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N€ô€F€ ƒăéĘ'ƒ€‰€ ‚ƒă"䀉€‚˙How are the soil spring constants calculated?What is the pressure behind the wall when you stress an anchor?…T J1 2€¨€B€ ƒăNĹ9€‰€‚˙How are horizontal stress increments derived from vertical stress incrementsŞ2Ĺôx ž€e€F€ ‚ăaꐀ‰€ ‚ƒăS§߀‰€ ‚‚ăÍň@ـ‰€ ‚ƒăÔ뀉€ ‚ƒă`Ö"Ҁ‰€ ‚ƒă]nźĽ€‰€‚˙Design / Codes of PracticeHow do I use WALLAP to satisfy a particular design code?Interpretation of resultsComparison of Subgrade Reaction and 2D Finite Element modelsAccuracy of calculated displacements How can I check the relationship between pressure changes, wall WűJK \ †€÷€B€ ƒă]nźĽ€‰€ ‚ƒă ił €‰€ ‚ƒăŽzą˘€‰€ ‚ƒă äş{€‰€‚˙ displacement and soil spring values?Vertical stress, cannot be reconciled with the soil densitiesUnreasonably low Factors of Safety for a wall with a single low level strutIdentical data files produce different results. ťôf ` Ž€w€F€ ƒă珀‰€ ‚ƒăŒ)!€‰€ ‚ƒăąAeˇ€‰€ ‚ƒăłň*Á€‰€ ‚€‚˙Strut forcesReporting of Applied MomentsLarge bending moments when re-watering under a basement slab.Large displacements or convergence failure in ULS analysisGK ­ - *€4€Băěm÷Ā‰€‚˙How to model .......ŒMf 9 ? N€š€F€ ƒăm‰ €‰€ ‚ƒăGMěՀ‰€‚˙Change from Undrained to Drained conditionsCut and cover tunnelp?­ Š 1 2€~€B€ ƒă<ˆćŽ€‰€‚˙Deflections which occured before the wall was installed9 6 Š  F€ ƒăeÔSr€‰€ ‚ƒă,°0€‰€ ‚ƒăë„Ő€‰€ ‚ƒăӑ$A€‰€ ‚ƒăĺÔü˜€‰€ ‚ƒăüfŸř€‰€ ‚ƒă“Ç3+€‰€ ‚€‚˙EarthquakesExcavation below the toe of the wallKing pile wallsMoment loads applied through a slab which also acts as a rotational restraintRotational resistance of a floor slabSubmerged bermsDouble wall cofferdams¨ZŠ Ţ N l€´€ă*ő€‰€‚€ ƒăŤ‡3€‰€ ‚€ ƒătÍ瀉€‚˙Run time errorsConvergence Cannot focus a disbled or invisible window'S!6 12 4€B€””€ ƒăq= €‰€‚˙Errors in Report Graphics;Ţ l' €(€€ ‚€‚˙20th April 2004= 1Š1Č˙˙˙˙˙˙˙˙ŠßvInstallation6lß& € €€€‚˙Installation—LŠvK f€˜€F€‚ăe;ÖĀ‰€ ‚ă?…怉€ ‚ă]‚Ş€‰€ ‚˙Installation instructions WALLAP updatesLost installationsCßš1T˙˙˙˙˙˙˙˙š @/CLost installations;v @& €*€€€‚˙Lost installationš @vť~šÇ@= J€ü€€‚€€€ăŤćȸ€‰€€‚‚˙This topic only relates to licenses protected with a copy protection software token (not a Lost hardware key). h! @/CG \€C€PĐT€ € ‚‚€ € ‚ƒ‚ƒƒ‚‚€ € € € €‚˙Q. The computer on which WALLAP was installed has suffered a disk crash and I can not uninstall WALLAP or recover the software token. How can I install the software on my new computer?A. First go to the Geosolve website and download the utility at www.geosolve.co.uk/recovery.zip Do not run the utility until you have contacted Geosolve. Then make sure you have the original master diskette(s) to hand and contact Geosolve for a reset code which will restore the ability of the master diskettes to install WALLAP again.[*Ç@ŠC1h˙˙˙˙˙˙˙˙ŠCŢCGKing pile wall with a berm - not permittedT./CŢC& €\€€€‚˙King pile wall with a berm - not permitted’eŠCpD- *€Ę€V””¸J€ € €‚˙Q. Wallap gives a data error if I specify a berm excavation combined with incompatible values ofl2ŢCÜD: D€d€””€€€ €€€ ƒƒƒ€‚˙Ka(wall) = 0 and Kp(wall) = 3b/s*Kp 9 pDG0 .€€V””¸J€ ‚€ € ‚‚˙ which are needed for modelling a King Pile wall (see Appendix K of the User Manual). How can I avoid this error?A. Apologies for this restriction - it is inevitable. The Berm calculation requires compatible values of Ka and Kp in order to backfigure the corresponding phi. The adjusted values of Ka and Kp for King piles are almost ineviatbly going to be "incompatible" in the sense that they cannot be related to a phi value. This is just a limitation of the software. There is no obvious way out of it.JÜD_G1 ˙˙˙˙˙˙˙˙_GŁGHInstallation instructionsDGŁG& €<€€€‚˙Installation instructions Ü­_GH/ ,€[€€‚‚€ ‚‚ƒ€‚˙Please copy the following link to your web browser and download the Installation Instructions from the Geosolve website at www.geosolve.co.uk/faq.htm#Installation; ŁGşH1´˙˙˙˙˙˙˙˙şHîHqJInput data4HîH& €€€€‚˙Data entryƒşHqJk ¤€1€F€‚ăm]=]€‰€‚ă¨âOD€‰€ ‚㣧Ň7€‰€ ‚ă×q)H€‰€ ‚ăjFS€‰€ ‚‚€‚˙Water pressure balancing at toe of wallCohesion varying with depthNon-Linear soil modulus parameterUndrained soil property gets re-set to drained automatically by WALLAPThe EC7 values of Kp given by WALLAP do not agree with the charts in Eurocode 7 FîHˇJ1˙˙˙˙˙˙˙˙˙ˇJöJÄLMethod of calculation?qJöJ& €2€€€‚˙Method of calculation+ˇJ!K& € €€ €‚˙ öŽöJLH ^€]€Fă×Úô€‰€ ‚ăéĘ'ƒ€‰€ ‚ă"䀉€‚˙How is the passive resistance of a berm calclated?How are the soil spring constants calculated?What is the pressure behind the wall when you stress an anchor?R!K–L- *€¤€BăNĹ9€‰€‚˙How are horizontal stress increments derived from vertical stress increments.LÄL( € €F€ ‚€‚˙ K–LM1Ď˙˙˙˙˙˙˙˙MSMńMDesign / Codes of PracticeDÄLSM& €<€€€‚˙Design / Codes of Practice&MyM# €€€‚˙xCSMńM5 :€†€FăS§߀‰€ ‚‚€ €‚˙How do I use WALLAP to satisfy a particular design code? U$yMFN1U˙˙˙˙˙˙˙˙FN”NĂExcavation below the toe of the wallN(ńM”N& €P€€€‚˙Excavation below the toe of the wall¸FNX7 <€€PĐT€‚€ € ‚‚‚‚€ € ‚˙Q. I am using your program to design a 11m deep basement excavation using steel sheet piles. Bedrock is at about 8m depth and the sheets will not be able to be driven beyond about 8.2m. The sheets will be supported with temporary ground anchors. As we are excavating below the toe of the piles, th”NXńMe Wallap program will not carry out the analysis. Is there any way of working around this issue to get a meaningful result using your program ?A. WALLAP version 5.03 introduced a facility for changing the stiffness of the wall over part of its length. This simplifies the modelling of excavation below the toe of the wall. l”NĂO l€;€PĐT€ ‚ăŹ|†Y€‰€ ‚€‚€ ăÓÁ뀉€‚€ ‚€‚˙ If you have WALLAP version 5.03 or later then follow this link to Model_excavation_below_the_toe_of_the_wall_using_version_5.03 If you have WALLAP version 5.02 or earlier then follow this link to Model_excavation_below_the_toe_of_the_wall_using_version_5.02 JXƒ1˙˙˙˙˙˙˙˙ ƒQƒ˝…Interpretation of resultsCĂQƒ& €:€€€‚˙Interpretation of results'§ƒx…€ ΀O€B€‚ăÔ뀉€ ‚ă`Ö"Ҁ‰€ ‚ă]nźĽ€‰€ ‚ă]nźĽ€‰€ ‚ă ił €‰€ ‚ăŽzą˘€‰€ ‚ă äş{€‰€‚˙Comparison of Subgrade Reaction and 2D Finite Element modelsAccuracy of calculated displacementsHow can I check the relationship between pressure changes, wall displacement and soil spring values?Vertical stress, cannot be reconciled with the soil densitiesUnreasonably low Factors of Safety for a wall with a single low level strutIdentical data files produce different results. EQƒ˝…1 2€(€Bă珀‰€ ‚€‚˙Strut forces= x…ú…1n˙˙˙˙˙˙˙˙ ú…0†mŠStrut forces6˝…0†& € €€€‚˙Strut forces&ú…V†# €€€‚˙xG0†Îˆ1 0€€PŽT€ € ‚‚€ € ‚˙Q. I have noticed a discrepancy between the strut force calculated in the stability analysis and that given by the Bending Moment and Displacement calculation at the same stage Please can you advise whether there is a problem in the software. Which figure is correct? A. This question is mentioned in the user manual (section 15.5) and also in the on-line help. Both the Stability and the Bending moment analyses will give a value of the prop force for singly propped walls. The results of the analyses will not necessarily agree and may in some instances diverge widely.ŸrV†mŠ- (€ĺ€PŽT€‚€ €‚˙ The reason for the disagreement is that the stability analysis assumes that all soil pressures on the active side of the wall are at the active limit and takes no account of the sequence of construction operations or pre-stressing of the struts. The Bending moment analysis will generally yield a higher strut force which should be used as the basis for design.U$ΈŠ1đ˙˙˙˙˙˙˙˙ Š‹ŰÉAccuracy of calculated displacementsN(mŠ‹& €P€€€‚˙Accuracy of calculated displacements,ŢŠ<ŒN j€˝€XBĐT€‚ăC:Ë퀉€ ‚㐡˛I€‰€ ‚㧜^€‰€‚˙Q. I get unreasonably large displacements from my WALLAP analyses - why?Q. It is often said that WALLAP over-predicts displacements. Is this true?Q. Can we calibrate WALLAP against observed displacements?â‹XŽ: B€Ĺ€PĐT€ ‚‚€ €‚‚€ € ‚‚‚‚‚˙Q. I get unreasonably large displacements from my WALLAP analyses - why?A. There are some common reasons - here are a few: 1. Inappropriate use of the NC cohesionless model which assumes very low modulus at ground level - please refer to the help on this item 2. Use of an inappropriate value for the "Non-linear modulus paramater". A value of zero combined with large horizontal distances to the distant boundaries will cause displacements to be overestimated.R<ŒśŔ7 <€7€PĐT€ ‚ăÔ뀉€ ‚‚‚‚‚˙ 3. Use of the Subgrade Reaction model instead of the 2D FE model, especially in the case of walls terminating at or just above a very stiff stratum e.g. rock. (see Comparison of SR and 2DFE analyses). 3. Switching off the Soil Arching option for 2D FE analyses. 4. Excessive water pressures on the passive side below ground level in drained soil. LaXŽśŔmŠrge pore pressures reduce the vertical effective stress and therefore the passive resistance. If the water pressures are realistic you may have to make the wall deeper.§lXŽ]Ă; D€Ů€PĐT€ ‚‚€ €‚€ ‚€ € ‚‚‚˙ Q. It is often said that WALLAP over-predicts displacements. Is this true?A. The lack of full and accurate observations combined with appropriate WALLAP analyses makes it difficult to refute the suggestion altogether. However it is clear that there is a common misconception that design and prediction can be combined in a single analysis. Users often select parameters for a SLS (or even ULS) design and then treat the calculated displacements as a prediction of what can be anticipated during construction. What they should be doing is to distinguish between analyses for A) design and B) prediction.b/śŔżĹ3 4€_€PĐT€ ‚‚ƒ‚ƒ‚ƒ‚ƒ‚ƒ‚‚‚˙....The (moderately conservative) parameters used for designing bending moments will almost certainly overpredict displacements. When you are "predicting" displacements you must use best estimates of working parameters e.g.High wall friction - possibly 100%Actual water levelsSoil suction where relevant (there is no direct facility for this, but you could introduce a bit of equivalent cohesion.Actual surcharges, not nominal ones. etc..... You will then find that discrepancies between observed and predicted displacements are minimal.Şy]ĂiČ1 0€ó€PĐT€ ‚€ €‚€ ‚˙Q. Can we calibrate WALLAP against observed displacements? We are currently trying to calibrate WALLAP generated results to known case histories as part of the design process for a significant contiguous wall project in north London. We may get to the point where we may say WALLAP computed X mm for "real" Case A when site results indicated Y mm, thus a correction factor of Y/X is applicable to "other" WALLAP generated movement results. Whilst I see logic in this approach I think it is possibly too simplistic as many other parameters are at play in the derivation of such results. Your comments would be appreciated.r@żĹŰÉ2 2€€PĐT€ ‚€ € ‚‚€‚˙A. I think you should be very careful in generalising. At least you should clasify your problems: Cantilever, Single prop, Multi propped and only extrapolate within the class of problem. Also the stiffness of supports would be very significant; I would not extrapolate from anchored to strutted walls etc... EiČ Ę1“˙˙˙˙˙˙˙˙ Ę^ĘŔËHow to model .......>ŰÉ^Ę& €0€€€‚˙How to model .......& ʄĘ# €€€‚˙j=^ĘîĘ- *€z€Bă<ˆćŽ€‰€‚˙Deflections which occured before the wall was installedŇq„ĘŔËa ’€â€FăGMěՀ‰€ ‚ăeÔSr€‰€ ‚ăüfŸř€‰€ ‚ăë„Ő€‰€ ‚ă,°0€‰€‚˙Cut and cover tunnelEarthquakesBermsKing pile wallsExcavation below the toe of the wallAîĘĚ1ť˙˙˙˙˙˙˙˙ Ě;ĚĹĚTrouble shooting:ŔË;Ě& €(€€€‚˙Trouble shootingŠ[ĚĹĚ/ .€ś€€‚€ ‚‚€ €‚˙Help with installation problems can be found at www.geosolve.co.uk/INSTALL_FAQ.HLP@;ĚÍ1˙˙˙˙˙˙˙˙Í>ÍpSubmerged berms9ĹĚ>Í& €&€€€‚˙Submerged berms&ÍdÍ# €€€‚˙ňž>ÍVĎ4 6€}€F€ €€ ‚‚€ €‚˙The help system states: You should try to avoid specifying submerged ground above a berm on the passive side. The calculation of the reduced passive resistance may lead to inconsistent results when a berm is submerged. If this restriction should prove inconvenient then you should excavate to an equivalent horizontal ground level which gives the same factor of safety as the berm before applying the submerged condition. Further adviceädÍp* "€É€””€ ‚€‚˙The way to find the equivalent horizontal excavation is to compare berm and horizontal excavation in a dry case and then use thVĎpĹĚe equivalent excavation in the submerged case. Do not resort to the use of equivalent surcharges@VĎ°1˙˙˙˙˙˙˙˙°é9King pile walls9pé& €&€€€‚˙King pile wallsP&°9* $€L€€‚€ €‚˙This topic is under development < éu1ł˙˙˙˙˙˙˙˙uŞ, Earthquakes59Ş& €€€€‚˙Earthquakes<uć: B€€PĐT€‚€ € ‚‚€ € ‚‚‚‚‚‚˙Q. How do I use the 'earthquake' values of Ka and Kp obtained from the Help facility in WALLAP A. This is not a simple matter. The following guidance should be of some assistance:1) The earthquake formula is provided "as is". It was introduced at the request of a client who provided me with the formula and seemed to know how to apply the Ka coefficients in design.2) Cohesion. The Ka values do not take account of cohesion and it is not clear how this would be introduced into the calculation.T*Ş:* "€U€PĐT€ ‚‚‚‚‚˙3) Earth pressure distribution The Ministry of Works and Development in New Zealand has a design document which refers to the procedure of Mononobe and Okobe. The MWD document makes it clear that the earthquake contribution to the pressure distribution is an inverted triangular distribution. In the light of the MWD document one sees that the Mononobe and Okobe formula only gives you the magnitude of the resultant and not the line of action. The introduction of Mononobe and Okobe Ka factors into WALLAP is therefore not straight forward.řČć20 .€‘€PĐT€ ‚‚‚‚‚‚‚€‚˙ In the meantime I can suggest an alternative way of obtaining the required distribution: 4) Suggested procedure Enter static values of Ka and Kp in the soil properties data. The earthquake component of force should be calculated by hand and applied as point loads:- The Earthquake formula (press F1 while editing Ka) can be used to calculate the Earthquake value of Ka (Kaeq). The additional force due to the earthquake, Peq is given by:Z&:Œ4 8€L€PĐT€ €€ €€ €‚˙Peq = 0.5gh˛(Kaeq - Ka)  u2, + $€ë€PĐT€ ‚‚‚‚‚‚˙ This force Peq should be applied as an inverted triangular distribution in addition to the usual static pressures i.e. its line of action is 1/3 of the way from the top of the wall.5) Water density correction The Water density correction suggested by Matsuo and O'Hara is difficult to implement within WALLAP and my advice for the time being is to ignore it.X'Œ„ 1]˙˙˙˙˙˙˙˙„ Ő Water pressure balancing at toe of wallQ+, Ő & €V€€€‚˙Water pressure balancing at toe of wallľ~„ Š 7 <€ý€PĐT€‚€ € ‚‚€ € ‚‚‚˙Q. What is the effect of using the water pressure balancing option?A. The automatic water pressure balancing option usually lowers the active water pressure and raises the passive water pressure compared to a simple hydrostatic distrbution (with the higher level on the active side). The effect of this will be to decrease active pressues but also to decrease the passive resistance. The nett result is difficult to predict. Bending moments due to active pressures will generally be lower when using water pressure balancing but the reduction of passive resistance may lead to excessive movements or even loss of stability.w;Ő < F€w€PĐT€ ‚‚€ € ‚‚€ € € € ‚˙Q. When should I use the water pressure balancing option?A. This is simply a question of what is the actual flow condition round the toe of the wall. If the toe is embedded in an impermeable stratum then do not use this option. If the base stratum is permeable then this option is probably appropriate.LŠ M1˙˙˙˙˙˙˙˙M’ @Cohesion varying with depthE’& €>€€€‚˙Cohesion varying with depthP&M @* $€L€€‚€ €‚˙This topic is under development ’ @C’O@1 ˙˙˙˙˙˙˙˙O@‹@ęJConvergence errors< @‹@& €,€€€‚˙Convergence errors{IO@C2 2€“€€‚€‚€‚€ ‚‚‚˙This topic is dealt with in the WALLAP help system. The help text is given here for your convenience:The equilibrium bending moment and displacement solution at each stage is obtained using an iterative procedure. Some ill-conditioned problems fail to converge and the result is a non-equilibrium force distribution."Convergence failure" is easily identified by an out of balance shear force at the toe of the wall. The degree of non-convergence and the extent to which the results may be in error can be gauged directly from the value of shear force at the toe of the wall.ĺ‹@E+ $€Ë€€ ‚‚‚‚‚‚‚‚˙An out of balance force in one construction stage will show up in all subsequent construction stages, even if the calculations in all subsequent stages are convergent. This is because the forces are calculated cumulatively.In rare cases the iterative procedure may diverge wildly. The analysis is interrupted with the message "ill-conditioned problem".Convergence failure is most likely to occur in the following circumstances.a) A very high ratio of soil to wall stiffnessÇ‚CÝGE X€€€ ‚‚‚‚‚€ ‚€‚€ ‚‚‚‚‚‚€ ‚€‚€ ‚˙b) A very great contrast between one soil stiffness and anotherc) 2D FE analysis with Open Tension Crack analysis switched ONd) The wall is close to failure Warning message with stage output*** Convergence failure - Out of balance shear force at elevation -12.34 is 5.67% of the maximum shear force. see Note.or*** Convergence failure - ill-conditioned problemExplanatory Note with summary outputConvergence errors have occurred in at least one Construction Stage. The errors are cumulative, and the results of all stages must be inspected for significant out of balance moment or shear at the toe of the wall.ßEĺH) €ż€€ ‚‚€‚˙Failure of the iterative procedure to converge to an equilibrium solution may be due to a very high ratio of soil stiffness to wall stiffness. The data should be reviewed to see if realistic values have been specifiedŮŞÝGžJ/ ,€U€€‚‚‚‚‚‚‚‚€‚˙----------------------------------------------| Out of balance shear forces. ||--------------------------------------------|| Percentage Error | Interpretation ||--------------------------------------------|| < 2% | Generally acceptable || 2% to 4% | Use with caution || > 4% | Should not be used |----------------------------------------------,ĺHęJ' € €ň€€‚˙ GžJ1K1˙˙˙˙˙˙˙˙1KqKĐMDouble wall cofferdams@ęJqK& €4€€€‚˙Double wall cofferdamsn?1KßK/ .€~€””€‚€ € €‚˙Q. How do I model a double walled cofferdam using WALLAP}OqK\M. *€Ÿ€€ ‚€ € €‚˙A. You can use WALLAP to calculate the stability of the individual walls and the bending moments but you still need to carry out the traditional extra checks on the combined stability of the 2 skins. The mechanisms to be considered are: sliding, toppling, internal shear and deep-seated failure. They are not covered by WALLAP. tLßKĐM( €˜€””€ €‚˙These additional checks may well influence the depth of the sheet piles.M\MN1Ť˙˙˙˙˙˙˙˙NhN[…Non-Linear modulus parameterK%ĐMhN& €J€€€‚˙Non-Linear soil modulus parametery6Ní€C T€m€PĐT€‚€ € ‚‚€ € ‚‚‚‚‚‚‚‚€ € ‚˙Q. What is the significance of the "Non-linear soil modulus parameter" .A. The manual is somewhat brief on the matter; here is a more detailed explanation:1.Stress-strain behaviour of soil is non-linear.2. This is not just to say that it deforms elastically and then fails; even the elastic phase is non-linear.3. The secant mhNí€ĐModulus at low (shear) stresses (and strains) is much higher than at stresses approaching failure.4. One cannot therefore speak of the modulus of a soil but only of the modulus for a certain stress (or strain) increment.ÚŻhNǃ+ $€_€PĐT€ ‚‚‚‚‚‚˙5. In the vicinity of a retaining wall, strain levels are commonly of the order of 0.2 to 1%. The moduli entered in the data should therefore correspond to this sort of strain level.6. The zone of soil which actually experiences strains of this order of magnitude might be about 1 to 2 x wall depth. Soil further away from the wall experiences much smaller strains and therefore has a much higher modulus for the purposes of the analysis.7. It is not convenient to enter a series of moduli for soil at different distances from the wall. WALLAP therefore offers the facility to specify a "basic" modulus for each soil type, which represents behaviour in the vicinity of the wall.”lí€[…( €Ů€PĐT€ ‚‚‚˙ The modulus of soil elements further away from the wall is derived from this basic value (Eo) according to an (arbitrary) formula of the form given in 13.4.4. The formula is exponential i.e. soil modulus increases rapidly with distance from the wall. This is simply a way of saying that soil a long way from the wall has little influence on its behaviour.h7ǃÅ1ô˙˙˙˙˙˙˙˙Å$†ç‹Deflections which occured before the wall was installeda;[…$†& €v€€€‚˙Deflections which occured before the wall was installedÄÅ4ˆL f€‰€PĐT€‚€ € ‚€‚€ € € € ‚‚€ €‚€ ‚‚‚˙Q. Can I discount the deflections due to surcharges which were applied before the wall was installed?A. This topic is dealt with in the WALLAP help system under 'Change Wall Stiffness'. Here is the part of the help message:Change Wall StiffnessThis facility permits the modelling of surcharges which were in place before the wall was installed. The procedure is as follows1. Specify the actual wall stiffness in the Wall Propertiesç$†FŠ+ $€Ď€PĐT€ ‚‚‚‚‚‚˙2. Define Construction Stage 1 as:- Change wall stiffness (EI) to a small value e.g. 10e-5 kN.m˛/m run (or whatever units you are working in).3. Define Construction Stage 2, 3 etc.. as surcharge stages to model the pre-construction surcharges.4. Define Construction Stage 4 as:- Change wall stiffness (EI) back to its value given in the Wall Properties - the program will prompt you with the value previously entered. Select "Reset displacements to zero" at this stage.Ąz4ˆç‹' €ő€PĐT€ ‚‚˙ The surcharges imposed in stages 2, 3 etc.. will cause some displacements but negligible moments in the wall because the wall has negligible stiffness. If "Reset displacements to zero" is selected, as suggested above, the initial displacements up to this stage will be ignored and the final result will represent the nett displacements due to subsequent excavation etc...MFŠ4Œ1Ü˙˙˙˙˙˙˙˙4ŒzŒ>ÁReporting of Applied MomentsF ç‹zŒ& €@€€€‚˙Reporting of Applied Moments&4Œ Œ# €€€‚˙I zŒ Ŕ@ N€€PŽT€ € € ăӑ$A€‰€ € € ‚‚‚˙Q. The amendment ( Moment loads applied through a slab which also acts as a rotational restraint ) appears to work and I like the way that you've added warnings giving the user the option to put a rotational restraint at a different level. One thing that I was not anticipating is the way that "applied moments" are reported in the output. I believe that what is happening is that the column headed "applied moment" is reporting the moment in the restraining member rather than only the moment that we put in. ie it reports the current moment which is the sum of all the externally applied moments plus those moments that arise in the moment restraint as a result of rotation of the wall due, for example, to excavation stages. Am I correct in my assumption?  Œ Ŕç‹@ ŒLŔ0 0€ €PŽT€ ‚€ € ‚€‚˙A. Yes! e6 ŔąŔ/ .€l€€ ăĺÔü˜€‰€‚˙see also Rotational resistance of a floor slabYLŔ>Á4 8€˛€F€ ƒăӑ$A€‰€ €‚˙ Moment loads applied through a slab which also acts as a rotational restraint p?ąŔŽÁ1Z˙˙˙˙˙˙˙˙ŽÁ,ÂUÇHow can I check the relationship between pressure changes, wall~X>Á,Â& €°€€€‚˙The relationship between pressure changes, wall displacements and soil spring valuesŚlŽÁŇÄ: B€Ů€PĐT€‚€ € ‚‚€ € ‚‚‚‚‚‚˙Q. How can I check the relationship between pressure changes, wall displacement and soil spring values?A. For the subgrade reaction method it is possible to make a numerical check by hand calculation:-(i) The check is done by comparing soil pressures, and wall displacements at 2 consecutive stages.(ii) Each check is carried for a specific node on one side of the wall.(iii) You require full printout of wall pressures for the 2 stages.(iv) The soil at the designated node must be operating within its elastic range - this is guaranteed if the soil was NOT at its active or passive limit at either stage.ƒ?,ÂUÇD V€€PĐT€ €€ €€ ‚‚‚‚€€ €€ ‚‚‚˙(v) To check the relationship between pressure changes, wall displacement and soil spring values, find the incremental displacement, Dx, and the incremental soil pressure, Dp, on the selected side of the wall between the 2 stages at the designated node. Note the spring constant, k, (last column) for the designated node on the selected side of the wall. You should find that: k = Dp/Dx For the finite element method it is NOT possible to make a numerical check by hand calculation because of the interaction between the springs at the nodes.c2ŇĸÇ1/˙˙˙˙˙˙˙˙¸ÇČÍHow is the passive resistance of a berm calclated?\6UÇČ& €l€€€‚˙How is the passive resistance of a berm calclated?"é¸Ç6Ę9 @€Ó€PĐT€‚€ € ‚‚€ € ‚‚‚‚‚˙Q. How is the passive resistance of a berm calclatedA. The reduced passive resistance due to berm excavation is calculated on the assumption that sliding may take place on horizontal planes in or below the berm. Sliding on a plane below the toe of the berm is accompanied by passive wedge formation beyond the toe of the berm. The passive pressure listings are annotated with the letter 'b to indicate where the passive resistance has been reduced on account of the berm.ܲČÍ* "€e€PĐT€ ‚‚‚‚‚˙ The calculation is done in 2 stages.(i) For each node elevation the program calculates the total passive resistance down to that elevation (force per metre run of the wall). As stated above the mechanisms considered are sliding on a plane within or below the toe of the berm, accompanied (where relevant) by passive wedge formation beyond the toe of the berm.(ii) Having obtained this profile of available passive FORCE at each elevation we come to the task of calculating a limiting passive PRESSURE distribution. The obvious way to do this is to differentiate the limiting force with respect to depth. This process is carried starting at the toe of the wall and working upwards.p?6Ę‚Í1Ć˙˙˙˙˙˙˙˙‚ÍëÍ€ĎWhat is the pressure behind the wall when you stress an anchor?iCÍëÍ& €†€€€‚˙What is the pressure behind the wall when you stress an anchor?•]‚Í€Ď8 >€ť€PĐT€‚€ € ‚‚€ € €‚˙Q. What is the pressure behind the wall when you stress an anchor? Can it exceed the Active or At Rest pressure?A As an anchor is stressed it forces the wall back into the soil. The only limit on the pressure generated on the back of the wall is the passive limit pressure. This may be well in excess of the Active or At Rest pressure.EëÍĹĎ1i˙˙˙˙˙˙˙˙ĹĎŠCut and cover tunnel>€Ď& €0€€€‚˙Cut and cover tunnelĹĎ€ĎĺĹĎ.: B€Ë€€‚€ € ‚‚€ € ‚‚‚‚‚‚ƒ‚˙Q. How do I model a Cut and Cover Tunnel where I want to fill above the slab which forms the tunnel roof?A. Having excavated to the full depth, here is the construction sequence for backfilling, including the construction of the slabs which form the tunnel base and roof:1 The water table must stay at or below the base slab.2. Backfill with 'Concrete' to represent the floor slab. Concrete properties are:Drained- cohesive, high cohesion value, high modulus value.1ô_= H€é€€ ƒ‚ƒ‚‚‚‚ƒ‚ƒ‚ƒ‚ƒ‚ƒ‚ƒ‚ƒ‚‚‚‚‚‚˙Ka = 1 Kac = 2Kp = 1 Kpc = 23. Backfill with "Air" to represent the space in the tunnel. Air properties are:Drained- cohesive, Density above water table = 0 Density below water table = density of water (a smaller value is not permitted)Zero cohesion Very small modulus (= 1 unit)Ka = 1 Kac = 2Kp = 1 Kpc = 24. Backfill with 'Concrete' to represent the roof slab. Concrete properties as above.5. Backfill above the roof slab with whatever soil is to be used.+.Š& € €€€‚˙ ^-_č1‰˙˙˙˙˙˙˙˙č?— How are the soil spring constants calculated?W1Š?& €b€€€‚˙How are the soil spring constants calculated?Đč]N j€Ą€PĐT€‚€ € ‚‚€ € ‚‚‚‚€€€ €€€ ‚‚‚‚˙Q.How are the soil spring constants calculated?A. The calculation of soil spring constants is described in the User Manual. Appendix B describes the calculation for the Subgrade Reaction method of analysis. Appendix C describes the calculation for the Finite Element method of analysis.Spring values, ks, are calulated by a formula of the form: ks = Es / [D * I(L,D,X, n) * (1 - n˛)] where Es is soil modulus,á?v 8 >€Ă€PĐT€ ‚‚‚€€ ‚€€ ‚‚‚˙ L is the length of the wall, D is the width of the loaded area as defined in Appendix B (Figure B.2) of the User Manual, X is horizontal distance to the rigid boundary n is Poisson's ratio of the soil I is an influence factor which is a function of L, D, X and n. The formula for I is equivalent to Steinbrenner's formulation (quoted by Bowles). I have actually used the equations as presented by Harr (1966).!ô]— - (€é€PĐT€ ‚‚‚‚‚‚‚‚˙ The formula for "I" assumes a uniform soil mass. WALLAP allows the user to specify a non-linear variation of modulus with distance from the wall. In that case the formula has been adapted for use in WALLAP by performing a piece-wise summation of the displacements contributed by layers of different modulus. References. Steinbrenner, W. (1934) Tafeln zur Setzungsberechnung. Die Strasse, Vol. 1, October, pp.121-124. Harr, M.E. (1966) Foundations of Theoretical Soil Mechanics?v Ö 1u˙˙˙˙˙˙˙˙Ö  R WALLAP Updates8—  & €$€€€‚˙WALLAP updatesDÖ R C T€€PĐT€‚€ € ‚‚€ € ‚ƒ‚ƒƒ‚‚€‚€‚˙Q. How do I obtain the latest WALLAP revisions and updatesA. You can help yourself to the latest revisions and updates from:www.geosolve.co.uk/update.htm Information about the latest revisions can be seen at www.geosolve.co.uk/news.htmwF É 1ľ˙˙˙˙˙˙˙˙É 9ÉBUndrained soil property gets re-set to drained automatically by WALLAPpJR 9& €”€€€‚˙Undrained soil property gets re-set to drained automatically by WALLAPĘÉ L@= H€•€PĐT€‚€ € ‚‚€ € ‚‚€ €‚˙Q. We have been trying to perform an undrained analysis. Although we put in consistent undrained strength parameters the program will not perform an undrained analysis. Every time we escape to the main menu to perform the analysis the data file automatically changes back to the drained option.A. Sorry - this is a trap for the unsuspecting and needs better documentation. Firstl9L@R y - it only occurs when you are doing a single pile analysisU-9ĄB( €[€PĐT€ ‚‚‚˙ This requires artificial adjustments to earth pressure coefficients i.e. Ka values are set to zero. This is not compatible with the "undrained" soil type for which Ka is always unity. The program used to automatically reset undrained soils to drained (without telling you!). The most recent revision does not reset the undrained soil property but issues an error message instead. If you want to model undrained behaviour, you will have to accept this limitation and use the drained soil type but enter values of undrained modulus, cohesion etc.. (L@ÉB% €€PĐT€‚˙n=ĄB7C1P˙˙˙˙˙˙˙˙7CžC˝FVertical stress, cannot be reconciled with the soil densitiesgAÉBžC& €‚€€€‚˙Vertical stress, cannot be reconciled with the soil densities÷Â7C•F5 8€…€PĐT€‚€ € ‚‚€ € ‚˙Q. The rate of change of vertical (total) stress, listed in the tables of active or passive pressures, does not correspond to the density of soil, even where there are no surcharges or water pressures?A. Vertical stresses are calculated taking into account the excavated or filled profile. If the width of excavation or fill is very great then the vertical stresses will simply be the sum of the weights of the soil layers. However for narrow excavations (or fill) the weight of soil beyond the excavation will have a significant effect on calculated stresses. In such a case the vertical stress at any depth cannot be calculated by simply summing the densities and thicknesses of all the layers.(žC˝F% €€PĐT€ ‚˙m<•F*G1–˙˙˙˙˙˙˙˙ *GGőLComparison of Subgrade Reaction and 2D Finite Element modelsf@˝FG& €€€€€‚˙Comparison of Subgrade Reaction and 2D Finite Element models{=*G J> J€{€PĐT€‚€ € ‚‚€ € ‚‚€ ‚€ ‚˙Q. I have a model which shows considerable difference in bending moments between Subgrade Reaction vs 2D Finite Element analyses. What are your thoughts on this? Could I use the results of subgrade reaction theory?A. There are many different factors which give rise to differences between the results obtained by the Subgrade Reaction and 2D-Finite Element methods of analysis. Two common ones are: Arching action Arching action in the 2D FE model tends to reduce bending moments and increase strut forces compared with the Subgrade Reaction model.ꚐGőL1 0€s€PĐT€ ‚€ ‚€ €‚˙ Strata below the toe of the wall The Subgrade Reaction model.takes no account of strata below the toe of the wall. The 2D FE model on the other hand allows the stiffness to restrain the wall. This effect is particularly noticeable when the toe of the wall lies in soft or medium stiff strata immediately overlying a very stiff stratum. The SR results reflect only the stiffness of the strata in which the wall is embedded whereas the 2D FE results show the restraining influence of the underlying strata. Toe displacements in the 2DFE analysis can be significantly smaller than in the SR analysis. The extra restraint will however tend to induce higher bending moments near the toe.}L JrM1+˙˙˙˙˙˙˙˙!rMčMׂHow are horizontal stress increments derived from vertical stress incrementsvPőLčM& € €€€‚˙How are horizontal stress increments derived from vertical stress increments/örMO9 @€í€PĐT€‚€ € ‚‚€ € ‚€‚˙Q. Why double the vertical stress increment when calculating the incremental horizontal stresses (WALLAP Manual, Appendix D.2.4)A. It goes like this:- 1. An infinite surcharge, q on a half space causes incremental horizontal stress FčM]O4 8€$€PĐT€€€€€€‚˙q.n/(1-n).ÔOj€- (€Š€PĐT€ ‚‚‚‚€‚˙ 2. Under this condition vertical planes remain plane - no horizontal displacement. 3. Therefore a semi-infinite]Oj€őL surcharge, q adjacent to a rigid vertical plane (wall) causes the same horizontal stress,F]O°€4 8€$€PĐT€€€€€€‚˙q.n/(1-n).­lj€]‚A P€Ů€PĐT€ ‚‚‚‚‚€€€€€€ ‚€‚˙ 4. The incremental vertical stress below an infinite surcharge, q, is q at all depths. 5. The incremental vertical stress (delta sigma v' in the manual) below the EDGE of a semi-infinite surcharge, q, is q/2 at all depths. 6. To get the correct horizontal incremental pressure [q.n/(1-n)] you have to double the incremental vertical stress i.e.N°€Ť‚7 >€.€PĐT€ €€€€€€‚˙2(q/2).n/(1-n),]‚ׂ' € €PĐT€ ‚‚‚˙@Ť‚ƒ1˙˙˙˙˙˙˙˙"ƒPƒ ƒRun time errors9ׂPƒ& €&€€€‚˙Run time errorsP&ƒ ƒ* $€L€€‚€ €‚˙This topic is under development |KPƒ„1ž˙˙˙˙˙˙˙˙#„‘„ŒUnreasonably low Factors of Safety for a wall with a single low level strutuO ƒ‘„& €ž€€€‚˙Unreasonably low Factors of Safety for a wall with a single low level strutG„؆C T€ €PĐT€‚€ € ‚‚€ € ‚‚€ € € € ‚˙Q. When strut level is below the mid-height of the wall the calculated factors of safety seem unreasonably lowA. The question of the low level strut comes up quite regularly. The situation is this: The fundamental concept behind the FoS calculation with one strut is that the wall is failing by forward rotation of the toe. It is assumed in the calculation that all soil pressures on the retained side are at the active limit and that all soil pressures on the pasive side are at the passive limit.‡‘„š‰; D€€PĐT€ ‚€ € ‚‚€ € € € ‚˙ The assumption with respect to active pressures is strictly true only when the strut is at (or above) active ground level. When the strut is below active ground level the movement of the upper part of the wall (above strut level) is backwards into the retained soil and that part of the wall will tend to generate reverse passive pressures. These reverse passive pressures have, in practice, a beneficial effect on safety. This effect is however ignored in the traditional calculation which assumes that the pressures are at the active limit. This is essentially an error in the calculation whose effects are on the safe side. \3؆ö‹) €g€PĐT€ ‚‚‚‚˙ A modified form of the calulation which takes account of reverse passive pressures above the strut will be introduced into WALLAP (one day). Meanwhile you must use the FoS results for very low level struts with great caution. (They will be unreasonably low and give the impression that the wall is failing when it isn't). To convince yourself that the wall is safe you could reduce all soil strengths by the required factor of safety and check that the wall does not fail in the bending moment calculation. This is proof that the required FoS exists.(š‰Œ% €€PĐT€ ‚˙h7ö‹†Œ1˙˙˙˙˙˙˙˙$†ŒčŒ8How do I use WALLAP to satisfy a particular design codeb<ŒčŒ& €x€€€‚˙How do I use WALLAP to satisfy a particular design code?P&†Œ8* $€L€€‚€ €‚˙This topic is under development `/čŒ˜1^˙˙˙˙˙˙˙˙%˜ňęÂIdentical data files produce different results.Z48ň& €h€€€‚˙Identical data files produce different results. šƒ˜ŤŽ6 :€€€‚€ € ‚‚€ € €‚˙Q. Apparently identical data files produce different results - why?A. Apologies for a bit of obscure WALLAP behaviour.Ć›ň}Á+ $€7€PĐT€ ‚‚‚‚‚‚˙ The value of wall friction in soil types 2, 4 and 5 are different in the two data sets. The value of tan(delta)/tan(phi) is only displayed when you edit the properties of a soil type. They can only be set by going into the help facility for Ka and Kp. Sadly the values of delta and phi doŤŽ}Á8 not appear on the printed output. For most puposes, only the values of Ka, Kap, Kp, Kpc actually matter. But there are 2 exceptions which arise when WALLAP needs to backfigure phi from the given Ka, Kap, Kp, Kpc values. This backfiguring is done using a formula that includes tan(delta)/tan(phi) (and beta, the backfill angle). The 2 cases to watch out for are:m:ŤŽęÂ3 4€u€PĐT€ ‚‚‚‚‚‚‚€€‚˙1) Berms. WALLAP uses phi rather than Kp to work out sliding resistance on horizontal planes in and below the berm.2) Use of the Strength Factor method. Ka and Kp are converted to phi. Phi and delta are scaled and new values of Ka and Kp are calculated.I will introduce some clearer warning messages. ‡V}ÁqĂ1k˙˙˙˙˙˙˙˙&qĂëĂ%ĘThe EC7 values of Ka and Kp given by WALLAP do not agree with the charts in Eurocode 7zTęÂëĂ& €¨€€€‚˙The EC7 values of Kp given by WALLAP do not agree with the charts in Eurocode 7&qĂÄ# €€€‚˙Č—ëĂŮĆ1 0€/€PĐT€ € ‚‚€ € ‚˙Q. I have compared the calculated Kp values based on EC7 in Wallap and the Charts given in the document. They do not agree, in fact it appears that the calculated Values for wall/soil friction ratio of 1.0 is equivalent to the values for a ratio of 0.66 on the charts. I will be interested to hear your views. I am looking at high values of friction angles say between 30 degrees and 50 degrees. A. There are some obvious difficulties and ambiguities in interpreting EC7. The charts give a single value of Kp for a given phi and delta whereas the formula introduces a number of variables such as m(t), m(w) and beta(0) to do with boundary conditions.ą†ÄŠÉ+ $€ €PĐT€ ‚‚‚‚‚‚˙ Are you concerned because the WALLAP values are adversely affecting the economy of your designs or because the discrepancy makes you doubt the reliability of WALLAP in principle? On the first count I would say that the effect cannot be too serious if you have such strong ground (phi = 50deg.!) and on the second count I am confident that WALLAP is thoroughly consistent and a bit conservative - all the better - do you agree? The implementation of the EC7 formula which is embodied in WALLAP is in accordance with recommendations of CIRIA Publication C580, Appendix F and agrees with the graphical information presented there.›jŮĆ%Ę1 2€Ô€PĐT€ ‚‚€ €‚€ ‚˙ReferenceEmbedded retaining walls: guidance for economic design. CIRIA Publication C580. ( 2003 )~MŠÉŁĘ1Ü˙˙˙˙˙˙˙˙'ŁĘËĹĎMoment loads applied through a slab which also acts as a rotational restraintwQ%ĘË& €˘€€€‚˙Moment loads applied through a slab which also acts as a rotational restraint‘bŁĘŤË/ .€Ä€F€‚€ € ‚€‚˙Q. How do I model moment loading via floor slabs which also provide rotational restraint. s?ËĎ4 6€€PŽT€ € €‚€ ‚€‚˙A. In WALLAP Version 5.01 Revision A11.B26.R18 (Dec. 2002) a new facility has been introduced which permits the application of structual moments at the same elevation as an exsiting rotational restraint. This facility is intended to be used for modelling the common situation where a floor slab or bridge deck (encastré into the wall) is subject to live loads which cause moment loading to the wall. Normally, all rotational restraints will apply at all stages regardless of the source of loading. The new facility creates an exception. Where an applied load is at the same elevation as an existing rotational restraint, the effect of the rotational restraint, is suspended during the application of the load. This gives the desired result that the rotational restraint does not absorb part of the applied moment. §^ŤËĹĎI b€ź€F€‚€ ăĺÔü˜€‰€ ‚ƒăŒ)!€‰€ ‚€€‚˙see also Rotational resistance of a floor slab Reporting of Applied Moments V%Ď'1[˙˙˙˙˙˙˙˙('v RotationalĹĎ'ĹĎ resistance of a floor slabO)ĹĎv& €R€€€‚˙Rotational resistance of a floor slabą„''- (€ €F€ ‚€ ‚€‚˙ Q. How do I model the effect of a floor slab which is encastré into the wall and resists the tendency of the wall to rotate?‡GvŽ@ N€€PŽT€ € € € € € ‚‚€ € €‚˙A. WALLAP offers a simple way to deal with this. The facility is found under the Loads button during data entry. The data block is entitled Horizontal and moment loads/restraints. The relevant parameters are defined in the WALLAP help system. A special difficulty may arise when it is necessary to model the effects of vertical loads applied to the floor slab. The floor slab is then applying a moment load to the wall at the same elevation as the exisiting rotational restraint. The way in which WALLAP deals with this situation is described in the following topic.('Ö% €€PŽT€‚˙ʈŽ B R€€F€ € ăӑ$A€‰€ ‚ƒăŒ)!€‰€‚˙see also Moment loads applied through a slab which also acts as a rotational restraint Reporting of Applied MomentsBÖâ1˙˙˙˙˙˙˙˙)âLost hardware key; & €*€€€‚˙Lost hardware keyĺľâ0 .€k€€‚€€€‚‚‚˙If your license was protected with a hardware key (dongle) which has been lost please email support@geosolve.co.uk explaining the circumstances in which the key was lost.DF1ď˙˙˙˙˙˙˙˙*F‰G Graphics in ReportsC‰& €:€€€‚˙Errors in Report GraphicsłFŽR r€g€€‚€ €‚€ ‚‚€ €‚€ €€€€‚€‚€€‚˙The symptomsSome users have experienced difficulties with graphics in reports. Typical symptoms are that part of the picture is obscured by black areas (see below). When does the problem occurThe problem occurs on some machines and not others. One user encountered the problem on an IBM ThinkPad T41p with XP pro Operating system. but not on a much slower, Pentium III machine with Win98 SE.Suggested work-around„U‰ / ,€Ť€€€‚‚€€‚˙Generate the report without graphics. Use the copy and paste facilities to get selected graphics from WALLAP and paste them into the report at the appropriate points. (To copy a graphic from WALLAP to the windows clipboard: Click on the graphic and then type Ctrl C) Units: kN,m5ŽG 0 0€ €Œ€ †"€€‚˙\+ Ł 1á˙˙˙˙˙˙˙˙+Ł ÷ § Cannot focus a disbled or invisible window'T.G ÷ & €\€€€‚˙Cannot focus a disbled or invisible window&îŁ  8 >€Ý€V””ŽT€ € €‚€ € €‚˙Q. Why do I keep getting the message 'Cannot focus a disbled or invisible window' during data entryA. You are running WALLAP version 5.02 or less. The latest revision solves the problem. You can help yourself to the update at: [-÷ x . ,€Z€””€!€ ƒƒƒ€‚˙http://www.geosolve.co.uk/update.htm / § * $€ €V””ŽT€€‚˙ ^-x  1{˙˙˙˙˙˙˙˙, \ ­DReferences to WALLAP in journals and articlesW1§ \ & €b€€€‚˙References to WALLAP in journals and articlesqF Í + &€Œ€€‚€ ‚€‚˙Please send any additional references to support@geosolve.co.ukM&\ ' €L€J€ €‚˙__________________________________ľ|Í Ď9 @€ů€””J€"€‚€€#‚€ €‚˙Deep underground basements for major urban building constructionPearlman, S.L., M.P.Walker and M.D.Boscardin. Geo-Support 2004: Drilled Shafts, Micropiling, Deep Mixing, Remedial Methods, and Specialty Foundation SystemsProceedings of Sessions of the Geo-Support Conference: Innovation and Cooperation in the Geo-Industry, held in Orlando, Florida, January 29-31, 2004 M&(@' €L€J€ €‚˙_________Ď(@§ _________________________˘gĎĘA; D€Ď€””J€"€#‚€€#‚€ €#€‚˙Design and constructionof temporary ground anchorages at Castle Mall development, Norwich. Barley, A.D., R.Eve and D.Twine Retaining structures, proceedings of the Conference on retaining structures held by the Institution of Civil Engineers, 20-23 July 1992, Robinson College, Cambridge, UK, ISBN 0-7277 19327, Thomas Telford, London, U.K., 1993. M&(@B' €L€J€ €‚˙__________________________________kBĘA‚B) "€„€””J€"€‚˙Design & performance of a temporary anchored soldier pile wallߎBaC1 0€]€ œ€$‚‚€‚€€‚˙3rd Car Dumper Pit, BHP Iron Ore Facility, Nelson Point, Port Hedland, AustraliaMarc A. Woodward CP Eng MICEAssociate Director - Soil & Rock Engineering pty. ltd.>‚BŸC; F€€ ‘€–!ąAŃańĄ1€‚˙šqaC9D) "€â€ œ€ ‚‚€‚˙Australian Geomechanics Society Issue 33/3 1998 pp. 41-50Download from www.geosolve.co.uk/Woodward.pdfM&ŸC†D' €L€J€ €‚˙__________________________________'9D­D$ €€ œ€‚˙\+†D E1 ˙˙˙˙˙˙˙˙- E^ELNChange from Undrained to Drained conditionsU/­D^E& €^€€€‚˙Change from Undrained to Drained conditions_' E˝F8 >€O€PĐT€‚€ € ‚‚€ € €‚˙Q. When carrying out a Wallap analysis which involves changing from undrained to drained parameters, do you have to make any adjustments to the pore water pressures in addition to changing the soil parameters?A. Apologies - the manual and help system are not at all explicit on this. ^8^EJ& €q€Ѐ ‚‚˙The initial conditions are by implication "drained" i.e. there is pore pressure equilibrium - even in undrained soil types. The initial stress state is calculated on the basis of the initial pore pressures.(The term "undrained" refers to a process, not an initial state). During construcion, undrained stress changes imply the generation of pore pressures (either positive or negative). As long as the undrained soil types remain undrained we don't really have to think about what those pore pressure changes are. If at some stage drainage is deemed to occur then one really ought to be defining the undrained pore pressure profile at the moment just before drainage occurs. This should be followed by a drained pore pressure profile so that we model the effect of the stress changes. The sequence might look like this :j˝F¸L3 4€Ő€Ѐ ‚‚‚‚‚‚‚‚‚‚‚€‚˙Stage 1. Define Initial pore water pressure profileStage 2. constructionStage 3. more constructionStage 4. more constructionStage 5. Define undrained pore water pressure profile (Analysis at this stage should not have any effect)Stage 6. Change undrained soil types to drained (Analysis at this stage should not have any great effect)Stage 7. Define drained pore water pressure profileExcavations in stiff clay should show increased movements and decreased factors of safety. Excavations in soft clay should show little or no additional movement and increased factors of safety. ”jJLN* "€Ő€””Đ€ €‚˙The difficulty is to estimate the undrained pore pressures to apply at Stage 5. This could be done in a fairly crude way by assuming that mean normal effective stress is unchanged plus an allowance for the change of shear stress according to whether the soil is overconsolidated (decreasing pore pressure) or normally consolidated (increasing pore pressure).g6¸LłN1B˙˙˙˙˙˙˙˙.łN+OW‚Excavation below the toe of the wall with version 5.03xRLN+O& €¤€€€‚˙Model excavation below the toe of the wall with WALLAP version 5.03 (or later)błN¸O+ &€Ä€€‚€ ‚€‚˙Please refer to the accompanying data file www.geosolve.co.uk/Excavate_Below_Toe_v503.dati+O-‚Q p€1€P•€o€ €‚€"€ ‚€"€ ‚‚€"€ ‚‚€"€ €¸O-‚LN"€ ‚‚‚˙Definitions Ytoe = True elevation of toe of wallYexc = Deepest excavation elevationStep 1. In the wall data define the "Toe" of the wall as being at an elevation (Yexc) just below the deepest excavation elevation.Step 2. Define Stage 1 as a "Change EI of Wall" stage in which you change the EI value of the wall between Ytoe and Yexc to a very samll value (say 1). Step 3 Define all the soil strata and construction stages as you would noramlly. You will be able to excavate below the true toe of the wall *¸OW‚' €€P•€o€‚˙V%-‚­‚12˙˙˙˙˙˙˙˙/­‚ü‚ý†Pre-stressing of struts in two stagesO)W‚ü‚& €R€€€‚˙Pre-stressing of struts in two stagesŔ­‚ý†A P€€P¸J€‚€ € €‚€ ‚€ € €€‚˙Q. How do I model ground anchors which pres-stressed in 2 stages? I intend to pre-stress the ground anchors to say 30% and then lock off at 110%.A. One way to tackle this is to define 2 anchors at slightly different elevations. One anchor represents the initial pre-stress and the second anchor represents the final stressing. You enter the initial pre-stress (30%) in the 1st anchor properties and the final pre-stress (110%) in the 2nd anchor properties. Make sure to define both struts (anchors) as "No tension allowed". You will find that the installation of the 2nd anchor absorbs most of the stress in the first anchor which is why you have to apply almost the whole 110% in the second anchor. It is important to interpret the WALLAP output correctly - the value in the column headed "Strut force" in the bending moment and displacements table is to be understood as the true force in the anchor. It is the combination of the two anchors. n=ü‚k‡1‹˙˙˙˙˙˙˙˙0k‡ć‡@ŒModel_excavation_below_the_toe_of_the_wall_using_version_5.02{Uý†ć‡& €Ş€€€‚˙Model excavation below the toe of the wall using WALLAP version 5.02 (or earlier)ák‡ú‰3 4€Ă€€ ‚‚‚ƒ‚‚‚‚€ € ‚‚˙Please refer to the accompanying data file www.geosolve.co.uk/Excavate_Below_Toe_v502.datThe following steps will enable you to model excavation below the toe:1. Assign a new soil type, "Rock (P)" to the Rock on the passive side. This soil type (soil type N, say) will have the same properties as the normal Rock but by making it a different soil type you can change its properties (without changing the propeprties of the soil at the same elevation on the Őć‡Œ4 6€Ť€€ ‚‚‚‚‚‚‚‚‚‚‚‚‚‚‚‚‚˙ active side)2. Define another new soil type called "Air" Bulk Unit above water table = 0 Bulk Unit above water table = Bulk Unit of water Drained Cohesionless Ko = 0 Ka = 0 Kac = 0 Kp = 0 Kpc = 03. Excavate to just above toe level in the usual way.4. Define final water pressure condition5. Simulate the excavation below toe level by defining a construction stage which changes soil type N (the passive rock)=ú‰@Œ$ €2€€ ‚‚˙ to soil type "Air"c2ŒŁŒ1ă˙˙˙˙˙˙˙˙1ŁŒ}ŔCorrelation between SPT Nvalue and Young's modulus]7@Œ& €n€€€‚˙Correlation between SPT N-value and Young's modulus›hŁŒ›Ž3 4€Ń€€‚€ ‚‚€ ‚‚‚€‚˙The User's Guide and interactive help do not give a reference for the correlation between SPT Nvalue and Young's modulus. It is taken from Figure 6 of:Stroud, M.A. and F.G.Butler.The Standard Penetration Test and and the Engineering Properties of Glacial Materials.Proc. Symposium on the Engineering Behaviour of Glacial Materials. Birmingham 1975.K%ćŽ& €J€€ €‚˙_________________________________‹Y›Ž}Ŕ2 2€ł€€ ‚‚‚‚€%€ ƒƒ‚‚‚˙The advice given in the User's Guide and interactive help is:The Young's modulus of an over-consolidated (compacted) cohesionless soil is approximately proportional to its SPT N value according to the equation:Young's modulus (ćŽ}Ŕ@ŒkN/m˛) @ F x SPT N valuewhere F is in the range 2000 to 6000 for retaining walls in sands and gravels.n=ćŽëŔ1÷ ˙˙˙˙˙˙˙˙2ëŔRÁÎLarge bending moments when re-watering under a basement slab.gA}ŔRÁ& €‚€€€‚˙Large bending moments when re-watering under a basement slab.Ş{ëŔüÁ/ .€ö€PĐT€‚€ € €‚˙Q. I am trying to model a "tanked" basement for the long term condition. (see www.geosolve.co.uk/TankedBasement.dat)Č›RÁÄÄ- (€7€6””ČȀ ‚‚€‚˙Stage 9 is the condition where the basement floor slabs have been installed, and the water pressures are hydrostatic but not balanced at the toe due to the presence of the impervious soil layer.Stage 11 models the "tanked" basement condition where the water pressures behind and in front of the wall (below excavation level) are the same. A surcharge load is included on the passive side to stop the slab from popping up.My question is why are the bending moments in Stage 11 about 50% higher than in Stage 9? I would have thought the final condition would not have been the critical case, given the water pressures behind and in front of the wall are the same.ĎüÁČĹ5 8€Ÿ€v””ĐČT€ € € € €‚˙A. Everything hinges on the water pressure distribution before the re-watering. Your model has hydrostatic distributions front and back. Thus there is a large out of balance water pressure at the toe.uCÄÄ=É2 2€‡€V””ĐT€ €#‚€ €‚˙ It is fairly clear what is happening. Most of the bending moment develops at stage 4 when excavating down to -1.15. The strut at excavation level fixes the wall at that level and so when the reverse water pressure is applied, extra moment is applied about the bottom strut - which was already the level of maximum moment. You might have thought that the reverse water pressure would simply be accommodated by a reduction of passive soil pressure and an increase in active soil pressure. This happens up to a point but it requires soil movement to mobilise the pressure change. Your soil at excavation level is not very stiff (E = 30000 kPa). If it were stiffer you would get less increase of moment. In fact the increase in bending moment due to re-watering is roughly inversely proportional to the stiffness of the soil.b)ČĹŸË9 @€S€v””ĐČT€ € €‚€ € € ‚˙ What if the founding stratum were permeable? If the wall were toed into a permeable stratum then there should be more of a match between the pore pressures at the toe. WALLAP offers a simple way to model this with the Automatic Water Pressure Balancing option. It is not a simple matter to assess the correct pwp distribution. Wrong estimates of water pressures probably constitute the largest source of error in many analyses just because we often have so little information about existing water levels and even less about permeability. y8=ÉÎA P€q€v””ĐČT€ € €‚€ ‚€ €‚€ €‚˙ What if you modelled the construction sequence with undrained properties? Since the soil at toe level is highly impermeable presumably it will behave in an undrained manner during construction with drained conditions developing slowly afterwards. You could then change to drained properties as a final stage. The Undrained soil properties are included in the above data file as Soil Type 4 Suggestion I suggest you consider a range of pwp distributions and form a judgement about the likelyhood of the least favourable ones occuring in practice.h7ŸË€Î1ƒ˙˙˙˙˙˙˙˙3€ÎáΖCan WALLAP calculate settlements of the ground surface?a;ÎáÎ& €v€€€‚˙Can WALLAP calculate settlements of the ground surface?řš€Îĺ? L€s€PĐT€‚€ € € ‚€‚€ € ‚€‚˙Q. Can WALLAP calculate the settlements of the ground surface.A. WALLAP does not actually calculate settlements. But it has been observed in practice that the settlement profile of the ground surface approximately áÎĺÎmirrors the deflection profile of the wall. Thus the settlement of the ground surface at a distance X from the wall is approximately equal to the horizontal displacement of the wall at depth X below ground level. ą…áΖ, &€ €PÚx‚ý€ €‚˙This observation is particularly relevant in the case of a wall with a single prop near the top. The prop ensures that there is very little movement of the top of the wall and consequently very little settlement just behind the wall. However the wall movements at depth which can be significant are reflected as settlements of similar magnitude at an equivalent distance from the wall.EĺŰ1Ą˙˙˙˙˙˙˙˙4ۉScope of the program>–& €0€€€‚˙Scope of the programp?ۉ1 2€~€F€‚ăů73〉€‚˙Can WALLAP calculate settlements of the ground surface?k:ô1W˙˙˙˙˙˙˙˙5ôX~Large displacements or convergence failure in ULS analysisd>‰X& €|€€€‚˙Large displacements or convergence failure in ULS analysis'ô$ €€R€‚˙TXÓA P€'€XRĐT€ € €&€ €‚‚€ € €€‚˙Q. I don't seem to be able to get Wallap to work correctly when attempting an Ultimate Limit State design. We seem to get large deflections and/or convergence problems A. It is to be expected that a ULS analysis will produce large displacements. It does not in any way invalidate the results - these are not dispalcements which you expect to see in practice. What you get out of such an analysis is the ULS bending moments and strut forces which the structure must be (just) able to sustain in an extreme condition. ƒQV2 2€Ł€^””RĐT€#€ €'€‚˙ It can happen that WALLAP fails to arrive at a solution at all. That could be due a weakness in the iterative procedure of the program or just that the structure has genuinely failed. To explore this further you could perform more analyses with a range of partial factors on soil strength - i.e. approach the ULS gradually. (Ó~% €€””€‚˙1VŻ1U˙˙˙˙˙˙˙˙6˙˙˙˙ŻÓ$~Ó" €€€˙1Ż˙˙˙˙1˙˙˙˙˙˙˙˙7˙˙˙˙˙˙˙˙˙˙˙˙Ľœ (äHelvFixedsysMS Sans SerifSymbolArialCourier NewTimes New Roman020206030504050203002070309020205020400000000000000000000sans-serif €@@€@@@@@@@@ @@@@    /&;)Lz˙˙8?0˙˙Contents4 Installation Lost installationsŸ‚King pile wall with a berm - not permittedm…Installation instructions8†Input data^‡Method of calculation‚ˆDesign / Codes of PracticećˆExcavation below the toe of the wallInterpretation of resultsőStrut forcesÁAccuracy of calculated displacementsTˆHow to model .......‰Trouble shootingŒ‰Submerged bermsKing pile walls9Earthquakes×Water pressure balancing at toe of wallť Cohesion varying with depth€Convergence errorsT‰Double wall cofferdamsH‹Non-Linear modulus parameterDeflections which occured before the wall was installed{ Reporting of Applied MomentsŸ€How can I check the relationship between pressure changes, wall˘…How is the passive resistance of a berm calclated?sŠWhat is the pressure behind the wall when you stress an anchor?ŒCut and cover tunnelŢHow are the soil spring constants calculated?´ WALLAP UpdatesÇ Undrained soil property gets re-set to drained automatically by WALLAP0‚Vertical stress, cannot be reconciled with the soil densities6…Comparison of Subgrade Reaction and 2D Finite Element modelslŠHow are horizontal stress increments derived from vertical stress incrementsšRun time errorsÓUnreasonably low Factors of Safety for a wall with a single low level strutăHow do I use WALLAP to satisfy a particular design codeE Identical data files produce different results.:The EC7 values of Ka and Kp given by WALLAP do not agree with the charts in Eurocode 7‡Moment loads applied through a slab which also acts as a rotational restrainth‹Rotational resistance of a floor slabLost hardware keyIGraphics in ReportstCannot focus a disbled or invisible window'ÂReferences to WALLAP in journals and articlesƒChange from Undrained to Drained conditions|‹Excavation below the toe of the wall with version 5.03Pre-stressing of struts in two stagesŸ˙˙ěModel_excavation_below_the_toe_of_the_wall_using_version_5.02Correlation between SPT Nvalue and Young's modulus€Large bending moments when re-watering under a basement slab.ʋCan WALLAP calculate settlements of the ground surface?…Scope of the programÜLarge displacements or convergence failure in ULS analysis„†el .......‰Trouble shootingŒ‰Submerged bermsKing pile walls9Earthquakes×Water pressure balancing at toe of wallť Cohesion varying with depth€Convergence errorsT‰Double wall cofferdamsH‹Non-Linear modulus parameterDeflections which occured before the wall was installed{ Reporting of Applied MomentsŸ€How can I check the relationship between pressure changes, wall˘…How is the passive resistance of a berm calclated?sŠWhat is the pressure behind the wall when you stress an anchor?ŒCut and cover tunnelŢHow are the soil spring constants calculated?´ WALLAP UpdatesÇ Undrained soil property gets re-set to drained automatically by WALLAP0‚Vertical stress, cannot be reconciled with the soil densities6…Comparison of Subgrade Reaction and 2D Finite Element modelslŠHow are horizontal stress increments derived from vertical stress incrementsšRun time errorsÓUnreasonably low Factors of Safety for a wall with a single low level strutăHow do I use WALLAP to satisfy a particular design codeE Identical data files produce different results.:The EC7 values of Ka and Kp given by WALLAP do not agree with the charts in Eurocode 7‡Moment loads applied through a slab which also acts as a rotational restrainth‹Rotational resistance of a floor slabLost hardware keyIGraphics in ReportstCannot focus a disbled or invisible window'ÂReferences to WALLAP in journals and articlesƒChange from Undrained to Drained conditions|‹Excavation below the toe of the wall with version 5.03Pre-stressing of struts in two 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