đź•‘ Reading time: 1 minute
Generally, the term retaining wall failure do not referred to the total failure or collapse but rather describes signs and indications by which failure possibilities and wall instability could be predicted and can be saved if dealt with properly. Retaining wall sliding, toppling, overturning are types of total collapses that cannot be rehabilitated, therefore rebuilding the wall the sole solution for these failures. However, full collapse of retaining wall is unlikely in addition to show signs of problems that could be observed and rehabilitate the wall before the wall fail entirely. By and large, most of retaining walls could be rehabilitated and saved after evaluating and specifying reasons of deficiencies.
In this article, various parameter, which might go wrong and consequently provide signs of deficiencies, are discussed in the following points.
Contents:
- Causes for Retaining Wall Failure
- Retaining Wall Failure due to Improper Reinforcement Placement:
- Retaining Wall Failure due to Saturated Backfill
- Retaining Wall Failure due to Weep Holes that do not Weep
- Design Error Resulted from Misinformation
- Retaining Wall Failure due to Calculation Errors
- Unanticipated Loads
- Mistakes in utilizing software
- Retaining Wall Failure due to Detailing errors
- Foundation Issues
- Inadequate specifications and notes
- Retaining Wall Failure due to Poor Construction
- Retaining Wall Failure due to Age
Causes for Retaining Wall Failure
Following the common causes for retaining wall failures:- Improper reinforcement placement
- Saturated backfill
- Weep holes that do not weep
- Design error
- Calculation errors
- Unanticipated loads
- Mistakes in utilizing software
- Detailing errors
- Foundation issues
- Inadequate specifications and notes
- Shoddy construction
- Retaining wall age
Retaining Wall Failure due to Improper Reinforcement Placement:
Reinforcement size, depth, and spacing should be checked when wall stem exhibits sign if issues such as cracking and extreme deflections. Reinforcement size and depth can be determined either by devices for example magnetic field measuring pachometer. This device is used to determine reinforcement position and depth up to around 100 mm with acceptable accuracy or to achieve more accurate measurement. This device can also locate steel bars and chip out concrete to find out the precise reinforcement size and depth. Surprisingly, there are situations where reinforcement was installed in wrong wall side that might be resulted from contractor error or detailing error. After actual steel reinforcement size, depth, location, and sometimes testing stem concrete strength by taken core sample, back design computation is employed to estimate actual design capacity then provide remedial measures.Retaining Wall Failure due to Saturated Backfill
It is assumed that backfill is granular and well drained during the design of retaining wall. Pressure against the wall is substantially increased if surface water is permitted to infiltrate into the backfill. This can be avoided by grading backfill surface that direct water away from the wall or by diverting water to disposal through drainage channels close to the retaining wall. Furthermore, poor backfill such as those containing clay swells and lead to increase pressure considerably. Finally, crushed and pea gravels are examples of good backfill that provide proper drainage and avoid creating pool water behind the wall. Figure-1 illustrates drainage system which can be used avoid hydrostatic pressure.
Figure-1: Retaining wall with proper drainage system
Retaining Wall Failure due to Weep Holes that do not Weep
Due to lack of filters, for instance line of gravel or crashed stone positioned along the base of the wall weeds turn into clogs and create problems for water draining. In masonry retaining wall, weep hole is made by removing mortar at the side joints and distance between weeps is around 80 cm. Weep hole in reinforced concrete retaining wall is at least 7.5 cm in diameter and spacing should not be more than 1 m or it can be specified by the designer. Figure-2 and Figure-3 show weep hole in retaining walls.
Figure-2: Weep hole in retaining wall
Figure-3: Providing weep hole in retaining wall to drain water
