Sheet pile depth rule of thumb


  • ELS – Sheet Piles
  • SPW911 Sheet Pile Design Software
  • A hinge is assumed to exist at each frame except the top one, and the spans between frames above the lowest are considered as simply supported beams.

    The load on each frame is the sum of the loads found by analysing each of these simply supported beams. Click the Apply grid button when the slope has been defined.

    Can SupportIT model wood or concrete walls Yes. Enter appropriate values for E, I and the other parameters in the wall properties page. Can SupportIT model soldier piles and lagging Yes. The method of support is selected on the Wall page of the Define Box.

    Can I work from elevation positions rather than depth? The datum is fixed at ground level. Explain the difference between the hinge and area distribution methods. No the difference in single propped walls. In multi-prop walls: Area Distribution: The loads on frames above the lowest are found by load distribution.

    The top frame load is the total load between the top of the excavation and the midpoint between the top frame and the frame below. The load on other frames above the lowest is the total load between the midpoints between each frame and the frames immediately above and below.

    The load on each frame is the sum of the loads found by analyzing each of these simply supported beams. Two methods of analysis are available for sloping ground: Modify K Values: The K values of each soil are recalculated using the given angle of slope. Note that the formula used demands that the angle of slope does not exceed the angle of soil friction. If such a condition exists, it is assumed that the angle of friction equals the angle of slope in any soil layer where it occurs, and a warning to this effect is displayed.

    This avoids the problem outlined above. Once this is applied, the toe should be extended until the program yields the factor of safety you need. How is the required toe calculated in granular soils in a design with multiple walers? When more than one support is present, the toe and load on the lowest frame are found by considering the lowest span as a single supported wall.

    Loads on the frames above the lowest are found using the current load model. The method used is selected in the Supports page of the define box. C and 5. How can the factor of safety FOS be set or changed? What method is used for the factor of safety calculation? How is water modeled in cohesive soils? Refer to the Help file for more details. Why did Ka and Kp not change when I changed the value of phi for my soil? This can happen if you have started adding a new layer, but have not applied it.

    Why does the pressure sometimes remain constant when a design is edited? Changes in soil parameters, water tables, etc sometimes produce no change in the calculated net pressure.

    This is probably due to the presence of soils with a high cohesion. In such cases, the calculated soil pressure may be negative, and the pressure values are being calculated using the minimum equivalent fluid pressure, MEFP. Why does SupportIT sometimes fail to calculate sheet penetration? The net pressure graph must cross from the active side to the passive side below the bottom of an excavation if a toe is to be calculated. This does not occur in some soils eg.

    In such cases, it may be possible to calculate a toe using the Terzaghi pressure model. In some cases the net pressure graph can cross to the passive side below formation, but cross back to the active side at greater depths.

    This can happen, for example, if Terzaghi is selected with Rankine for the active side below formation level in firm clay with a water table, and Apply Hydrostatic is selected in the Cohesive Soils Hydrostatic panel of the Pressure page of the define box.

    No toe can be calculated in such cases. To verify that one of the above is responsible for failure to calculate sheet penetration, select Manual in the Penetration panel of the Wall page of the define box, then enter a large toe in the edit box provided and superimpose the pressure graph. Why does the same input sometimes give different results? The soil K values have probably been modified inadvertently.

    Check the K values before and after the changes — they must be the same if the same results are to be found. For example, load Demo2 and note P, waler load, toe, etc. Open the Excavation page, and select a 20 degree slope — P, etc all change.

    Now select level ground again — they change again, but do not go back to what they were. However, the Kvalues in the Demo2 file, which is an example taken from the BSPH, do not agree with the theoretical values, calculated from the angle of friction.

    Similar things can happen when the pressure model is changed. If the pressure appears to have changed, then check the K values at each depth. Why does the pile length change when I select Coulomb then Rankine again or vice-versa?

    The soil coefficients are changed when you switch from Rankine to Coulomb and back again. Each time you switch, the K values revert to their theoretical values under the selected model. The pile length changes because a different pressure is being calculated due to the changed soil coefficients.

    However, fewer features are available in SupportIT Lite, and these items cannot be edited, even though a SupportIT file containing them has been loaded.

    General Program Features How do I add a new soil layer? Open the Soils page of the define box by double clicking the soil on the active side of a design. Click the New Layer button: Enter the depth of the top of the layer in the depth box. Select a soil from the database by clicking the down arrow to the right of the Name box.

    The soil parameters may be edited. Alternatively, enter a new soil name and properties in the relevant boxes without selecting from the database. Click the Apply button: The new layer is not added to the design until the Apply button is clicked.

    How do I place a support above ground level? Open the Wall page of the define box by double clicking the sheet pile. Enter an Upstand in the box provided eg.

    Open the Supports page of the define box. Enter a negative value for the support position eg. The support must be within the upstand. How do share load between two supports? Open the Supports page of the define box by double clicking an existing support.

    Place two frames close together 0. Select the lower of the two supports in the grid. Click the Share load check box. The total linear load on the two frames is shared equally.

    A link is displayed in the main design diagram to indicate that load is being shared. How many levels of wales may be entered? Twenty The options between braces and walers is really for presentation purposes; it informs the installer what kit is being installed. Why does the pressure remain constant when a design is edited? Changes in soil parameters, water tables, etc sometimes produce no change in the calculated net pressure.

    This is probably due to the presence of soils with a high cohesion. In such cases, the calculated soil pressure may be negative, and the pressure values are being calculated using the minimum equivalent fluid pressure, MEFP.

    How do I change units? You can change units in the Setup page of the define box. The best time to do this is when you first open a job. Doing so later can create problems with the database; the only way to deal with it then is to reinstall the program.

    If you work consistently in U. Double click on the center of the screen, in the drawing. You can then proceed to enter the rest of the job information. If you do have to reinstall the program and have made entries to the database, you can do the following: Select the unit setting which gives metric VALUES eg. E should be 2.

    Exit the software. Copy the files Client. These will hold metric values. Reinstall SPW It should be already set to metric units. How do I model soldier piles using SPW ? What kind of surcharges can be input into the program? Only uniform surcharges can be input into the program. The program does not consider point loads, strip loads, etc. When driving a cofferdam to rock for keying bridge bent footings into rock , how do I show this in the define soil layers screen?

    Define a new soil with appropriate properties for rock, e. Does SPW handle broken back fills? Horizontal loads to be applied to the sheeting to model guardrail impacts? I have a situation where the soil at the base of the sheeting is sloping down and away from the base at a 3 horizontal, 1 vertical slope. How can this be modeled in SPW ? It depends very much on the ground. In cohesionless soils, you could draw a line from the bottom of the wall at an angle of phi angle of internal soil friction to the horizontal.

    Draw a horizontal line from where this meets the slope on the passive side back to the wall. With cohesive soils, the problem is not so acute, where the shear strength is much higher. Some provisions would probably need to be made in the case of soft clays, but it would be up the judgment of the engineer.

    Can SPW be used to design wood or concrete sheeting walls? I entered data for a new sheet pile section into the database while analysing a wall design. While analysing the wall, I realized I needed to change some of the sheet pile properties. Can I work to elevation vs. No, the datum is fixed at ground level. To change this would interfere with the calculation methods of the program.

    Why would the anchor force for a single propped or anchored bulkhead be greater than the maximum shear? Thus, the difference between the two shear values immediately on either side of the support will equal the magnitude of the support load. We are noticing that the same input is giving us different results. For example: We input data soil types and properties, surcharges, depth of excavation, etc…. We then change our data to see what different results we get.

    That is fine but when we change back to the original data we will get different results than what was input before. The soil K values have probably been modified inadvertently. Check the K values before and after the changes — they must be the same if the same results are to be found.

    For example, load Demo2 and note P, waler load, toe, etc. Open the Excavation page, and select a 20 degree slope — P, etc all change. Now select level ground again — they change again, but do not go back to what they were. This happens because the K values are recalculated to their theoretical values, based on phi, when slope or level ground is selected.

    Similar things can happen when the pressure model is changed. If the pressure appears to have changed, then check the K values at each depth. Email us if this does not solve the problem. The steel piling have a limiting stress of 25 ksi for maximum bending moment.

    The sheeting I am considering will allow more. How can I change it? The 25 ksi value was placed for conservatism. You can change this value in the database for each individual section. Can the active and passive soil properties be entered as separate layers? No; all layers in SPW are horizontal. I am designing a wall with a sloping backfill. I have changed the water level.

    If I change the pressure method to, say, Coulomb and then back to Rankine, the pile length reduces signficantly. The soil coefficients are changed when you switch from Rankine to Coulomb and back again.

    Each time you switch, the K values revert to their theoretical values under the selected model. The pile length used when you switch back to Rankine is because a different pressure is being calculated due to the changed soil coefficients. How can I add different sections to the sheetpile database and not lose the information? Program Operation How do I ensure graphics and tables are set correctly? Your computer should be set to Small Fonts when using SPW, or some tabular output will extend beyond the right edge of the window or overlap.

    You may also prefer to set the following on the same page, although the settings shown are not critical: Colour Palette should be set at High Colour 16 bit. This produces shading on the side elevation diagram.

    Other settings give a hatched pattern. Desktop Area should be set at x pixels. The side elevation diagram fits the screen exactly on this setting when Fit Screen is set. Less than x will mean that you cannot see the whole diagram, even with Fit Screen set, while larger than x will result in white space around the diagram this white space can be useful in some cases.

    Click the Apply grid button when the slope has been defined. Can SupportIT model wood or concrete walls Yes. Enter appropriate values for E, I and the other parameters in the wall properties page. Can SupportIT model soldier piles and lagging Yes. The method of support is selected on the Wall page of the Define Box. Can I work from elevation positions rather than depth?

    The datum is fixed at ground level. Explain the difference between the hinge and area distribution methods. No the difference in single propped walls. In multi-prop walls: Area Distribution: The loads on frames above the lowest are found by load distribution. The top frame load is the total load between the top of the excavation and the midpoint between the top frame and the frame below. The load on other frames above the lowest is the total load between the midpoints between each frame and the frames immediately above and below.

    The load on each frame is the sum of the loads found by analyzing each of these simply supported beams. Two methods of analysis are available for sloping ground: Modify K Values: The K values of each soil are recalculated using the given angle of slope.

    ELS – Sheet Piles

    Note that the formula used demands that the angle of slope does not exceed the angle of soil friction. If such a condition exists, it is assumed that the angle of friction equals the angle of slope in any soil layer where it occurs, and a warning to this effect is displayed.

    This avoids the problem outlined above. Once this is applied, the toe should be extended until the program yields the factor of safety you need.

    How is the required toe calculated in granular soils in a design with multiple walers? When more than one support is present, the toe and load on the lowest frame are found by considering the lowest span as a single supported wall. Loads on the frames above the lowest are found using the current load model. The method used is selected in the Supports page of the define box. C and 5. How can the factor of safety FOS be set or changed?

    What method is used for the factor of safety calculation? How is water modeled in cohesive soils? Refer to the Help file for more details. Why did Ka and Kp not change when I changed the value of phi for my soil? The relationship between grade of steel and sheet pile thickness are variables to balance the relative stiffness of soil.

    These variable are important to note for assurance of a hydraulic barrier, but when a corner is necessary the type and grade of sheet pile may not be sufficient. As sheet piles must interlock to attain a designed strength the location of ELS corners can not achieve the designed strength and must be designed to form a hydraulic barrier separate from the sheet pile wall.

    SPW911 Sheet Pile Design Software

    From experience, there is a contrast in opinion between engineers as to what is truly necessary. The common factor throughout is that missing sheet pile connections must account for the local reduced strength of sheet pile wall and gap in hydraulic barrier leading to greater groundwater draw-down.

    Gaps in sheet pile wall will require lagging plates which must account for the relative connections to adjacent sheet piles. Lagging plate design for sheet pile walls will generally assume transferring soil and groundwater pressures to multiple adjacent sheet piles. If only one sheet pile is connected to the lagging plate, then it may cause torsion of said sheet pile which can cause adjacent piles to experience unaccounted tension on the interlocking fold. Performance of the sheet pile wall is dependent on the longitudinal friction between sheet piles.

    The transverse tension from lagging plates may cause a reduction in longitudinal friction and compromise the designed strength and deflection behavior. Photo 2: Excavation for laying of utilities with sheet pile walls utilized. In general, sheet piles are a cost effective construction method for excavation as the unit cost is low and the sheet piles can be recovered after back-filling.


    Sheet pile depth rule of thumb