Excavation Conveyor System – April 2018
Bellevue, Washington
An underground contractor was awarded a bid to excavate and remove native material from an inner city downtown location to prepare the site for a high-rise building with a small footprint. Since the location was fronted by existing buildings and two adjacent busy streets, shoring was required on all sides during excavation. The deep vertical walls provided by the shoring created a challenge to remove the material and load trucks by conventional methods. Due to the busy pedestrian and congested traffic area with bikers and automobiles, permit restraints included limited working hours and flagman traffic controls as trucks hauled the excavated material from the jobsite. The contractor envisioned removing and hauling a minimum of 2,000 tons per day of material employing 24 bottom dump trucks making round trips of up to 1-1/2 hours from the jobsite to selected dump sites. An excavator and dozer was selected to harvest the material as they moved around the site at the lower level.
The contractor selected Rock Systems to design and furnish a material handling system to accept minus 10” excavated material from the excavator and transfer it into the trucks at a rate of 500 tons per hour. A semi-portable feed hopper with 18 tons storage capacity including a variable speed belt feeder was selected to mate to the capacity of the excavator. Two 100’ long deep truss conveyors positioned at an incline of 19 degrees transfer the material from the feed hopper up to a surge hopper mounted at the street level. This large surge hopper includes a discharge conveyor equipped with a fluid coupling designed for quick start/stop intervals as the empty trucks enter and the loaded trucks exit. An operator’s station is positioned near the street so the operator can watch the trucks being loaded and also see the excavator at the lower level. The operator’s station is enhanced with the use of remote cameras.
The equipment includes the following:
- Rock Systems Model 101-36 Feed Hopper with 36” Wide Belt Feeder
- Rock Systems 36” Wide x 100’ long Transfer Conveyors
- Rock Systems Model 105-20 Truck Loadout Hopper with 42” Wide Discharge Conveyor
