Selection of Foundation Based on Soil Conditions

This article aims to focus specifically on the impact of soil type on foundation selection, selection of foundation based on soil conditions pdf, soil bearing capacity and type of foundation, foundation soil types, selection of foundation, best foundation for clay soil, different types of foundation and soil use and best foundation for loose soil.

When selecting the appropriate foundation for a structure, there are several important factors that must be taken into consideration. These factors include the type of soil present at the site, the previous usage of the land, nearby constructions, the scale of the development, and any limitations that may exist. Among these factors, the type of soil present at the site is especially significant in determining the ideal foundation for the structure.

By understanding the characteristics of different types of soil, it becomes possible to make informed decisions about the most appropriate foundation type for a given structure. Ultimately, the success and longevity of a structure are heavily dependent on the quality and appropriateness of its foundation, making this a crucial decision that cannot be taken lightly.

Selection of Foundation based on Different Types of Soils

When it comes to building a solid foundation for any structure, it is important to consider the soil type on which it will be built. There are several types of soil that may be encountered during construction, including rocks, uniform firm and stiff clay, soft clay, and peat.

For rocky soil, the foundation can be directly built on top of the rock itself, provided that it is strong enough to support the weight of the structure. However, if the rock is too brittle or uneven, additional measures may need to be taken to ensure stability.

Uniform firm and stiff clay is a good soil type for building foundations, as it is stable and able to bear weight well. The foundation can be built directly on top of this soil type without much additional preparation.

Soft clay, on the other hand, is more challenging to build on top of, as it can shift and settle over time. To build a foundation on soft clay, the soil must be properly compacted and stabilized to ensure that it will be able to support the weight of the structure.

Finally, peat is one of the most difficult soil types to build on, as it is composed of organic matter and is often unstable. In order to build a foundation on peat, it may be necessary to remove the peat and replace it with more stable soil or to use specialized foundation techniques such as piling.

1. Rocks

This category of materials includes various types of geological substances that are typically hard and solid. Examples of such substances include rocks, as well as chalk that produces a hard sound when struck. Additionally, this category encompasses materials such as sand and gravel, which typically have a low percentage of clay content. Finally, dense silty sand is also included within this category. Overall, this group of materials is defined by their hardness and geological origin.

Recommended foundation types

Based on the characteristics of the soil in question, there are three types of foundations that can be used: strip, pad, and raft.

Strip foundations are a type of shallow foundation that is ideal for soils that have good bearing capacity. They consist of a continuous strip of concrete that is placed at a shallow depth, usually around the perimeter of the building.

Pad foundations are also a type of shallow foundation that are suitable for soils with relatively low bearing capacity. They consist of individual concrete pads that are placed at intervals under the load-bearing walls or columns of the building.

Raft foundations are a type of deep foundation that are used in soils with poor bearing capacity. They consist of a large, reinforced concrete slab that is placed directly on the soil and distributes the weight of the building over a larger area. Raft foundations are particularly useful for buildings with heavy loads or where the soil is subject to significant movement.

Factors need to be considered

When selecting the appropriate foundation type for a building, there are several important factors that must be considered. If the building is situated in an area prone to frost, a minimum depth of 450mm must be used for the foundation in order to provide adequate protection. In addition, if possible, a strip or trench base should be used that is above the groundwater table.

The engineer must also take into account any running sand conditions that may be present in the area. If sand slopes are potentially eroded by surface water, then it is crucial to protect the foundation by implementing perimeter drainage measures.

When inspecting the site, the engineer should carefully evaluate any weathered rock that may be present. This is an important consideration, as the quality and stability of the rock can significantly impact the foundation’s performance.

Lastly, if the building is located in an area with chalk deposits, the engineer must be aware of swallow holes that may be present. These holes can cause instability in the ground, which can affect the foundation’s stability and must be taken into account.

2. Uniform firm and stiff clay

There are three cases which are discussed below:

Case I

The context suggests that either the foundation should not be constructed near vegetation, or the presence of vegetation is not significant for the foundation. Thus, the sentence could be rewritten as follows:

When building a foundation, it is advisable to steer clear of vegetation or choose a location where the presence of vegetation is not a critical factor. This is because the vegetation may interfere with the foundation’s stability or cause damage over time. However, if the foundation has already been constructed in an area with vegetation, it is important to monitor and maintain the vegetation to prevent any adverse effects on the foundation. Ultimately, the decision to build a foundation near or far from vegetation will depend on various factors, such as the type of foundation, the nature of the vegetation, and the intended use of the building.

Recommended foundations

Strip foundations, pad foundations, and raft foundations are all types of foundations used in building construction.

Strip foundations are long and narrow footings that are typically used to support load-bearing walls. They are constructed by digging a trench and pouring concrete into it, creating a flat surface on which the wall can be built.

Pad foundations, on the other hand, are shallow and wide footings that are used to support isolated points of load, such as columns or pillars. They are typically circular or rectangular in shape and are also constructed by pouring concrete into a prepared hole.

Raft foundations are large, flat concrete slabs that are used to support entire buildings. They are typically used in areas with weak soil or where the building is very heavy, as they can distribute the weight of the building over a larger area, reducing the risk of settlement or collapse.

Overall, the choice of foundation type depends on a variety of factors, including the soil conditions, the weight of the building, and the load-bearing capacity of the foundation itself.

Factors to be considered in this case are as follow:

According to the building regulations, the minimum depth requirement for the underside of a foundation is 900mm. This is an important requirement that must be adhered to when constructing a building, as it ensures the stability and safety of the structure.

When constructing a strip foundation in desiccated clay in dry soil, it is particularly important to follow this regulation. This is because desiccated clay is known to shrink and crack when it becomes dry. If a foundation is not constructed deep enough, it can be affected by these changes in the soil, which can cause it to become unstable and potentially compromise the integrity of the building.

To ensure the stability of the foundation, it is recommended that the building be loaded onto the foundation before the return of rains. This means that the weight of the building will help to compact the soil and prevent any movement or settlement of the foundation. By following these guidelines, builders can help to ensure that their structures are safe, stable, and built to last.

Case II

If trees, hedges, or shrubs are situated near the foundation of a building or if there is a plan to plant them in the vicinity of the structure, it can pose a potential problem. The close proximity of these plants can cause damage to the foundation, which could lead to costly repairs. Therefore, it is important to take appropriate measures to ensure that these plants are not planted too close to the foundation or to remove them altogether if they are already present. Proper planning and management of landscaping around a building can help to prevent foundation damage and maintain the structural integrity of the building.

Recommended foundation

When designing a building’s foundation, there are various types to choose from depending on the specific site conditions and requirements. One option is to use concrete piles to support reinforced concrete ground beams and precast concrete floor, which can provide a sturdy base for the structure.

Another choice could be to use concrete piles that carry an in-situ concrete slab, which can offer added stability and durability. In certain clay soils where trees may be present, specially designed trench fills may be necessary to prevent soil movement and ensure the foundation remains intact.

Lastly, a raft foundation may also be considered, which involves a large slab of concrete that spreads the building’s load evenly across the ground. The choice of foundation ultimately depends on factors such as soil type, building weight, and the presence of nearby trees. Proper foundation design is crucial for ensuring the safety and stability of any structure built on it.

Factors to be considered

The size and type of pile foundation chosen for a project should take into consideration economic factors. It’s important for engineers to be aware of this when making decisions about the foundation. By choosing the most cost-effective option that meets the project requirements, the overall cost of the project can be reduced.

When using an in situ concrete ground slab, engineers need to be careful to avoid creating any voids underneath the slab. This is particularly important when laying the slab in dry weather conditions in desiccated clay. Voids can compromise the integrity of the slab and cause it to fail over time, so it’s essential to take preventative measures.

When deciding on the type of foundation to use, the distance between recently planted trees and the foundation position should be considered. If the distance is at least one to two times the height of a mature tree, it may be appropriate to use a strip foundation. This will help to prevent damage to the tree roots, which could affect the stability of the foundation.

In some cases, reinforced trench fill may be the best option for a project. For example, in clay soils with low to medium shrinkage potential, or in areas close to the perimeter of a tree root system. This type of foundation can help to prevent soil movement and ensure the stability of the structure. Engineers should carefully evaluate the soil conditions and other factors before deciding on the best foundation type.

Case III

Before the construction of a building foundation, trees in the area are cut down. This is done in preparation for the building work to begin.

Recommended foundation

Reinforced concrete pile is a type of foundation that is commonly used in construction to support structures such as buildings, bridges, and other large-scale infrastructure. It involves drilling or driving a cylindrical shaft made of concrete and steel rebar into the ground, which then serves as a sturdy base for the structure above.

A strip foundation is a type of shallow foundation that is used to support a load-bearing wall or a row of closely spaced columns. It consists of a strip of concrete that is poured directly onto the soil, with steel reinforcement bars placed inside the concrete for added strength.

A raft foundation, also known as a mat foundation, is a type of shallow foundation that is used to spread the weight of a building over a large area. It consists of a reinforced concrete slab that is poured directly onto the soil, with steel reinforcement bars placed inside the concrete for added strength. Raft foundations are commonly used in areas where the soil is weak or unstable, or where the building loads are particularly heavy.

Factor needed to be taken into accounted

Proper tying of piles into suspended reinforced concrete slabs or ground beams is crucial to ensure structural stability. It is important to provide sufficient length of slab to withstand the force of clay heave. Additionally, sleeving the top section of the pile can be effective in reducing friction and uplift.

For clay slopes greater than 1 in 10, a special pile design may be necessary due to the possibility of creep. In such cases, the pile design should take into account the lateral thrust and cantilever effect.

Reinforced trench fill may be a viable option in certain situations, such as in clay with low to medium shrinkage potential or in the perimeter zone of the tree root system. Employing this technique can enhance the stability of the structure and ensure the longevity of the construction.

3. Soft clay

Soft soils refer to a category of soil types that are characterized by their low shear strength, making them prone to deformation and instability. This category encompasses several types of soil, including soft clay, soft silty clay, soft sandy clay, and soft silty sand.

Soft clay is a type of soil that contains high percentages of fine-grained particles, such as clay minerals. It is known for its high compressibility, low strength, and poor drainage characteristics. Soft silty clay, on the other hand, contains a higher proportion of silt particles, which can improve its drainage properties to some extent.

Soft sandy clay is a soil type that contains a significant amount of both sand and clay particles. Its mechanical properties are influenced by the relative proportions of sand and clay present, with higher sand content generally leading to improved strength and lower compressibility. Finally, soft silty sand is a type of soil that contains a higher percentage of sand particles than silt, but still has some fine-grained material present. Its properties are intermediate between those of sandy soils and silty soils, with higher silt content generally resulting in lower strength and higher compressibility.

Recommended foundations

When dealing with a particular type of soil, there are several options available for laying foundations that will provide sufficient support for the structure. Wide strip footings, raft foundations, and piles to firmer strata below are all valid options that can be considered.

Wide strip footings involve laying a wider base of concrete or masonry underneath load-bearing walls to spread the weight of the structure more evenly across the soil. Raft foundations, on the other hand, are large concrete slabs that cover the entire area beneath the structure, distributing its weight more evenly across the soil.

Another option is to use piles that extend deep into firmer strata below the soil. These piles can be made of concrete or steel, and they provide a more stable foundation by transferring the weight of the structure to the stronger soil or rock below the weaker soil layer.

For smaller projects, a pier and beam foundation to firm strata can be a suitable option. This type of foundation involves building a series of piers or columns that support a beam structure above the soil, which in turn supports the weight of the building. The piers are usually placed in areas where the soil is firmer, providing more stable support for the structure.

Factors to be considered

A wide strip footing is typically utilized in cases where the bearing capacity of the soil is sufficient, and the anticipated amount of settlement is deemed acceptable. To reinforce the strip footing, the thickness and projection beyond the wall face are taken into consideration. It is important for services entries to be flexible in order to accommodate the needs of the building. In many cases, the subsoil can be improved through the use of vibro treatment. Employing vibro treatment in conjunction with a strip or raft foundation can be an economical solution.

4. Peat

Recommended foundation

There are different types of foundation systems that can be used depending on the size and nature of the project. For small projects, a pad and beam foundation is commonly used, which involves constructing a concrete pad that rests on compacted soil and supports a series of beams. This type of foundation is suitable when there is a firm soil layer below.

On the other hand, for larger projects, concrete piles can be extended down to the firm soil layer below. This involves driving or drilling concrete piles into the ground until they reach a layer of soil that can support the weight of the structure. This type of foundation is commonly used for larger buildings or structures.

In cases where a firm soil layer is not available at a reasonable depth, a raft foundation can be used. This type of foundation involves laying a large concrete slab on the ground, which spreads the weight of the structure over a larger area. Raft foundations are commonly used when there is a hard surface crust with a suitable bearing capacity of 3-4 meters thickness.

Factor to be considered

When it comes to constructing a foundation on soft soil or peat, different types of piles can be used, including bored cast-in-place with temporary casing, driven cast-in-place, and driven precast concrete piles. These piles are designed to allow for peat consolidation drag, which can occur when the weight of the structure causes the peat layer to compress and consolidate.

If a raft foundation is used on soft soil or peat, it’s important to ensure that entries to the building are flexible. Additionally, special high-grade materials and protection may be required in aggressive peat environments.

If the peat layer is shallow and there’s a firm layer of soil below it, one solution is to dig out the peat and replace it with compacted fill. Depending on the anticipated settlement, either a raft or reinforced wide spread foundation can be used for this.

Vibro treatment is another technique that can be used to improve sub-soil conditions. This can be an economical solution when used in conjunction with a strip or raft foundation. By using vibro treatment, the soil can be compacted and strengthened, which helps to reduce settlement and improve the overall stability of the foundation.

Best Foundation for Cay Soil

Clay soils are known for their low permeability and high compressibility, which can lead to foundation settlement and structural damage. To mitigate these issues, the best foundation types for clay soils are those that can distribute the building load over a larger area and reduce the potential for differential settlement. Here are some foundation types that are suitable for clay soil:

1. Raft foundation: A raft foundation, also known as a mat foundation, is a continuous slab that covers the entire area of the building footprint. It can provide a large base area to distribute the building load evenly over the clay soil, reducing the potential for differential settlement.
2. Piled foundation: Piled foundations are deep foundations that transfer the building load to deeper, more stable soil layers. In clay soils, pile foundations can be drilled to reach more stable soil layers, providing additional support to the building.
3. Strip foundation: A strip foundation is a shallow foundation that consists of a continuous concrete strip or pad that is placed at the base of the building walls. It can be used in clay soils if the clay has adequate bearing capacity, and the building loads are not too heavy.
4. Suspended timber floor: A suspended timber floor can be used as an alternative to a traditional foundation in some cases. The floor is suspended above the ground on timber joists or beams, reducing the need for extensive excavation in the clay soil.

The best foundation type for clay soil depends on various factors such as the type of building, loads, and site conditions. It is crucial to consult with a qualified engineer or geotechnical expert to determine the most suitable foundation type for your specific project to ensure the stability and safety of the building.

Foundation Soil Types

There are several types of soils that can be encountered during foundation construction. Here are some common foundation soil types:

1. Clay soil: Clay soil is composed of fine-grained particles that have low permeability and high compressibility. It can lead to foundation settlement and damage if not appropriately managed.
2. Sand and gravel soil: Sand and gravel soil have larger particle sizes and better drainage than clay soil. They are generally considered to be good foundation soils as they have high bearing capacity and are stable.
3. Silt soil: Silt soil is composed of fine particles that are smaller than sand and larger than clay. It has moderate permeability and compressibility, and its bearing capacity can vary depending on the soil’s density.
4. Rock soil: Rock soil consists of solid rock formations that can provide excellent bearing capacity and stability for foundation construction.
5. Organic soil: Organic soil is composed of decomposed plant material and is generally not suitable for foundation construction due to its low bearing capacity and high compressibility.

It is important to conduct a thorough soil investigation before selecting a foundation type to ensure that the soil type and characteristics are adequately considered. A qualified engineer or geotechnical expert can provide recommendations based on the soil investigation results to determine the most appropriate foundation type for the project.

Foundation on Loose Soil

Building on loose soil can be challenging as it can lead to foundation settlement and structural damage. However, there are several methods for constructing foundations on loose soil, including:

1. Soil stabilization: One method for building on loose soil is to stabilize the soil by adding materials such as lime or cement. This can improve the soil’s strength and stability, providing a more suitable foundation base.
2. Deep foundation: A deep foundation, such as a pile foundation, can be drilled or driven deep into the soil until it reaches a more stable layer. This can provide additional support for the building.
3. Raft foundation: A raft foundation, also known as a mat foundation, can be used to distribute the building load over a larger area, reducing the potential for differential settlement. This can be particularly useful on loose soil where a traditional strip foundation may not be appropriate.
4. Geotechnical engineering: Consulting with a geotechnical engineer can help determine the best approach for building on loose soil. They can conduct soil testing and provide recommendations on the most suitable foundation type for the specific soil conditions.

It is important to address loose soil before construction begins to ensure the stability and safety of the building. Consulting with a qualified engineer or geotechnical expert can help determine the best approach for constructing a foundation on loose soil.

FAQs

1. How do I choose a foundation based on soil condition?

Choosing the right foundation for a building project depends on several factors, including the soil conditions of the site. Here are some general guidelines for selecting foundations based on soil conditions:

1. Sand and Gravel Soil: Sand and gravel soils are considered the best soil conditions for foundation construction. These soils are stable, offer good bearing capacity, and do not retain water. The most suitable type of foundation for this soil is a shallow foundation or a raft foundation.
2. Medium and Hard Clay Soil: Medium and hard clay soils are considered good for foundation construction. These soils have reasonable bearing capacity and are stable. The most suitable type of foundation for this soil is a deep foundation like piles or a pier foundation.
3. Silts and Soft Clay Soil: Silts and soft clay soils are considered poor soil conditions for foundation construction. These soils have low bearing capacity and are unstable. The most suitable type of foundation for this soil is a deep foundation like piles or a pier foundation.
4. Organic Silt and Clay Soil: Organic silt and clay soils are generally considered undesirable for foundation construction. These soils are unstable, have low bearing capacity, and can settle over time. The most suitable type of foundation for this soil is a deep foundation like piles or a pier foundation.
5. Peat Soil: Peat soils are unsuitable for foundation construction. These soils are very unstable, have low bearing capacity, and can compress easily. The most suitable type of foundation for this soil is a deep foundation like piles or a pier foundation, but in some cases, it may be necessary to remove the peat soil entirely and replace it with a more suitable soil type.

In summary, it’s crucial to conduct a soil investigation to determine the soil conditions of the site before selecting a foundation type. Soil investigations involve taking soil samples and analyzing them to determine their strength, bearing capacity, and other factors that affect foundation design. Based on the soil investigation report, a qualified engineer or geotechnical expert can provide recommendations for the most suitable type of foundation for the project.

2. Which foundation is suitable for which soil?

Different types of soil require different types of foundations to ensure that the building is stable and secure. Here are some general guidelines for which foundation is suitable for which soil:

1. Sand and Gravel Soil: Shallow foundations, such as strip foundations, are suitable for sand and gravel soils.
2. Medium and Hard Clay Soil: Deep foundations, such as pile or pier foundations, are suitable for medium and hard clay soils.
3. Silts and Soft Clay Soil: Deep foundations, such as pile or pier foundations, are also suitable for silts and soft clay soils.
4. Organic Silt and Clay Soil: Deep foundations, such as pile or pier foundations, are the most suitable for organic silt and clay soils.
5. Peat Soil: It is generally unsuitable to build foundations on peat soil. However, if necessary, deep foundations such as pile or pier foundations can be used.
6. Loam Soil: Loam is a good soil for supporting a foundation, as long as no miscellaneous soils find their way onto the surface.
7. Rock Soil: Types of rock such as bedrock, limestone, sandstone, shale, and hard chalk have high bearing capacities and are very strong and good for supporting foundations because of their stability and depth. Foundations for these soils can be shallow or deep depending on the characteristics of the specific rock type.

In summary, it is essential to conduct a thorough soil investigation to determine the soil type and characteristics before deciding on the appropriate foundation type for a building project. A qualified engineer or geotechnical expert can provide recommendations based on the soil investigation report to ensure the stability and safety of the building.

3. What is foundation type selection based on?

The selection of the right type of foundation for a building project is based on several factors, including:

1. Soil type and characteristics: The type and characteristics of the soil, such as its strength, compressibility, and bearing capacity, play a critical role in determining the type of foundation suitable for the project.
2. Site conditions: Site conditions such as the presence of water, slope, and vegetation can affect the type of foundation selected.
3. Building type and load: The type of building, the intended use of the building, and the loads that the building will impose on the foundation must also be considered when selecting the foundation type.
4. Construction method: The construction method, such as traditional or prefabricated construction, can affect the type of foundation selected.
5. Environmental factors: Environmental factors such as seismic activity, wind loads, and frost heave can also impact the selection of the foundation type.

In summary, the selection of the right type of foundation for a building project requires a thorough understanding of the soil type and characteristics, site conditions, building type and load, construction method, and environmental factors. A qualified engineer or geotechnical expert can provide recommendations based on a thorough soil investigation and consideration of these factors to ensure the stability and safety of the building.

4. What are four 4 factors that guide the selection of foundation types?

The selection of the appropriate foundation type for a building project is based on several factors. Here are four critical factors that guide the selection of foundation types:

1. Soil conditions: The type and characteristics of the soil, such as its strength, bearing capacity, and compressibility, play a critical role in determining the type of foundation suitable for the project.
2. Building load and type: The type of building, the intended use of the building, and the loads that the building will impose on the foundation must also be considered when selecting the foundation type.
3. Environmental factors: Environmental factors such as wind loads, seismic activity, frost heave, and water table level can also impact the selection of the foundation type.
4. Cost and constructability: The cost and constructability of different foundation types should also be considered. Factors such as ease of construction, available materials, and required equipment can influence the selection of the foundation type.

In summary, the selection of the appropriate foundation type for a building project requires a comprehensive analysis of soil conditions, building load and type, environmental factors, and cost and constructability. A qualified engineer or geotechnical expert can provide recommendations based on these factors to ensure the stability, safety, and economic viability of the building.