Soldier Pile wall with Tiebacks-Software?

[Dasovich]

Hello,

We're interested in purchacing software that will aid in the design of a soldier pile wall with tiebacks. Can anyone out there recommend a software we can use to aid us in our design? What are it's pluses and minuses? Ideally we would like something that can handle stratified soil deposits, water table, varying wall heights, etc...

On a side note, we have been following the methodology outlined in the FHWA Geotechnical Engineering Circular No. 4 - Ground Anchors and Anchored Systems. What other methodologies are there out there? I'm just trying to become more educated with different methods and standard methods of design.

Dont worry, we are also consulting with a geotech who will review all our work.

 

[PEinc]

Shoring Suite Plus by CivilTech Software is pretty good. It is used by many who sheeting design walls on a steady basis.

http://www.civiltech.com

Now for the warnings.
1. Do not use a computer design program unless you know how to do the design by hand calculations. You need to know if the computer answer looks reasonable and is correct.
2. Do not use a computer program unless you know exactly how the program solves the design and you can duplicate the solution by hand calculations.
3. Computer programs are written with certain assumptions or use design methods that you or others may not agree with.
4. Some sheeting wall design programs use only triangular earth pressure distributions. Some use other distributions. You need to know which distrubution is appropriate for your particular design case.
5. The cheaper a design program, the more limited it use will be.
6. FHWA's Circular 4 is written for highway projects. Its emphasis is on PERMANENT anchored walls. Its methods and recommendations may be unnecessary or conservative for projects that are private, non-highway projects or temporary projects.
7. FHWA and some state DOT's, such as PADOT, are very heavily pushing for LRFD design of temporary and permanent sheeting walls. I don't know of any LRFD sheeting design programs and have never even seen any LRFD hand calculations. But somebody better start developing an LRFD program fast.

 

[Dasovich]

Thank you PEinc, your response was very helpful. I do have a question though to your comment #7. What does LRFD stand for? Thanks!

 

[PEinc]

LRFD stands for Load & Resistance Factor Design. Simply put (ha-ha), it is a glorified ultimate stress design method. It uses factored loads with resistance factors instead of using service loads with allowable stresses. I believe that schools are now teaching steel and concrete design using LRFD rather than ASD. I'm not up on LRFD. I'm pre-LRFD. I don't really see the reason for using LRFD when soils and wood are so variable in nature, unlike steel and concrete. How comfortable will you be designing footings for ultimate bearing capacities? What will probably happen is that designers will factor up the loads and also still use an allowable (or factored down) bearing stress (essentially a "double safety factor"?).

Anyway, the push is on to switch from allowable stress design (ASD) to LRFD for design of sheeting, anchored walls, soil nail walls, etc. The switch is taking long because "they" are trying to develop LRFD design methods that give the same answers as ASD. They are trying to back into an LRFD method. Why should they try to invent another method to give us the same answer as the method we've used for ages?

Many in the earth support business are fighting the switch but are losing ground to the LRFD'ers. FHWA and AASHTO will eventually get their way I'm afraid. But their specifications do not necessarily apply to non-highway, non-transportation projects. So, if you don't have to use AASHTO or FHWA (including Circular 4), don't. Other traditional methods will still continue to work fine and may give better , more economical designs.

 

[Dasovich]

Thanks again for the quick response. Would you (or someone else reading this) mind providing me with a list of some references that cover some of these other non-highway related methods in detail? I'm not familiar with the other commonly used methods that are out there and would like to be.

 

[PEinc]

Most foundation engineering books include information on designing sheeting which does not reference AASHTO or FHWA. Check out any of Bowles' Foundation Analysis and Design editions. Try Ratay's Handbook of Temporary Structures in Construction. Check out publications available from Pile Buck. Check publications form ASCE and USACOE. AREMA (formerly AREA) has a section on designing sheet pile walls.

 

[PEinc]

Also, check out Tiebacks in Foundation Engineering and Construction (1st edition by Schnabel, 2nd edition by Schnabel & Schnabel).

 

[DRC1]

Civil Tech is good allows for a lot of variability in loading conditions. Other Programs are SPW-911 by Pile Buck

http://www.pilebuck.comOther

programs include SOLDIER_WALL by Geodesign (email info@geodesign.net0 and Arbed Steel (sheetpiling producres) also distrbute a program. A good reference for designing tied back walls is "Pile Buck Sheet Pile Design Mannual" If you are doing this, I strongly reccomend you get a copy. Additonal resources are available from

http://www.sheetpile.com

(L.B. Foster, another sheeting supplier)

 

[PEinc]

I believe that Pile Buck's SPW-911 handles only triangular loads. The same for Arbed's sheet piling program. Arbed also only analyzes cantilevered and single tier steel sheet pile walls and can not design soldier beams or model a truncated slope behind the wall. For the right situation, I like and use Arbed's program.

Pile Buck's Sheet Pile Design Manual is a reprint of the out of print 1975 US Steel Sheet Pile Manual with much added material. While both are basically good references, I believe they are referred to too often by engineers and contractors who think of them as the "bible" of sheet pile design. Too many people try to blindly follow along with these manuals. As good as the manuals are, they do not cover many cover many actual field conditions. A lot of new information has been developed for the design of sheeting since 1975.

 

[JYChen]

I have used the program, PYWALL, to analyze/design several soldier pile and lagging with tieback retaining walls. You will need to come up with a variety of parameters to model the tiebacks using p-y curves, the properties of either driven or drilled-in soldier beams, widths for active and passive soil resistance, reasonable earth pressure distribution (The program can compute the triangular earth pressure distribution internally. However, this is not valid for most of the tieback walls.), and of course reasonable soil properties. You will need to know how this type of wall is constructed and some basic soil-structure-interaction concepts to come up with good model parameters.

 

[PEinc]

JYChen,
Sounds like you too need a new sheeting program!

 

[JYChen]

Dear PEinc:

I think that Dasovich was asking about a program for designing soldier pile walls with tiebacks but not sheet pile walls in the first place. I am pretty happy using PYWALL to analyze soldier pile with tieback wall system. I have developed a MathCAD template to obtain those parameters efficiently. For sheet pile walls, I have used CWALSSI, Prosheet, PYWALL, and PLAXIS to analyze the problems. PLAXIS is good for the cases where groundwater flow is a major issue, because it has a flow module to calculate the flow field during staged construction. Plus, it's the most user-friendly FEM program I have ever used.

 

[PEinc]

JYChen,

You are correct. Dasovich did ask about software for designing tiedback soldier beam walls rather than steel sheet piling. However, I was responding to DRC1 who suggested Pile Buck's SPW-911 program, their sheet pile design manual, and Arbed's ProSheet design program.

With respect to my previous comment to you, I would like to point out that, from my experience, US companies engaged in design-build earth retention systems generally do not use finite analysis or other design methods or programs as "sophisticated" as those you seem to be using. I have worked for and with a number of both regional and national specialty design-build earth retention companies and have not used or seen used FEM, Plaxis, PYWALL, or CWALSSI. Your programs sound relatively complicated and probably more expensive than those with which I am familiar. Certain complicated projects may require more sophisticated programs but the vast majority of sheeting walls do not.

 

[Ginger]

Has anyone considered using pencil, paper and a few text books??

 

[BigH]

Just to throw in a late word of caution - I think that PEinc gives good advice (see his list of 7). As in other threads, you might think I'm a bit of a dinasour, but, remember that any computer program using sophisticated models really, in the end, is only as good as the input put in. How many times have I, or you, designed for retaining walls where we design for phi = 35 but, 'ell, it could have been phi = 37 or phi = 33????? I sometimes laugh at drawings that put in a statement such as: "Backfill shall consist of soil having a phi = 35deg; gamma = 130pcf; delta of 10deg." Now, contractor chooses to use a coarse to medium sand - does it have 35, 130, 10??????? Are you reallly sure??????? Just think about it. What if he compacts the soil to 98% MDD heavy (oops, modified) and not 95% as indicated in the specs? Does this affect your calculations?? Focht3 has stated nicely before that sophisticated programmes will allow you to look at potential scenarios in models than the old hand calcs - where you can explore more, but . . . GI/GO. And as PEinc said, "1. Do not use a computer design program unless you know how to do the design by hand calculations. You need to know if the computer answer looks reasonable and is correct.
2. Do not use a computer program unless you know exactly how the program solves the design and you can duplicate the solution by hand calculations."

- - - now a solicitation - a request for help!! Please, send to the threadmaster a request that we start a thread under geotechnical regarding "flexible pavements/materials for" and "rigid pavements/materials for" . I would appreciate this immensely. Now the big query for the night - is it Raiders? or is it Buckaneers? Sounds sort of piratish to me, eh, mates?????

 

[Focht3]

BigH:
I don't care which flavor of pirate wins. I'm just glad that Bud Adams and his Tennessee Titans didn't make it. He's the biggest pirate of the bunch.

PEinc has done a commendable job discussing this topic - he has given very sound advice. And BigH's comments about parameters are right on target. A true story to illustrate the point:

About 15 years ago, I was involved in a project in a port facility along the Texas Gulf coast. Our firm was a "subcontractor" to the project geotechnical engineer - we monitored inclinometers for him. (He had instrumented the bulkhead and anchor rods with strain gages - most had failed. Inclinometers were his best instrumentation.) Inclinometer monitoring showed that the steel of the bulkhead was at the yield stress at the end of construction. (We had made multiple readings per visit and used the averages - got beautiful shear and moment curves via numerical differentiation.) "The" geotechnical engineer decided our results were wrong; went to great lengths to prove his point. I predicted the bulkhead would fail after dredging was completed in front of the bulkhead (lowering the mudline about 7 feet) - when the first "blue norther" passed through and lowered the channel level by 4 or 5 feet. And I made my prediction without the benefit of FE codes, etc.

The bulkhead failed over five years after it was completed - and within six months of the completion of the dredging work. To quote a past Terzaghi lecture, "It's better to be approximate and correct than precise and wrong." It failed when the first cold front passed after the dredging was completed.

What were his mistakes? In my view,

DESIGN: He assumed K_a = 0.33 (0.30?) for a "clean" fine to medium sand behind the bulkhead. Yet he knew the sand would be a dredged material placed after the "European" section bulkhead, A-frame deadmen and cast-iron tie rods had been completely installed. (The system was very stiff.) He should have designed for a K₀ = 1 condition (and phi of about 28 degrees) for a "dirty" fine sand behind the bulkhead. After all, the bulkhead system, construction sequence and fill placement technique virtually guaranteed that the full weight of the backfill would act against the bulkhead.

POST-CONSTRUCTION RESPONSE: He should have acknowledged his error. But his arrogance wouldn't allow him to admit his mistake.

 

[PEinc]

BigH & Focht3,
Thank you. Your comments are greatly appreciated.

 

[JYChen]

Wow, it's a surprise to me that I will get so many follow-ups. Fortunately, pretty much all of them are the good points that I agree with. In fact, I believe that a good model should be calibrated against field performance. For example, the inclinometer data will be very helpful in adjusting the numerical model.

The benefit of a computer program is to save you time. As long as you know how the program does its work, how does the model fit in the problem(s) you are analyzing to avoid the GI/GO issues, and you are comfortable with it, the program can be a valuable tool to you. For example, you can perform sensitivity analyses quickly and identify the important parameters you want to obtain in the additional subsurface investigation or the right field instrumentations you want to incorporate into the project. You can idealize how the construction sequence impact the performance of constructed facilities. I have done hand calculations (actually with the help of MathCAD) of a FE formulation at the element level, but I can never do such a task at the global mesh level without the aid of a computational tool.

BTW, I am working in a consulting firm in the U.S. We use those tools on a regular basis, especially on big projects, or projects with difficult site conditions or complicated construction. I was sharing my experience to answer Dasovich's question about selecting a tool for his need.

I am happy to see so many good comments from professionals in this field. Best wishes.