Monitoring vibrations in a residential project
The blasting operations were so complicated that there was a risk the project might not get the go-ahead. With Nitro Consult’s help, the vibrations can be kept in check, and new residential housing can become a reality.
Just north of Stockholm, on the boundary between Solna and Sundbyberg, the Järvastaden development is taking form. This will be a new district with mixed settlement in an attractive and expansive part of Greater Stockholm.
“One of the neighbourhoods on the Solna side of Järvastaden is called Grankällan. In that neighbourhood there are plans for 200 new houses in the form of detached and terraced housing. It will be a valuable addition to the residential housing market, as very little housing of this type is built in Solna. Furthermore, the houses are being built in an excellent location, close to the commuter rail system”, says Enrique Oyarzun, Project Manager at Järvastaden AB.
The company Järvastaden AB is owned by Skanska and Vasakronan and primarily works with the production of detailed plans for the development of residential housing in the area. When it comes to the Grankällan neighbourhood, the planning includes preparations for the terracing of the rock on the site. Blasting is required.
“We need support in the form of specialised know-how and have chosen to work with Nitro Consult. They have helped with different phases of the project planning process and have also participated in the actual rock blasting operations”, says Enrique Oyarzun.
Managing the switchgear at the site has been a particularly sensitive issue.
“The switchgear at the site is extremely sensitive to vibrations” Enrique Oyarzun, Project Manager at Järvastaden AB
“The switchgear dates from the 1950s and is extremely sensitive to vibrations, since it contains gas-insulated high voltage circuit breakers.”
The collaboration began in 2014 with test blasting to determine the maximum charges that could be used in compliance with the vibration limits for the blasting activities.
“At the beginning it wasn’t even certain that the project would be able to be carried out. We knew that the successful implementation of this project would require complicated blasting operations that would be expensive and very time-consuming”, explains Enrique Oyarzun.
Nitro Consult performed the test blasting, determined the permitted charge sizes and designed a model for how the blasting operations could be carried out.
When the decision was made the following year to proceed with the project, Järvastaden once again contacted Nitro Consult, who then contributed to the continued project planning, designed the tender documentation and helped with the procurement of the blasting services.
“We made the right choice when we engaged the services of Nitro Consult. It is a company with the right expertise and know-how for this type of complicated assignment, and the collaboration has worked extremely well”, says Enrique Oyarzun.
The actual blasting operations were started in 2016, with Nitro Consult present in a monitoring capacity.
“We have had continuous monitoring of the blasting activities on site to ensure optimisation of the charges”, says Sophie Ahrengart, rock technician at Nitro Consult.
“The limits in place were very restrictive. Based on the original test blasting, we have carried out regression analyses to arrive at the size of the charges that can be used without creating vibrations that are too great, how deep the drill-holes should be and how close together they can be located, and which interval times that should be used for the blasting rounds. We then monitor all these parameters during the actual blasting operations.”
More about this project
Autumn 2014 – Spring 2018
We did: Test blasting, determination of maximum permitted charges, design of model for blasting activities, design of tender documentation for procurement of blasting services, monitoring of blasting operations.