concrete crib retaining wall repair options?

[gte447f]

I am looking at a concrete crib retaining wall that is loosing backfill through the face of the wall during heavy rain events. There is an obvious surface water drainage problem that is contributing to the loss of backfill through the face of the wall, in that their is a tennis court upslope from the top of the wall that is discharging a lot of runoff toward the wall. There are several area drains that are supposed to collect the runoff from the tennis court, but until recently those drains were completely clogged. The area drains have recently been cleaned out, but I am skeptical that it will significantly reduce the amount of runoff getting to the top of the crib wall. I am going to recommend that a swale be constructed parallel to the top of the wall to intercept runoff and direct it around the wall.

In addition to the drainage problem described above, the cribs appear to be backfilled with local site soils with a high clay/silt content. In my opinion, this is not an ideal backfill material for a crib wall, because it is susceptible to erosion/washout, which is exactly what is happening. There is a geotextile fabric located behind the front stretchers of the wall that is intended to retain the backfill soils, but the geotextile is degraded and failing over large areas of the wall, so it no longer retains the backfill.

Questions: If the surface water drainage problem can be solved and controlled, will that be enough to prevent further loss of backfill? If not, is it even possible to replace the geotextile fabric facing without excavating all of the backfill, or is there another option for retaining the backfill, like maybe shotcreting the face of the wall, or establishing a vegetative covering on the face of the wall?

 

[r13]

Swale, or ditch, on top parallel to the wall is a good preventive measure. If the drains can be cleaned, I don't see the urgency to modify the backfill. Is shotcrete an acceptable method to protect the exposed surface?

 

[gte447f]

r13, that's what I am debating: what to do about the failed geotextile facing? I think addressing the surface water drainage problems upslope from the top of the wall will go a long way toward slowing down the washout of the backfill, but I am afraid it may continue to happen no matter what without the geotextile barrier, considering it is very erodible clay/silt. I'm trying to brainstorm alternatives to the geotextile, like shotcrete or vegetation, because I don't think it is possible/practical to replace the geotextile.

 

[r13]

I am not aware any method to replace the geotextile without demolish the wall. So the best you can do, other than rebuild, is to prevent the runoff from running over the wall. If you can slop the grade backward towards surface drains will help too. Without the topping water, I doubt there will be significant amount of soil be washed away. You may only need to find ways to repair/stabilize the worst locations with severely deteriorated fabric.

 

[oldestguy]

Any treatment of the wall in front, such as sealing the openings will likely prevent proper drainage. '
The result would be total failure of the wall system because of that water pressure behind the wall.. Plugged drains indicate they were not backfilled with a filter of some type, such as fabric or concrete sand. Single sized stone is not a filter. Piecemeal adding of proper filter in the openings of the concrete sections is possible, but a labor intensive thing.

 

[gte447f]

oldestguy, weep holes would be added if shotcrete was used on the face of the wall, but that is not something I am seriously considering at this point, just brainstorming ideas. Plugged wall drains are not the problem; the clogged drains I was talking about are area drains that are 20 or 30 feet upslope from the top of the wall and are intended to collect stormwater runoff from a tennis court. The wall itself drains just fine; streams of water literally flow out through the face of the wall during heavy rain. The problem is, these streams of water carry with them a lot of the soil fines from the wall backfill, since the geotextile at the face of the wall has degraded and failed. Obviously getting rid of the majority of the surface water runoff that is infiltrating the backfill is critical, and will be addressed by installing swales to collect and divert the water at the top of the wall. I am wondering what can be done to replace the functionality of the geotextile to retain the soil fines. I am leaning toward trying to establish a vegetative cover on the face of the wall to replace the functionality of the geotextile. What do you mean when you say, "Piecemeal adding of proper filter in the openings of the concrete sections is possible, but a labor intensive thing." Are you talking about geotextile filter or graded aggregate filter? How would you actually go about installing either of these to the existing wall?

 

[oldestguy]

Not practical, but masonry built into each "opening" might be considered. Attachment to the structure of the wall system would be needed. Drill and insert dowels. Filter fabric backing also needed..

 

[PEinc]

So, gte447f, how high and long is the crib wall?

http://www.PeirceEngineering.com

 

[gte447f]

PEinc, the height varies, but its about 12 feet max. It's L-shaped and probably 50-100 feet long total. I haven't measure it.

 

[Settingsun]

Geotextile on front with wire mesh to hold it in place?

 

[Obregon]

gte447f "I am going to recommend that a swale be constructed parallel to the top of the wall to intercept runoff and direct it around the wall."

gte447f "I'm trying to brainstorm alternatives to the geotextile, like shotcrete or vegetation, because I don't think it is possible/practical to replace the geotextile."

I believe you already got most of the solution: drainage on the top, weep holes (pvc/geotextile), wire mesh and shotcrete façade. Once you have done your shotcreting (you´re gonna need confinement), you will need to address the backfill density deficiencies through consolidation grouting. That would do the job.

Regards,

Carlos R. Obregón

http://www.sueloanclado.com