Precast concrete manhole adjustable bolt slot for securing cast iron frame and cover and method for casting same

摘要

A top concrete section for a manhole assembly is cast with a plurality of bolt slot inserts each insert having a substantially inverted T-shaped hollow interior for slideably receiving a nut which may be moved to any desired position along the base of the insert for threadedly engaging a threaded rod employed to rigidly secure a cast iron cover frame to the top section. The method for casting a manhole top section comprises the steps of releasably mounting each insert within the mould assembly by means of a retaining slide which itself is slideably received within a pair of holding brackets provided on each of the inner and outer mould members, the insert being substantially fully closed on all sides thereof and having a top surface formed of a thin web which is easily fractured or cut away after the top manhole section is cast. The fully enclosed insert prevents any concrete from entering into the interior thereof. The nut may be moved along the length of the insert base in order to bring it into alignment with bolt hole centers in the cast iron frame.