## Analyzing Sheet Pile Walls with SPW 2006: Part I, Introduction

The design of sheet pile walls–and specifically analyzing them from the standpoint of sliding, overturning, and excessive bending stresses–is one of the more challenging aspects of geotechnical design.  That’s because sheet piling are totally dependent upon balancing the lateral earth pressures on both sides of the wall while at the same time insuring their structural integrity.

Simple solutions for the problem are given in texts such as Verruijt and can be analyzed using charts such as one sees in DM 7.02. But real world problems are seldom this simple.  The methodology used to analyze sheet pile walls using “classical” techniques is described in detail in Sheet Pile Design by Pile Buck, and software for that purpose–very useful to simplify the complex calculations from multi-layer soil profiles–is available in packages such as SPW 911.  The expense of this software is easily justified for the practitioner who needs to design these walls in a timely and accurate fashion.

But how does one learn the basics of sheet piling software?  And how can educators teach their students the basics of its use?  The purpose of this article is to introduce the SPW 2006 software, from providing a download link to giving the basics of its use to showing some examples for both cantilever and anchored walls.

## The Basics

SPW 2006 was developed by Arnold Verruijt and some description of the software is given in the download.  It has several important features that need to be mentioned up front:

1. It doesn’t require installation; it’s a standalone executable that can be run, say, from a flash drive.  That makes it simpler to run on systems other than your own (like a university’s.)  It’s a Windows 32-bit executable; it runs fine in just about any Windows environment from 2000 onward (and maybe before) and will also run nicely in Linux under Wine.
2. Unlike some of Verruijt’s software, it has a data file, which is an ASCII file that can be edited if you know what you’re doing.  (If you don’t, don’t.)  When you start the program, it’s very important to load a previously developed file (such as Demo.spw) before you start, for reasons given below.  You’ll need to be diligent in saving it often, because the program isn’t consistent in telling you if you’ve altered the file before the program closes.
3. The program is capable of printed output; however, I strongly urge you to have on your computer the capability of putting the printed output into an Adobe Acrobat file.  Doing this will make it easier for you to save the output for use later.  You can also do screen shots of some of the output, as will be evident shortly.
4. The program input and output is strictly in SI units.

When you run the software and open the demo file, you are greeted with something like this:

You’ll notice the toolbar on the upper right; the first three are obviously (from left to right) open file, new file, and save file.  Next to that is the print command.  The “check mark” is for the output options:

I strongly suggest that all of these be checked.  After that we have the soil layer properties, which come up like this:

You will note the “Loading Step” Option.  This is a departure from some earlier sheet pile programs in that the first loading step shows the soil layering on both sides to be the same.  Subsequent loading steps show the soil layering after “excavation” from the “original state.”  Thus for this, Loading Step 1 show this for the left side:

And for the right side:

Note that the right side looks pretty much like the original.  The left side’s first two layers have zero Wd (dry unit weight) which is the way you tell the program the layers are “excavated” for a given side.  The “?” mark is the button for online help, which explains the variables, for each of the input tables.

One variable that needs some explanation is the Dw, or “stroke” of the soil.  SPW 2006 incorporates soil-structure interaction (SSI,) which means that the force of the soil varies as the wall moves away (or towards it) rather than the “all or nothing” approach common with classical methods.  We’ll discuss this in more detail with the cantilever wall example.

The next button is for the anchors, we’ll explain those when we get to the anchored wall example.  Unlike some classical software packages, SPW 2006 designs for a non-rigid anchor.  This, it’s necessary to note the maximum allowable anchor force and the displacement necessary to achieve that force.  We’ll explain this in more detail with the anchored example.

After this is the axial force exerted on top of the wall.  Using sheet pile walls for bearing is common in Europe but hasn’t quite caught on in the US.  Provisions for forces at both bottom and top of the sheet pile and a moment at the top of the pile are available.

The last input dialogue box is the sheet pile catalogue.  It contains a selection of steel sheet piling (although the program can certainly accommodate other materials.)  The input of sheet pile section properties is probably the strangest aspect of the program for the following reasons:

1. The database is limited to twenty (20) sections.
2. The database is at the end of every data file.  That’s why you need to start with a data file already developed; if you don’t, you won’t get the database.
3. Verruijt’s original database had a collection of U-sheeting from Larssen and Hoesch.  In our download in the demo, cantilever and anchored examples we give the database you see, which includes some Z-shapes.
4. To pick one of these, you don’t pick one directly from the table, but the last entry in the General Data is the Profile number; the number you pick is the profile from the table.
5. The database doesn’t feature the moment of inertia directly but an $EI$ quantity which is the product of the modulus of elasticity and the moment of inertia.  This becomes significant in estimating the maximum moment and stresses.
6. The “h” variable is confusing the way Verruijt defines it: “height of cross-section, in m.”  For U-sheeting and the European practice of using two U-sections as one bending beam, that amounts to making the “h” the same as $c$ in $\frac{Mc}{I}$.  American designers have always been reluctant to allow this.  On the other hand, Z-sections have never had this dispute.  For this database, the “h” is the distance from the outer face of the sheeting to the neutral axis, or the “$c$ in $\frac{Mc}{I}$, assuming American practice for Z-sheets and European practice for U-sheets.

The two examples will show how this data is used.

The program gives a simple profile that, for the “Loading Step 1” looks like this:

It is important to inspect this before running the program, using the “calculator” button.  It’s easy to make a mistake, especially if you have more than one loading step (i.e., are modeling a progressive excavation, which is a common problem in sheet piling design.)

Unlike more sophisticated programs, it’s necessary to manually increment the pile penetration beyond the dredge line to determine the necessary length of the pile.  You can do this in meter increments, 500 mm increments, or whatever step you would like, but you need to start with a very short penetration beyond the dredge line and increase it until you don’t get a floating point error in the calculations.   This is done by changing the depth of the last layer in the soil profile input and re-running the calculations.

Once you’ve done this and arrived at a pile penetration, you can output the beam results for the sheet piling.  This comes out in two ways: first, tabular:

And graphical:

We will discuss how to analyze this data with the cantilever wall example.  The printed output has much more detail than this.

## Inverse Method for Pile Dynamics Using a Polytope Method: IFCEE 2018

This paper–which is part of the STADYN project–was presented at the IFCEE 2018 conference in Orlando, FL, 7 March 2018. The slide presentation for the paper is below.

The preprint for this paper can be found at ResearchGate.

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## Back in the Saddle at the Deep Foundations Institute

Vulcan Iron Works was involved in its industry in a number of ways other than simply selling and renting its product.  One of these was its years in the Deep Foundations Institute.  Although Vulcan was not a charter member of the organisation, it joined very shortly after its beginning and was active during the 1980’s and early 1990’s, until about a year before the merger with Cari Capital.  This webmaster was the Program Chairman for the 1992 DFI Annual Meeting in New Orleans.

So it is with pleasure that I have joined the DFI once again, continuing another tradition of the “Old Vulcan.”  My thanks to Theresa Engler, DFI’s Executive Director, who helped make this a reality.

## Mating Pipe Piles to Pipe Pile Caps

Pipe pile caps have been around as long as pipe piles, but mating them to a pile hammer via a pipe cap may be new to some users.  The diagram above (which, as you can see, dates from 1931) shows how this is done.

The cross-section shows three diameters of pipe piles mating with a pipe cap.  Pipe caps typically have steps to mate with more than one size of pipe pile.  It’s also possible to drive pipe caps “flat face” (with no steps) but you lose the alignment assistance of the cap when you do.

The outer two pipes mate with “male steps,” those which face the inside diameter of the pipe.  It’s necessary thus to know the ID of the pile, which usually means the OD and the wall thickness.  A little clearance is allowed to make mating simpler and to take into account the fact that pipe pile isn’t always perfectly round (especially at the ends, where it gets bent.)

On the small onshore caps, the steps are typically straight.  On the offshore caps, Vulcan typically put in a draft angle to make stabbing the pile easier.

With caps with multiple steps, it’s possible for the steps to interfere with each other because the diameter of one step is too small to accommodate the OD of the pile below it.  To avoid this problem requires some layout before the cap is machined.

Male pipe caps can be used with wall thicknesses thinner than originally intended with the use of welded shims.

The inner pile mates with the “female” portion of the cap, i.e., the OD of the pile.  This eliminates the ID mating problem but requires a completely different cap design.

Some other information is shown below.

## Pulling Adapters for Vulcan Extractors

Vulcan pile extractors were largely designed to extract sheet piling.  The standard connection had two (2) or three (3) holes that needed to be burned into the sheeting.  While this provided a very durable connection, it was time consuming and is not really applicable to piling such as wood piling.

Above is a diagram, taken from Vulcan’s literature around 1960, showing various types of pulling adapters for piling other than sheeting.  In addition to these there were two other types of connections that were used on Vulcan extractors:

1. The Heppenstall tongs, which were similar to the clamp used by the Nilens extractor.
2. The Wood Pile Puller.

## New Version of TAMWAVE Online Wave Equation Program Now Available

The completely revised TAMWAVE program is now available.  The goal of this project is to produce a free, online set of routines which analyse driven piles for axial and lateral load-deflection characteristics and drivability by the wave equation. The program is not intended for commercial use but for educational purposes, to introduce students to both the wave equation and methods for estimating load-deflection characteristics of piles in both axial and lateral loading.

We have a series of posts which detail the theory behind and workings of the program:

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## TAMWAVE 7: Analysis for a Cohesive Soil

With the analysis of the concrete pile in cohesionless soils complete, we turn to an example in cohesive soils.

The analysis procedure is exactly the same.  We will first discuss the differences between the two, then consider an example.

### Differences with Piles in Cohesive Soils

• The unit weight is in put as a saturated unit weight, and the specific gravity of the soil particles is different (but not by much.)
• Once the simulated CPT data was abandoned, the “traditional” Tomlinson formula for the unit toe resistance, namely $latex q_t = N_c c$, where $latex N_c = 9$, was chosen.
• The ultimate resistance along the shaft is done using the formula of Kolk and van der Velde (1996).  This was used as a beta method, for compatibility with the method used for cohesionless soils.  Unless the ratio of the cohesion to the effective stress is constant, the…

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## TAMWAVE 6: Results of Wave Equation Analysis

With the data entered for the wave equation analysis, we can now see the results.  There’s a lot of tabular data here but you need to read the notes between it to understand what the program is putting out.  If you are not familiar at all with the wave equation for piles, you need to review this as well.

 Time Step, msec 0.04024 Pile Weight, lbs. 15,000 Pile Stiffness, lb/ft 600,000 Pile Impedance, lb-sec/ft 57,937.5 L/c, msec 8.04688 Pile Toe Element Number 102 Length of Pile Segments, ft. 1 Hammer Manufacturer and Size VULCAN O16 Hammer Rated Striking Energy, ft-lbs 48750 Hammer Efficiency, percent 67 Length of Hammer Cushion Stack, in. 16.5 Soil Resistance to Driving (SRD) for detailed results only, kips 572.7 Percent at Toe 35.39 Toe Quake, in. 0.220 Toe Damping, sec/ft 0.07

For those familiar with the…

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## TAMWAVE 5: Wave Equation Analysis, Overview and Initial Entry

With the static analysis complete, we turn to the wave equation analysis.  TAMWAVE (as with the previous version) was based indirectly on the TTI wave equation program.  Although the numerical method was not changed, many other aspects of the program were, and so we need to consider these.

### Shaft and Toe Resistance

Most wave equation programs in commercial use still use the Smith model for shaft and toe resistance during impact.  Referencing specifically their use in inverse methods, Randolph (2003) makes the following comment:

Dynamic pile tests are arguably the most cost-effective of all pile-testing methods, although they rely on relatively sophisticated numerical modelling for back-analysis. Theoretical advances in modelling the dynamic pile-soil interaction have been available since the mid-1980s, but have been slow to be implemented by commercial codes, most of which still use the empirical parameters of the Smith (1960) model. In order to allow an appropriate…

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## TAMWAVE 4: Shaft Resistance Profile, ALP and CLM2

With the basic parameters established, we can turn to the static analysis of the pile, both axial and lateral.

### Shaft Resistance Profile

 Depth at Centre of Layer, feet Soil Shear Modulus, ksf Beta Quake,inches Maximum Load Transfer, ksf Spring Constant for Wall Shear, ksf/in Smith-Type Damping Constant, sec/ft Maximum Load Transfer During Driving (SRD), ksf 0.50 48.4 0.163 0.0022 0.009 4.03 45.394 0.009 1.50 83.9 0.163 0.0038 0.027 6.99 19.911 0.027 2.50 108.3 0.163 0.0050 0.045 9.02 13.572 0.045 3.50 128.1 0.163 0.0059 0.063 10.68 10.543 0.063 4.50 145.3 0.163 0.0067 0.081 12.11 8.730 0.081 5.50 160.6 0.164 0.0074 0.098 13.38 7.509 0.098 6.50 174.6 0.164 0.0080 0.116 14.55 6.623 0.116 7.50 187.6 0.164 0.0086 0.134 15.63 5.948 0.134 8.50 199.7 0.164 0.0091 0.152 16.64 5.414 0.152 9.50 211.1 0.164 0.0097 0.170 17.59 4.980 0.170 10.50 222.0 0.164 0.0102 0.188 18.50 4.618 0.188 11.50 232.3 0.164

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