WALLAP is a powerful, fast and user-friendly program for analysing the stability of cantilevered and propped retaining walls. WALLAP is suitable for the analysis of both temporary works, such as sheet pile walls, and permanent works such as reinforced concrete diaphragm walls and contiguous bored pile walls.

Factors of safety are computed according to standard codes of practice while wall displacements and bending moments are calculated by a finite element analysis which models the actual sequence of construction of the wall. Earth pressures are calculated automatically from basic soil properties.

The strata profile consists of up to twenty different soil types with hydrostatic or non-linear water pressure distributions. Surcharges may be applied and removed while struts and anchors may be installed and removed. The program is menu driven with context sensitive Help and on-line access to the comprehensive User Manual.

      Key Features:

• Cantilever walls

• Anchored walls

• Strutted excavations

• Sheet pile walls

• RC Diaphragm walls

• Factor of Safety calculation in accordance with Eurocode 7 and BS 8002

• Bending moments and wall displacements calculated by finite element analysis

• Construction sequence and Berm excavation modelled

• Soil arching and Soil-wall gap modelled

• Non-linear elastic/plastic soil model

• Hydrostatic or non-hydrostatic water pressures. Automatic water pressure balancing option

• Uniform or variable surcharges applied at or below ground level

• Structural loads applied to the wall

• Fully automatic calculation of earth pressures

• Simple data input with interactive Help

• Hot Keys for instant Help, Error reporting, Data plot and Summary output

• Free choice of units

• Graphical output of data and results

• Fully documented

Methods of Analysis   

• BS 8002 (Burland-Potts)
• Eurocode 7 (Strength factor method)
• British Standard Code of Practice No.2
• BSC Piling Handbook
 

Bending moment and Displacement Analysis
Modelling of the stage by stage development of forces and wall movements as construction proceeds. The wall and soil are modelled as a beam and springs. Two spring models are available:

• Subgrade reaction analysis (for routine design)

• 2-D Finite element analysis (for a more rigorous approach)

Modelling the Construction Sequence   

• Excavate (including berms)
• Fill
• Change water pressures
• Install and remove struts or anchors
• Apply and remove surcharges
• Apply loads to the wall
• Apply rotational restraints to the wall
• Change soil properties
• Change wall stiffness
 

Soil Properties   

A maximum of 20 different soil types can be defined including:

• Cohesive / cohesionless
• Drained / undrained
• Normally / over-consolidated
 

Soil strength is defined in terms of Ka, Kac, Kp, Kpc and cohesion. There is a Help facility to derive Ka etc.. from soil, wall friction and backfill angles.
Soil stiffness is expressed in terms of Young's modulus and Poisson's ratio.
Optional soil properties include:

• Linear variations of cohesion and modulus with depth.
• Arching active behaviour
• Simple non-linear elastic soil model
 

Struts and Anchors
Struts or anchors can be installed at up to 20 levels and may be pre-stressed. Struts can also be removed after installation.

Water Pressures
Hydrostatic or non-hydrostatic Water Pressure Profiles may be defined on both sides of the wall, to model a variety of complex conditions including:
• Seepage
• Submerged ground
• Perched water tables
• Uplift pressures under structures.

Automatic water pressure balancing option
This offers a convenient way of balancing water pressures at the toe of the wall by assuming a linear variation of piezometric head between the water levels either side of the wall.

Surcharges
Surcharges can be applied at or below ground level on the active or passive side of the wall. All surcharges are defined over a rectangular loaded area. Ramp surcharges can be defined i.e. Surcharge magnitude may vary linearly with distance from the wall.
 

Data Input and Editing
Data entry is menu driven. Data values are checked for permissible ranges. A list of data Errors and Warnings is displayed if unacceptable or inappropriate data combinations are detected. Data can be checked visually at any time during data entry or editing.
Units
Data may be entered in any consistent set of units e.g. (kN,m), (lb,feet). All print-out from the program is automatically annotated in the appropriate units.
Hot Keys
Special Hot Keys give instant access to Help facilities, Error reporting, Data plotting (during edit) and Summary output (during analysis).
 

Output from the Program
Printed output from the program consists of the following:
• Listing of input data
• Output at selected stages of:
- Factors of safety
- Bending moments and shear forces
- Wall pressures
- Displacements
- Strut/anchor forces
• Summary output of:
- Factors of Safety at each stage
- Strut forces at each stage
- Maximum/minimum bending moment and displacement at each stage
- Cumulative bending moment and shear force envelopes
- Cumulative displacement envelope

Graphics
Data and results are displayed in graphical form either on the screen or in hard copy form on a wide range of printers. Graphical display of the data shows:
• The soil profile
• Water pressure profiles,
• Surcharges,
• Applied loads/restraints,
• Strut positions
• Boundary conditions.
Results are displayed in the form of:
• Bending moment diagrams
• Shear force diagrams
• Wall pressure diagrams
• Wall displacement diagrams.

Help
Help is provided at two levels:- Press F1 at any time for context sensitive help on data entry or current activity. Press Alt+H at any time to use the Help Index. Subjects covered include advice on the selection of values of earth pressure coefficients and soil modulus.
Hardware Requirements
WALLAP can be run on any DOS or WINDOWS based computer. Program files occupy about 1Mb of disk space. Operation of the program requires about 530kb of RAM.