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

vulcanhammer.net

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.

View original post

Advertisements

Back in the Saddle at the Deep Foundations Institute

dfi

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.

D100178
Vulcan’s choice of pipe cap design deserves some explanation. Below is a diagram of the three basic types of pipe caps in use, both during the heyday of Vulcan offshore hammers and now. Male Caps (left) were the standard Vulcan configuration. The cap is stepped for different pipe sizes and is fitted to the I.D. of the pipe. To align the leads and the pile (especially important with the batter piles common offshore) the pipes were passed through a stabbing bell (at the bottom) which itself was stepped to the O.D. of the piles. The arrangement was preferred with Vulcan’s customers (especially those in the Gulf of Mexico) because the cap is easy to modify and shim for different size piles and the stabbing bell is easy for the crane operator to thread the hammer assembly over the pile for driving. Female Caps (centre) was most common with the Menck hammers. All of the steps were mated to the O.D. of the cap. Although mating it to piles was more straightforward, since the maximum plate moment of the cap was in the centre, the thicker centreline of the male cap was an advantage. Flat Face Caps (right) were preferred by the diesel manufacturers such as Delmag (and later IHC and Pileco.) Since there are no alignment steps on the cap, all of the alignment takes place with the adjustable keys under the cap facing the O.D. of the pile. (It’s better to have two sets of keys than the one shown.) Although the cap is much simpler, the carrier required for the cap and keys can be complicated to produce.

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

vulcanhammer.net

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:

View original post 25 more words

TAMWAVE 7: Analysis for a Cohesive Soil

vulcanhammer.net

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…

View original post 3,746 more words

TAMWAVE 6: Results of Wave Equation Analysis

vulcanhammer.net

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.

General Output for Wave Equation Analysis
2018-01-06T10:13:03-05:00
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…

View original post 2,482 more words

TAMWAVE 5: Wave Equation Analysis, Overview and Initial Entry

vulcanhammer.net

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…

View original post 1,087 more words

TAMWAVE 4: Shaft Resistance Profile, ALP and CLM2

vulcanhammer.net

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

Shaft Resistance Profile

Shaft Segment Properties
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

View original post 1,756 more words

TAMWAVE 3: Basic Results of Pile Capacity Analysis

vulcanhammer.net

With the soil properties and lateral loads finalised, we can proceed to look at the program’s static results.  These are shown below.  We will concentrate on cohesionless soils in this post; a sample case with cohesive results will come later.

Pile Data
Pile Designation 12 In. Square
Pile Material Concrete
Penetration of Pile into the Soil, ft. 100
Basic “diameter” or size of the pile, ft. 1
Cross-sectional Area of the Pile, ft2 1.000
Pile Toe Area, ft2 1.000
Perimeter of the Pile, ft. 4.000
Soil Data
Type of Soil SW
Specific Gravity of Solids 2.65
Void Ratio 0.51
Dry Unit Weight, pcf 109.5
Saturated Unit Weight, pcf 130.5
Soil Internal Friction Angle phi, degrees 32
Cohesion c, psf
SPT N60, blows/foot 20
CPT qc, psf 211,600
Distance of Water Table from Soil Surface, ft. 50
Penetration of Pile into Water Table, ft. 50

View original post 1,894 more words