Introduction:
The lowest level of a building is its base, also called its foundation. So, the structure’s load (or loads) can be safely transferred to the ground below. The stability of a building’s foundation is one of the most important parts of how well it works. A good foundation ensures the ground is kept from what it can handle. Even though it can, the ground sinks under the weight. The amount of the settlement is in a good range.
Additionally, many factors, such as soil type and how the foundation is constructed, can affect the total amount of foundation settlement. Foundations built on bedrock move very little. On the other hand, foundations in other kinds of soil, like clay, may sink much more. Since it was built in the early 1930s, the Mexico City Palace of Fine Arts has settled more than 15 feet (4.5m) into the clay soil on which it is built. On the other hand, foundation settlement is usually limited to millimeters or fractions of an inch. When a building’s foundation settles quickly, it can cause damage to the building.
What is Foundation Settlement?
Foundation settlement refers to the gradual sinking or movement of a building’s foundation into the soil or ground on which it rests. It can happen due to soil type and condition, building weight and distribution, moisture content changes, and environmental factors. As a building settles, it can cause various problems, including cracks in walls, floors, or ceilings, uneven floors, doors and windows that stick or won’t close properly, and other structural issues. These issues can affect the building’s safety, stability, and value and may require costly repairs.
Foundation settlement can occur in new and old buildings, although it is more common in older structures. The extent and severity of settlement can vary widely depending on the specific conditions affecting the building and may require the services of a qualified engineer or other professional to assess and address the issue. Preventing or mitigating foundation settlement may involve proper site preparation, appropriate building materials and techniques, and ongoing maintenance and monitoring of the building’s foundation and surrounding soil.
Causes of Foundation Settlement:
Foundation settlement can be caused by many things, including::
i) Soil Consolidation:
It is the most common cause of foundation settlement. It occurs when the weight of the building compresses the soil beneath the foundation, causing it to settle.
ii) Poor Soil Quality:
If the soil beneath the foundation is of poor quality, it may not be able to support the weight of the building, leading to settlement.
iii) Changes in Moisture Content:
When the moisture content in the soil beneath the foundation changes, it can cause the soil to expand or contract, leading to foundation settlement. It can happen due to changes in weather patterns or inadequate drainage around the foundation.
iv) Poor Construction:
If the foundation was not constructed properly or if the building was constructed on unstable ground, it can lead to foundation settlement.
v) Natural Disasters:
Natural disasters such as earthquakes, floods, and landslides can cause foundation settlement.
vi) Plumbing leaks:
Water leaks from pipes beneath the foundation can cause soil erosion and settlement.
vii) Trees:
Trees located too close to the foundation can cause foundation settlement by absorbing moisture from the soil, creating voids beneath the foundation.
Types of Foundation Settlement:
Fig: Types of Foundation Settlement
Courtesy: geotech.hr
1. Uniform Settlement:
The overall sinking of the structure is reflected in the uniform settlement. The building’s pillars move to the same degree in this foundation settlement. The entire building sinks vertically. This type of foundation, therefore, has little effect on the structure. The low SBC of the soil, consolidation of the soil, and a change in the soil moisture throughout the entire area are all factors in producing the uniform settlement. Uniform settlement is defined by the fact that it barely compromises the integrity of the building.
However, because of the new level, the piping, sewer lines, conduits, cables, etc., connected to the building’s utilities are now at risk of damage. As a result, fixing any resulting damage (such as a leak or a twisted pipe) is necessary.
2 Tipping Settlement:
Tipping settlement occurs when the soil or rock beneath a building becomes too weak to support the structure’s weight. Many factors, such as compaction, fluctuating water tables, erosion, and sloppy building practices, can contribute to this problem. The settlement of a building’s foundation can cause structural damage, such as cracks in the walls or floors, misaligned doors and windows, or sloping floors. A building’s stability can be restored and further damage prevented by promptly addressing a foundation that has begun to tip.
Fixing a tipping settlement of a foundation typically involves assessing the damage’s extent and identifying the settlement’s cause. Then, remedial measures are implemented to prevent further settlement and repair any damage that has occurred. Depending on the severity of the tipping settlement, methods such as underpinning, soil stabilization, or foundation replacement may be used.
It’s essential to address the tipping settlement of the foundation promptly because delaying repairs can result in more extensive damage and a higher cost of repairs. Additionally, structural damage caused by a tipping settlement can affect the safety and usability of the building, so it’s crucial to address the issue as soon as possible to avoid further damage and ensure the safety of the occupants.
3. Differential Settlement:
Differential settlement of a foundation refers to the uneven or unequal settlement of different parts of a building foundation. Settlement occurs when the soil beneath a foundation compresses, causing the foundation to sink. Differential settlement happens when some parts of the foundation settle more than others, resulting in a tilt or uneven structure.
Several factors can contribute to differential settlement, including variations in soil conditions, load distribution differences, and underground utilities or other buried objects. For example, load distribution differences, and the oil layer, may settle more than the rest of the foundation, leading to differential settlement.
Differential settlement can cause walls, floors, and ceilings to crack and collapse. Thus, foundation and building design must minimize differential settlement. It may require soil testing, improvement, and structural elements like beams and columns to distribute the load evenly across the foundation. Foundation inspections and maintenance can also detect and address differential settlement before it becomes a major issue.
Preventive Measure of Settlement in Foundation:
Foundation settlement occurs when the soil beneath the building compresses or shifts, causing the foundation to sink or become uneven. There are several preventive measures for foundation settlement, which are as follows:
1. Mudjacking:
This method involves injecting a mixture of cement, water, and soil beneath the settled foundation. The mixture fills the voids and raises the foundation to its original position. This method is less expensive than other methods and can be done quickly.
2. Piering:
This method involves installing steel piers beneath the foundation to support it. The piers are driven into the ground until they reach stable soil, and then the weight of the building is transferred onto them. This method is more expensive than mudjacking but provides a more permanent solution.
3. Underpinning:
This method involves excavating soil beneath the foundation and pouring concrete footings to support it. This method is more invasive and expensive than the previous two methods, but it can be necessary if the foundation has severely settled or the soil is unstable.
4. Grouting:
This method involves injecting grout, a mixture of cement, water, and other additives, beneath the foundation. The grout fills voids and helps to stabilize the soil. This method is less invasive than underpinning and can be effective for minor settlement issues. It’s important to note that the correction method used will depend on the specific situation, including the type of soil, the extent of the settlement, and the type of foundation. It’s recommended to consult with a professional engineer or foundation repair specialist to determine the best course of action.
Conclusion:
The foundation settlement describes the gradual downward movement of a building’s base into the surrounding soil. It may occur for several reasons, such as a wrong soil type, insufficient site preparation, or environmental shifts. Cracked walls, uneven floors, and structural issues are consequences of a foundation that has settled. Furthermore, it may make the building unfit for human habitation.
It’s important to identify the cause of foundation settlement to determine the appropriate repair method and prevent further damage to the building. Regular maintenance and inspections can identify potential issues and address them before they become more serious.
References:
1. Steffen, J. (2021, December 13). What is Foundation Settlement | Deal with Foundation Settlement Problems – ConstructUpdate.com. ConstructUpdate.com. https://www.constructupdate.com/foundation-settlement-causes-types-and-solution/
2. 6 Common Causes of Foundation Settlement. (2015, August 12). Angi. https://www.angi.com/articles/4-common-causes-foundation-settlement.htm
3. P. (2022, July 22). Foundation Settlement | a detailed discussion – Structural Guide. Structural Guide. https://www.structuralguide.com/foundation-settlement/
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https://wrengineers.in/what-is-structural-settlement-causes-for-structural-settlementwhat-is-soil-
5. Fox, A. (2018, September 25). Foundation Settlement – The Brick Kicker. The Brick Kicker. https://www.brickkicker.com/foundation-settlement/
6. Hancock, N. (2021, May 28). What is Foundation Settlement? 7 Types in Foundation Repair Terms – Anchor Foundation Repair. Anchor Foundation Repair. https://anchorfoundationrepair.net/blog/what-is-foundation-settlement/
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