huangyhg

loading from concrete as backfill to wall
i have a concrete wall that behind will be backfilled with mass concrete. the concrete will be liquid state (or thereabouts) when poured so what loading criteria should be used? treat as hydrostaic with unit weight of 24 kn/m2? probably conservative?

i'd say absolutely hydrostatic. i'm sure you mean m^3.
either design your wall for full hydrostatic pressure, or pour the slurry backfill in lifts and allow it to partially set before pouring the next lift. you don't need to allow full cure, just enough time between lifts for the concrete to stiffen so that it no longer behaves as a liquid.
yes sorry, m3.
see aci 347-04, there are formulas provided for given concrete properties. i see this as similar to pressure against formwork which is what aci 347 addresses. i would expect some locked in stresses in your existing wall & ftg after the newly placed concrete hardens behind it.
look up the formwork code, your retaining wall will be acting as permanent formwork.
i've had two instances of contractor's filling cavities between blockwork leaves with liquid concrete without phasing it in lifts.
the pressures from wet concrete can be significantly higher than those from the ground. insist that the work is done in lifts, not all at once.
use a drier concrete mix if you can.

__________________
借用达朗贝尔的名言：前进吧，你会得到信心!
[url="http://www.dimcax.com"]几何尺寸与公差标准[/url]