8 Cause Of Failure Of Foundation And Its Remedies
What Is Failure Of Foundation?
Failure of Foundation means a developed crack or rupture or uprooting of foundation footings or rafts can be caused by many reasons. In general, the failure of the foundation takes place because of the condition of the soil underneath, the foundation.
The Overview Of Foundation Failure
In this post, we will discuss the many possible reasons for the failure of the foundation and some technical methods to prevent failure. The failure mainly depends on the soil condition but the poor condition of the soil is not the only concern to failure there are some other reasons too. So let me explain to you all the major cause that can lead to a failure of the foundation
Mejor Causes Of Failure Of Foundation
Under this section will see the list of the possible cause of foundation failure
1. Unequal Settlement Of Soil
Unequal settlement of the sub-soil may develop to cracks or rupture in the structural component of the foundation ( i.e. Footing or raft ) the cause of failure of foundation due to unequal settlement of soil may be of many reasons such as:
- Non-uniform nature of sub-soil below the foundation.
- Unequal distribution of the load of the foundation on the soil strata.
- Eccentric loading.
2.Moisture Movement Of Soil
One of the major causes of the failure of foundation footings is the cohesiveness of soil, where the sub-soil water level varies. When the water table drops down, shrinkage of soil takes place. Due to this, there is a lack of soil support to the foundation footings or rafts which leads to crack, the building. During upward movement of moisture, the soil (especially if it is expansive) swells causing high swelling pressure. If the foundation and super-structure are unable to resist the swelling pressure, cracks are developed. For such cases, special precautionary measures are to be taken.
3.Lateral Pressure On The Building Walls.
The walls of the building transmit the load to the foundation which may be subjected to lateral pressure or thrust from a pitched or sloped roof or an arch or due to wind action. Because of this, the foundation will be subjected to a bending moment (or resultant eccentric load). If the foundation is not designed to bear such bending moments, it may fail by either overturning or by developing tensile stresses on one side and high compressive stresses on the other side of the footing which will lead to a rupture of footing.
4.Lateral Movement Of Soil
This is possible to very soft soil which is likely to move out or squeeze out laterally when subject to vertical loads, especially at locations where the ground is at the slope. This sort of situation may also arise in granular soils where a large pit is excavated in the near vicinity of the foundation. Due to this kind of movement, extensive settlements take place, or the structure may even badly collapsed. Lateral movenment of soil may be the casue of failure of foundation due to earthquake.
5.Unequal Settlement Of Masonry.
As discussed earlier, the foundation includes the portion of the structure which is below ground level. This portion of masonry has mortar joints that are situated between the ground level and concrete footing (base) that may either shrink or compressed, leading to an unequal settlement of masonry below ground level because this, the superstructure above the ground level will also develop cracks.
6.Weathering Of Soil
Sometimes, small trees, shrubs, or hedge is grown very near to the foundation wall. The roots of these shrubs absorb the atmospheric moisture from the foundation soil, Causing a production of voids and even weathering. Due to this, the ground near the wall depresses down and sometimes the roots of those trees might penetrate the foundation resulting in the decay of foundation concrete and leads to crack and accordingly foundation failure. This kind of mishap occurs due to the lack of maintenance in and around the building.
The behavior of the foundation may be adversely affected due to atmospheric actions such as drought, storm, flood, and earthquakes. If the depth of the foundation is shallow, excessive moisture fluctuation due to flood or drought may cause serious trouble. If the building lies in a low-lying area, the foundation may even be scoured during the heavy floods and even if the water remains stagnant near the foundation, it will remain constantly damp, resulting in a decrease in the strength of footing or foundation wall.
Plumbing and drainage lines are often channeled under the foundation of the building and it can lead to the damage of foundation concrete thereby causing a failure of the foundation.
Remedies Against Foundation Failure
1.Checks Against Unequal Settlement of Soil
Unequal settlement of soil can be controlled by :
- Resting the foundation on rigid strata, such as rock or hard moorum.
- proper design of the base of footing, so that it can resist cracking,
- limiting the pressure in the soil
- avoiding eccentric loading.
2. Protection against Moisture Movement Of Soil
The movement or absence of moisture can be controlled by the below-mentioned points
- Using mortar of proper strength.
- Using thin mortar joints.
- Reducing the height of masonry to 1 m per day if lime mortar is used and 1.5 m per day if cement mortar is used.
- Properly watering (curing) the masonry.
3.Prevention Of Lateral Pressure On The Building Walls
This is a kind of problem where post-construction rectification is difficult that is why preventive or precautionary measures must be taken during designing the building and also during the construction.
4.Prevention Of Lateral Movement Of Soil
Lateral movement of soil can be prevented in two ways.
- Satcknenet of heavy materials or deep excavation near and existing foundation soil should be avoided to prevent the lateral movement of foundation soil.
- In a case of deep excavation is to be done near an existing foundation the area must be secured by doing sheet pilling to avoid the soil escape due to lateral pressure.
5.Protection Against An Unequal Settlement Of Masonry.
The unequal settlement could be checked by
- Using mortar of proper strength.
- Using thin mortar joints
- restricting the height of masonry to 1 m per day if a lime mortar is used and 1.5 m per day if cement mortar is used.
- properly watering the masonry.
6.Remedies Against Weathering Of Soil
This is a problem caused by the natural growth of trees and bushes near the foundation wall of a building If proper maintenance is done it can be avoided.
7.Protection Against Atmospheric Action
As we all know the failure of a foundation caused by a natural disaster is an act of God, that is why the structural/geotechnical engineer should design the structure in such a way that the building can resist all the possible.
8.Remidies Against Plumbing Leaks
Plumbing pipes to be laid under the building shall be of good quality or the pipeline channel should be avoided.