Iss26 Art2 - Local Ice Chrushing Analysis of Pile Wall.pdf - Plaxis

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Plaxis Practice: Mohr-Coulomb parameters for modelling of concrete structuresPlaxis practice: Local ice crushing analyses of OPEN CELL SHEET PILE® Wall by 3DFoundationInitial Analyses ResultsThe initial ice crushing analyses results arepresented in Table 3. Results are organizedcorresponding to the varied ice contact areas andloading elevations defined in Table 2. The boldnumbers indicate the relative deflection anglebetween adjacent sheet piles exceeds the ultimatedeflection angle criteria of 20 degrees.Crushing IceContact AreaCrushing LoadElevation (feet)Assumed Ice CrushingPressure (psi)2 ft 2 +2 to -10 3500+4.5 to +2 400-10 to -39 300Table 2. Ice Loading Conditionsin PlaxisSelected deformation contours of the enclosedgravel fill and OPEN CELL SHEET PILE wall are alsoshown in Figure 6. In Figure 7, the total incrementalsoil deflection contour (|u|) presents a very distinctfailure surface in the soil block at the loaded area.The analyzed sheet pile deflections of thenineteen pile segments are presented in Figure8. The deflection of sheet pile along various wallelevations are plotted separately. The vertical axisrepresents the X coordinates (unit in feet) to locateeach sheet pile segment in PLAXIS 3D. The plotsalso indicate the maximum pile deflection occurswithin the range of elevation +4 feet to elevation-6 feet, where 100 ft 2 crushing ice was loaded.Soil ReinforcementInitial numerical analysis (Table 3) indicated thatthawed fill soil and sheet piles alone were notsufficient to resist the local ice pressure at thehigher elevations. Thus, soil improvement wasrecommended within this zone and the preliminarydesign assumed jet grouting was utilized forthis purpose. A revised Plaxis model was thendeveloped assuming the grouted columns wereinstalled from approximately 8 feet below gradeto 23 feet below grade, stiffening approximately15 feet of soil at the face of the sheet piles. Theinitial cohesion c and friction angle { for jetgrouting was assumed to be 22 ksf and zero10 ft 2 +2 to -10 1130+4.5 to +2 300UnfrozenSandyGravel-10 to -39 200100 ft 2 +2 to -10 225+4.5 to +2 200-10 to -39 100Calculation CaseMax Horizontal Def.of Soil (in)Max Relative RotationAngle (deg)400 psi @ 2 ft 2 0.5 3.73500 psi @ 2 ft 2 31.0 40.0300 psi @ 2 ft 2 0.3 negligible300 psi @ 10 ft 2 16.0 28.01130 psi @ 10 ft 2 57.0 78.0200 psi @ 10 ft 2 0.5 negligible200 psi @ 100 ft 2 48.0 17.0225 psi @ 100 ft 2 32.0 13.0100 psi @ 100 ft 2 1.0 negligibleTable 3 Initial Ice Crushing Analyses Results SummaryFigure 6. Maximum Horizontal Deformation of Fill and OPEN CELL SHEET PILE at Failure(200 psi with 100 ft 2 contact area @ Elevation +4.5 feet)www.plaxis.nl l Autumn issue 2009 l Plaxis bulletin 15
Plaxis practice: Local ice crushing analyses of OPEN CELL SHEET PILE® Wall by 3DFoundationPlaxis Practice: Simulation of Soil Nail Structures using PLAXIS 2DFigure 7. Soil Failure Surface at Failure-Total Incremental Deformation (200 psi with 100 ft2 contact area @ Elevation +4.5 feet)degrees, respectively. Results from this revisedanalysis are presented in Table 4 and indicatedpositive behavior. Figure 9 also depicts the totalincremental soil deformation contours associatedwith the analysis.Discussion and conclusionsPLAXIS 3DFoundation provides a very usefultool for analyzing the performance of an OPENCELL SHEET PILE wall system under localizedice impact. The initial ice crushing analysesindicated that ice crushing loads on the sheetpile wall exceeded the strength capacity of thethawed granular fill soil and sheet piles alone.Subsequent analyses utilizing soil reinforcementwas found to provide greater resistance andstructural integrity within the failure zone andprovided positive results. Shear strain analysesin Plaxis showed that the proposed jet groutingsoilcrete could have some cracking develop underhigh crushing pressure between elevations +4.5feet to -10 feet. Considering the frequency ofany anticipated ice loading events and that thestatic ice crushing analyses in Plaxis is relativelyconservative, the assumed width and depth of thejet grouting zone was believed to be adequate,but additional analyses may be required tofurther refine the design. For reinforced soil, therelative rotation angle of adjacent sheet pileswas reduced significantly with the use of soilreinforcement, resulting in a maximum value of6 degrees as compared to a 78 degree angle forthe unreinforced case. The very low result forreinforced soil indicates that jet grouting or othersimilar means could have voids yet still providesufficient resistance.Reinforced SoilCalculation CaseTable 4 Initial Ice Crushing Analyses Results SummaryMax Horizontal Def.of Soil (in)Max Relative RotationAngle (deg)400 psi @ 2 ft 2 0.4 3.53500 psi @ 2 ft 2 1.8 6.0300 psi @ 2 ft 2 0.1 negligible300 psi @ 10 ft 2 1.3 4.51130 psi @ 10 ft 2 1.7 5.0200 psi @ 10 ft 2 0.3 negligible200 psi @ 100 ft 2 1.6 3.5225 psi @ 100 ft 2 1.2 3.0100 psi @ 100 ft 2 0.8 negligible16 Plaxis bulletin l Autumn issue 2009 l www.plaxis.nl
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Iss26 Art2 - Local Ice Chrushing Analysis of Pile Wall.pdf - Plaxis

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