Library Settlement Repair

Boston University's Office of Space Planning and the Physical Plant recommended that the engineering department library be moved from the 2nd floor of its current location to the basement to provide space for a new research laboratory. The current building, built in 1910, is a four-story reinforced concrete structure with flat slab construction consisting of 27 and 25 ft (8.2 and 7.6 m) column spacing. The basement slab is a 6 in. (152 mm) concrete slab on grade with lightly reinforced steel wire mesh. Concrete columns are supported by pedestals and single footings that rest on a layer of dense sand, 15 to 18 ft. (4.5 to 5.5 m) in thickness, at a depth of 5 to 8 ft (1.5 to 2.4 m) below the basement slab. This article looks at sub-surface soil investigation; design of slab and mini-piles; and construction procedures.