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         README5b File,  January 27, 1994


         NOTES REGARDING REVIEW PROGRAM: XSTABL (Version 4.960)
         ======================================================

         The enclosed slope stability analysis program, XSTABL, represents
         a future upgrade that has been developed with partial financial
         support provided by the USDA Forest Service, the University of
         Idaho and Interactive Software Designs, Inc.  This upgrade
         provides the user with as many as TWELVE different procedures for
         calculating the Factor of Safety for a single, specified failure
         surface.

         THIS SOFTWARE IS BEING MADE AVAILABLE TO YOU FOR AUTHORITATIVE
         REVIEW AND TEST PURPOSES ONLY AND SHOULD NOT BE USED FOR DESIGN.

         However, it is hoped that you will use the program to compare
         your current analyses and report on any inconsistencies that may
         become apparent.  Also, a "useability" critique concerning the
         effectiveness of the software will be appreciated greatly.

         The XSTABL program on this disk, named XSTABL5.EXE, is the NEW
         executable version and requires about 450,000 bytes (440 kb) of
         free RAM to operate on a personal computer.  

         FOR SUPERIOR PERFORMANCE, THE AVAILABILITY OF 384 KB OF EXPANDED
         EXTENDED OR MEMORY WILL GREATLY ENHANCE PROGRAM PERFORMANCE.
         
         This version automatically uses a coprocessor (80x87), if
         available.  You may have difficulty viewing some plots if using
         CGA graphics.


         HARD-DISK INSTALLATION
         ======================

         The XSTABL diskette contains all the necessary program and
         example files in an uncompressed format.  To copy these files to
         a subdirectory on your hard disk, please follow the instruction
         listed below:

                1.  create a directory on your hard disk
                    (e.g. MD XSTABL5 etc....)

                2.  change to this newly created directory
                    (e.g. CD XSTABL5 etc....)

                3.   from this directory type either :

                      (a) XCOPY A:*.*     --> if disk is in "a" drive, or

                      (b) XCOPY b:*.*     --> if disk is in "b" drive

                                                                   Page 2/6


         This will copy the program files to the current directory and
         create a subdirectory, "EXAMPLS", where the four example files
         (CASE_?.IPT) will be located.  The program can then be started by
         typing, XSTABL5 at the DOS prompt and the data input and output
         files may be read/written to any PRE-EXISTING directories.  The
         program will NOT operate without the SETUP1.STB file.

         If you have problems, please give me a call at (208) 885-6403,
         and remember that Moscow, Idaho, is in the Pacific Time Zone.


        NEW FEATURES INCLUDED IN TEST VERSION 4.950 (January 13, 1994)
         ==============================================================

         The major feature that is new to this version is the ability to
         calculate the FOS of a single surface using more rigorous
         procedures that include effects of interslice forces and also
         satisfy complete static equilibrium.

         The analysis of single surfaces has been made more interactive as
         the same input data file can be used to calculate FOS values
         employing as many as TWELVE different procedures.

         Following analysis of a single surface, a one page plot is
         produced showing:

                (1)  Location of the resultant interslice force 
                     (i.e. thrust-line)

                (2)  Total Vertical and Normal stress, as well as the pore
                     water pressure, at the base of slices

                (3)  magnitude of interslice forces

                (4)  Interslice force angles

         These plots are absolutely necessary for reviewing the
         reasonableness of the calculated FOS values and should be
         included with the *.GP3 plots of the critical surface.


         User can insert a "cracked" zone that may or may not include the
         effects of water.  This option is selected from the PROFILE menu.

        Compatibility between previously created data files has been
         maintained in this version.  The only change is the different
         implementation of the anisotropic data.  However, if the user
         reads the (old-format) data into the "editor" and then saves it,
         it will be converted automatically.


                                                                   Page 3/6

         NEW PROCEDURES FOR CALCULATION FACTOR OF SAFETY
         ===============================================

         A generalized limit equilibrium procedure has been programmed
         using an extension of SPENCER'S METHOD for calculating the FOS
         according to several different methods.  These methods can be
         grouped according to assumptions made concerning the distribution
         of interslice forces and conditions satisfied for static
         equilibrium.

         COMPLETE FORCE AND MOMENT EQUILIBRIUM
         -------------------------------------

           A.   SPENCER'S METHOD (1973)

           B.   GENERAL LIMIT EQUILIBRIUM, assuming:

                  1.  that interslice forces are distributed
                      according to a half-sine function

                 2.  that interslice forces are distributed
                      according to a CLIPPED half-sine function

                 3.  the distribution of interslice forces follows
                      a user-specified function.

                  4.  the distribution of interslice forces, f(x),
                      along the shear surface is related directly
                      to the slope of the ground surface

                  5.  the distribution of interslice forces, g(x),
                      along the shear surface is related directly
                      to the average inclination of the ground
                      surface and failure surface


          B.   JANBU'S GENERALIZED METHOD

                This method is now available.  Upon selecting this
                procedure, you will prompted for normalized location of
                of the thrust line with respect to the interslice height.
                A starting value in the range: 0.2 - 0.4 is recommended.

         SATISFACTION OF FORCE EQUILIBRIUM ONLY
         --------------------------------------

                  1.  Janbu's simplified method assumes
                      horizontally inclined interslice forces.
                      Please note that this method uses a
                      correction to modify the calculated value of
                      the FOS.

                  2.  Corps of Engineers Method 1 -- assumes a
                      constant interslice force angle represented
                      by the inclination between the first and last
                      coordinate points of the failure surface
                                                                   Page 4/6

                  3.  Corps of Engineers Method 2 -- assumes a
                      variable interslice force angle that is equal
                      to the inclination of the ground surface at
                      the vertical interslice boundary

                  4.  Corps of Engineers Method 3 -- assumes a
                      constant, user-specified interslice force
                      angle.  The user will be prompted for this
                      value before start of analysis.

                  5.  Lowe and Karafiath's method assumes an
                      interslice force angle that is equal to the
                      average inclination of the ground surface and
                      failure surface at the vertical interslice
                      boundaries.


         VERTICAL FORCE EQUILIBRIUM AND 
         OVERALL HORIZONTAL MOMENT EQUILIBRIUM

                The simplified Bishop method.  Please note that this method
                is restricted to analysis of CIRCULAR failure surface only.


         EXAMPLE DATA FILES
         ==================

         The data file CASE_1.IPT is used to illustrate one possible
         approach that may be used to determine the factor of safety for
         the example problem included in the XSTABL Reference Manual,
         Appendix A. The file CASE_1.IPT is the same as the example file
         EX3.IPT provided with previous versions of XSTABL.

         However, as the upper 11 feet of the soil unit is "cracked", we
         can directly include this data with version 4.950 rather than
         simulate this condition using a soil unit with zero strength.

           1.   Use CASE_1.IPT (with zero strength for soil unit 2)

                      Minimum FOS (Janbu, simplified)  =  1.402

           2.   The critical surface was next entered into the model of file
                CASE_1.IPT and is included as file CASE_2.IPT.  This file
                may be used to generate the following FOS values based on
                the different procedures of analysis that satisfy complete
                equilibrium conditions:

                                                                   Page 5/6


                      Spencer, constant angle,          FOS  =  1.608

                      GLE, Half-Sine,                   FOS  =  1.552
                      GLE, Clipped Sine, (0.2, 0.4)     FOS  =  1.570
                      GLE, function f(x),               FOS  =  1.659
                      GLE, function g(x),               FOS  =  1.609
                      GLE, Trapezoidal (4 points)
                        (0.0,0.0), (0.2, 1.0),
                        (0.8,1.0), (1.0, 0.0)           FOS  =  1.591

                      Generalized Janbu (y/H=0.25)      FOS  =  1.572
                      (unreasonable solution !??)

                Please note that the solution using the clipped-sine and
                function f(x) resulted in a single erroneous location of an
                interslice force.

           3.   The data file CASE_1.IPT can be loaded and then modified by
                removing the subsurface layer, eliminating soil unit 2,
                changing the soil unit references for the surface layer and
                include a cracked zone down to eleven feet below the ground
                surface.  This file is named CASE_3.IPT and upon analysis,
                the search reveals:

                      Minimum FOS (Janbu, simplified)  =  1.505

                Please note that the generated surfaces are automatically
                terminated at the eleven-foot cracked depth and the reported
                FOS is slightly higher, as expected, due to a reduction in
                the weight of the slide mass.

           4.   File CASE_4.IPT includes the coordinates of the critical
                surface determined in (3), above.  This file may be used to
                generate the following FOS values based on the different
                procedures of analysis:

                COMPLETE EQUILIBRIUM

                      Spencer, constant angle,          FOS  =  1.656

                      GLE, Half-Sine,                   FOS  =  1.600
                      GLE, Clipped Sine, (0.2, 0.4)     FOS  =  1.624
                      GLE, function f(x),               FOS  =  1.693
                      GLE, function g(x),               FOS  =  1.702
                      GLE, Trapezoidal (4 points)
                        (0.0,0.0), (0.2, 1.0),
                        (0.8,1.0), (1.0, 0.0)           FOS  =  1.663

                      Generalized Janbu (y/H=0.25)      FOS  =  1.828
                      (unreasonable solution !??)


                                                                   Page 6/6

                Please note that the solution using the constant angle for
                the interslice force resulted in a single erroneous location
                of an interslice force.

                FORCE EQUILIBRIUM
                      Corps of Eng., Method 1,          FOS  =  1.815
                      Corps of Eng., Method 2,          FOS  =  2.048
                      Constant Angle = 10 deg,          FOS  =  1.621
                      Lowe and Karafiath,               FOS  =  1.849


         OTHER FEATURES THAT HAVE BEEN ADDED SINCE Ver. 4.900 ARE :
         ============================================================

           1.   Use of shear strength as a function of vertical stress for
                undrained analysis

           2.   Ability to read the nonlinear M-C envelope data from
                a *.NLM data file that has been created previously.

           3.   Ability to read the pore pressure grid data from 
                a *.PWG data file that has been created previously.

           4.   After a search for the most critical surface has been made,
                the user will be able to extract (interactively) the
                coordinate data for use in re-analyzing the same surface
                employing one of the more rigorous procedures.

           5.   The soil data, strength-type and water surface data
                preparation tables have been made considerably more
                user-friendly and (hopefully) intuitive.

           6.   The clipped sine function has been added as an interslice
                force angle function to the GLE analysis.

           7.   XSTABL5 can now run on PCs with only about 460 kb of
                free-ram.  Greater performance can be attained with
                460 kb of free-RAM and 256 kb of extended memory.
                In contrast, version 4.1 required about 490 kb of
                free-RAM and thusthis version can be expected to help
		networked users considerably.



                Sunil Sharma
		University of Idaho, 
		Dept. of Civil Engineering
		Moscow,  ID 83844-1022

                Phone:  (208) 885-6403
                FAX: (208) 885-6608
                                                         January 27, 1994


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