The installation of pipe canopy on the west portal will be going on until mid January, 2011. The pipe canopy will support the earth above the tunnel during the first 190 feet of excavation.
The next step will be tunnel excavation of the west portal. The tunneling machinery at the West Portal will be smaller, but more versatile than at the East Portal. For more details about the West Portal tunneling excavation check out www.caldecott-tunnel.org. Source:
What’s it like to work on a $400 million project in California, removing tons of rock and debris along more than 3,300 feet? Watch the Caldecott Tunnel fourth bore construction crew and the 130-ton, 54-foot-long roadheader hard at work in the following Caltrans video:
The giant roadheader made a small ceremonial cut Aug. 8 for a public event, but it had to back out and wait for crews to use torches and other tools to cut out metal reinforcement embedded into the hill to stabilize the east portal of the tunnel.
The giant roadheader, which has a rotating cutter mounted on a boom, started boring Wednesday and had carved out about 10 feet of the new tunnel by midday Friday, Caltrans reported. “It’s exciting to see it finally boring through the mountain, scooping up the dirt, and moving it away,” Caltrans spokesman Jeff Weiss said at the construction site just north of the existing three bores of the Caldecott Tunnel on Highway 24.
Crews will be operating the roadheader 10 hours a day this week and 20 hours a day next week.
The wall shown in the photos below will eventually become the east portal wall. According to Caldecott-tunnel.org, most walls are built from the base upwards.
First, an auger drills large holes, ninety feet deep and several feet apart. Concrete is poured into the circular holes and allowed to harden. Next, a series of holes are drilled between the original holes, overlapping the edges. Steel cages are dropped into the holes for extra support and then concrete is poured into the hole. When the concrete hardens, it forms a series of underground interlinking piles.
Starting at the top of the wall, the dirt in slowly excavated revealing the front of the wall. Supports are added to the wall as the excavation goes deeper. According to Caldecott-tunnel.org, the machine in the lower photo is drilling holes to insert tie-back cables, which as the name indicates, will tie back the wall against the hillside. The semi-circular pattern on the wall in the top photo is the outline of the tunnel. The tunnel will be excavated straight through the portal wall. This could begin in as little as three weeks.
A giant roadheader, which was built in Northeastern Germany, was shipped to Oakland and assembled at the east portal of the Caldecott Tunnel. There are several weeks worth of work that must happen before the excavation can begin. According to Caldecott-tunnel.org, the $3.5 million dollar machine weighs 130 tons and has been attended to by several German workers who arrived with the machine to oversee its assembly and testing.