ReSSA

Program ReSSA is an interactive, graphically rich program, allowing the designer to explore various design options of reinforced and unreinforced earth slopes and embankments. 

Here are some of the features of program ReSSA (3.0):  

ReSSA can analyze stability of  reinforced and unreinforced slopes and embankments considering circular failure surfaces (Bishop method) and two- and three-part wedge failure surfaces (Spencer method).

While in Results, using the mouse right-click function, the soil properties or reinforcement details can be changed so as to facilitate design.

An exclusion zone for slip surfaces can be specified to limit a search to ‘internal stability’, ‘external stability’, and more.

Data files generated by MSEW(3.0) or ReSlope(4.0) can be imported to ReSSA for in-depth global stability analysis.  Elements such as connection strength generated in MSEW can be considered in ReSSA.

User can select any color for soils and reinforcements.  

ReSSA can display color coded safety map, a powerful diagnostic tool for assessing the stability of the slope and for optimizing the reinforcement. It follows the procedure introduced by Baker and Leshchinsky, "Spatial distributions of Safety Factors," Journal of Geotechnical and Geoenvironmental Engineering, ASCE, 127 (2), 2001, 135-145.

Each dialog in ReSSA has its own extensive.

Units can be SI or English.

User can specify up to 25 layers of soil, each possessing different strength properties. 

Complex geometry can be input using mouse functions.  

Slopes are divided into three types: simplified, tiered and general.  Simplified slope allows for quick input data but is limited to three soils.   Tiered geometry allows for quick input of up to ten-tiered slopes, each defined by its height, inclination and offset.  The number of soils in tiered geometry is limited to three.  General geometry allows for input of detailed geometry and soil profile.  

The effects of elements such as tension crack (depth specified), water pressure (either phreatic surface or piezometric heads), vertical and inclined surcharge loads, and seismicity can be considered.

Total stress, effective stress and mixed type analysis can be conducted.  Total stress corresponds to undrained shear conditions; effective to drained; and mixed analysis corresponds to alternating layers of soil where some layers are likely to exhibit drained conditions at failure (e.g., gravel) while other layers are likely to fail under undrained conditions (e.g., clay).

ReSSA was specifically developed for convenient implementation of horizontal reinforcement layers.  Either geosynthetic or metallic can be specified. 

ReSSA allows for reduction factors (construction damage, aging and creep) associated with polymeric reinforcement.  ReSSA can assess the corrosion of metallic reinforcement over the life span of the slope and implement its effects in calculations.

Up to five types of reinforcement in a section can be specified for a slope.  Parameters such as strength, reduction factors (polymer), coverage ratio, and cross sectional area (metal) characterize each 'type' of reinforcement.

User can create unlimited databases, each with up to 100 different types of reinforcement, each saved under a different name.  The database includes designated name of reinforcement, its strength and the relevant reduction factors.  One can easily retrieve and modify this database.  Data retrieved from the database can be overridden.

ReSSA calculates the pullout resistance along the rear- and front-end of each reinforcement layer automatically. Front-end pullout signifies a case in which the soil moves outward relative to the embedded reinforcement layer. As a result, ReSSA can assess potential surficial instability. ReSSA incorporates in the analysis the available strength at each intersection as dictated by the pullout resistance or the reinforcement long-term strength, whichever is smaller. 

User can input the reinforcement resistance at its front-end.  This parameter can signify the strength of connection to a facing unit.  It cannot exceed the long-term strength of the reinforcement layer.  Moving away from the face, ReSSA increases the specified reinforcement resistance according to the overburden pressure and the reinforcement-soil interaction parameters.

User can specify the interaction parameters, signifying the pullout resistance or interfacial resistance to sliding.  Effects of adhesion can be; such an option is useful in forensic studies.  If a layer is embedded in more than one soil, its pullout resistance will be calculated cumulatively along its length considering the relevant interaction parameters at each location.

ReSSA checks along each reinforcement layer for resistance to direct sliding using 2-part wedge combined with Spencer.  If the active wedge intersects layers of reinforcement, their available strength is incorporated in the analysis.  Consequently, trapezoidal layout with shorter reinforcement layers at the bottom can rationally be evaluated.

Tiered slopes can be analyzed using the general structure scheme.  Rotational (circles) and translational (2- and 3-part) through and away from the reinforcement can be considered.

For circular surfaces, the user tangibly specifies the points of entry and exit of all circles.  ReSSA checks many circles for each combination of entry and exit point until it finds the critical circle.  The user can display all the specified circles to be analyzed and judge whether a reasonable search domain was specified.

For 2-part wedge surfaces, the user can specify points along the reinforcement and foundation interface defining the boundary between the passive wedge and the active one.  ReSSA checks many possible surfaces for each point to render the critical surface.  The user can display all the specified wedges.

For 3-part wedge surfaces, the user specifies a grid of points for the boundary between the passive and the central wedge and for the boundary between the active and the central wedge.  ReSSA checks all possible surfaces to capture the critical surface defined by the search domain.

In Bishop results, the user can view the distribution of Fs along the specified entry and exit points.  Such review implies whether the problem has several minima or whether the absolute minimum has been captured; in case it has not, rerun using modified search domain needs to be conducted.  The normal stress and porewater distribution over the critical slip surface can be displayed.  Also, the detailed results of Fs corresponding to circles can be viewed.  All analyzed circles can be displayed as well.  In case of circles away from the reinforcement, results can be viewed though the reinforcement data then is not relevant.  The displayed information as a whole is important for judgment on 'reasonableness' of results. 

Results are presented in tabulated as well as graphical fashion.  Detailed results can be viewed by clicking on the desired parameter in the drop menu.

In Spencer results, the user can view the distribution of Fs along each reinforcement layer, the corresponding critical surface, the associated normal stress and porewater distribution, and the line-of-thrust for this surface.  Also, the detailed results, such as the imbalance of the limit equilibrium equations and the inclination of the interslice resultant force, can be viewed.  All analyzed slip surfaces can be displayed as well. The displayed information as a whole is important for judgment on 'reasonableness' of results.

In the results of Bishop, the user can view the distribution of Fs along the specified entry and exit points.  Such review implies whether the problem has several minima or whether the absolute minimum has been captured. In case it has not, rerun using modified search domain needs to be conducted.  The normal stress and porewater distribution over the critical slip surface can be displayed.  Also, the detailed results of Fs corresponding to circles can be viewed.  All analyzed circles can be displayed as well. The displayed information as a whole is important for judgment on 'reasonableness' of results. 

Results can be printed as a report.  The user can select from a print menu the desired material to be printed.  The user can also print quantities. All selected material for printing can be previewed before printing.

All graphical results can be captured as bitmap or jpg files.  Most graphic programs and word-processors can retrieve these bitmap files. 

Graphical results can be saved as a DXF (Drawing Exchange Format) file.  Such files can be read by AutoCAD® for further processing and implementation in design blueprints. 

 

 

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