Permanent Vertical Shoring with Near-Surface G.W.
Permanent Vertical Shoring with Near-Surface G.W.
(OP)
I am designing a flood channel that will outlet in an extremely environmentally sensitive marsh area. The portion of my channel that must extend into the marsh will be a trench approximately 10 to 15 feet wide and 300-feet long. Do to the environmental concerns, I want to minimize my footprint within the habitat areas. The trench will be excavated/dredged 4 to 7 feet deep, and surface (or near surface) water is expected during construction and through out the design life. The soils investigation is not complete yet, but a generally clayey soil is expected.
I am looking for a way to permanently retain a vertical excavation for this trench. The requirements are:
1) The trench must be soft-bottom (e.g no channel linings like concrete)
2) Disturbance outside the ~10-15' base width must be minimal (i.e. no reinforced earth strips extending behind the retaining system)
3) Need to be constructable in a manner that is minimally invasive to the habitat area.
4) The entire retaining system will likely be underwater - at least partially - for its entire life.
5) Because of the environmental sensitivity of the area, the area will be considered unmaintainable, so I am looking for a durable, maintenance free installation.
My first thought was a Soldier pile and concrete lagging type installation, but have read that these don't work well for installations with Ground Water.
Does anyone have any recommendations?
I am looking for a way to permanently retain a vertical excavation for this trench. The requirements are:
1) The trench must be soft-bottom (e.g no channel linings like concrete)
2) Disturbance outside the ~10-15' base width must be minimal (i.e. no reinforced earth strips extending behind the retaining system)
3) Need to be constructable in a manner that is minimally invasive to the habitat area.
4) The entire retaining system will likely be underwater - at least partially - for its entire life.
5) Because of the environmental sensitivity of the area, the area will be considered unmaintainable, so I am looking for a durable, maintenance free installation.
My first thought was a Soldier pile and concrete lagging type installation, but have read that these don't work well for installations with Ground Water.
Does anyone have any recommendations?





RE: Permanent Vertical Shoring with Near-Surface G.W.
RE: Permanent Vertical Shoring with Near-Surface G.W.
Thanks though!
RE: Permanent Vertical Shoring with Near-Surface G.W.
In my area marshes generally are overlain with peat of one type or another. I have seen dredged peat situations where the internal fiber structure of the peat holds it together nicely with a steep slope of cut, relatively permanently. Since the material is under water, its submerged unit weight is very low, especially if high in organic content (some peats float). Then, not much tendendy to slough in.
Consider leaving a steep natural slope under water. Certainly the restrictions can't be so bad as to require vertical side slopes
Can natural vegitation be used to reinforce this slope?
For excavation, I'd look at a dragline sitting on wood mats. Start out at end and re-handle the stuff to get to shore.
If cold climate, best time is in the winter. Much easier then.
RE: Permanent Vertical Shoring with Near-Surface G.W.
RE: Permanent Vertical Shoring with Near-Surface G.W.
I think you should reconsider the concrete U sections. You could create a soft bottom by placing the bottoms of the structers several feet deeper than the flowline and placing soil in the structure. These may be easier to transport to the site and place than the sheetpiles or solider piles and lagging.
Can the materials be brought in by barge from the discharge side?
RE: Permanent Vertical Shoring with Near-Surface G.W.
RE: Permanent Vertical Shoring with Near-Surface G.W.
f-d
¡papá gordo ain’t no madre flaca!
RE: Permanent Vertical Shoring with Near-Surface G.W.
R.A. Hassett, P.E.