The Stendafjellet Rock Quarry and Underground Waste

Singapore – 11 November 2016

The Stendafjellet Rock Quarry and

Underground Waste Disposal site

Frode Siljeholm Arnesen, MSc.

Senior Engineering Geologist

Multiconsult ASA, Bergen, Norway

Stendafjellet Rock Quarry and Underground Waste Disposal Site – Frode S. Arnesen


Stakeholders

Owner: Fana Stein & Gjenvinning Holding AS/ Fana Rock and Recycling

Holding LTD (FSG)

Managing Company: Fana Stein & Gjenvinning AS/Fana Rock and

Recycling LTD (FSG)

Land Owner: Hordaland County

Design, geological and environmental engineering:

Multiconsult ASA, Bergen

Stendafjellet Rock Quarry and Underground Waste Disposal Site – Frode S. Arnesen


The Stendafjellet Quarry and Depositing site is a story of

commercial success

• The setting

• Geological Conditions

• Products

• Future development


Location of site near Bergen, Norway


All cities use aggregate

• Norwegian average usage of aggregate is more than one ton a year.

• The local aggregate market of Bergen is in the range of 300 000 tons per

year.

• Aggregates is produced locally or delivered to the city by boats.


Fana Stadion was once a Quarry


Høiehallen athletics hall, a former quarry tunnel


Rådalen quarry and landfill site


Former crusherplant was relocated


Situation today, new incineration plant


Landfill replaced by agriculture


New location for quarry and depositing


The nearby hill Stendafjellet has good quality rockThere was already a tunnel and a water storage cavern inside the hill


Early design


Visible footprint


Pukkverk under jord

Primary chrusher

Secondarychrushers, screening and conveying

Crusher plant and aggregate distribution


Vertical section of plant

Dato: 05.10.2016 FSG Pukkverk Side: 21

22 different grain sizes is accessible


Map of cavernsand tunnels

Singapore – 11 November 2016 Dato: 05.10.2016 FSG Pukkverk Side: 21

Dump shaft is established to chrusher pocketVentilation and emergency escape adit through short shaftto terrain from top level


Groundwater control

• The average permeability of the rock mass is generally

low ( 10e-7m/s).

• There are systematically placed drilled wells in different

distances surrounding the site.

• The groundwater level is registered automatically.

• Chemical content of groundwater is tested and reported

annually.

• The small quantity of water pumped out are generally

cleaner than water drained from the traffic tunnels in

Bergen city.


Rock blasting methods for Quarrying underground

Top header is excavated by drill and blast, but the contentof dust are high.

Benching requires special attention to:

• Minimize fines.

• Geometrical control.

• Proper block size for existing crusherplant.

• Bench height must adapt what can practically be scaledand supported with available equipment.

• Limitation of access is determined by safety in thecavern.


Bech blasting experiences

• Maximum 76mm borehle diameter, preferably 51 mm contour charge.

• Usage of evenly distributed blast agent with high detonation velocity.

• Denser drilling than normally recommended.

• Blast agent usage below 0,4kg/m3.

• Bench height maximum 13m.

• Top Bench + 3 benches.

• There are a mid level access from both sides of the cavern.


Ventilation

• There are one vent shaft in each end of the cavern system, one having a

suction fan ensuring underpressure independent of wind direction.

• Air inlet is through the low level tranportation tunnel.

• Vent shafts serves also as escape routes.

• Rock drilling requires installed dust control, or use of water.


Rock support

• Scaling by demolition rig, reaching 25m upwards.

• Bolting in walls by remote controlled drill rig.

• Mainly use of grouted bolts.

• Top bench : Systemetic rockbolts 4 – 5 m long and steel fiber shotcrete.

• Walls: Scaling and spot bolting, occasionally shotcreting.

• Grouted cable bolts when required.

• Fracture zones supported by fiber shotcrete, bolts and reinforcement.


Sub-title

Typical weakness zone in wall


Sub-title

Where support is discussed

Singapore – 11 November 2016 Dato: 05.10.2016 FSG Pukkverk Side: 21


Experiences from quarrying

• 5 of 8 caverns have very good rock conditions.

• The last three caverns has successively poorer rock, due

to fracturing.

• Fracture zones with swelling clay requires much more

extensive support.

• Excavation and crushing gives a fair profit.

• Depositing is a much more profitable

activity.


Conditions for profitable underground quarry:

• Good Rock Quality, UCS > 130 Mpa, Q > 10.

• Acceptable hydrological conditions, a system of groundwatersurveillance and testing must be established.

• Existing market close by, enabling effective transportation.

• Other competing quarries have longer transport distances.

• Neighbour houses minimum 250 m from tunnel opening, and restrictions on future usage of area above caverns.


Criteria necessary for depositing

• Inward flow of water.

• Groundwater control and testing, annually.

• Low permability rocks, small water volumes.

• Terrain is not harmed by low groundwater table.

• Drainage to low pump sump, pumping water to approvedlocation.

• Acquiring approvals for deposisting, including reducedtaxes for depositing compared to landfill usage.

• No harmful or explosive gases from deposited materials.


Examples of deposited materials • Foundry sand

• Sand blasting sand

• Iron sand from metal recycling

• Heat treated drilling mud

• Microsilica dust from smoke filters

• Concrete with and without PCB

• Bricks with and without PAH ( chimneys)

• Construction waste

• Glass from refurbishment of housing

• Soils with dangerous contamination

• Removed materials with asbestos content (bagged)

• Sand and materials for street and drainage cleaning

• Fluff – remnants from car and metal recycling

• Contaminated soils from city and street excavations


Experiences from depositing so far.

• 55m high cavern requires procedures for filling due to

stability issues.

• Dust must be controlled by ventilation.

• Deposited materials has very low permeablity.

• The small quantities of inleaking water have limited

contact with the deposited soils.

• The level of water contaminaton from drainage water is

of same scale as the ordinary drain water from roads in

the city.


Future layout


North–south section

Top level ofdepositing


New highway crossing under the siteMitigation of groundwater effects is planned

Mitigation zone along highway section


Thankyoufor

yourattention!

Documents

The Stendafjellet Rock Quarry and Underground Waste