‘Construction Techniques’ Tag

Concrete Screeding and Pouring

Photo Credit: Alex Mead

Seen here is a concrete pour crew in the middle of placing a mat foundation. The process that is happening here is the beginning of leveling the slab of concrete to the final depth. The tool the man in maroon is using is a called a screed and is basically a gas powered leveler. The two workers behind the screed move excess concrete out of the way and add concrete to areas that are lacking to allow the screed to make a relatively flat surface. Other finishing methods are then used to make a final slab that is within a tolerance of the specified depth.

Auger Cast Pile Wall Failure

Photo Credit: Alex Mead

Seen here is the failure of an auger cast pile wall. This type of wall is designed to be a watertight retaining structure for the construction of an underground project. Although it is hard to tell from this photo, the wall appears to have failed due to weak concrete in the piles. One pile broke and released the material it was suppose to keep out of the excavation. This failure formed the mound of dirt seen in the photograph and a “sink hole” approximately 20 ft by 10 ft by 30 ft deep behind the green fence screen. This is what a bad day looks like for a geotechnical engineer.

Concrete Pour at Night

Photo Credit: Alex Mead

When pouring concrete contractors cannot simply begin or end placing concrete at any given location in a structure during a given pour. Due to many reasons, including rebar placements and concrete’s inability to stick to itself once dry, pours need to be done in a manner that completes a predetermined structural element. In some cases, this means pouring thousands of yards of concrete in one continuous operation for hours and even days. Pictured above is a concrete pumper’s boom working into the night on a 2 000 yard pour, comprised of approximately 200 trucks, that lasted more than 12 hours. In the background of the photograph is the job’s tower crane silhouetted against the setting sun.

Scaffolding Tent for Masonry Finishes

Photo Credit: Alex Mead

Why is the front of that building covered in a tent of plastic? This construction technique is used to raise the temperature of the work space within the plastic and to block the wind. Inside that scaffolding and plastic encasement the temperature is much warmer than the single digit temperatures experienced outside. This warmer space allows for the construction of masonry finishes which would be nearly impossible in the freezing temperatures of winter.

Foundation Tieback Placement

Photo Credit: Alex Mead

Featured in this photograph is a worker placing tiebacks for an auger cast retaining wall system. Such retaining wall systems are designed to resist all the lateral loads imposed by the sides of an excavation. To place tiebacks the worker first drills into the earth behind the wall using the machine shown, and secures cables with grout in the hole. After the grout has cured and the cables are secure they are pulled tight using jacks and fastened to the wall to hold it in place. Excavation then continues deeper until the next layer of tiebacks is needed. The process is then repeated until the desired depth of the excavation is reached.

Checking Depth during Excavation

Photo Credit: Alex Mead

So what is that guy doing so close to that excavator? He is measuring how deep the hole is to make sure the foundation is built to the proper dimensions called out in the plans. When digging a hole for a foundation it is crucial that the footings, piles, and foundation walls are built to the proper size. By using a pole with a sensor on it, the worker is able to guide the excavator operator to dig the exact depth needed. Typically the pole will have a sensor on it that picks up a laser beam being emitted at the proper height. The sensor beeps when it is level with the laser and thus the bottom of the pole is at the proper depth of excavation. This method of hole depth measuring allows rough digging of the foundation to be done with machines. Workers can then finish the hole by hand to the more exact dimensions needed for the future building.