Blasting without problems in sensitive quarries?

A contractor in Haninge, Stockholm found the answer

Blasting bed-rock for mining near populated areas requires vibration measurement. If you need to blast in the same place for a number of years, measurement can be very costly. The company, Hans Andersson Entreprenad AB, has drastically reduced their costs by purchasing INFRA equipment from Sigicom and managing their own measurements.

There is a solid, rocky area at the border of Jordbro, an industrial area near the city of Haninge south of Stockholm, which needs to be removed to prepare the land for more industrial sites. The blasting residue will be used as crushed rock and sold for other uses. Currently the site is known as Haningekrossen (“The Haninge crushing site”).

Concern was high from local neighbors – a computer business, a light bulb warehouse and a cargo terminal – before blasting began in the spring of 2007.

“Continuous vibration measurement in these three buildings was required,” says Roberth Andersson, Haningekrossen’s manager in the family business with many years of experience in blasting and excavation.

But would it be possible to reduce the costs for consultants and instrument rental? The measurements might need to continue for 10–12 years.

Cost savings with bonus effects

A quick search on the Internet led to contact with Sigicom. Since the blasting started there has been a geophone with an INFRA master unit activated in each of the three neighboring buildings. The equipment was purchased and maintained by the contractor, except for the yearly calibration of the sensors, which is done by Sigicom. This means no consultant fees or instrument rental costs.

“We have saved considerably,” Roberth says. “Besides that, there have been several bonus effects with the INFRA system: We don’t need to bother our neighbors with visits to their property where the equipment is installed, except for calibration once per year. The automatic reports generated after each blast are sent to us via SMS and this saves us a lot of work. When the project is completed and Haningekrossen is closed down, we can move the equipment to other projects.”

Immediate reporting of measurement results

An SMS (text message) is sent directly to the blasting manager, to Roberth and to an emergency telephone at the company’s office. Any deviation from the objective value (max 3 mm/s) is immediately displayed on the respective mobile telephones and can be discussed with the blast manager and corrective measures can be taken for future blasts. In addition, the affected companies can login to an Internet site to check measurement data via Sigicom’s easy to use web based interface, which helps to inspire trust.

On average, there is one blast per month at Haningekrossen, which results in around 20,000 tons of blasted rock. Vibrations in the neighboring buildings have not exceeded allowed limits during over a year of blasting with the help of Sigicom’s measurement equipment. On some occasions, cleaning operations in the facilities housing the INFRA equipment have sent out readings, but the blaster’s journal clearly shows which vibrations originate from blasting.

No maintenance of the equipment is required beyond calibration. Everything runs on 220 volt power, so battery backup is not required either. “Sigicom are real professionals,” says Roberth. “The calibrations go smoothly and everything works, really, really well.”