huangyhg

building settlement
hi all;
we have a project where a building is settling both vertically and rotating as well.(almost like the wall tipping over) the building is quite old (over 100 years) and quite heavy construction (concrete and masonry/brick). the geotech is proposing a helical pier system. i understand that this would help the vertical settlement, but i have huge concerns over the rotation/horizontal movement.has anyone used this method before for a similar situation? any input/comments would be appreciated.
as well, we are thinking of installing a geogrid system to look after the horizontal "thrust".
are the settlement and rotation new phenomena? . . . or has this been ongoing for 100 years? if relatively new, what is causing the settlement and rotation? any new construction nearby? please provide some details on these questions. we need to have a clear picture of the building, topography outside (is part of the building holding up earth fill (or recent origin)), nearby construction, soil stratigraphy, etc.
i second bigh's advice. maybe you have a leaking underground pipe or a broken gutter. 100 year old buildings don't just start to settle. your fix might be different once you track down the root cause.
geoffdale...ditto on bigh and jedclampett. in addition, i would question the use of a geogrid system for "horizontal thrust"...first because i don't consider it effective for that and secondly because i doubt you have any horizontal "thrust".
after 100 yrs if you are getting recent movement, sounds like a broken water water or sewere pipe or it could be that work in the vicinity has changed subsuface water flow
and the water is now running under your structure and undermining.
helical peirs might work. mudjcking of the structure might bring it back up to the correct height provided that you have resonably sound ground material under the structure.pump a mixture of sand cement grout but re
sorry for not enough info. the most likely cause of the settlement is the fact that new sewers were installed not that long ago, dropping the water table down. the geotech report suggests the helical piers, and installed on an angle to "help out" with the horizontal loading. we really are looking at stabilizing the structure, and the repairs (cracks) will be filled in, with the intent of stopping the settlement.

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