This noteendeavours to set out and justify some of the choices which must be made during the design process sothat the WALLAP user cana) arrive at a rational design.b) justify it to the wider world.NotationaULS, aSLS ULS and SLS seismic accelerationsagR Peak Ground Acceleration (PGA)A Accidental actionC' Drained shear strengthC'k Characteristic value of C'CU Undrained shear strengthCUk Characteristic value of CUCSOFT Undrained shear strength of softenedsoil at excavation levelCSOFTk Characteristic value of CSOFTDA1 Design Approach 1EU Young's modulus of soil - undrainedE' Young's modulus of soil - drainedF Generic actionFk Characteristic value of an actionFrep Representative value of an actionFd Design value of an actionG Permanent actionKo Coefficient of in situ earth pressureMWk Characteristic bending resistance ofthe wallN60 SPT N valueQ Variable actionTAk Characteristic strength of strut / anchorSLS Serviceability Limit StateULS Ultimate Limit StateX Generic material propertyXk Characteristic value of a material propertyXd Design value of a material propertyoa, op Angle of wall friction (active, passive)|' Drained angle of shearing resistance|cs= |cv Critical state (= constant volume)angle of shearing resistance|d Design angle of shearing resistance|k Characteristic angle of shearing resistance|peak Peak angle of shearing resistanceF Partial factor on an actionCu Partial factor on undrained shear strengthG Partial factor on a permanent actionM Partial factor on a material propertyMw Partial factor on bending strength of wallQ Partial factor on a variable actionTa Partial factor on strength of strut / anchor| Partial factor on tan| Partial factor on weight density of soilv Poisson's ratio Load combination factor1.0 Relevant documentsReferredReferences to asEN 1990 Eurocode: Basis of structural designUnderlying principles of Eurocodes for all types of structuresEN 1991 Eurocode 1: Actions on structuresDesign guidance and definitions of Actions for all types of structuresEN 1997-1 Eurocode 7: Geotechnical design - General rules EC7General principles and requirements to ensure safety, stability anddurability of earthworks and foundations. The requirements of EC7 are not always easy tounderstand or implement and in practice one encounters a variety of interpretations. This allows the user to investigate both Ultimate and Serviceability Limit States.Separate data sets (SLS and ULS parameters) are required to fully investigate the two limit states.The purpose of this note is to summarise the requirements of EC7 as they relate to embedded retainingwalls and the use of WALLAP in their design. It remains to be seen whether all or part of the design process will be automated infuture.WALLAP carries out Limit Equilibrium and Linear Elastic-Plastic analyses at each stage of theconstruction sequence. For the time being the assistance provided in WALLAP will be restricted to thefollowing advice.
There are no automatic features for introducingpartial factors although WALLAP does have a convenient method for factoring the strength and stiffnessgroups of soil properties. DRAFT 21.10.09The use of WALLAP in the context of Eurocode 7(EN 1997-1, Eurocode 7:Geotechnical Design)WALLAP allows you considerable freedom to follow the design requirements of Eurocode 7 (EC7) andmany other codes of practice.As things stand at present (WALLAP version 5.04), it is up to the user to select appropriate soilproperties, excavation levels, surcharges and water pressures for the various different cases - short andlong term conditions, load combinations, ULS and SLS.