What is Overbreak in tunneling?
Overbreak in tunneling is defined as a part of damaged zone beyond the profile calculated for the support elements that falling during rock excavation. It increases total cost of tunneling to a level of 15% or even more of the scheduled cost of construction .
What equipment is used for tunneling?
A tunnel boring machine (TBM), is used to excavate tunnels with a circular cross-section through a variety of soil and rock strata. They may also be used for micro tunneling. They can be designed to bore through anything from hard rock to sand.
How do you control Overbreak in tunnels?
Overbreak caused by perimeter charge factor can be reduced by optimum advancement in a blasting round. This is due to the availability of better of free face and lesser burden on the contour holes. Greater advancement may reduce negative impacts of perimeter charge factor on overbreak.
What is Overbreak?
overbreak (plural overbreaks) (civil engineering, geology) Rock or earth excavated beyond the planned extent; caving in of material near the edge of an excavation.
How does a continuous miner work?
Continuous miners cut and gather the material simultaneously and convey it into shuttle cars, haul trucks or a continuous haulage system. They are typically used for full-scale production in room-and-pillar mining operations.
What is tunneling and rock drilling equipment?
Tunneling and rock drilling equipment is machinery used to create huge holes in the earths subsurface. The holes can be used to construct infrastructure projects such as underground tunnels or to extract minerals. A rapid increase in technology is the primary driver of the market.
What are the modern methods techniques used in tunneling?
Methods of Tunnel Construction
- Cut and cover method.
- Bored tunnel method.
- Clay kicking method.
- Shaft method.
- Pipe jacking method.
- Box jacking method.
- Underwater tunnels.
What is over break in geology?
Overbreak is the volume of rock outside the minimum excavation line removed during excavation operations . Conventionally, overbreak is expressed in percent of theoretical rock volume produced in each round of blast.
What can roadheaders be used for in tunnels?
Equipped with geometrically optimized transverse cutter heads, these flexible machines can be used for a wide range of applications. They can also be used for rehabilitation of existing tunnels, and excavation of underground caverns. Need to know more?
What kind of machine is the roadheader?
Roadheaders are massive excavating machines fitted with a mounted cutting head which will mine out the caverns for both State Library and Town Hall stations.
Which is the best roadheader for rock cutting?
Sandvik’s MT series of roadheaders offers the best cutting performance in a wide range of rock formations. Equipped with geometrically optimized transverse cutter heads, these flexible machines can be used for a wide range of applications. They can also be used for rehabilitation of existing tunnels, and excavation of underground caverns.
What are the selection criteria for a roadheader?
Selection criteria for Excavation method Parameter on Roadheader Cuttability Current Roadheader technology Roadheader projects SELECTION CRITERIA FOR EXCAVATION METHOD 6 ROCK PROJECT ENVIRONMENT Drill & Blast Shield Machines Hard rock TBM’s Excavator Attachments Roadheaders Compressive Strength Stability / Fracturing