Propped Cantilever Retaining Wall Design Example Pdf

[Katina Piccirilli]

Ourprevious article, Retaining Wall: A Design Approach discusses the principle and concept behind and when and where to consider a retaining wall in our design. We have learned the different checks against the mode of failures in the retaining wall should be considered in the design. To further understand the designed approach, here is a worked example of the design of the retaining wall.

This example is intended to be readily calculated by hand although a lot of structural spreadsheets and software such as Prokon are available. The purpose of this article is for the reader to fully understand the principle behind it.

The next thing to consider is the assumptions that we can make in terms of the geometry of the retaining wall that we are designing. Given the height, H of the retaining wall, we can assume or counter check our initial design considerations should at least according to the following geometric proportions:

Sketches of the retaining wall forces should be considered to properly distinguish the different forces acting on our retaining wall as tackled in the previous article, Retaining Wall: A Design Approach. Based on our example in Figure A.1, we have the forces due to soil pressure, due to water and surcharge load to consider. Figure A.3 below is most likely our analytical model.

Considering the Figure A.3, we can derive the following equation for the active pressures, Pa and passive pressure Pp. Notice that the pressures acting on the wall are equivalent to the area (triangle) of the pressure distribution diagram. Hence,

There are two checks to consider the stability of the retaining wall. One is the check for an overturning moment and the other one is the check for sliding. The weight of the retaining wall including the gravity loads within it plays a vital role in performing the stability check. Refer to Figure A.4 for the mass or weight calculations.

The sliding check should be carried out with reference to the Figure A.4 diagram and considering the summation of vertical forces for resisting force and horizontal forces for sliding force conservatively neglecting the passive pressure, hence:

The foundation bearing capacity usually governs the design of the wall. The soil, particularly under the toe of the foundation, is working very hard to resist the vertical bearing loads, sliding shear, and to provide passive resistance to sliding. The bearing capacity of the soil should be calculated taking into account the effect of simultaneous horizontal loads applied to the foundation from the soil pressure.

For the footing to be safe in soil pressure, the maximum soil pressure under working load shall be less than the allowable soil bearing capacity. The maximum soil bearing pressure under the footing considering 1m strip is:

The presented calculations above are actually too tiring to perform manually especially if you are doing a trial and error design. Thanks to structural design soft wares and spreadsheets, available nowadays, our design life will be easier.

What do you think about this article? Tell us your thoughts! Leave a comment on the section below. Subscribe to our newsletter to be updated with the latest posts or follow us on our social media pages on the below icons.

Thanks for pointing out. We have checked and found out that that is merely a typo error and it has been updated accordingly. We have also double-checked the attached spreadsheet and it is not affecting the results as we conservatively neglect the effect of passive pressure in the calculation.

Also ,would you be able to explain how is the d in critical shear calculated ? number 1.044 is used for similar triangles,however I struggle to find exact theory how you arrived to this number as I get different.

we have to learned the different checks against the mode of failures in the retaining wall should be considered in the design. Here some worked examples of the design of the retaining wall are described.I like the I have also found this resource Rfmasonry.co.nz useful and its related to what you are mentioning.

Hi Ruben, you can actually put your own logo on the space provided. Either editing some option setting on your excel or typing your company name on it. If none of these options are working, do it manually. Once you finish the design, convert the file to pdf and paste your logo from there.

Thanks, Aaron for pointing it out. We have checked and found out that that is merely a typo error and it has been updated accordingly. We have also double-checked the attached spreadsheet and it is not affecting the results in the calculation.

There is also a comment earlier about a typo of MoT = 57.91, the figure was right at 60.02, the weight of section 1 was not added to the equation. Though all of these moments are taken from the top of the toe and not the furthest point, thus moments are not accurate.

sir, Thank you for your valuable information. this is very much useful and one more plea that can we have any examples for considering wings & returns with head wall can be treated as a retaining wall any such kind of examples please post to mail if any thanks in advance

The shear strength is based on an average shear stress on the full effective cross section (bw x d). In a member without shear reinforcement, shear is assumed to be carried by the

concrete web. In a member with shear reinforcement, a portion of the shear strength is assumed to be provided by the concrete and the remainder by the shear reinforcement.

Thank for this detailed design to follow; It has been very helpful. One thing I noticed is that the calculation for the wall stem does not match the value you then indicated for the moment when checking for wall stem flexure. You have listed that Mu=19.40KNm again for tension, but the calculation comes out to the 29.33KNm you used. I believe it was just a typo but it made it a bit confusing to follow then. Thanks again, and God bless.

There are two basic types of retaining structures: backfilled and embedded retaining structures. Backfilled retaining structures are gravity walls, reinforced concrete cantilever walls, gabion walls, reinforced soil structures. Embedded retaining structures are: diaphragm walls, pile walls and sheet pile walls.

For smaller open pit depths it is possible to use embedded retaining structures without additional protection (cantilever load transfer) but for larger depths, it is necessary to support the retaining structure with additional structural elements such as props, anchors or slabs of the future structure.

The increasing demand for underground constructions in urban areas highlights the need for achieving more economic design of retaining structures. The requirement of limiting ground movements and the need to ensure that no failure of the support system occurs is an important factor in design.

In limit equilibrium analysis the equilibrium of the wall is assessed under the action of assumed lateral pressure distributions, usually based on limiting (active and/or passive) lateral earth pressure coefficients. Limit equilibrium methods are directly applicable for some structures (cantilever walls) than others (multi-propped walls).

These soil-structure interaction analyses model the ground and the wall and its construction sequence, using a finite element or finite difference methods.

Ground movements, wall movements, bending moments and prop loads are calculated.

The design load acting on the props will depend upon the analysis method adopted for the design of the wall. Prop loads calculated from limit equilibrium analysis may be unconservative, as the effects of soil-structure interaction are not included.

Soil structure interaction methods allow stress redistribution and provide more realistic values of prop loads. The calculated prop loads should be compared with those derived from comparable experience.

The DPL method for calculating prop loads for propped temporary excavations is based on the back analysis of field measurements of prop loads relating to 81 case studies, of which 60 are for flexible walls (steel sheet pile, king post walls) and 21 are for stiff walls (contiguous, secant, diaphragm walls). The case study data relate to excavations ranging in depth from 4 m to 27 m, typically 5 m to 15 m in soft and firm clays (soil class A), 10 m to 15 m in stiff and very stiff clays (soil class B) and 10 m to 20 m in coarse-grained soils (soil class C).

Steel sections are commonly used for temporary props. The design load acting on the props will depend upon the analysis method adopted for the design of the wall. Soil structure interaction methods allow stress redistribution and provide more realistic values of prop loads. The calculated prop loads should be compared with those derived from comparable experience.

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This video will walk you through a variety of retaining wall options including designing uniform, sloped, stepped, cantilever or propped retaining wall options. For more information, visit our website at -started-tekla-tedds.

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