Saturday, October 8, 2011

Anchored retaining wall

             Anchored wall-is a  wall that is usually pinned both top and bottom using cables, or other stays, which are anchored in the rock or soil behind it.Anchors are driven into the material and then expanded at the end of the cable, either by mechanical means or by injecting pressurised concrete into the hole. The concrete expands to form a bulb in the soil.
The anchor wall may be embedded at the base and tied to a slab at the top or to a “deadman anchor” — a concrete structure which is driven into the ground or anchored to the earth with sufficient resistance. The horizontal cable, rod or helical anchor, and deadman structure resists forces that would otherwise cause the wall to become unstable.This method, though technically complex, is useful where high loads are expected, or where the wall itself has to be slender and would be too weak without anchoring.

     For this type of wall we recommend the same programs as for the piling walls  for they are the most suited for this subject and because anchored walls  are sugested when the piling walls  will not fit the both desired partial and global stability safety factors,and they are:
  • Prosheet- a free comprehensive  software  for Cantilever and Anchored Sheet Wall Systems according to the Blum theory. The ProSheet 2.2 defines all the forces required for determing a sheet piling structure.
The results produced by this method have to be checked carefully by the user in order to make sure that modelization of the soil-structure interaction is accurate enough (e.g. arching effects leading to higher anchor forces and lower bending moments in the wall).
   For the design of the head wall three static systems are possible:

- cantilever
- free earth support with one layer of anchor or struts
- fixed earth support with one layer of anchor or struts.

The anchor wall may be free-earth or fixed-earth supported.

The following loads are taken into consideration for the head wall as well as for the anchor wall:
- earth pressure behind the wall
- earth pressure in front of the wall

- water pressure behind the wall

- water pressure in front of the wall

- uniform infinite surcharges on the soil surface (Caquot) 

- concentrated linear surcharges (max 5) at any location (Boussinesq)

- point forces at any location of the wall (Concentrated Forces)

- a pressure diagram on the back of the wall.

The program defines the design characteristics based on the input data given by the user and the results are printed out in graphical as well as tabular form.
The design can be made in either metric or imperial units-you can download the sofware by clicking here .

  • SLOPE/W-from GEO-SLOPE a comprehensive program that you can download for free only a trial version and you can view a sheet pile wall design example by clicking -here (a specific case study for such a wall after EC7 can be viewed here !
  • GEO5-Sheeting Design-program  used to design sheet pile structures,it provides required pile embedment lengths (for fixed and hinged toes), pile bending moments, internal forces and anchor loads program that can be downloaded by clicking here .

Main features of the GEO5-Sheeting Design:

-Analysis according to the theory of limit states and safety factor
-Generally layered soil environment
-Verification analysis can be performed employing EN 1997-1, LRFD or classical approach (limit states, factor of safety)
-EN 1997 – option to choose partial factors based on National Annexes
-EN 1997 – option to choose all design approaches, consider design situations
-Built-in database of soil parameters
-Arbitrary number of surcharges applied to structures (strip, trapezoidal, concentrated load)
-Modelling of water in front of and behind structures, modelling of artesian water
-General shape of terrain behind the structure
-Earthquake effects (Mononobe-Okabe, Arrango)
-Analysis of earth pressures in effective and total parameters
-Multiple levels of struts
-Application of specified forces and moments
-Analysis of soldier beams
-Verification of external stability of a wall using program Slope Stability .

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