## Soldier Pile Wall on slope

## Soldier Pile Wall on slope

(OP)

We are proposing a soldier pile wall with drilled caisson for a slope repair project. The height of the wall is 13'. The pile embedment is 30.5' in soil. No ground water table encountered.

The soil parameters for the fill: phi- 30, unit weight - 120 pcf

The soil properties below subgrade: phi- 36, unit weight- 130 pcf

Slope- 1.5:1.

Geotech subconsultant did deflection check in PY wall software and recommends W18 x283 fpr soldier pile section. They used a 0.45 p-multiplier to account for the reduction in the passive pressure due to slope. The section seems to be huge. Have anyone come across a similar situation. Please let me know your thoughts.

Thanks

The soil parameters for the fill: phi- 30, unit weight - 120 pcf

The soil properties below subgrade: phi- 36, unit weight- 130 pcf

Slope- 1.5:1.

Geotech subconsultant did deflection check in PY wall software and recommends W18 x283 fpr soldier pile section. They used a 0.45 p-multiplier to account for the reduction in the passive pressure due to slope. The section seems to be huge. Have anyone come across a similar situation. Please let me know your thoughts.

Thanks

## RE: Soldier Pile Wall on slope

Mike McCann, PE, SE (WA)

## RE: Soldier Pile Wall on slope

## RE: Soldier Pile Wall on slope

From similar designs that I've done, W sections are rarely the best way to reinforce these types of drilled shafts. Much more efficient to use rebar cages.

Mike Lambert

## RE: Soldier Pile Wall on slope

They did slope stability analysis. Tie back would be the next option if this doesn't work.

Please see the attached sketch.

Thanks

## RE: Soldier Pile Wall on slope

Frankly I would be surprised that the W section you listed at 6 foot centers would work at all.

Mike Lambert

## RE: Soldier Pile Wall on slope

Figure 10-3 from my copy of the Navy Design Manual for geotechnical shows the Ka as 0.8 for that slope. Your flat area will change that some.

Kp is about 1.5 on the downhill side, not the usual .

Have you looked at making that flat area all in cut, rather than fill. It might have less risk.

We are not here for designing things, but my comments are that, instinctively, I don[t like the idea at all.

## RE: Soldier Pile Wall on slope

I would expect you looked at slope stability at a few places to, including above and below the wall. Also to fully mobilize passive pressure you need some movements, so even with that, a significant reduction makes sense.

You said that the wall is 13 feet, but is the w-section extending to the bottom of the hole. In other words, do you have an concrete encased w-section below ground line, and exposed above ground, making a total pile length of 43.5 feet? Or are the W-sections connected via a base plate at the top of the piles? I guess either of these methods would affect the size, but I agree the W-section is a little hefty. I would would on piles w-sections encased in concrete of similar height, but on flat area to withstand E-80 train loads, and the sections were much lighter. I would check the geotech structural design parameters to ensure the were using reasonable structural analysis.

How big are the caissons?

## RE: Soldier Pile Wall on slope

## RE: Soldier Pile Wall on slope

## RE: Soldier Pile Wall on slope

Remember that the angle of repose for a saturated cohesionless slope is one-half the friction angle. You can't afford to have stormwater seeping into a ditch on the uphill side of the road.

Be careful. You have a tiger by the tail.

## RE: Soldier Pile Wall on slope

I agree that the top and toe slopes need to be carefully considered by a real geotechnical engineer. There are also arching considerations assumed by lateral load on pile calculations. These arching considerations may or may not be invalidated by the toe slope. In other words, I hope that the p-y calculations and ultimate load safety factors consider the toe slope.

I hate the term, "Angle of repose." I don't allow cohesion in my slope analysis. Cohesion doesn't hold up over time and the freezing and thawing, wetting and drying, etc. of the design life will reduce cohesion to zero. As such, the safety factor of slope (in infinite slope failure mode) is tan(phi)/tan(beta). You can't return a 1.5:1 slope with a safety factor of 1.3, irrespective of the drilled shaft design.

I agree, the design has problems.

f-d

ípapß gordo ainÆt no madre flaca!