%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
%  New template code for TAMU Theses and Dissertations starting Fall 2012.  
%  For more info about this template or the 
%  TAMU LaTeX User's Group, see http://www.howdy.me/.
%
%  Author: Wendy Lynn Turner 
%	 Version 1.0 
%  Last updated 8/5/2012
%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%%                           APPENDIX B 
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

\phantomsection
\label{protocol}
\chapter{\uppercase{Electrical Resistivity Imaging and Induced Polarization Unknown Foundation Prediction Protocol}}
\section{Introduction}
\noindent This manual is intended to guide users for optimal setup and use of a survey using electrical resistivity imaging (ERI) and induced polarization (IP) for predicting the depth of unknown bridge foundations.  The ERI/IP Unknown Foundation Prediction Protocol can be used as a guide for investigating other subsurface infrastructure, but it is specifically tailored to bridge foundations. 

\section{Equipment}
\noindent The equipment used for this research and described herein is an Advanced Geosciences, Inc. (AGI) SuperSting R8/IP\texttrademark system.  The SuperSting R8/IP\texttrademark is capable of simultaneously measuring voltage potentials over eight channels allowing for faster data acquisition in the field.  The other necessary pieces of equipment are at least one 12 V deep cycle marine battery, a minimum of two sets of passive land cables with electrode take-outs at a minimum of 1 m spacing, stainless steel (SS) electrode stakes for one cable, and non-polarizable (NP) electrodes for the second cable. 

The SuperSting R8/IP\texttrademark can also be powered using a 12 V generator.  If a battery is used, two batteries can be connected in parallel to reduce the draw down on the battery or they can be connected by an AGI produced boost cable that switches between the two batteries internally as shown in Fig.~\ref{fig:supersting}.  The boost cable is recommended over connecting the batteries in parallel to prevent the operator from accidentally connecting the batteries in series.  Connecting the batteries in series can potentially damage the SuperSting R8/IP\texttrademark.  For optimal data collection (particularly for IP data collection) the external power should remain above 11.75 V.  Below 11.75 V the SuperSting R8/IP\texttrademark will switch to power saving mode and will reduce the maximum possible injected current, potentially lowering the data quality.  The SuperSting R8/IP\texttrademark will shut down below 11.5 V.  The current battery level can be constantly monitored on the SuperSting R8/IP\texttrademark in the bottom right corner of the screen on the top face of the box during surveys.

The current injecting SS electrodes are 45 cm long, 1 cm diameter stainless steel rods that connect directly to the cable take-outs.  The NP electrodes have a porous tip with a plastic casing that contains a copper rod surrounded by a copper sulfate solution in contact with the porous stone.  The NP electrode is shown in Fig.~\ref{fig:npapp}; the copper sulfate solution is the blue liquid inside the chamber.  The NP electrodes are used because polarization voltages at the contact between the SS electrodes and the ground can cause debilitating noise to the survey.  IP is a phenomenon captured during resistivity surveys, so the NP electrodes are not required.  It is shown in Chapter~\ref{chap:Experiment} that NP electrodes are necessary to collect data that are able to be numerically modeled for predicting the depth of bridge foundations.

\begin{figure}[!ht]
\centering 
\begin{subfigure}[SuperSting R8/IP\texttrademark]
{\includegraphics[width=50mm, height=60mm]{figures/supersting}\label{fig:supersting}}
\end{subfigure}
~~
\begin{subfigure}[Non-polarizable electrode]
{\includegraphics[width=50mm, height=60mm]{figures/npapp}\label{fig:npapp}}\end{subfigure}
\caption{Field equipment} 
\label{fig:stupersting}
\end{figure}

\subsection{Field Setup}
\label{equipsetup}
\noindent To collect quality ERI and IP data simultaneously two sets of electrodes are necessary.  The SS electrodes should be pushed or driven straight into the ground until the cross bar is approximately 2 cm above the ground surface in a straight line at set intervals.  If the soil is very loose, such as a loose sand, see the section on Trouble Shooting.  The NP electrodes should be buried approximately 0.3 m from each stainless steel electrode so that the full porous stone tip is in the ground.  The stone must also have good contact with the ground.  If the ground is soft, the soil can be slightly loosened and the NP electrode pushed into the soil.  If the ground is very stiff, a hole is dug deep enough so the stone can be buried and the soil is mixed with distilled water and back filled so the stone can be pushed in with out damaging it.  If the porous stone does not have good contact with the soil (i.e. there are voids around the stone caused by soil clumping after the hole is dug) the IP decay curves will appear jagged and will be removed from the data set.

The electrode cables are numbered for each electrode take-out where an electrode is connected.  Each NP electrode is connected to the cable take out using alligator clips so that the copper rod exposed above the chamber is in contact with the takeout or using alligator to alligator cables (Fig.~\ref{fig:npconnect}).  The SS electrode crossbars must be in contact with the cable take-out during a survey.  Each electrode has a spring attached to it so that the cable is held in place on the crossbar during the survey.  The spring over the cable holding it in place is seen in Fig.~\ref{fig:electrodeset} along with the minimum depth of installation for each electrode.
\begin{figure}[!ht]
\centering 
\begin{subfigure}[Non-polarizable electrode connection]
{\includegraphics[width=70mm, height=60mm]{figures/npconnect}\label{fig:npconnect}}\end{subfigure}
~~
\begin{subfigure}[Electrode installation]
{\includegraphics[width=70mm, height=60mm]{figures/electrodeset}\label{fig:electrodeset}}
\end{subfigure}
\caption{Electrode connections} 
\label{fig:connect}
\end{figure}

The Texas A\&M University (TAMU) system is four cables, with electrode take-outs spaced every 2 m.  Two cables are numbered 1--14 and two are numbered 15--28.  For a typical ERI/IP data set, one of each cable section is connected to another so that two long cable sections are made numbered 1--28.  For bridge foundations, the electrodes should be spaced equal to or less than the width of the foundation tested.  The electrodes should be installed so that the SS electrodes are on one side of the foundation and the NP electrodes are on the other side of the foundation for a pile, column with a spread footing, or column with an embedded pile cap, with the pile/column in the center of the array as shown in Fig.~\ref{setup}.  If an abutment is tested or a foundation that is larger than the take-out spacing above the ground, the line of SS electrodes should be as close to the abutment as possible and straight along the side of the abutment.  The line of NP electrodes should be offset from the SS line with approximately 0.3 m space between the two lines.  

A schematic of the field set up is below in Fig.~\ref{setup} including the cable layout.  Note that sections of the cables are removed for space in the schematic but the continuous string of electrodes are necessary in the field.   The 28th takeout with the NP electrodes must be connected to the low address port and the 1st takeout with the SS electrodes must be connected to the high address port.  The free ends of the cables away from the test box should \emph{not} be connected.  The cable sections must be installed exactly as shown to use the command file described in the following section.
\begin{figure}[!ht]
\setlength{\unitlength}{0.8cm}
\centering 
\begin{picture}(18.89,5)
\put(0,0){\includegraphics[width=\textwidth]{figures/electrodelineshort}}
\put(2.75,3.1){1}
\put(4.15,3.1){2}
\put(5.6,3.1){3}
\put(7,3.1){4}
\put(8.35,3.1){13}
\put(9.75,3.1){14}
\put(11.25,3.1){15}
\put(12.65,3.1){16}
\put(14.1,3.1){25}
\put(15.55,3.1){26}
\put(16.95,3.1){27}
\put(18.4,3.1){28}
\put(0.6,1.2){\rotatebox{90}{SuperSting}}
\put(2.6,1.5){28}
\put(4,1.5){27}
\put(5.45,1.5){26}
\put(6.9,1.5){25}
\put(8.35,1.5){16}
\put(9.75,1.5){15}
\put(11.25,1.5){14}
\put(12.65,1.5){13}
\put(14.25,1.5){4}
\put(15.7,1.5){3}
\put(17.1,1.5){2}
\put(18.55,1.5){1}
\put(2.75,3.85){High Address}
\put(2.75,0.75){Low Address}
\end{picture}
\caption{Field setup of SuperSting R8/IP\texttrademark with 28 take-outs}
\label{setup}
\end{figure}


\section{File Writing}
\noindent Prior to field testing, a command file should be written in the office and loaded on the SuperSting R8/IP\texttrademark for later use.  The SuperSting R8/IP\texttrademark comes with software to write command files and to add/remove files to the system.  AGI SuperSting Administrator automatically creates data collection files for the Wenner, Schlumberger, dipole-dipole, pole-dipole, pole-pole, and inverse Schlumberger arrays.  For bridge foundations the dipole-dipole array is preferred as it yields the highest quality data for foundations.  

From the Command Creator interface in the Administrator program, type 28 in the number of electrodes section and select 'Dip-Dip' as the array type when using a field setup with 28 NP and 28 SS electrodes as shown in Fig.~\ref{setup}.    Beneath the number of electrodes is the option for `Extended data coverage.'   Checking this will force the command file to be written so that all eight channels are used to measure potentials for each measurement instead of only those necessary for the dipole-dipole array.  Extended data coverage will allow the user to gather more data without adding time to the survey.  Because some data from the basic dipole-dipole array may not meet the criteria to be used in the model, collecting more data around these points increases the number of usable data in the model and the overall quality of the model.  

The other two options, `Create reverse array' and `Include reverse array' can be used if proving data quality is necessary.  Theoretically, if an array is run from left to right or right to left the results should be the same.  These options allow the researcher to show that the data is in fact the same forward and back, but it is not necessary for determining the depth of a bridge foundation.  The electrode spacing units must also be specified.  The best way to ensure an acceptable signal to noise ratio for the dipole-dipole array is to keep the ``Max n'' less than or equal to eight.  If an $n$ of eight is used with the electrodes spaced every 1 m the maximum distance between the current sink and current source is 8 m.   The ``Max Dipole'' should be less than or equal to six for this array.  The dipole is the factor that the spacing is multiplied by between the current and potential reading electrodes.  If a max dipole of six is used with the electrodes spaced every 1 m the maximum distance between the set of current electrodes and potential electrodes is 6 m.  

The last step before creating a command file is to select 'Use IP'.  This changes the measurement times from the shorter ERI only survey times to the longer IP measurement times.  The options for an IP survey are 0.5, 1.0, 2.0, 4.0, and 8.0 seconds.  For bridge foundations, two seconds is recommended.  Any shorter period yields lower quality results but longer time windows only add to the length of time for the survey to run without improving results.  This is proved in Chaper~\ref{chap:Experiment}.  

Once all of these options are selected name the program in Prog. ID.  It is recommended to name the file something that informs the user in the field what the file is designed for.  The Prog. ID will be the name shown on the SuperSting.  The SuperSting can hold several files so to avoid confusion, for example, the name '28ddNP' tells the user how many electrodes should be installed, to use NP electrodes as well as SS (all surveys require SS electrodes), and that this file uses the dipole-dipole array.  After the command file is named, click `Save Cmd File.'

The command file is now ready to be used in the field if only SS electrodes are used.  Note that it is possible to collect ERI and IP data using only SS electrodes.  For optimal results, NP electrodes should be used as well.  In order to use NP electrodes the command file must be altered.  Command files have three required sections, `:header', `:geometry', and `:commands.'  After automatically creating a command file, the `:header' section should not be altered, this section gives the SuperSting R8/IP\texttrademark and the data processing system information about the survey such as the name of the file and the array type.  The `:geometry' section is the first section that must be altered.  

The three numbers in the geometry section refer to the electrode ID, the location in the $x$--direction, and the location in the $y$--direction.  The electrode ID is correlated to the ID numbers on the cable sections, this is why it is important to set up the cables as shown in Fig.~\ref{setup}.  The current geometry in the file is the geometry for the NP electrodes so another 28 electrodes need to be added for the SS electrodes.  Even though the two cables connected to the stainless steel electrodes are also labeled 1--14 and 15--28, the electrode ID for the stainless steel electrodes should be numbered 29--56.  The $x$--location, on the other hand, must correspond to the $x$--location in the field.  This means that the 29th electrode ID corresponds to an $x$--location of 27 m away from the switch box.  The sections of the geometry section for a 28 electrode survey with NP electrodes is included in Table~\ref{tab:geometry}.

\begin{table}[H]
\centering
\caption{Geometry of a Command File with NP Electrodes.}
\begin{tabular}{|c c c|}
\hline
  &  :geometry  &  \\
\hline
1, & 0.00, & 0.00 \\
2, & 1.00, & 0.00\\
3, & 2.00, & 0.00\\
... & ... & ...\\
26, & 25.00, & 0.00\\
27, & 26.00, & 0.00\\
28, & 27.00, & 0.00\\
29, & 27.00, & 0.00\\
30, & 26.00, & 0.00\\
... & ... & ...\\
55, & 1.00 & 0.00\\
56, & 0.00 & 0.00\\
\hline
\end{tabular}
\label{tab:geometry}
\end{table}

After adding the extra cable sections to the ':geometry' section of the command file the ':commands' section must also be updated.  The geometry section has been updated for the 29--56 electrode ID as the SS electrodes.  The SS electrodes inject the current into the ground, therefore the electrode IDS corresponding to 29--56 should inject the current in the command file.  `A' and `B' indicate current electrodes and `P1' through `P9' indicate potential measuring electrodes.  So, all the `A' and `B' electrode IDs must be updated to the current electrode IDs that corresponds to the same $x$--location as the initial NP electrode.  For example, this first command line

;A,B,P1,P2,P3,P4,P5,P6,P7,P8,P9,channels

2,1,3,4,5,6,7,8,9,10,11,12345678

\noindent should be updated to 

;A,B,P1,P2,P3,P4,P5,P6,P7,P8,P9,channels

\emph{55},\emph{56},3,4,5,6,7,8,9,10,11,12345678

\noindent This can be done one line at a time or easily calculated and made into a string in a program like \emph{Microsoft Excel}.  After these updates are made, the command file is complete for a 28 electrode array using stainless steel and NP electrodes.

\subsection{SuperSting Settings}
One the equipment is setup and powered on there are a series of settings that must be addressed before running a test.  An image of each screen is included for ease of use.  From the home screen  in Fig.~\ref{home}, press ``1'' on the keypad to select the Automatic mode.  Automatic mode indicates that the SuperSting R8/IP\texttrademark will automatically switch between the electrodes following a previously written command file.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\centering
AGI SUPER STING
\vskip 1mm
Date: 19860125 Time: 08:49:41
\begin{enumerate}
\item Automatic mode
\item Manual mode
\item Test mode
\item Log settings
\item File management
\item System settings
\item System information
\end{enumerate}
\raggedright
Select mode:
\vskip 1mm
Current method: RES/IP
\vskip 1mm
Battery voltage: 12.53 V
\end{spacing}
\vskip 3mm
\end{framed}
\caption{AGI home screen}
\label{home}
\end{figure}
This screen can also be used to run tests of the equipment to check that it is working and to adjust the display settings.

The next screen, Fig.~\ref{autoset}, allows the user to open and existing file if a survey has already been started or to created a new file for a new survey.  This screen contains all the information pertaining the current survey that is open.  If no data file is open, the screen will look like Fig.~\ref{autoset}.  To create a new survey, press ``2'' on the keypad.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\raggedright
M1 Automatic Mode

\begin{enumerate}
\item Select data file
\item Create data file
\item Edit Survey
\end{enumerate}
\vskip 1mm
Command file:$<$none$>$
\vskip 1mm
Data file:$<$none$>$
\vskip 1mm
Scaling factor =
\vskip 1mm
x =\hspace{1 in}  y =\hspace{1 in}   z=\hspace{1 in}
\vskip 1mm
Command line \#: \hspace{1 in} /
\vskip 1mm
Roll-along:
\vskip 5mm
MEA: Start measurement
\vskip 5mm
MEN: Up Level
\end{spacing}
\vskip 3mm
\end{framed}
\caption{Automatic mode settings}
\label{autoset}
\end{figure}
Upon selecting create data file the current survey must be named.  Once a name is typed into the SuperSting R8/IP\texttrademark press ENTR to continue the setup.

Fig.~\ref{command} is what the command file selection screen looks like.  The command files shown in Fig.~\ref{command} have already been loaded on the SuperSting R8/IP\texttrademark using the AGI Administrator program and a cable to connect the equipment to a laptop or computer.  The ``$+/-$ keys are on the keypad.  The command file ``28ddNP'' is used for most of this research as a 28 electrode array with NP electrodes and using the dipole-dipole array.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\centering 
Select Command File
\vskip 1mm
\raggedright
dd28res
\vskip 1mm
28ddNP
\vskip 1mm
wen56res
\vskip 25mm
+/- Scroll List
\vskip 1mm
Press ENTR to Select
\vskip 5mm
\end{spacing}
\end{framed}
\caption{Select command file screen}
\label{command}
\end{figure}

The geometry of the field is included in Fig.~\ref{datafile}.  Each option will blink, once the desired quantity is selected press enter to move to the next option.  If, for example, feet are used instead of meters, press the ``+'' key to change the option to feet, then press enter and feet will be used.  Now the scaling factor will be blinking.  Enter the electrode spacing in the field, a 0.85 m spacing is used for this survey.  All other options should look like Fig.~\ref{datafile}.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\centering 
Data File Setup

\raggedright
\vskip 5mm
Command File: 22ddNP

\vskip 5mm
Measure Units= meter
\vskip 1mm
Scaling factor= 0.50 m
\vskip 1mm
Start X=0.00\hspace{0.5in}m
\vskip 1mm
Start Y=0.00\hspace{0.5in}m
\vskip 1mm
Start Z=0.00\hspace{0.5in}m
\vskip 1mm
Roll-along=NO
\vskip 1mm
End Address=OFF
\vskip 5mm
F1: OLD \hspace{0.5in} BSP:BSP \hspace{0.5in} ENTR:ENTER
\vskip 5mm
\end{spacing}
\end{framed}
\caption{Data file setup}
\label{datafile}
\end{figure}

The SuperSting allows the user to exit the setup with the screen shown in Fig.~\ref{continue}.  Press ``ENTR'' to continue to setup this survey.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\centering 
\vskip 25mm
Press ENTR to continue setup

OR

Press MEN to exit setup
\vskip 25 mm

\end{spacing}
\end{framed}
\caption{Continue setup screen}
\label{continue}
\end{figure}

For surveys that use both NP and SS electrodes, the distributed switch system must be used.  Press ``2'' when the screen looks like Fig.~\ref{switch}.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\raggedright
Select Switch System Type

\begin{enumerate}
\item Switch Box
\item Distributed
\end{enumerate}
\end{spacing}
\vskip 25 mm
\end{framed}
\caption{Switch system type}
\label{switch}
\end{figure}

The SuperSting R8/IP\texttrademark has the term ``R8'' in its name because it is an eight channel instrument.  This means that it can measure the voltage potentials over eight channels simultaneously, reducing the time for each survey.  Press ``2'' to use all eight channels as shown in Fig.~\ref{eight}.
\begin{figure}
\begin{framed}
\begin{spacing}{0.5}
\raggedright
Select R1 or R8 Switch System

\begin{enumerate}
\item Single Channel
\item Eight Channel
\end{enumerate}
\end{spacing}
\vskip 35 mm
\end{framed}
\caption{Switch system channels}
\label{eight}
\end{figure}

Fig.~\ref{cable} is the screen that allows the user to setup the cable sections.  The Texas A\&M system has four cable sections that should be connected as shown in Section~\ref{equipsetup}.  Two use 28 NP and 28 SS electrodes the cable address screen must look like Fig.~\ref{cable} so the two sets of two cables can be used.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\centering
Cable Address Setup

\begin{enumerate}
\item Add cable section
\item Clear table
\end{enumerate}
\raggedright
\hspace{0.15in} Elec Low: \hspace{2.25 in} High: \hspace{1 in}
\vskip 1mm
\hspace{0.2in}Section \hspace{1 in} ElecL \hspace{0.95 in} ElecH
\vskip 1mm
\hspace{0.2in}1 \hspace{1.5 in} 1 \hspace{1.25 in} 28
\vskip 1mm
\hspace{0.2in}2 \hspace{1.5 in} 29 \hspace{1.16 in} 56
\vskip 5mm
+/- Scroll \hspace{0.5in} ENTR:Edit \hspace{0.5in} F3:Delete
\vskip 1mm
MEN: Exit
\vskip 5mm
\end{spacing}
\end{framed}
\caption{Cable address setup}
\label{cable}
 \end{figure}
 The measurement settings should be set to look like Fig.~\ref{measure}.  Press the number on the keypad that corresponds to the field that needs to be changed in order that activate the setting.  The measure time of two seconds is the proven ideal time for surveys of unknown bridge foundations.  
 \begin{figure}[!ht]
 \begin{framed}
 \begin{spacing}{0.5}
 \centering
 Measurement Settings
 
 \begin{enumerate}
 \item Cycles: 2
 \item Max error: 2.0
 \item Max current: 2000 mA
 \item Measure time: 2 s
 \item Separate potential: OFF
 \item Measure mode: RES/IP
 \item Single--Step Cmd Lines: OFF
 \item Use Address Table
 \item Defaults: $<$none$>$
 \item Save user defaults
 \end{enumerate}
 \vskip 5mm
 MEN: Exit
 \vskip 5mm
 \end{spacing}
 \end{framed}
 \caption{Measurement settings}
 \label{measure}
 \end{figure}
 
 The survey is now ready to be run with the current settings.  Before returning to the screen from Fig.~\ref{datafile}, the SuperSting R8/IP\texttrademark forces the user to consider running a contact resistance test.  This test will alert the user if there is an installation problem with an electrode before a survey is conducted.  First, the start address and end address must be entered to only check the SS electrodes.
 \begin{figure}[!ht]
 \begin{framed}
 \begin{spacing}{0.5}
 \centering 
 Contact Resistance Test
 \vskip 1mm
 \raggedright
\begin{enumerate}
\item Start address:
\item End address:
\end{enumerate}
 F1: Start/Again
 \vskip 1mm
 F2: Skip \& Continue
 \vskip 10mm
 MEN: Exit
 \end{spacing}
 \vskip 5mm
 \end{framed}
 \caption{Contact resistance test}
 \label{CR}
 \end{figure}

The Start address must be 29  and the End address 56 to match the command file that has been described and the cable setup shown.  After these are entered, press ``F1'' to start the test.  If the electrodes are connecting properly, the test will inject current in the ``A'' electrode and measure the resistance on the next electrode in the line (the ``B'' electrode).  The results will be shown below the start and end addresses as shown in Fig.~\ref{CRT}.
\begin{figure}
 \begin{framed}
 \begin{spacing}{0.5}
 \centering 
 Contact Resistance Test
 \vskip 1mm
 \raggedright
\begin{enumerate}
\item Start address: \hspace{1in} 29
\item End address:   \hspace{1.08in} 56
\end{enumerate}
 F1: Start/Again
 \vskip 1mm
 F2: Skip \& Continue
 \vskip 5mm
 A=31 \hspace{1in} B=32 \hspace{1in} R = testing
 \vskip 1mm
 A=30 \hspace{1in} B=31 \hspace{1in} R = 179.9
 \vskip 1mm
 A=29 \hspace{1in} B=30 \hspace{1in} R = 185.9
 \vskip 1mm
 MEN: Exit
 \end{spacing}
 \vskip 5mm
 \end{framed}
  \caption{Contact resistance test}
  \label{CRT}
 \end{figure}
 For surveys with NP electrodes, a contact resistance below 300 $\Omega$ is ideal.  If the contact resistance is over 2,000 $\Omega$, refer to the Trouble Shooting section because above 2,000 $\Omega$ resistance the maximum current injected will automatically be below 2,000 mA.  If the contact resistance test stops and reads HVOVL this means that the stake is not properly connected.  HVOVL stands for high voltage overload.  Check the electrode pair and restart the test to ensure that all electrodes are installed correctly.HVOVL will also appear if the electrodes are installed incorrectly and the current injecting electrodes are the NP electrodes instead of the SS electrodes.

Once the contact resistance test is complete, press MEN to exit the test.  This will return the user to the screen with the survey information now loaded as shown in Fig.~\ref{final}.  Note that the information shows the user what command file is being used, what the data file is named, the electrode spacing, and the command line that the survey is currently on.  If the survey is stopped at any time this screen will tell the user on which command line the survey will restart.
\begin{figure}[!ht]
\begin{framed}
\begin{spacing}{0.5}
\raggedright
M1 Automatic Mode

\begin{enumerate}
\item Select data file
\item Create data file
\item Edit Survey
\end{enumerate}
\vskip 1mm
Command file:28ddNP
\vskip 1mm
Data file:DavidPile3
\vskip 1mm
Scaling factor = 0.5m
\vskip 1mm
x =\hspace{0.25 in}  0.0 m \hspace{0.5 in}y =\hspace{0.25 in} 0.0 m \hspace{0.5 in}  z=\hspace{0.25 in} 0.0 m \hspace{0.5 in}
\vskip 1mm
Command line \#: \hspace{1 in} /
\vskip 1mm
Roll-along:
\vskip 5mm
MEA: Start measurement
\vskip 5mm
MEN: Up Level
\end{spacing}
\vskip 3mm
\end{framed}
\caption{Final screen before starting a survey}
\label{final}
\end{figure}
Once the user is satisfied with the installation of the electrodes press ``MEA'' to start the survey.

\section{Trouble Shooting}
\noindent If the instructions for field installation, writing a command file, and equipment setup are followed exactly the SuperSting R8/IP\texttrademark will collected a field survey.  The quality of the survey is related to the soil type and the amount of current that can be injected into the subsurface.  If the contact resistance of a stake is over 1,000 $\Omega$ the value can be lowered using different methods.  First, wet the ground around the stake with some water, if the water contains some salt the contact with the ground will be improved.  If watering the stake does not lower the contact resistance, multiple stakes can be driven around the initial stake and attached to each other to create a cluster of electrodes.  This can easily and quickly be done for one or two electrodes, but is not advisable if all 28 electrodes have contact resistances that are too high.  The final remediation for electrodes is to dig a hole where the electrode is located and fill the hole with a mixture of water and bentonite or water and local mud.  Bentonite holes are useful if the site consists of sand and gravel and will reduce contact resistances by over half of the original value.  

If the contact resistance is less than 300 $\Omega$ but the IP decay curves do not match the calculated IP curves the NP electrodes need to be adjusted.  First, ensure that all electrodes are connected to the cable takeouts and that there is copper sulfate and distilled water in each electrode.  The tips of the electrodes should always be moist.  If they are stored for long periods of time, the porous stones should be stored in distilled water.  If they are being used on a regular basis, insert damp sponges into the caps covering the stones so they do not dry out.

Once it is insured that the electrodes are properly maintained and in contact with the cable takeouts, the soil around the NP electrodes can also be wet with water to increase the contact with the stone.  If the ground is too stiff to push the electrode into the ground, dig a hole and break up the removed soil.  Mix this soil with water and back fill the hole so the electrodes can be pushed into the soil.  If the soil is loose sand or gravel the hole can be filled with bentonite and water or local mud before the electrodes are pushed into the hole.  This will ensure that the small signal does not dissipate while measurements are being taken.

\section{Data Processing}

\noindent The data processing described herein uses the commercial software EarthImager created by Advanced Sciences, Inc.  EarthImager is designed to specifically process the data files output by the SuperSting  R8/IP\texttrademark .  Before loading a command file, the user must specify the settings for the forward modeling, the inversion method, and the inversion of the resistivity and IP data.  A good starting point for changing these settings is to first set the defaults by using the drop down arrow in the bottom of the pop up and selecting ``Surface'' as the setting.  Next, select ``Robust Inversion'' as the inversion method on the Initial Settings tab.  The Forward Modeling tab does not need to be altered so next click the Resistivity Inversion tab and remove the option for Error Reduction by un-checking the box.  Make sure that the Starting Model is Average Apparent Resistivity.  On the IP Inversion tab, select Linear IP Inversion as the IP Inversion Method and check the box for Positivity.  Finally, change the Start to two on the IP Window Range.  Typically, for bridge foundations, the first IP window is very noisy, this will improve the calculated decay curves.  

Open the data file using the Read Data option from the File drop down menu or the folder with a green arrow.  Next, if survey data is available, load the terrain file from the File drop down menu.  A terrain file is simply a list of the electrode ID with its associated elevation.  It is easiest to open an example terrain file (*.trn) and to change the relative elevations and add or remove electrodes if necessary.  EarthImager will alert the user of any data that will be removed prior to inverting the data if over 10\% is marked for removal due to the user settings.  Next click the green arrow to start the inversion.  Once the inversion is complete, consider where the foundation is located relative to the survey line and check the RMS value for the inverted resistivity section and the inverted IP section.  If no large anomaly is seen on the IP inversion where the foundation is located or if the RMS values are above 5\%, on the View pull down menu open the Data Misfit Histogram from the Convergence and Data Misfit option (Fig.~\ref{data})
\begin{figure}[!ht]
\centering
\includegraphics[width=0.75\textwidth]{figures/datamisfit}
\caption{Data misfit histogram}
\label{data}
\end{figure}
Removing this data will reduce the dumber of poorly-fit data in the forward model and will decrease the RMS of the inversions to an acceptable level.  Engineering judgment must be used to determine the amount of data that can be removed from the data and to still be a good representation of the subsurface.  As a rule of thumb, removing more than 20\% of the data is extreme and indicates that a new survey of the foundation needs to be carried out.

After the noisy data is removed, rerun the inversion and both RMS values should now be reduced.  The final results of a foundation with no topographic data is shown in Fig.~\ref{foundation}.
\begin{figure}[!ht]
\setlength{\unitlength}{0.8cm}
\centering 
\begin{picture}(18.89,11)
\put(0,0){\includegraphics[width=\textwidth]{figures/foundation}} 
\put(0,10){(a)}
\put(0,4.6){(b)}
\end{picture}
\caption{Output of EarthImager of a bridge foundation survey:  (a) inverted resistivity section; (b) inverted IP section}
\label{foundation}
\end{figure}
The foundation of this bridge is located 13 m along the line and is seen as a large highly chargeable zone in the Inverted IP section.  The inverted resistivity section has a zone of high resistivity at the top of the pile, but nothing is seen below this point.  The actual depth of this foundation is 6.08 m.  It is difficult to estimate the depth of the foundation using the IP section because the highest zone of chargeability stops around 5 m, but the region more chargeable than the surround soil penetrates through the inversion.  For this reason, the post processing algorithm is used.

After each inversion three files are automatically saved in the folder where the data file is opened from.  These files are the configuration settings (the command file), the inversion output file, and the data file.  Each of these can be manually inspected by opening them in a text editor like the open source Programmer's Notepad.    When EarthImager calculates and inverts the apparent resistivity and  apparent chargeability pseudosections the calculated data and inverted data are saved in an output text file that EarthImager uses to visually display the results.  This text file includes the following information in the order listed below: 
\begin{enumerate}
\item \label{it:one} Headings
\item \label{it:two} Summary of data and electrodes
\item \label{it:three} Initial settings
\item \label{it:four} Surface electrode locations
\item \label{it:five} Commands, raw V/I, Geometric Factor, Apparent Resistivity, IP (V/V), Correlation
\item \label{it:six} Mesh size
\item \label{it:seven} Node location in $X$ (m)
\item \label{it:eight} Node location in $Y$ (m)
\item \label{it:nine} Timing
\item \label{it:ten} Convergence
\item \label{it:leven} IP Convergence 
\item \label{it:twerve} Output of data and model of all iterations
\end{enumerate}
The inputs necessary for the post processing code are Item~\ref{it:six}, Item~\ref{it:seven}, Item~\ref{it:eight}, and Item~\ref{it:twerve}.  These are copied and pasted into the MATLAB\textregistered m--file in the labeled sections.  The following inputs are necessary from the user for the code to run: number of elements, number of elements in the $x$--direction, number of elements in the $y$--direction, and the range of $x$--nodes where the foundation is located.  The last item is found using the known horizontal distance of the foundation at the time of testing.  For example, if the foundation is located 6.5 m from the start of the line and is 1 m wide these nodes are identified in the $X$--node section.  The node number is first, followed by the distance in the $x$--direction in m.  If node 35 is at 6.5 m and node 39 is at 7.5 m 35:39 (where the colon indicates a range in MATLAB\textregistered) should be used as the input for the foundation.  No other inputs are necessary for the code to run.

The MATLAB\textregistered code has four main sections: loading the data, organizing the elements into a numerical pseudosection, isolating the elements around the bridge foundation, and calculating the vertical ratio of these elements as well as the slope of these elements.  The vertical ratio of the elements and the slope of the elements are used instead of the inverted chargeability values because chargeability is not an intrinsic value.  Therefore a range of typical chargeability for reinforced concrete is be misleading.  The results from Fig.~\ref{foundation} are used as this post processing example.  First, the ratio of the elements are calculated as
\begin{equation}
R_{i} = \epsilon_{i}/\epsilon_{i+1}
\end{equation}
\noindent where $R_{i}$ is the ratio value, $\epsilon_{i}$ is the $i^{th}$ element, and $\epsilon_{i+1}$ is the element directly below it.  Only the elements that coincide with the location of the foundation are plotted.  The chargeability ratio plot from Fig.~\ref{foundation} is shown in Fig.~\ref{fig:charge}.

\begin{figure}[!ht]
\setlength{\unitlength}{0.8cm}
\centering
\begin{picture}(18.89,12)
\put(1.2,0){\includegraphics[width=0.85\textwidth]{figures/chargeapp}}
\put(5,4.28){Element 1}
\put(5,3.74){Element 2}
\put(5,3.2){Element 3}
\put(5,2.66){Element 4}
\put(5,2.12){Data Depth}
\put(5,1.58){Foundation Depth}
\put(3.2,0.75){0}
\put(4.2,0.75){0.2}
\put(5.42,0.75){0.4}
\put(6.67,0.75){0.6}
\put(7.93,0.75){0.8}
\put(9.22,0.75){1.0}
\put(10.42,0.75){1.2}
\put(11.71,0.75){1.4}
\put(12.94,0.75){1.6}
\put(14.2,0.75){1.8}
\put(15.59,0.75){2}
\put(2.5,1.2){-10}
\put(2.8,2.14){-9}
\put(2.8,3.125){-8}
\put(2.8,4.10){-7}
\put(2.8,5.075){-6}
\put(2.8,6.05){-5}
\put(2.8,7.06){-4}
\put(2.8,8.03){-3}
\put(2.8,9.01){-2}
\put(2.8,9.98){-1}
\put(2.8, 10.95){ 0}
\put(1.75,4.5){\rotatebox{90}{Depth (m)}}
\put(9.27,0){$R$}
\end{picture}
\caption{Chargeability ratio}
\label{fig:charge}
\end{figure}
The horizontal black line in Fig.~\ref{fig:charge} is the depth to which the data is collected and the horizontal blue line is the depth of the foundation.  The first criteria for estimating the foundation depth is the maximum $R$ value for all elements on the foundation.  For  Fig.~\ref{fig:charge} this occurs at -4.6  m.  The depth beneath the maximum is taken as the predicted depth for this criterion, or -5.7 m.

Next, the slope of the elements are calculated such that 
\begin{equation} 
\frac{\textrm{d} \epsilon}{\textrm{d} y} = \frac{\epsilon_{i + 1}-\epsilon_{i}}{\textrm{d} y}
\end{equation}
where $\epsilon$ are the vertical elements and ${\textrm{d} y}$ is vertical change in the $y$ direction.  The criterion for the slope shown in Fig.~\ref{fig:slopeapp} is the element depth beneath where all of the elements on the foundation are the minimum.

\begin{figure}[!ht]
\setlength{\unitlength}{0.8cm}
\centering
\begin{picture}(18.89,12)
\put(1.2,0){\includegraphics[width=0.85\textwidth]{figures/slopeapp}}
\put(5,4.28){Element 1}
\put(5,3.74){Element 2}
\put(5,3.2){Element 3}
\put(5,2.66){Element 4}
\put(5,2.12){Data Depth}
\put(5,1.58){Foundation Depth}
\put(2.85,0.75){-40}
\put(4.4,0.75){-30}
\put(6,0.75){-20}
\put(7.55,0.75){-10}
\put(9.4,0.75){0}
\put(10.8,0.75){10}
\put(12.425,0.75){20}
\put(14,0.75){30}
\put(15.5,0.75){40}
\put(2.5,1.2){-10}
\put(2.8,2.14){-9}
\put(2.8,3.125){-8}
\put(2.8,4.10){-7}
\put(2.8,5.075){-6}
\put(2.8,6.05){-5}
\put(2.8,7.06){-4}
\put(2.8,8.03){-3}
\put(2.8,9.01){-2}
\put(2.8,9.98){-1}
\put(2.8, 10.95){ 0}
\put(1.75,5.5){\rotatebox{90}{Depth (m)}}
\put(9.27,0){$\frac{\textrm{d} \epsilon}{\textrm{d} y}$}
\end{picture}
\caption{Slope of the elements}
\label{fig:slopeapp}
\end{figure}

The minimum slope also occurs at -4.7 m, so the predicted depth is -5.7 m.  The average of the two criteria is the predicted depth, -5.7 m for this example.  The actual foundation is embedded 6.08 m, thus the foundation is under predicted by 0.38 m.

If this foundation was a truly unknown foundation the results of the post processing algorithm may be adjusted based on an acceptable level of risk.  A probability of non-exceedance curve has been created to account for the uncertainties in these predictions.  The curve is shown in Fig.~\ref{fig:problogapp}.
\begin{figure}[!ht]
\setlength{\unitlength}{0.8cm}
\centering
\begin{picture}(18.89,11.75)
\put(1.2,0){\includegraphics[width=0.85\textwidth]{figures/poelog}}
\put(3.2,0.75){0}
\put(5.425,0.75){0.5}
\put(8.15,0.75){1}
\put(10.425,0.75){1.5}
\put(13.15,0.75){2}
\put(15.4,0.75){2.5}
\put(2.3,1.2){$10^{-6}$}
\put(2.3,2.9){10$^{-5}$}
\put(2.3,4.5){10$^{-4}$}
\put(2.3,6.1){10$^{-3}$}
\put(2.3,7.8){10$^{-2}$}
\put(2.6,9.4){0.1}
\put(2.95,11){1}
\put(1.05,1.9){\rotatebox{90}{Probability that the foundation is more}}
\put(1.55,1.75){\rotatebox{90}{ shallow than the depth predicted by IP}}
\put(7.925,0){$\xi = \frac{D_{\textrm{actual}}}{D{\textrm{predicted}}}$}
\end{picture}
\caption{Probability of non-exceedance curve}
\label{fig:problogapp}
\end{figure}
Using this curve that has been calculated using experimentally predicted foundations and the actual depth foundation depth, the predicted depth can be reduced or increased.  The variable $\xi$ is the ratio of the actual depth of the foundation to the predicted depth of the foundation.  It is analogous to a factor of safety.  Using Fig.~\ref{fig:problogapp}, if the predicted depth of the foundation shown herein is used, so 5.7 m, then $\xi$ is one and there is a 39.01\% probability that the actual foundation is less than the predicted depth.  If at 39.01\% probability is too high for the level of confidence needed in a prediction, if the foundation depth is multiplied by 0.13, for example, the probability that the actual foundation depth is less than the predicted is 0.000001\%, or a one in one million chance that the predicted depth is more shallow than the actual.  This curve should be used based on the acceptable risk level determined by the engineer estimating the bridge foundation.

\section{Conclusions}
\noindent This manual is intended for assisting engineers using ERI and IP for predicting the depths of unknown bridge foundations.  It is written under the assumption that users are using the AGI SuperSting R8/IP\texttrademark system and the accompanying commercial software EarthImager.  The post processing code is an open source code that can be altered if other equipment or software are used.