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aspects of the geometry. In carrying out parametric studies, especially the effects of different failure modes, the slope geometry can be run and rerun using any of the four analytical methods provided. The CAD approach really does cut down on input time and so allows the user to conduct a far wider ranging parametric study in a given time.

T.S. lngold

GEOWall (vl.1) & GEOPlot (vl. l) - - Geosynthetic Reinforced Soil Walls.

Bathurst, Jarrett and Associates, Inc. 60 Cartwright Point, Kingston, Ontario, Canada K7K 5E2.

Written by Dr Richard Bathurst this little suite of programs is a gem for making a rapid assessment of preliminary designs of geosynthetic reinforced soil walls. GEOWall is used to carry out analyses while GEOPlot provides a neat one page summary including a wall cross section showing wall dimensions, surcharge and reinforcement locations. GEOWall may be run in metric (kN and m) or imperial (lbs and ft) units, which can be switched to and fro at any stage in the analysis. The program accommodates full height panels or modular facing units for walls up to 12 m high as well as block facings where the wall face may be battered at up to 30 ° offthe vertical, ie a 60 ° slope angle. However, as the manual and pop-up menus point out, the analysis becomes conservative for batters greater than 10 ° off the vertical. Where block facing is being analyzed there is facility for selecting the height and width of blocks as well as block/wall face batter or, if using cuboid blocks, the face step or inset of the blocks.

GEOWall allows the inclusion of an inclined back slope as well as a uniform surcharge loading. User options for calculating lateral earth pressures, and thereby reinforcement loads, include the use of Rankine earth pressure theory or Coulomb wedge. Separate sets of parameters, comprising cohesion, peak friction angle and bulk unit weight, can be defined for the fill used in the reinforced zone, the retained backfill and the foundation soil. Alternatively these three soil components can be selected from a menu of soils classified according to the Unified Soil Classification System, in which case appropriate values of cohesion, friction angle and unit weight are predefined.

External stability is assessed based on considerations of forward sliding, overturning, bearing capacity and base eccentricity. Factors of safety against these modes of failure, and acceptable base eccentricity, may be set at default values or the user may use a pop up menu to select

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values within a predefined range. GEOWall does not check for overall stability which must be considered separately. The width of the wall, and thereby the length of the basal reinforcing layer, may be user specified~ and subsequently changed if external stability is not satisfied~ or the program will calculate a min imum wall width consistent with external stability.

The design strength of the reinforcement, with respect to tensile failure~ is based on the short term tensile strength~ such as defined by the wide width strip tensile strength test to ASTM 4595~ which is factored down~ to allow for creep~ environmental attack~ construction damage and overall margin of safety, using the partial factors of safety prescribed by Task Force 27 for preliminary design. Although the user can specify individual partial factors within the range specified by Task Force 27~ these can not all be set to a value of unity. Consequently~ where the user has knowledge of the reinforcement design strength, derived from criteria other than those given by Task Force 27, it is necessary to enter a dummy short term strength which, once factored down, leads to the desired value. Factor of safety on pull out of the reinforcement may be set to the default value of 1.5 or a user specified value as is the coefficient of soil-reinforcement interaction, eg tan 6.

Having assessed internal stability, results can be called up on screen, for each layer of reinforcement~ for layer number, elevation~ length~ applied tensile load, factor of over tensioning (eg ratio of applied load to design load), vertical stress, anchorage length, pull out capacity and factor of safety against pull out, There is facility to adjust the maximum reinforcement spacing, min imum reinforcement length, anchorage length and depth of cover above the footing at the front of the wall.

Printout includes a four page listing of input data and analytical results. Graphical output, via GEOPlot which is contained in the same directory as GEOWall, gives a cross section of the wall, a block of notes and materials data~ which can presented in portrait or landscape format. Hardware requirements for GEOWall include 370 Kb memory, ideally 2 Mb extended memory, a min imum EGA monitor or graphics card and MS DOS 3.0 or higher. Production of graphics output from GEOPlot require a pen plotter or laser printer supporting HPGL. Recommended graphics hardware include HP 7470/7450 or 7550 pen plotters or an HP LaserJet III. HP LaserJet II printers may be used with an HPGL cartridge and both LaserJets II and III require a 2 Mb memory upgrade to take full advantage of the features available in GEOPlot.

The suite of programs is intended very much for preliminary design based on force equilibrium and therefore does not consider serviceability requirements such as face or reinforcement deflections. Being menu

Computer software reviews 507

driven, the analytical program is extremely fast and simple to use, particularly when optionally operated with a mouse. Although selling price has not been quoted this is a neat, friendly, little package which has been designed to be foolproof.

T.S. Ingold