Drill and install bolts and mesh – gunite
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Micon installed bolts and mesh, then applied gunite to the tunnel’s roof and ribs.
Installed arches to support the tunnel structure and backfilled sinkhole above with lightweight concrete.
Inject PUR grout behind tunnel liner
Install and pressure grout (16) 40′ hollow core anchor bolts and (12) 20′ packer holes.
Install 10,500 sq/ft Geogrid on highwall above (4) projected mine openings w rock bolts.
Install covered from first bench to and including both sides of the mine openings.
Injection of material in advance of highwall miner into uncharted auger holes .
Setup onsite beside highwall miner pumping material as mining progressed.
Drill and inject chemical grout (21) holes 30′ deep above portal entries.
A group of teens entered an abandoned mine portal and posted their potentially deadly exploration on social media. MICON entrusted to mitigate the public danger permanently. Design of this civil mine closure project solution involved complex field factors, including:
- Gravitational complications of pumping cement fill over a 380’ total elevation drop and over 1000 linear feet
- 3 separate mine openings in a crumbling, unstable brick building
- Intermittent low oxygen levels at flowable fill installation sites
- Remote, steep terrain & dense vegetation
MICON successfully installed over 300 cubic yards of fast-setting cementious material truckloads to fill the portals and building. This required over 25 concrete mixer loads. Despite record heat that challenged the consistency and proper cure of both the pumping lines and final fill location, MICON completed the completed project ahead of schedule and on budget.
MICON Polyurethane Grouting returns structural integrity through void filling at Mt. Washington Tunnel-Port Authority of Allegheny County, PA
During routine inspection of the 76 year old Mt. Washington tunnel, deterioration of the brick liner was observed. Further studies showed that the original timber sets had rotted out causing incompetence of the immediate rock strata and uneven load distribution on the brickwork. This caused the occurrence of void spaces throughout the entire 1000 meter length of tunnel. The void spaces varied between a few millimeters to several meters in height
Grouting was permitted only between 1 and 5 AM. Liquidated damages of $500 per minute were to be levied for each minute that the contractor delayed tunnel traffic after 5 AM.
Using technology MICON developed in the coal mining industry to support incompetent rock, MICON injected a low density high strength polyurethane foam into the void areas, not only filling the voids but also consolidating the surrounding strata. During the pumping process, the brickwork was monitored for the slightest movement; no movement was detected at any time during the project.
The result was a removal of the problem of point loading and uneven load distribution on the brickwork. This allowed the liner to function as designed and maintain its structural integrity. The polyurethane grout provided a semi-rigid liner behind the rigid brickwork, with capability of absorbing uneven or isolated loading conditions without transmitting these loads onto the liner itself. Subsequent core samples showed that all void spaces were filled by this method.
The project was completed on schedule in five months operating within the tight working periods. The 174,000 gallons of Hquid polyurethane makes this project one of the largest applications of rigid polyurethane foam grout.