Deep Foundation Testing Solutions (DFTS) refers to a range of testing methods used to assess the integrity and load capacity of deep foundation systems. Deep foundations are typically used to support heavy structures such as buildings, bridges, and transmission towers that require a foundation to be placed at a considerable depth below the ground surface.
DFTS involves testing techniques such as pile testing, drilled shaft testing, and static load testing, which provide valuable information about the performance of the foundation system. The testing methods can be used to determine the load capacity, integrity, and deformation characteristics of deep foundation elements, such as piles, drilled shafts, and micropiles.
Some of the common testing methods used in DFTS include:
- Pile load testing: This involves applying a load to the pile and measuring the displacement and stress response to determine the load capacity and behavior of the pile.
- Sonic logging: This involves measuring the velocity of sound waves through the pile to detect any defects or anomalies in the pile, such as cracks or voids.
- Crosshole sonic logging: This involves measuring the velocity of sound waves between pairs of parallel access tubes embedded in the foundation element to detect any defects or anomalies in the pile.
- Thermal integrity profiling: This involves measuring the temperature distribution along the length of the pile using thermal sensors to detect any defects or anomalies in the pile, such as voids or delaminations.
Overall, DFTS plays an important role in ensuring the safety and reliability of deep foundation systems, by providing critical information about their load capacity and integrity.
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Types of deep foundation Testing
Deep foundations are used when the shallow soil layers near the ground surface cannot support the weight of a structure, or when a structure needs to be supported on soft or unstable soil layers. Deep foundations are installed at a depth below the ground surface, where the soil has sufficient load-bearing capacity to support the structure. Here are some of the common types of deep foundations:
- Pile foundations: Pile foundations are long slender columns made of materials such as concrete, steel, or timber that are driven into the ground to a sufficient depth to support the structure. Pile foundations are typically used in soils with poor bearing capacity, where the loads from the structure need to be transferred to deeper and stronger soil layers.
- Drilled shafts: Drilled shafts, also known as drilled piers or caissons, are deep vertical or inclined columns that are created by drilling a hole into the ground and filling it with concrete. Drilled shafts are typically used to support heavy structures or structures that are subjected to high lateral forces, such as bridges and high-rise buildings.
- Micropiles: Micropiles are small diameter piles that are typically less than 12 inches in diameter and are used to support structures in soils with limited space or access, or where soil conditions are unfavorable for larger diameter piles. Micropiles are also used to reinforce existing structures that have settled or experienced structural damage.
- Diaphragm walls: Diaphragm walls are deep underground walls that are typically used to provide support for excavation and retaining structures. Diaphragm walls are constructed by excavating a trench and installing a reinforcing cage, followed by the placement of concrete into the trench.
- Sheet piles: Sheet piles are thin, interlocking steel or concrete sheets that are driven into the ground to form a continuous wall that provides lateral support for excavation or retaining structures.
Overall, the choice of deep foundation type depends on various factors such as soil conditions, structural requirements, and site constraints. An experienced geotechnical engineer or foundation specialist can help determine the most appropriate deep foundation type for a particular project.
What are the instruments used in deep foundation testing?
There are several instruments and equipment used in deep foundation testing to evaluate the integrity and load capacity of foundation systems. Here are some of the commonly used instruments:
- Pile testing equipment: Pile testing equipment includes various types of load cells, displacement sensors, and data acquisition systems that are used to apply loads to the pile and measure the pile’s response to determine its load capacity and behavior.
| Pile Driving Analyzer® (PDA-8G) | Pile Installation Recorder (PIR) | Pile Integrity Tester |
|---|---|---|
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- Sonic logging equipment: Sonic logging equipment includes ultrasonic transducers, signal generators, and receivers that are used to measure the velocity of sound waves through the foundation element. This equipment is used to detect defects, voids, and anomalies in the foundation element.
- Crosshole sonic logging equipment: Crosshole sonic logging equipment includes pairs of ultrasonic transducers that are placed in parallel access tubes embedded in the foundation element. The equipment is used to measure the velocity of sound waves between the access tubes to detect any defects or anomalies in the foundation element.
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- Thermal integrity profiling equipment: Thermal integrity profiling equipment includes thermal sensors that are used to measure the temperature distribution along the length of the foundation element. The equipment is used to detect any defects or anomalies in the foundation element, such as voids or delaminations.
- Dynamic pile testing equipment: Dynamic pile testing equipment includes impact hammers, accelerometers, and data acquisition systems that are used to measure the response of the pile to an impact load. This equipment is used to determine the pile’s load capacity, stiffness, and damping properties.
- Bi-directional load testing equipment: Bi-directional load testing equipment includes hydraulic jacks, load cells, and displacement sensors that are used to apply a cyclic load to the foundation element in both directions. This equipment is used to determine the foundation element’s load capacity, stiffness, and damping properties.
The choice of testing equipment depends on the type of foundation element and the testing method being used. A qualified foundation testing specialist should be consulted to determine the most appropriate testing equipment for a particular project.