Choosing the appropriate pile foundation for a project is crucial for both cost efficiency and structural integrity. The selection process is based on data obtained from soil exploration boreholes, which provide information about soil conditions at different depths. The collected data is used to determine the type of pile that will meet the desired strength and other requirements of the project.
It’s important to note that the soil conditions can vary greatly depending on the location of the project. As a result, careful consideration should be given to selecting the right pile for the specific site conditions. Making the right choice can help to reduce costs and improve the overall efficiency of the project.
Overall, selecting the right pile foundation is a critical aspect of any construction project. By analyzing the soil exploration data, project managers can make informed decisions about the type of pile that will work best for the project’s unique requirements.
Factors affecting the selection of Pile Foundation
The selection of pile foundations depends on various factors such as the characteristics of the soil, the magnitude and type of loads that the structure will impose on the foundation, the number of piles required to support the structure, and the cost of construction.
The soil conditions play a crucial role in determining the suitability of pile foundations. Factors such as soil type, bearing capacity, and soil consistency are considered to ensure that the foundation can support the loads of the structure.
The loads from the structure are another important consideration, as the foundation must be able to withstand the weight of the building and any other loads that may be imposed on it. The nature of the loads, such as static or dynamic, also affects the selection of the appropriate type of pile foundation.
The number of piles required to support the structure is also a factor in the selection process. The spacing and arrangement of the piles must be optimized to ensure that the load is distributed evenly across the foundation and that the foundation can support the weight of the structure.
Finally, the cost of construction is a critical factor in the selection of pile foundations. The cost of materials, equipment, and labor must be considered, along with any additional costs such as transportation and site preparation. A cost-effective solution that meets the required design standards is typically preferred.
Types of Pile Foundation
Piles, which are structural members used to transfer the load of a structure to the soil or rock beneath, can be classified into three main types based on different factors. The classification of piles helps in selecting the most suitable type of pile for a particular construction project.
The first type of pile is end bearing piles, which derive their carrying capacity from the soil or rock located at the bottom of the pile. These piles are designed to transfer the load of the structure through the shaft of the pile and onto the bearing stratum at the end of the pile. End bearing piles are commonly used in the construction of high-rise buildings, bridges, and other heavy structures.
The second type of pile is friction bearing piles, which derive their carrying capacity mainly from the skin friction between the surface of the pile and the surrounding soil. These piles are designed to transfer the load of the structure through the shaft of the pile and the skin friction resistance along the length of the pile. Friction bearing piles are commonly used in the construction of tall buildings, bridge abutments, and retaining walls.
The third type of pile is a combination of end bearing and friction bearing piles, which are designed to carry the load of the structure through both the end bearing and the skin friction along the shaft of the pile. These piles are commonly used in soft soil conditions where the end bearing capacity is limited, and the skin friction along the pile’s length is the primary means of support. The selection of the type of pile depends on various factors such as soil conditions, load requirements, construction method, and budget.
1. End Bearing Pile Foundation
Point-bearing piles, which are also known as end bearing piles, are a type of foundation used in construction projects. These piles are typically chosen when the site has a hard soil layer or bedrock at a reasonable depth.
To determine the appropriate length of the pile, soil exploration borehole records are examined to determine the depth of the bedrock. Based on this information, the length of the pile can be easily calculated.
Overall, point-bearing piles are a useful foundation option in situations where there is a hard soil layer or bedrock at a manageable depth, and can be tailored to meet the specific needs of a construction project.
Fig 1: End Bearing Pile
The method of pile foundation where loads from structures are directly transferred to hard soil through bearing action of pile bottom tip is cost-effective as it does not require the use of skin friction to resist loads. The ultimate capacity of a pile or pile group in this case is dependent on the bearing capacity of bedrock or hard strata. To determine the number of piles required, one must consider both the loads from the structure and the individual capacity of the piles.
In situations where hard bedrock is not available at a reasonable depth, but fairly compacted hard soil strata exists, piles should be extended a few meters into the hard soil strata to ensure stability. The equation QU = QP represents the relationship between the ultimate load capacity of pile foundation and the load carried by the end bearing pile or pile group. By using this equation, engineers can determine the maximum capacity of the foundation based on the load-carrying capacity of the individual piles.
Overall, the cost of construction for pile foundations is optimized through the use of end bearing piles or pile groups, which transfer loads directly to the hard soil below. The number of piles required will depend on the load requirements and individual capacity of the piles. Additionally, in cases where hard bedrock is not available, piles should be extended into hard soil strata for added stability. The equation QU = QP is a useful tool for engineers in determining the maximum capacity of the foundation based on individual pile capacity.
2. Friction Pile Foundation:
Friction piles are a type of foundation that can withstand the loads from structures by utilizing the skin friction between the pile and the surrounding soil. These types of piles are typically chosen when a hard layer of soil is present at a significant depth and constructing end bearing piles would not be cost-effective.
When using friction piles, the number of piles in a group is carefully selected to ensure that the load from the structure can be adequately supported through skin friction. Although this type of pile foundation can also resist loads from end bearing, the value of this resistance is relatively small and is usually disregarded in calculations.
Overall, friction piles are an efficient and effective way to support structures when end bearing piles are not a viable option. By utilizing the skin friction between the pile and the soil, these types of piles can provide the necessary support for even the most complex and demanding structures.
Fig 2: Friction Pile.
In order to select the appropriate length of a friction pile, several factors must be taken into consideration. These include the shear strength of the soil, the loads that will be imposed on the structure, and the size of the piles. Once these factors have been assessed, the capacity of each individual pile can be determined based on the skin friction resistance provided by the selected pile length.
To ensure optimal efficiency and cost-effectiveness, it is important to choose the most appropriate length for the pile. The number of piles required for a particular project can then be calculated based on the individual capacity of each pile.
In cases where the soil is composed of loose sand or soft clays, it may not be able to provide sufficient skin friction or adhesion resistance to support heavy loads from structures. In such instances, it becomes crucial to carefully evaluate and determine the most suitable approach for the foundation, so as to ensure the stability and safety of the structure.
3. Combined End Bearing and Friction Pile Foundation:
One type of pile foundation commonly used in construction can withstand loads from structures through both end bearing and friction resistance, making it advantageous. This pile has a high capacity and is cost-effective. It is typically employed when soil exploration results indicate hard bedrock or compacted soils at reasonable depths, with soil above the bedrock providing support for skin friction resistance.
In this case, the ultimate load capacity of the pile foundation (QU) is determined by adding the load carried by the friction pile or pile group (QS) to the load carried by the end bearing pile or pile group (QP). The load is transferred to the soil through friction for sandy soil and adhesion for clayey soil.