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  • Cagatay Konuk
    Does anyone have an idea about why the limit of eccentricity is B/4 for shallow foundations laid on rock? ... From: mojtabasamadi2003
    Message 1 of 9 , Jun 20, 2011
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      Does anyone have an idea about why the limit of eccentricity is B/4 for shallow foundations laid on rock?

      --- On Wed, 3/16/11, mojtabasamadi2003 <mojtabasamadi2003@...> wrote:

      From: mojtabasamadi2003 <mojtabasamadi2003@...>
      Subject: [Geoengineer Group] Re: GRS walls
      To: Geoengineer@yahoogroups.com
      Date: Wednesday, March 16, 2011, 2:49 PM

       



      --- In Geoengineer@yahoogroups.com, "Roberto" <roberto.more@...> wrote:
      >
      >
      >
      > --- In Geoengineer@yahoogroups.com, "mojtabasamadi2003" <mojtabasamadi2003@> wrote:
      > >
      > >
      > > Dear engineering
      > > I want to model one GRS wall (geosynthetic reinforced soil wall) with FLAC3D.
      > > My question about connection between geogrids and blocks.
      > > Do I must a simple connection or fix connection use?
      > > Thanks.
      > >
      > there are two different type of connection between blocks and geogrids.
      > The first one is a frictional connection the resistence of pull out force is develop only by the vertical load respect to the top of the wall.
      > The second type is a mechanical connection that have a pull out force of geogrids that could develop a resistance that is measured like a percent of the LTDS of geogrids
      >
      Thanks Mr or Roberto.

    • David Oliveira
      I m not sure if you are talking about RSW (i.e. MSE wall) but if that s the case I believe its only to limit tensile stresses within the stabilised soil block.
      Message 2 of 9 , Jun 21, 2011
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        I'm not sure if you are talking about RSW (i.e. MSE wall) but if that's the case I believe its only to limit tensile stresses within the stabilised soil block. It has nothing to do with the rock foundation capacity.

        Best regards
        -- 
        DAVID OLIVEIRA PhD, MIEAust, CPEng
        Senior Associate Geotechnical Engineer 
        Coffey Geotechnics
        8/12 Mars Road Lane Cove West NSW 2066 Australia
        T +61 2 9911 1000 F +61 2 9911 1001 M +61 431 441 882
        ---------------------------------------------
        Visiting Research Fellow
        Centre for Geomechanics and Railway Engineering 
        Faculty of Engineering - University of Wollongong


        On 21/06/2011, at 6:55, Cagatay Konuk <afrochaltey@...> wrote:

         

        Does anyone have an idea about why the limit of eccentricity is B/4 for shallow foundations laid on rock?

        --- On Wed, 3/16/11, mojtabasamadi2003 <mojtabasamadi2003@...> wrote:

        From: mojtabasamadi2003 <mojtabasamadi2003@...>
        Subject: [Geoengineer Group] Re: GRS walls
        To: Geoengineer@yahoogroups.com
        Date: Wednesday, March 16, 2011, 2:49 PM

         



        --- In Geoengineer@yahoogroups.com, "Roberto" <roberto.more@...> wrote:
        >
        >
        >
        > --- In Geoengineer@yahoogroups.com, "mojtabasamadi2003" <mojtabasamadi2003@> wrote:
        > >
        > >
        > > Dear engineering
        > > I want to model one GRS wall (geosynthetic reinforced soil wall) with FLAC3D.
        > > My question about connection between geogrids and blocks.
        > > Do I must a simple connection or fix connection use?
        > > Thanks.
        > >
        > there are two different type of connection between blocks and geogrids.
        > The first one is a frictional connection the resistence of pull out force is develop only by the vertical load respect to the top of the wall.
        > The second type is a mechanical connection that have a pull out force of geogrids that could develop a resistance that is measured like a percent of the LTDS of geogrids
        >
        Thanks Mr or Roberto.

      • Cagatay Konuk
        - Greetings, Allow me to clarify the previous statement. The following section is quoted from FHWA Manual-Load and Resistance Factor Design (LRFD) for Highway
        Message 3 of 9 , Jun 21, 2011
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          -

          Greetings,

          Allow me to clarify the previous statement. The following section is quoted from FHWA Manual-Load and Resistance Factor Design (LRFD) for Highway Bridge Substructures

          “In addition to bearing capacity and sliding failure, spread footings are checked for stability against

          overturning based on an evaluation of the bearing pressure resultant location with respect to the

          centroid of the footing. In AASHTO ASD, the location of the bearing pressure resultant must be

          maintained:

          * Within B/6 of the center of the footing for footings on soil

          *Within B/4 of the center of the footing for footings on rock”

           

          Now, B/6; i can relate to the calculations that include the radius of gyration of the foundation; the occurance of negative stresses within the soil(which are theoratically impossible to occur) are prevented this way and so on... I just demand to know if anyone has any suggestion on B/4, and the special case in rock base.

           

          In addition: In AASHTO LRFD manual, the numbers B/4 and B/6 are entirely different. But i would not intend to cause any confusions at this stage.

           

          Thanks

           

           

          -- On Tue, 6/21/11, David Oliveira <dafo407@...> wrote:

          From: David Oliveira <dafo407@...>
          Subject: Re: [Geoengineer Group] Re:
          To: "Geoengineer@yahoogroups.com" <Geoengineer@yahoogroups.com>
          Date: Tuesday, June 21, 2011, 1:18 PM

           
          I'm not sure if you are talking about RSW (i.e. MSE wall) but if that's the case I believe its only to limit tensile stresses within the stabilised soil block. It has nothing to do with the rock foundation capacity.

          Best regards
          -- 
          DAVID OLIVEIRA PhD, MIEAust, CPEng
          Senior Associate Geotechnical Engineer 
          Coffey Geotechnics
          8/12 Mars Road Lane Cove West NSW 2066 Australia
          T +61 2 9911 1000 F +61 2 9911 1001 M +61 431 441 882
          ---------------------------------------------
          Visiting Research Fellow
          Centre for Geomechanics and Railway Engineering 
          Faculty of Engineering - University of Wollongong


          On 21/06/2011, at 6:55, Cagatay Konuk <afrochaltey@...> wrote:

           
          Does anyone have an idea about why the limit of eccentricity is B/4 for shallow foundations laid on rock?

          --- On Wed, 3/16/11, mojtabasamadi2003 <mojtabasamadi2003@...> wrote:

          From: mojtabasamadi2003 <mojtabasamadi2003@...>
          Subject: [Geoengineer Group] Re: GRS walls
          To: Geoengineer@yahoogroups.com
          Date: Wednesday, March 16, 2011, 2:49 PM

           


          --- In Geoengineer@yahoogroups.com, "Roberto" <roberto.more@...> wrote:
          >
          >
          >
          > --- In Geoengineer@yahoogroups.com, "mojtabasamadi2003" <mojtabasamadi2003@> wrote:
          > >
          > >
          > > Dear engineering
          > > I want to model one GRS wall (geosynthetic reinforced soil wall) with FLAC3D.
          > > My question about connection between geogrids and blocks.
          > > Do I must a simple connection or fix connection use?
          > > Thanks.
          > >
          > there are two different type of connection between blocks and geogrids.
          > The first one is a frictional connection the resistence of pull out force is develop only by the vertical load respect to the top of the wall.
          > The second type is a mechanical connection that have a pull out force of geogrids that could develop a resistance that is measured like a percent of the LTDS of geogrids
          >
          Thanks Mr or Roberto.

        • David Oliveira (Gmail)
          Konuk Note that B/4 is less restricting than B/6. For example, suppose that your foundation width is 6 m in soils e = b/6 = 1 m, and in rocks e = b/4 = 1.5 m.
          Message 4 of 9 , Jun 21, 2011
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            Konuk
             
            Note that B/4 is less restricting than B/6. For example, suppose that your foundation width is 6 m in soils e = b/6 = 1 m, and in rocks e = b/4 = 1.5 m. 
             
            FHWA allows for a greater eccentricity in rock  because it is stiffer and capable of withstand higher stresses with likely less deformation, which makes sense. The objectives are still the same:
             
            1) Limit potential tensile stresses in the foundation (suppose there is adhesion between the footing and the rock)
            2) Limit rotation
             
             
            Regards
            --
            DAVID OLIVEIRA PhD, MIEAust, CPEng
            Senior Associate Geotechnical Engineer
            Coffey Geotechnics
            8/12 Mars Road Lane Cove West NSW 2066 Australia
            T +61 2 9911 1000 F +61 2 9911 1001 M +61 431 441 882
            www.coffey.com
            ------------------------------------------------------------------------
            Visiting Research Fellow
            Centre for Geomechanics and Railway Engineering
            Faculty of Engineering - University of Wollongong
            On 21 June 2011 22:41, Cagatay Konuk <afrochaltey@...> wrote:
             



            -

            Greetings,

            Allow me to clarify the previous statement. The following section is quoted from FHWA Manual-Load and Resistance Factor Design (LRFD) for Highway Bridge Substructures

            “In addition to bearing capacity and sliding failure, spread footings are checked for stability against

            overturning based on an evaluation of the bearing pressure resultant location with respect to the

            centroid of the footing. In AASHTO ASD, the location of the bearing pressure resultant must be

            maintained:

            * Within B/6 of the center of the footing for footings on soil

            *Within B/4 of the center of the footing for footings on rock”

             

            Now, B/6; i can relate to the calculations that include the radius of gyration of the foundation; the occurance of negative stresses within the soil(which are theoratically impossible to occur) are prevented this way and so on... I just demand to know if anyone has any suggestion on B/4, and the special case in rock base.

             

            In addition: In AASHTO LRFD manual, the numbers B/4 and B/6 are entirely different. But i would not intend to cause any confusions at this stage.

             

            Thanks

             

             

            -- On Tue, 6/21/11, David Oliveira <dafo407@...> wrote:

            From: David Oliveira <dafo407@...>
            Subject: Re: [Geoengineer Group] Re:
            To: "Geoengineer@yahoogroups.com" <Geoengineer@yahoogroups.com>
            Date: Tuesday, June 21, 2011, 1:18 PM


             
            I'm not sure if you are talking about RSW (i.e. MSE wall) but if that's the case I believe its only to limit tensile stresses within the stabilised soil block. It has nothing to do with the rock foundation capacity.

            Best regards
            -- 
            DAVID OLIVEIRA PhD, MIEAust, CPEng
            Senior Associate Geotechnical Engineer 
            Coffey Geotechnics
            8/12 Mars Road Lane Cove West NSW 2066 Australia
            T +61 2 9911 1000 F +61 2 9911 1001 M +61 431 441 882
            ---------------------------------------------
            Visiting Research Fellow
            Centre for Geomechanics and Railway Engineering 
            Faculty of Engineering - University of Wollongong


            On 21/06/2011, at 6:55, Cagatay Konuk <afrochaltey@...> wrote:

             
            Does anyone have an idea about why the limit of eccentricity is B/4 for shallow foundations laid on rock?

            --- On Wed, 3/16/11, mojtabasamadi2003 <mojtabasamadi2003@...> wrote:

            From: mojtabasamadi2003 <mojtabasamadi2003@...>
            Subject: [Geoengineer Group] Re: GRS walls
            To: Geoengineer@yahoogroups.com
            Date: Wednesday, March 16, 2011, 2:49 PM

             


            --- In Geoengineer@yahoogroups.com, "Roberto" <roberto.more@...> wrote:
            >
            >
            >
            > --- In Geoengineer@yahoogroups.com, "mojtabasamadi2003" <mojtabasamadi2003@> wrote:
            > >
            > >
            > > Dear engineering
            > > I want to model one GRS wall (geosynthetic reinforced soil wall) with FLAC3D.
            > > My question about connection between geogrids and blocks.
            > > Do I must a simple connection or fix connection use?
            > > Thanks.
            > >
            > there are two different type of connection between blocks and geogrids.
            > The first one is a frictional connection the resistence of pull out force is develop only by the vertical load respect to the top of the wall.
            > The second type is a mechanical connection that have a pull out force of geogrids that could develop a resistance that is measured like a percent of the LTDS of geogrids
            >
            Thanks Mr or Roberto.

            Recent Activity:
            Please inform your colleagues about the Group.
            .
              
             

          • Cagatay Konuk
            Exactly, i agree with all those statements. Still, i was wondering if there was any analytical(if not experimental) background to the problem.   Best Regards.
            Message 5 of 9 , Jun 21, 2011
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              Exactly, i agree with all those statements. Still, i was wondering if there was any analytical(if not experimental) background to the problem.

               

              Best Regards.

              --- On Tue, 6/21/11, David Oliveira (Gmail) <dafo407@...> wrote:

              From: David Oliveira (Gmail) <dafo407@...>
              Subject: Re: [Geoengineer Group] Re:
              To: Geoengineer@yahoogroups.com
              Date: Tuesday, June 21, 2011, 4:18 PM

               
              Konuk
               
              Note that B/4 is less restricting than B/6. For example, suppose that your foundation width is 6 m in soils e = b/6 = 1 m, and in rocks e = b/4 = 1.5 m. 
               
              FHWA allows for a greater eccentricity in rock  because it is stiffer and capable of withstand higher stresses with likely less deformation, which makes sense. The objectives are still the same:
               
              1) Limit potential tensile stresses in the foundation (suppose there is adhesion between the footing and the rock)
              2) Limit rotation
               
               
              Regards
              --
              DAVID OLIVEIRA PhD, MIEAust, CPEng
              Senior Associate Geotechnical Engineer
              Coffey Geotechnics
              8/12 Mars Road Lane Cove West NSW 2066 Australia
              T +61 2 9911 1000 F +61 2 9911 1001 M +61 431 441 882
              www.coffey.com
              ------------------------------------------------------------------------
              Visiting Research Fellow
              Centre for Geomechanics and Railway Engineering
              Faculty of Engineering - University of Wollongong
              On 21 June 2011 22:41, Cagatay Konuk <afrochaltey@...> wrote:
               


              -

              Greetings,

              Allow me to clarify the previous statement. The following section is quoted from FHWA Manual-Load and Resistance Factor Design (LRFD) for Highway Bridge Substructures

              “In addition to bearing capacity and sliding failure, spread footings are checked for stability against

              overturning based on an evaluation of the bearing pressure resultant location with respect to the

              centroid of the footing. In AASHTO ASD, the location of the bearing pressure resultant must be

              maintained:

              * Within B/6 of the center of the footing for footings on soil

              *Within B/4 of the center of the footing for footings on rock”

               

              Now, B/6; i can relate to the calculations that include the radius of gyration of the foundation; the occurance of negative stresses within the soil(which are theoratically impossible to occur) are prevented this way and so on... I just demand to know if anyone has any suggestion on B/4, and the special case in rock base.

               

              In addition: In AASHTO LRFD manual, the numbers B/4 and B/6 are entirely different. But i would not intend to cause any confusions at this stage.

               

              Thanks

               

               

              -- On Tue, 6/21/11, David Oliveira <dafo407@...> wrote:

              From: David Oliveira <dafo407@...>
              Subject: Re: [Geoengineer Group] Re:
              To: "Geoengineer@yahoogroups.com" <Geoengineer@yahoogroups.com>
              Date: Tuesday, June 21, 2011, 1:18 PM


               
              I'm not sure if you are talking about RSW (i.e. MSE wall) but if that's the case I believe its only to limit tensile stresses within the stabilised soil block. It has nothing to do with the rock foundation capacity.

              Best regards
              -- 
              DAVID OLIVEIRA PhD, MIEAust, CPEng
              Senior Associate Geotechnical Engineer 
              Coffey Geotechnics
              8/12 Mars Road Lane Cove West NSW 2066 Australia
              T +61 2 9911 1000 F +61 2 9911 1001 M +61 431 441 882
              ---------------------------------------------
              Visiting Research Fellow
              Centre for Geomechanics and Railway Engineering 
              Faculty of Engineering - University of Wollongong


              On 21/06/2011, at 6:55, Cagatay Konuk <afrochaltey@...> wrote:

               
              Does anyone have an idea about why the limit of eccentricity is B/4 for shallow foundations laid on rock?

              --- On Wed, 3/16/11, mojtabasamadi2003 <mojtabasamadi2003@...> wrote:

              From: mojtabasamadi2003 <mojtabasamadi2003@...>
              Subject: [Geoengineer Group] Re: GRS walls
              To: Geoengineer@yahoogroups.com
              Date: Wednesday, March 16, 2011, 2:49 PM

               


              --- In Geoengineer@yahoogroups.com, "Roberto" <roberto.more@...> wrote:
              >
              >
              >
              > --- In Geoengineer@yahoogroups.com, "mojtabasamadi2003" <mojtabasamadi2003@> wrote:
              > >
              > >
              > > Dear engineering
              > > I want to model one GRS wall (geosynthetic reinforced soil wall) with FLAC3D.
              > > My question about connection between geogrids and blocks.
              > > Do I must a simple connection or fix connection use?
              > > Thanks.
              > >
              > there are two different type of connection between blocks and geogrids.
              > The first one is a frictional connection the resistence of pull out force is develop only by the vertical load respect to the top of the wall.
              > The second type is a mechanical connection that have a pull out force of geogrids that could develop a resistance that is measured like a percent of the LTDS of geogrids
              >
              Thanks Mr or Roberto.

              Recent Activity:
              Please inform your colleagues about the Group.
              .
                
               

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