In many cases one might have to backfill over soft soil and carry a heavy load (such as a railway). One approach to stabilizing such a retaining wall is to construct a soldier pile wall system and fill the space behind the soldier pile wall with structural backfill. The density of the structural backfill would be in the order of 120 to 125 pcf (19 kN/m3), and will exert a considerable load on the soldier pile system especially if compaction is carried out.
One way to create significant savings is to replace the structural backfill with cellular concrete. One such case was examined with DeepXcav, where the pile spacing could be increased from 6ft to 15 ft and savings in the order of 30% could be realized. Switching to cellular concrete would be more beneficial when the length of retaining wall is greater and mobilization costs form a smaller part of the total project cost. The following figure presents the basic results of our analyses: Case A) presents conditions without the cellular concrete, while Case B) presents conditions where cellular concrete is introduced.
|Design with structural backfill||Design with Cellular Concrete Backfill|
|Number of piers||16.67||6.67|
|Lagging Square feet||1,500||1,500|
|Lagging $/SF||$ 10.00||$ 10.00|
|Lagging Cost||$ 15,000.00||$ 15,000.00|
|$/lb steel||$ 1.00||$ 1.00|
|Cost of steel||$ 2,450.00||$ 980.00|
|$ Concrete/CY inplace||$ 250.00||$ 250.00|
|total concrete cost||$ 38,159.72||$ 5,814.81|
|drilling rate $/day||3500||3500|
|cost of drilling||$ 29,166.67||$ 11,666.67|
|Cost of Cellular/CY||0||45|
|total cellular cost||$ -||$ 30,645.00|
|CY/LF soil Backfill||6.81||0|
|Cost of soil backfill/CY||$ 10.00||$ 10.00|
|total soil backfill cost||$ 6,810.00||$ -|
|Total Cost||$ 91,586.39||$ 64,106.48|
|Total Cost /LF||$ 915.86||$ 641.06|
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