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BLUM THEORY 1
- Thread starter Ash2007
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Steel manufacturer, TradeArbed,Inc., had a sheet pile design manual titled, Practical Design of Sheet Pile Bulkheads, 2nd Edition. Pages 27 to 29 have an explanation of Blum's method. They contacting Arcelor or Skyline Steel for a copy of the manual or its successor.
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- #3
Thank you so much, but I already have that manual, besides my main concern is I tried using PROSHEET for calculating the stresses on the Sheet pile, and when compared with my own excel sheet ( simple basics applied to calculate stresses using principles of soil mechanics) they somehow do not seem to tally.
Besides while dealing with BLUM i am trying to compare its main working priciple with design of sheet pile using some other theory.
Besides while dealing with BLUM i am trying to compare its main working priciple with design of sheet pile using some other theory.
I believe that ProSheet checks moment equilibrium when solving for the sheet pile length. The user then adds the extra embedment as desired. Or the user can input a reduced Kp to give embedment with the desired safety factor. The input safety factor in ProSheet addresses only the bending stress of the sheet pile.
If you apply a safety factor to Kp, you will need a bigger sheet pile section than if you use full Kp, solve for moment equilibrium, and then increase the embedment length by about 20%.
Certain text books add extra sheet pile embedment in order to get force equilibrium in the x direction. This seems like baloney to me. For a cantilevered wall, the passive resistance is a reaction, not a force. Due to its shorter moment arm in checking moment equilibrium, the total passive pressure will always be greater than the total active pressure. Even though the total passive presure is greater than the total active pressure, the wall cannot move backwards. If it could, the active side would become passive and the passive side would become active. The process would then keep repeating. Makes no sense. For cantilevered sheet pile walls, I solve for moment equilibrium only, get the required embedment depth, then add at least 20% to the embedment length. Then, I'm done.
Good luck in trying to match your Excel calcs with the ProSheet results.
If you apply a safety factor to Kp, you will need a bigger sheet pile section than if you use full Kp, solve for moment equilibrium, and then increase the embedment length by about 20%.
Certain text books add extra sheet pile embedment in order to get force equilibrium in the x direction. This seems like baloney to me. For a cantilevered wall, the passive resistance is a reaction, not a force. Due to its shorter moment arm in checking moment equilibrium, the total passive pressure will always be greater than the total active pressure. Even though the total passive presure is greater than the total active pressure, the wall cannot move backwards. If it could, the active side would become passive and the passive side would become active. The process would then keep repeating. Makes no sense. For cantilevered sheet pile walls, I solve for moment equilibrium only, get the required embedment depth, then add at least 20% to the embedment length. Then, I'm done.
Good luck in trying to match your Excel calcs with the ProSheet results.
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- #5
Ok I appreciate your comment, fully agree to it, neverthless I have a question for you and will kindly appreciate if you let me know.
In Prosheet, when you enter the value for Ka and Kp and similarly the Densities submerged, for example U have a elevation of 6 m and 7m. the soil profile changes at 6 m and at 7 m. ( which means diff densities and different Ka values at 6 and 7 M). I want to know when Prosheet calculates the pressure / stress does it take the soil properties below 6 m for its calculation or above 6 m for its calculation ( for calculating stress at 6 m).
I guess my question cud be a bit confusing, but I know this understanding when applied to my excel calculation solves the problem.
In Prosheet, when you enter the value for Ka and Kp and similarly the Densities submerged, for example U have a elevation of 6 m and 7m. the soil profile changes at 6 m and at 7 m. ( which means diff densities and different Ka values at 6 and 7 M). I want to know when Prosheet calculates the pressure / stress does it take the soil properties below 6 m for its calculation or above 6 m for its calculation ( for calculating stress at 6 m).
I guess my question cud be a bit confusing, but I know this understanding when applied to my excel calculation solves the problem.
It uses the appropriate soil valuse for each soil layer. Look at the earth pressure diagram printout to see how the pressures change at the layers.
You may want to call an engineer from Skyline Steel in New Jersey who can answer your questions. Try calling 973-428-6100. Ask for David Borger in engineering.
You may want to call an engineer from Skyline Steel in New Jersey who can answer your questions. Try calling 973-428-6100. Ask for David Borger in engineering.
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- #7
Thank you for your Kind Reference. I will call him and talk to him. But I somehow do not quite agree with PROSHEET considering the appropiate soil value for each layer. neverthless will think upon it more.
I will aslo ask Mr Borger regarding further information dealing with Corrosion,and the difficulties a Design engineer faces for encountering corrosion allowance for sheet piles, as that per EUROCODE is NOT based upon the semi-probabilistic approach.
once again appreciate your best reply.
I will aslo ask Mr Borger regarding further information dealing with Corrosion,and the difficulties a Design engineer faces for encountering corrosion allowance for sheet piles, as that per EUROCODE is NOT based upon the semi-probabilistic approach.
once again appreciate your best reply.
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in PROSHEET, it calculates the CROSS FORCE, I suppose that it is done from the total pressure diagram. If I am right, the cross force is calculated by the area of the total pressure diagram, AT THE RESPECTIVE ELEVATION.
BTW to Note PROSHEET DOES NOT GIVE THE RIGHT BOUSSINESQS FORMULA BUT ON CORRECTING IT THEN THE TOTAL PRESSURE DO MATCH.
IN THAT CASE FROM THIS PRESSURE DIAGRAM HOW DO U CANCULATE THE CROSS FORCE?
APPRECIATE YOUR REPLY,
BTW to Note PROSHEET DOES NOT GIVE THE RIGHT BOUSSINESQS FORMULA BUT ON CORRECTING IT THEN THE TOTAL PRESSURE DO MATCH.
IN THAT CASE FROM THIS PRESSURE DIAGRAM HOW DO U CANCULATE THE CROSS FORCE?
APPRECIATE YOUR REPLY,
The cross force is the shear force in the sheet pile wall. It is calculated just like it would be for any beam design.
I also believe that ProSheet, when calculating the Boussinesq surcharge pressure, multiplies the classical Boussinesq lateral pressure by Ka because sheeting is not a rigid wall as is the basis for the Boussinesq analysis. Therefore, ProSheet should be giving a lateral force that is less than what you would expect from the regular, classical, Boussinesq equation.
You should confirm my above statements with Skyline or Arcelor.
I also believe that ProSheet, when calculating the Boussinesq surcharge pressure, multiplies the classical Boussinesq lateral pressure by Ka because sheeting is not a rigid wall as is the basis for the Boussinesq analysis. Therefore, ProSheet should be giving a lateral force that is less than what you would expect from the regular, classical, Boussinesq equation.
You should confirm my above statements with Skyline or Arcelor.
Bousinesq does not depend on Ka, but uses u which is similar. Most lateral pressure calculations that are a variation of bosinesq do not have a lateral pressure coefficent. The difference betweena sheeted wall and a rigid wall is a factor of 2, with the rigid wall having the higher pressure. The deformation of the flexible wall allows for a reduced lateral pressure.
Blum theroy is detailed in the old pile buck manual and possibly in the old US Steel sheetpile manual, which is availble on sliderule era's website. Blum theroy assume embedment is sufficient to develop full cantilevr capacity in the lower portin of an ancored sheet. With one row of anchors the system is determinate. this is done by assuming a shear hinge at the point of zero pressure below the dredge line. It is then broken into 2 detrminate beams and solved. The Blum method (also called equivelent beem or fixed earth) uses deeper sheets than the free earth, but sheeting size and anchor loads are less.
Blum theroy is detailed in the old pile buck manual and possibly in the old US Steel sheetpile manual, which is availble on sliderule era's website. Blum theroy assume embedment is sufficient to develop full cantilevr capacity in the lower portin of an ancored sheet. With one row of anchors the system is determinate. this is done by assuming a shear hinge at the point of zero pressure below the dredge line. It is then broken into 2 detrminate beams and solved. The Blum method (also called equivelent beem or fixed earth) uses deeper sheets than the free earth, but sheeting size and anchor loads are less.
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I once again appreciate this knowledge of BLUM, but now I am more inclined on the name of the software which I can use or rely upon which exactly follows the BLUM THEORY OF DESIGN. I completely agree with your statement of Boussinesq is completely INDEPENDENT ON Ka.
I also agree with in Blum it develops enough embedment depth in order to achieve fully rigidity at base. I tried using a software SPW 2006 for a simple example of SPW length = 11 m. This example requires excavation on the left of the SPw = 6.5 m NOW WITH THIS EXCAVATION DEPTH, using SPW 2006 it says no equiliubiurm is achieved. Now inspite of using depth of Sheet pile as 100 m ( that is impossible ) yet for the sake of input it still says no equilibrium is achieved. hence I NEED ONE SOFTWARE WHICH I CAN FULLY RELY ON WHICH FOLLOWS THE BLUM APPROACH. AND IF THAT IS PROSHEET THEN I STILL HAVE A PROBLEM OF SHEAR FORCE CALCULATION.
I also agree with in Blum it develops enough embedment depth in order to achieve fully rigidity at base. I tried using a software SPW 2006 for a simple example of SPW length = 11 m. This example requires excavation on the left of the SPw = 6.5 m NOW WITH THIS EXCAVATION DEPTH, using SPW 2006 it says no equiliubiurm is achieved. Now inspite of using depth of Sheet pile as 100 m ( that is impossible ) yet for the sake of input it still says no equilibrium is achieved. hence I NEED ONE SOFTWARE WHICH I CAN FULLY RELY ON WHICH FOLLOWS THE BLUM APPROACH. AND IF THAT IS PROSHEET THEN I STILL HAVE A PROBLEM OF SHEAR FORCE CALCULATION.
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- #14
Just to add to my above thread, while using SPW the software decides the level of phgreatic level for achieving equilibrium of the sheet pile, this seems a bit bizarre to me, because everytime to decide the length of SPW having the desired phreatic level is not in our hands.
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Another Interesting point observed in PROSHEET
1) The surcharge Load if entered in the initial stage of INput as Caqout Surcharge = Value (kN/ m2) . And if the same is entered in Boussinesqs then it will calculate the Surcharge twice ( in its calculation of Total Pressure). So basically the point is in calculation of Simnple Earth Pressure it consideres ( asks) if there is any Caquot Surcharge ( to either right or left) and then besides this if u enter in Boussinesq's. The final pressure diagram will have considered Surcharge twice.
PLEASE CORRECT ME IF I AM WRONG!!!
1) The surcharge Load if entered in the initial stage of INput as Caqout Surcharge = Value (kN/ m2) . And if the same is entered in Boussinesqs then it will calculate the Surcharge twice ( in its calculation of Total Pressure). So basically the point is in calculation of Simnple Earth Pressure it consideres ( asks) if there is any Caquot Surcharge ( to either right or left) and then besides this if u enter in Boussinesq's. The final pressure diagram will have considered Surcharge twice.
PLEASE CORRECT ME IF I AM WRONG!!!
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Why is it asked twice?
secondly while checking the same results using SPWALL 2006 and also MSHEET, the same profile of sheet pile fails due to high phreatic level which is unidentifiable using PROSHEET.
All I am trying to say is PROSHEET is not at all a conclusive software! for an analysis of SPW
secondly while checking the same results using SPWALL 2006 and also MSHEET, the same profile of sheet pile fails due to high phreatic level which is unidentifiable using PROSHEET.
All I am trying to say is PROSHEET is not at all a conclusive software! for an analysis of SPW
I have never used PROSHEET I have downloaded it to fool around with it. I think you are right about the software. T he website contains the following diclaimer:
"The following software will be useful in a preliminary design but should in no way be used for final design. The technical and marketing department of ARCELOR COMMERCIAL RPS will provide you the necessary technical assistance to lead your project to a great success and will help you if you encounter problems using the software."
On the other hand, Blum theory is fairly easy to do by hand. So you could simply do the calculations with out the software.
"The following software will be useful in a preliminary design but should in no way be used for final design. The technical and marketing department of ARCELOR COMMERCIAL RPS will provide you the necessary technical assistance to lead your project to a great success and will help you if you encounter problems using the software."
On the other hand, Blum theory is fairly easy to do by hand. So you could simply do the calculations with out the software.
ProSheet is free. You get what you pay for. Be careful with SPW911. Compared to hand calcs and CT Shoring, I have found that SPW911 gives much higher moments and brace loads when using multiple soil layers where at least one layer is a significantly weaker soil.
I second PEinc's caution about SPW911. I like the program and use it alot. I think the user interface is very well done. But I have also had problems with it when the wall supports multiple soil layers. I always carefully check the results and make sure that they make sense.
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