Landfill Dewatering SPT 1

[Highstepper]

I am working on a concrete cap design for a landfill that has crushed tile and a slurry mixture of mostly small pebbles and some small amounts of clay in it. The landfill is about 5 acres in surface area and roughly 20 feet deep. The landfill will be partially closed until the open area (which is filled with water) is filled with the tile and then the slab will be connected to another slab. We did the geotech investigation yesterday and the SPTs were 40-50 in the first 18 inches, water was encountered (roughly level with water in the open space), then the SPTs were 4-6 until 9 feet (when borehole collapsed). I told the client that we need to dewater the open area and after that we should use a compactor before placing the slab as there will be several inches of settlement. He does not see the slab as having any problems with water in it. Is my recommendation reasonable? I will wait on the geotech report but this seems prudent or am I off? Client is hot to trot to lay the slab as they need the room for storage and 18-wheelers will be driving on it.

 

[oldestguy]

Without a significant overloading surcharge first applied for this site, I think you need to compare this to building over muskeg or other very bad support. Very heavy reinforcing is needed and all joints must have full load transfer reinforcing, as I view the job. Expect plenty of settlement of the operating areas.

Your surface compacting will not prevent the deep material from compressing later on. Consider running a rolling surcharge across the site with a pile maybe 10 to 15 feet high. Much better that just hitting the surface.