Drag down loads on manhole shafts
Drag down loads on manhole shafts
(OP)
Storm drain lines located up to 65 feet below existing grades will be supported by consolidated, sedimentary bedrock. Conventional grading methods will be used to install the lines, therefore at locations of manholes, the adjacent soils will consist of granular (SM and SP-SM with gravels) compacted trench backfill. Manhole sections will be installed as the backfill is brought up. Considering the granular nature of the backfill, is it safe to assume that drag down loads on the manhole shaft will be negligible?





RE: Drag down loads on manhole shafts
Down drag is normally associated with the settlement or consolidation of soft or loose layers of clay or sand when an additional load placed on top.
Depending upon the density of the native soils, you may end up with insufficient material to backfill the excavation after it is properly compacted, but I wouldn't be concerned about down drag.
RE: Drag down loads on manhole shafts
RE: Drag down loads on manhole shafts
RE: Drag down loads on manhole shafts
yes I agree does seem to be quite a job. If in an urban area it is generally the case that, if possible, open cut is less expensive than pipe jacking or micro-tunneling. But at the depths mentioned I would expect pipe jacking to be less expensive. What is the drain diameter?