Scheltzke Grout Plant Used in Installation of Grouted Micropiles in West Memphis, AR
As older infrastructure needs replacing, engineers often create more complex designs to address new issues. Such is the case with the replacement of a railroad bridge owned by Burlington Northern crossing the Mississippi River, which connects Memphis, TN to its West Memphis, AR.
Sitting near the New Madrid Fault Zone, the region is prone to infrequent but severe earthquakes. To mitigate potential damages down the road, the new bridge design calls for micropiles to reinforce the stability of the new bridge piers.
Terrafirm is installing dual string 9 5/8” casing and a 3” diameter micropile 141’ in length for this bridge. Drilling conditions at the site are not too difficult. As it is close to the river, most of the material is sand and silts, while drilling the final 30’ through clay. Using a Scheltzke MPS 510-D-C-AUT to mix grout, Terrafirm is pressure grouting through the sands in 10 foot increments to pressure filtrate and bond the grout column to obtain a pile with a bearing capacity of 750 kips in a 72’ bond zone.
The foundations for the piers are constructed in phases. Case Foundation, using their own equipment, drills a cased hole, 12’ dia, approx. 54’ deep, pump bentonite to contain the sand inside the hole, desands the bentonite, installs a rebar cage and pipe assemblies and pumps concrete into the cased hole. The bentonite is then extracted and used on the next pier. After Case Foundation moved on, Terrafirm’s role would begin. They drill the double string through the previously installed pipe, an inner string and outer casing, in 10’ segments. They then extracted the casing in these 10’ segments and pressure grout at 80 psi.
Mike Morris, project manager for Terrafirm, had this to say about the Schelztke:
“The grout plant that we purchased works very well. It has met our expectations and we look forward to using these types of plants in our other drilling and grouting operations.”
Once the new piers are completed and bridge deck installed, the old bridge will be torn down.