
3.20: Blasting Parameters:
Each of the blast holes in both the system is to be charged with 250 gms of
explosives. Air column method can be incorporated as explained earlier along with
the already existing line drilling.



We introduce a new method of cracking the rock that is known as EXPANSIVE MORTAR CHEMICAL METHOD. It is sound less and cracks the rock like hair crack.How to use the Expansive Mortar Chemical is given below:

A. Mixing:
EXPANSIVE MORTAR is a powder that must be thoroughly mixed with clear water before used in a ratio of 30% of the overall weight (3.0 liters of each 10kg. packages). Gradually add the powder to water stirring all the time to obtain a smooth lump free mortar.
B. Filling:
Pour the mortar into the prepared holes within 5 to 10 minutes only. Stop horizontal holes to allow an easy pouring of EXPANSIVE MORTAR (should some of the mortar leak out of hole. Stop it with a piece of soft sponge) or fill the holes with mortar of EXPANSIVE MORTAR.
C. Drilling:
The distance between holes varies depending on the size of hole (from 32 mm daim. to 42 mm diam) and the type of materials to be demolished or cut. For rock or nonreinforced concrete should be 30 to 60 cm. and reinforced concrete should be 20 to 30.

Safety precautions for EXPANSIVE MORTAR:
1. Wear safety goggles, rubber gloves and helmet during EXPANSIVE MORTAR mixing and filling.
2. Do not get your face close to or stand near filled holes for at least 3 hours after filling completion, stop the hurt to eyes in case of blow out shots.
3. Skin contact with EXPANSIVE MORTAR must be rinsed off with large amounts of clod water immediately.
4. Should you get spray form EXPANSIVE MORTAR in your eyes, do not rub but wash them immediately with plenty of clod water and consult doctor.


All the excavation rock shall be removed with the help excavator’s buckets to loading in to the dumpers. Once our loaded dump trucks exist from the plot area, it will be exclusively our responsibility during logistic movement upto the disposal area. We shall take care of the liabilities including traffic authorities, local issues, etc. complete. We will also ensure adequate measures of preventing any pilferage from our dump trucks onto the road route of the disposal area. For disposal of excavated materials, we shall arrange adequate size of dump plots at various locations. This shall be informed to you after award of the contract only.


We shall take necessary safety precautions to safeguard our personnel, plant, machinery, labour, equipment at site. We will comply with all the requirements of safety norms as per prevailing norms. We will remain solely liable for any claims or damages arising out of non-compliance of such safety precautions and would indemnify the Employer from any such claims or damages. Further we should provide safety shoes, safety helmets to our workers, supervisors staff and equipments operators. In the time of blasting operation we provide red flag to in all four corners of premises with our staff and also give them wheeseal to alert. Further we take more safety precautions in controlled blasting like we take 6mm thick steel plate for cover all the holes and loaded with sand bags above the plates. At the time of blasting we take bondobast from the police station. Two nos. of police also stand at the time of blast time i.e. between 1.00 PM to 2.00 PM.


Our Controlled Blasting consultant Mr. C. B. Navalkar. He always presents at the time of blasting with his vibromiter for measure the vibration and monitoring the blast and maintains vibrations of 5mmp per second and sound below 1.20. We operate the special Controlled blasting methods to be incorporated to reduce the blast induced ground vibrations. We submit the daily report according to the blasting. Further precaution for not flying of rock piece or debris we keep 6mm thick plate on blast holes and keep load of sand bags on it. We always keep in mind to not disturbing the neighbors and adjoining society or complex. Further in EXPANSIVE MORTAR Chemical methods there is no any type of sounds or vibrations. And also no chance for flying of rock piece or debris.

All necessary permissions from statutory authorities such as traffic department, labour department, BMC, collector, local problems, about noise pollution, water supply and drainage department etc. shall be obtained by you at your own cost. The work shall be executed with the help of our experience, skilled, discipline, honest and efficient workers only. We shall work round the clock hence entry and exist of our equipments/ machineries and workers should be made easy for smooth and fast working. As the site is located in residential area and just adjacent to hospital complex, due care will be taken to reduce the noise pollution from our machinery/equipment, however breakers will be used for which there will be noise pollution which cannot be avoided by us. You will take care about this. In case the
stoppage of work for this reason of noise pollution, we shall not be held responsible and necessary care shall be taken from your end.
All disputes arising out of this contract will be to be referred to arbitration as per Indian Arbitration and Conciliations Act, 1996 with two arbitrators to be selected by each party and the 3rd arbitrator pre-selected as Umpire. We shall be permitted to work round the clock once we mobilize to the site. We shall be continuously working so that our machinery and labour shall not be kept idle.production of documentary evidence.

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