Version 5.203--December 23, 1998

• Fixed problem with display of 2-digit year (date) for beyond 1999.
• Fixed the mis-drawn profile in the top-left plot in *.GP4 output for right-facing slopes.

Version 5.202--February 7, 1997

• Fixed program to allow use of negative values for a GLE function during execution phase.
• Corrected the "wording" of the reported error message 51.

Version 5.201a--December 17, 1996

• Modified the scaling options by including consistent starting values on the x and y axes.

Version 5.201--November 21, 1996

• Program automatically uses the moist unit weight if the user fails to specify the saturated unit weight. Please note that an error is NOT reported..... the value shows up in the output.
• There were problems with a "diminishing" plot for right-facing slopes. After the first analysis, the minimum x-axis value on the plots would start changing. This has been fixed, but could be avoided by starting the profile with x-minimum of zero.
• The labels on the hard-copy plots failed to print properly if the scale increment was 2.5. They worked fine for ALL other increments.
• Version 5.200 allowed scale increments that were limited to factors of 1, 2, 2.5, 5 and 10, unlike the previous versions. This doubling was (perhaps) too fast and so three more increment factors--3, 4 and 6--have been added to make sure that the scales do not expand too quickly. Also, these agree with most scales (rulers) used by the enginering profession.

Version 5.200--July 10, 1996

• Fixed problem with surcharge load intensities for right-facing slopes. Program adjusted coordinates, but incorrectly flipped the VALUES of the load intensities. Not a problem for a single boundary load, or for loads with the same intensity.
• Improved the scale annotation for the screen plots and hard copies. This version uses "nice" multiples of 1, 2, 2.5, 5 and 10 for tick-mark increments. Overall this may reduce the plot resolution, but the hardcopy plots (often included in reports) will now have a more professional look.
• Fixed some additional minor bugs concerning screen plots and potential scaling problems.

• Program underestimated the vertical effective stress used to assign the "undrained" strength values in cases of high pore water pressures.

Version 5.106--April 15, 1996

• For cases where a soil unit was specified as undrained AND anisotropic, the program would use the c-value specified in the isotropic properties table rather than the anisotropic value. This is an error and may be serious if the isotropic c-value is greater than the anisotropic one.
• Fixed some formatting errors in the writing of the undrained input data. Also fixed a very minor formatting error in writing the input anisotropic parameters.

Version 5.105a--March 15, 1996 (no change)

• In cases where XSTABL generated more than the 100 slices limit, the program reported ERROR 50. This should have been ERROR 28.

Version 5.105a--January 23, 1996

• Minor problem with *.GP4 plot for cases where the y-coords are much greater than the x-coords (e.g. y ranges from 5800 to 6000 and x ranges from 400 to 800). Version 5.105 plot did not always correctly scale within the displayed axes.

Version 5.105--September 22, 1995

• Fixed problem concerning the save of a *.?P4 file for cases where the *.GLE or *.RJM file is read from disk. XSTABL would give a warning message and allow user to continue with a viewing of the final plot, which also could not be saved. This problem could be bypassed if the *.GLE file was NOT read immediately before the analysis, i.e. perform a dummy run.

Version 5.104--July 1, 1995

• Modified program to accommodate negative values of an interslice force angle function. Previously, only positive values were allowed by the program.

Version 5.103a---June 16, 1995

• Problems in correctly assigning the alternative strength types if there are more than 9 soil units. In the interface, the new data were incorrectly assigned to the soil unit that was next to the one originally intended; i.e. if soil 9 was to be "undrained", the screen would show soil 10 as being "undrained". This problem also has occurred for the isotropic/anisotropic option. However, please note that the resulting data file was written correctly.

Version 5.103---April 20, 1995

• Fixed potential difficulties associated with generating more than 9999 surfaces. Program will now work for up to 32,000 surfaces, which is the restriction imposed by the adopted integer size.
• Fixed problem with the Ru value NOT being zeroed properly if a new *.IPT file was read into the tables. This problem would result in a lower FOS value being calculated as the "old" Ru value may be used in error. This "bug" can be easily by-passed by explicitly setting the Ru value in the appropriate table.
• Fixed some minor formatting problems.

Version 5.102 --- March 1, 1995

• The summary table following a "REINFORCEMENT" analysis listed the driving moments/forces rather than the resisting moments/forces. This has been fixed and the numeric values are now consistent with the column label.
• Following use of Janbu's Method, the REINFORCEMENT summary had an incorrect label for units of resisting force. This has been fixed.
• The y-coordinate for the circle center is now written to TWO decimal places in the final summary table following a circular search.

Version 5.101a --- February 20, 1995

• Version 5.101 would display the *.GP3 plot even if there was an error in the data file or if the analysis was terminated. This problem is tolerable but may lead to some confusion as different geometries may get mixed-up. Version 5.100 did not do this.
• Version 5.101a now correctly reports ERROR 50.
• Small modification made to the algorithms that control the FOS iterations. This may eliminate cases where the iteration sequence incorrectly leads to a very small FOS value.

Version 5.101 --- January, 25, 1995

• Program did not allow a GP3 file to be saved if GP2 file was saved earlier in the same analysis. This condition can be bypassed by performing two identical runs .... but was fixed.
• If user exits analysis by pressing ESCAPE before all the requested surfaces have been analyzed, program will NOW provide a summary of the TEN most critical surfaces. This summary was not provided in earlier versions as the ESCAPE was construed as a request for termination of the analysis.

Version 5.100 ---January, 1, 1995

• Up to TWENTY search boxes can now be used to generate block-shaped surfaces. The previous limit was 10 boxes.
• Improvements made to the iteration function used for the FOS calculations. This now gives a better "chance" for convergence, especially for cases where NLMC soils have been specified.
• Fixed potential problem concerning files being viewed following a directory search. Previously, the program would (possibly) have the wrong screen information, terminated or locked-up.
• Other minor code fixes that improve on the readability and functionality of the complete program.

Version 5.007 --- November 14, 1994

• Inconsistencies noted for NLMC data option. It is possible that XSTABL may assign NLMC data for a soil unit, which may have linear strength parameters. Problem does NOT occur if ALL soil units have NLMC parameters or if the a fresh XSTABL session has been started. The NLMC option is now correctly initialized before the start of each analysis.

Version 5.006a --- October 28, 1994

• The convergence routine for the GLE iteration was modified with the addition of an accelerator function that speeds up the solution. This is based on the bisection method and is very useful for cases where the rate of convergence was very slow, or (just) failed to complete within the allocated 50 iteration steps.
• In a very few, unique cases, the ground surface would not be plotted above the thrust-line and failure surface for the GLE option. This problem has been fixed in this version.

Version 5.006 --- October 11, 1994

• The NLMC properties were not correctly assigned if there was a mixture of conventional and NLMC soil units. Versions prior to 5.006 incorrectly assigned the first NLMC data set to soil unit-1, the second NLMC data set to soil unit-2, and so on.
• XSTABL now checks for consistency between the defined water surfaces and the water surface numbers assigned to each soil unit. An appropriate WARNING message is now printed to the output file if any defined water surface is not used by any soil unit. The analysis is then performed by ignoring the unused water surface.

Version 5.005 --- August 10, 1994

• XSTABL did not always allow user to enter a negative value for the upper/lower angular limits. This has been now fixed.
• The failure surface coordinate data could not be read directly into the data table for a specified noncircular surface. This problem was traced to a mismatch of file identifiers and has now been fixed in this version.

Version 5.004 --- May 25, 1994

• Corrected the anisotropic option. Previous versions did not assign the correct anisotropic strength values for any soil unit that was numbered as unit #1. So if the subsoil model had more than one soil unit and the anisotropic soil was NOT unit #1, the analysis would use the assigned isotropic values.
• Problem reported with single circular surface generation for right-facing slopes.
• Clipping problems with display of slope profile for the Thrust Line Location graph following analysis of a single surface.
• Fixed problem with display of current seismic coefficients. Program failed to display the kh and kv values if either one happened to be zero. Analysis was OK if the *.IPT file had these values written to it.
• Fixed problems with the creation of a *.GP2 file if the analysis was aborted due to errors with weight calculation or use of the nonlinear M-C envelope.
• Some minor Network capability added for printing plots to networked printers.
• The on-screen graphs displayed following the analysis of a single surface can now be seen on monochrome displays.

Version 5.003 ---May 20, 1994

• Corrected the anisotropic option. Previous versions labeled this data "ANISO2" in the input datafile (*.IPT) and thus it was rejected during the analysis phase as the correct name should have been "ANISO".

Version 5.002 ---May 8, 1994

• Changed the OLD error messages #48, #49 and #50 to WARNINGS. This is considered to be a more appropriate report as, logically speaking, errors should be followed by automatic termination of the analysis.

Version 5.001 --- April 29, 1994

• The *.CP? graphics format has been "dropped" due to an unknown incompatibility with WordPerfect 6.0b (for DOS). However, you can save a graphics file using the native WordPerfect Graphics (WPG) format with THIS version under the *.WP? file extension offered by version 5.001. For third-party software that cannot read the WordPerfect Graphics format, try saving plots to the *.HP? (HPGL) format.
• This version will operate successfully on all computers that have an EGA/VGA graphics adapter. If you want to use XSTABL with a CGA/EGA/VGA combination, please contact Interactive Software Designs, Inc., for a SPECIAL version. This change has been implemented as the support for the Color Graphics Adapter (CGA) tends to slow the graphic screen displays.

Version 4.111 --- October 21, 1993

• User is now prompted for decision on option to handle negative normal stresses for cases where slope has nonlinear and linear M-C strength specified. Otherwise program would exit with error 11.

Version 4.110 --- August 27, 1993

• If soil at base of slice was affected by piezometric surface, program would neglect any influence of submerged conditions above the slice.

Version 4.109 --- August 1993

• Minor cosmetic fix to plotting routine with availability of SciPlot 5.0

Version 4.108 --- May 13, 1993

• Fixed problem with FOS calculation that suggested lack of convergence "too-early"

Version 4.107 --- May 13, 1993

• Improved chances of convergence for cases where the FOS may be less than 1.0

Version 4.106 --- April 16, 1993

• Program did not include surcharge loads for right-facing slopes

Version 4.106 --- April 23, 1993

• This version release fixes a problem where a right facing slope is being analyzed with a surcharge load. For such cases, prior XSTABL versions did not correctly place the surcharge within the assumed geometry. The user would see the surcharge located correctly on the screen and hardcopy plots, but the location of the surcharged zone was incorrectly established for the analysis. Typically, the analysis would have neglected the surcharge loads or applied them to wrong slices.
• If such an analysis was performed, the reported factor of safety values would be incorrect. The magnitude of this error would be a function of the size, direction and position of the applied surcharge. Typically, the reported FOS will have been (slightly) overestimated!

Version 4.103 --- October 5, 1992

• version 4.103 of the XSTABL program,
• a prototype version (2.01) of Spencer analysis program XSP, and all of the example input files from the XSTABL technical reference manual.

Version 4.100 --- August 1, 1992

• Changed consequences of ERROR 48. Now the user has three options available to control the handling of negative effective stresses. See "Slope Analysis with XSTABL" for more information.
• The current unit-system (English or Metric) is indicated in the upper right hand corner of the screen menus.
• User can switch between English and metric unit systems without exiting program. The F4 key, as shown in lower right corner of all menu screens, is the selected toggle switch.
• All data files generated by XSTABL are stamped with the unit-system that was being used at the time the file was saved as a *.IPT file. Upon reading this file again, XSTABL will automatically switch to the appropriate unit-system.
• The saved *.IPT files have the filename, and the time, written on the first line. This allows printed data files to be quickly associated with the correct output files.
• The option to vary the number of plots shown on-screen and written to the output files is now accessible from within the program. Previously the user had to exit the program, modify file: SETUP1.STB, and then restart the program. This option is available via the F5 key from the screen where the user elects to proceed with the analysis.
• Inconsistencies between the number of decimal places displayed on-screen in the data tables and the data written to the *.IPT file have been eliminated. Now, the on-screen, *.IPT and *.OPT files comply with the same format.
• Negative effective stresses calculated as a consequence of excessive pore water pressures are now handled internally. If the specified pore water pressure is greater than the calculated total normal stress, XSTABL reduces the magnitude of the pore water pressure such that the shear strength (c' + [sigma]' tan[phi]) is always greater than or equal to zero. A message is still printed to the output file, but only once! Previous versions used the negative effective stress, but reported a misleading factor of safety along with an error message.
• If the user elects to use option 3 for controlling negative effective stresses, an abbreviated message is now printed to the *.OPT file in an attempt to reduce the size of the file. Previously, about 15 lines were printed for each anomalous failure surface.
• At the request of many users, the beep that accompanied the calculation of a "misleading" factor of safety has been eliminated, even though such errors are less likely with this version.
• If the user specifies a vertical surface boundary segment, ERROR 51 will now be reported to the user and the execution terminated. The current version would "crash" with a reported floating point error.
• The algorithms, for the FOS calculation, have been modified considerably to implement the various options now available. The theory along with the select limit equilibrium equations is now published in a supporting technical manual.
• Units for all data are now reported in the *.OPT output file. This should prevent any further confusion regarding the slice-data printed following the analysis of a single surface.
• The program will only acknowledge the existence of a maximum of 200 files in any subdirectory. This limitation was not always known and thus an added emphasis is indicated if more than 200 XSTABL files are ever found to reside in a single subdirectory.
• The plot for the reinforced soil analysis now indicates the projected FOS value along with the required force.
• Plots that currently show a FOS = 500.000 (i.e. a misleading FOS) will now show "*******" which is probably a more realistic label for such cases.
• This version assumes that the connected printer is switched on and ready to print a file. This eliminates the request for a user-response following the selection of the print command.
• A separate demonstration program for calculating the FOS according to Spencer's Method is now available. This program uses an XSTABL output file (*.OPT) generated following the analysis of a single surface. It is expected that a new version of XSTABL with an integrated Spencer's method of analysis will be available in 1993.

Version 3.22 --- July 30, 1990

Version 1.03 --- April 1989