PROWEAP

Introduction

PROWEAP

PROWEAP is a module that allows the back-analysis of driving data, making use of the GRLWEAP calculated bearing graph of the selected hammer. The bearing graph and the driving data are individually imported first, then the back-analysis is performed by comparing the measured energy and the measured set during driving with the bearing graphs to estimate the resulting SRD.

Note

The accuracy of the back-analysis is related to the accuracy of the blowcount versus SRD curves of the bearing graph for the relevant blow count and energies recorded in the driving data.

List of PROWEAP used abreviations in OPILE:

  • Set : the penetration generated by one hammer blow as measured at pile top at end of blow, expressed in m/bl

  • Rut : notation used by GRLWEAP for SRD, the resistance opposed to the pile by the soil during driving excluding the damping (or dynamic) effects.

  • EMX : the energy transmitted to the pile top as measured by the sensors

  • Entrhu : the calculated maximum transferred energy at the pile top


GRLWEAP

GRLWEAP is a one-dimensional Wave Equation Analysis program that simulates the pile response to pile driving equipment. GRLWEAP predicts driving stresses, hammer performance and the relation between pile bearing capacity and net set per blow. The last relationship being the blowcount versus SRD, if plotted for a series of incremental hammer energies, is the bearing graph. The produced bearing graph is dependent on hammer type, hammer efficiency (hammer energy), soil resistance and pile. More information about GRLWEAP can be found on their website: http://www.pile.com/pdi/products/grlweap.

The bearing graph is assembled by importing the GRLWEAP .GWO files, where the last table includes the blowcount versus SRD information. After importing, a bearing graph per pile section is produced and presented in the tab “Imported GRLWEAP Results”. Note that the minimum of a pile section where the bearing graph is applicable is not necessary the maximum of the previous section.

An example of a bearing graph for a particular soil profile and driving hammer is provided below.

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Example of PROWEAP (extract of Worked out Example 12).


Driving data

The required driving data must contain the pile penetration, the total number of blows and the measured energy transmitted to the pile top (EMX).

The PROWEAP module was originally written to handle the typical PDA driving data export file, where each line corresponds to 1 blow. However, the blow count is taken over penetration increments of length IP (IP is generally 0.25 m). Depth increments are calculated from the pile penetration measurements. The average of the energy of all the blows in that increment is then calculated and will be representative for that depth increment.

The imported driving data becomes one line per penetration increment in the tab “Imported Driving Records”.


Back analysis interpolation

For each increment, the following two interpolations are performed:

  1. From the calculated blow count per increment, derived from the driving files, the corresponding SRD values are extracted from each Blow Count vs. SRD curve from the bearing graph of the corresponding pile section (by linear interpolation).

  2. From the calculated average EMX per increment, derived from the driving files, the corresponding SRD value is linearly interpolated from the SRD values of the Blow Count vs. SRD curves, with respect to the curves ENTRHU energy.

The back analyzed SRD is plotted versus depth in the tab “Imported Driving Records”. When no enveloping Blow Count number or ENTHRU energy number was found to interpolate with, no data is plotted.


WEAP Import

To import GRLWEAP results, browse to the folder which contains the GRLWEAP output files.

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In the main GRLWEAP data grid input the pile section limits and also select the relevant WEAP files for each pile section (see below). Up to 10 files can be selected for each of 10 pile sections. It is necessary to specify top and bottom depths for each pile section, these are used later to look up the relevant GRLWEAP data when analyzing driving records data.

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After clicking on “Import Results”, PROWEAP will open and read the selected GRLWEAP files and extract the Blow Count vs. SRD data (usually last table in the .gwo file) according to the lookup parameters set as standard in the GRLWEAP Data Lookup Parameters:

_images/PROWEAPImportGRLWEAPdatalookupparameters.png

Note: the WEAP line identifier (e.g. “ENTHRU”). This is used to identify the lines in the WEAP file which precede the final output table, as shown in the figure below. This must be a keyword/words which can be used to identify this line, for example the whole of this line could be used.

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Some parameters are also imported from GRLWEAP, including damping coefficients etc.

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Driving Records Import

To import the driving records, Browse to the folder which contains the driving records and select the file(s) to import. The file delimiter is a reference for the .txt or .csv structured documents and can be ignored for excel files.

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After selection of the driving record data, the file is read and presented in the two windows below. Clicking on the Header Row in the left window will populate the combo boxes below with the list of column headers available in the driving records data. For each of these select the relevant column header that corresponds to blow number, elevation, max compressive stress, etc.

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Once the column headers for the driving record data have been selected, press “Import Records”. The default refusal criteria of 1000 Blows per meter can be overwritten by the user. This Refusal criteria also defines the Blows per meter limit for plotting.

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