KennyRogers
Structural
- Jan 8, 2014
- 8
Afternoon,
We are looking to dewater an old defunct canal for the purpose of backfilling the canal with fill materials (mostly clays). I've searched for existing plans of the sheet piles walls with no luck. However, many of the walls were built in the early to mid-1900's and are a mix of timber and steel. The newer walls are mostly steel sheeting with tie-backs. Dewatering the canal will likely cause an overstress of the wall systems and could lead to failures since we are relieving the water pressure which is counteracting the overturning pressures (I am assuming the water table behind the wall is the same as the water level in the canal and drop as the canal is dewatered, however it will drop slower than the canal water level).
I've been thinking about methods to reinforce the wall to prevent failure. We can do additional tiebacks or we can also relieve the pressure from behind the wall by excavating the soil. However these methods would require us to know the as-built configurations which we don't have. One idea is to place broken concrete, rip-rap, or other granular backfill on the front of the wall to help stabilize. This backfill can then become part of the clay fill as work filling the canal progresses.
Does anyone know how, or has anyone calculated the amount of passive resistance a pile of granular would provide? The back fill would slope away from the wall face roughly at the angle of repose. When submerged, I would tend to think the angle of repose might change a little (+ or -) but not much. Is this a safe assumption?(I figure that effective stress is reduced, but also so is the weight, so the change in angle of repose is a wash) I had already though about building it out away from the wall far enough that the failure plane would extend beyond the sloping point, but this would require a lot of material and we obviously want to minimize this.
Thanks for any input!
We are looking to dewater an old defunct canal for the purpose of backfilling the canal with fill materials (mostly clays). I've searched for existing plans of the sheet piles walls with no luck. However, many of the walls were built in the early to mid-1900's and are a mix of timber and steel. The newer walls are mostly steel sheeting with tie-backs. Dewatering the canal will likely cause an overstress of the wall systems and could lead to failures since we are relieving the water pressure which is counteracting the overturning pressures (I am assuming the water table behind the wall is the same as the water level in the canal and drop as the canal is dewatered, however it will drop slower than the canal water level).
I've been thinking about methods to reinforce the wall to prevent failure. We can do additional tiebacks or we can also relieve the pressure from behind the wall by excavating the soil. However these methods would require us to know the as-built configurations which we don't have. One idea is to place broken concrete, rip-rap, or other granular backfill on the front of the wall to help stabilize. This backfill can then become part of the clay fill as work filling the canal progresses.
Does anyone know how, or has anyone calculated the amount of passive resistance a pile of granular would provide? The back fill would slope away from the wall face roughly at the angle of repose. When submerged, I would tend to think the angle of repose might change a little (+ or -) but not much. Is this a safe assumption?(I figure that effective stress is reduced, but also so is the weight, so the change in angle of repose is a wash) I had already though about building it out away from the wall far enough that the failure plane would extend beyond the sloping point, but this would require a lot of material and we obviously want to minimize this.
Thanks for any input!
