Retaining Walls – What is Global Stability?

Retaining Walls – What is Global Stability?

Retaining walls are structures, which are used to retain the earth, to prevent from the sliding away. These structures are used for slope’s stability. Types of Retaining Walls are:

  1. Gravity Walls
    1. Reinforced Gravity Walls
  2. Brick
  3. Brick Masonry retaining walls
  4. Stone
  5. Reinforced Soil Walls
  6. Hybrid System
    1. Anchored Earth
    2. Tailed Gabion
    3. Tailed Concret Block
    4. Miscellaneous
retaining-wall

Figure 1. Different Types of Retaining Wall

SLOPE by the Geostru uses global stability analysis, and it includes soil reinforcing elements. The simple sliding analysis may be appropriate for simple structures, but for complex structures we should use global stability analysis. The global stability analysis represents a compound failure mechanism, which provides lower calculated factors of safety. The minimum safety factor is 1.3, but this factor can be increased for 1.5.

Further is presented the calculation of a cantilever wall and a piling wall using software SLOPE by the Geostru.

The cantilever wall

The cantilever wall is made of reinforced cement concrete, and it has a stem and a base part. The base slab helps to increase the stability of the retaining wall.  The cantilever wall in this study has the following characteristics:

slope-model

Figure 2. The SLOPE model- The cantilever wall

 

 

 

 

 

 

 

 

 

 

 

 

 

The dimensions of the cantilever wall are:

tab1

Tabel 1. Geometrical characteristics of the cantilever wall

 

 

 

 

The geometrical parameters and the stratigraphy of the soil can be observed in the following table:

Tabel 2. Geotechnical parameters used in the study

Tabel 2. Geotechnical parameters used in the study

 

 

 

 

 

 

 

 

In this study we introduced distributed loads on the top of the slope. The value of the load is 80kN/m2.

Results of analysis of a cantilever wall. Bishop method
The calculations are based on Bishop’s method. The results can be found in the following figure:

tab-3

 

 

 

 

Tabel 3. Results. Bishop method

Tabel 3. Results. Bishop method

Tabel 4. Results. Fellenius method

Tabel 4. Results. Fellenius method

 

 

 

 

 

 

 

 

 

 

The minimum safety factor is 1.139 in this case. This method results lower safety factor than Bishop’s method Fs=1.367. The center of the surface with minimum safety factor is the same in both cases.

The piling wall 

To analize the safety factor of the slope we have introduced the same distributed loads on the top of the slope (80 kN/m2). We have also introduced the same soil characteristics.

slop2

 

 

 

 

 

 

 

 

 

 

Tabel 5. Geometrical characteristics of the piling wall

Tabel 5. Geometrical characteristics of the piling wall

 

 

 

 

Results of analysis of a piling wall. Bishop method
In the following table is presented the results of the Bishop method:

tab-9

 

 

 

 

Tabel 6. Results. Bishop method

Tabel 6. Results. Bishop method

Results of analysis of a cantilever wall. Fellenius method
Further is presented the results of a piling wall, using Fellenius’ method:

tab11

 

 

 

 

Tabel 7. Results. Fellenius method

Tabel 7. Results. Fellenius method

 

 

 

 

 

 

 

 

 

 

 

The minimum safety factor calculated by Fellenius method is 0.486, which value is lower than the safety factor calculated by Bishop method Fs=0.738.

 

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