Vulcan Materials contracted Drill Tech to build a 12’ diameter by 268’ tunnel, enabling the relocation of a conveyor belt subsurface that constituted a larger reconfiguration of an aggregate mine located in Irwindale, California. Drill Tech constructed the tunnel with an open face digger shield and installed steel ribs and channel lagging for support. This job included the design and construction of both the portal shoring to create access via a permanent soil nail wall totaling 1,000 SF, and a jacking frame to launch the machine using wide flange beams that extended 10’ below surface using micropiles.
This project included excavation and temporary excavation support for the Loudoun County Raw Water Intake. Drill and blast excavation was performed near a very high-end residential community on the bank of the Potomac River in Leesburg, VA. Mitigation of stakeholder impacts included multiple innovative blasting techniques to reduce the air pressure and vibration, in addition to thorough monitoring of blasting operations.
A temporary cofferdam was constructed at the Potomac riverbank to allow for tunnel portal excavation to be implemented. Drill Tech designed the shaft and tunnel ground support in addition to performing the work. Excavation support consisted of 2″ thick shotcrete and rock bolting in the shaft and tunnel with permanent structural steel sets near the river intake portal.
The overall purpose of this contract is to rehab an existing Ren exploration drift near the Meikle Shaft via additional fully encapsulated bolts throughout for longevity of the drift. Additionally, to fully support further exploration and eventual mining activities there is a need to drive a parallel drift (7,000’ of lateral mine development at 20’ x 21’) for the eventual ore exploration/production and ventilation circuit. In the short term this parallel drift will also allow for a primary airflow loop through the area (currently on an exhausting hardline system) that will allow for an increase in airflow and help manage the extreme geothermally influenced heat hazards in the area, as well as provide a secondary means of egress from the area to support future mining. Environmental conditions require chillers and continued monitoring of personnel for heat encountered.
Work scope began rehab bolting through an existing Exploration Drift including clean and re-support areas with 8’ Swellex bolts and wire prior to full installation of grouted and tensioned rehab or hollow bar bolts (8’ through drift, 16’ bolts in intersections and passing bays). As rehab progressed a twin drift to the Exploration was driven to the East of the Ren EXP. It started development from the 3665 Level in Banshee and break through into Ren decline at multiple locations for ventilation continuity.
The project also included the installation of a paste mine backfill system. As part of the Project, the Owner requires that the Paste Distribution system that will supply the paste to all underground areas in the Rodeo and North Post sections of the underground be installed with Engineered supports.
Work consisted of two sections, the Meikle to Extension Run which will require 7 drilled raise boreholes (varying in length from 80’ to 750’), and 6,116 feet of 6-inch piping. The second will be the Banshee to Ren run which will consist of 3 boreholes, and 6,649 feet of piping. Banshee Development consists of drill/blast for 2100’ drift at 17’ x 18’ drift to reach production stopes.