Signs of Construction: Grade PreparationOnce existing debris is cleared, grading is the next step in preparing the ground to its final profile. The elevation of the new structures and track is dependent on how the train will traverse the 10.5-mile rail alignment, either climbing over existing roadways and bridges or operating within city streets, much as you see today in downtown Denver.
To achieve this, crews will excavate down, or "cut," to lower the grade elevation in some areas and will build up, or "fill," large embankments to reach the desired grade in others. "Balancing" the grade process requires hauling massive quantities of dirt from the cuts to the fills and then compacting the dirt.
Once the dirt is in the right location, it is compacted to the required density or strength using either static or vibratory rollers. The use of a vibrating drum increases the force applied by the roller achieving the desired density quicker. This vibration can sometimes be felt in areas adjacent to the work site.
Traditional compaction tests are performed using a handheld nuclear density gauge to measure the soil compaction. New advancements in intelligent compaction technology allow the contractor to calculate soil density immediately using accelerometers located in the drum's roller. The position of the roller and density measurements are electronically transmitted to a Global Positioning System "GPS" model used to calculate compaction density and identify areas requiring additional compaction.
These technological advancements equate to a cost and time savings on design/build projects such as the I-225 Rail Line.