Drilled shafts

Definition

Drilled shafts, also known as auger cast piles or drilled piers, are a type of deep foundation that is constructed by drilling a hole into the ground and then filling it with concrete. This method provides a strong support structure for buildings and other heavy loads, making them a preferred choice in areas where soil conditions are challenging. Drilled shafts can reach considerable depths and are often used in combination with other foundation types, such as piles and caissons, to ensure stability and load distribution.

5 Must Know Facts For Your Next Test

1. Drilled shafts can be designed to withstand high axial loads and lateral forces, making them suitable for high-rise buildings and bridges.
2. The construction process of drilled shafts involves boring a hole to the required depth, placing steel reinforcement, and then pouring concrete to create the shaft.
3. Drilled shafts can be installed in various soil conditions, including loose sands, clays, and even bedrock, allowing for versatile applications.
4. The use of drilled shafts often reduces noise and vibration during installation compared to driven piles, which is beneficial in urban settings.
5. Quality control during the drilling and pouring process is essential to ensure that the concrete bonds effectively with the surrounding soil for optimal performance.

Review Questions

• How do drilled shafts differ from other types of deep foundations like piles and caissons in terms of construction methods?
  • Drilled shafts are constructed by drilling a hole into the ground and filling it with concrete, while piles are typically driven into the soil using a hammer or vibratory equipment. Caissons involve creating a large watertight structure that is then filled with concrete after being placed in position. This distinction in construction methods leads to differences in load distribution and suitability for various soil conditions.
• Evaluate the advantages of using drilled shafts over traditional foundation methods in challenging soil environments.
  • Using drilled shafts in challenging soil environments offers several advantages, including their ability to reach greater depths than traditional foundations, which helps to access more stable soil layers. The reduced vibration during installation minimizes disturbances to surrounding structures, making them ideal for urban areas. Additionally, drilled shafts can be tailored in size and depth based on site-specific conditions, improving overall stability and safety.
• Assess the impact of quality control measures on the performance of drilled shafts in supporting heavy structures.
  • Quality control measures during the drilling and pouring processes are crucial for ensuring that drilled shafts perform effectively under heavy loads. Proper bonding between the concrete and surrounding soil enhances load-bearing capacity and stability. Without rigorous quality checks, defects can lead to reduced strength or failure of the foundation. As such, incorporating quality control not only ensures compliance with engineering standards but also significantly mitigates risks associated with structural failure.

Related terms

piles: Long, slender columns driven into the ground to transfer loads from structures to deeper, more stable soil layers.

caissons: Watertight structures used to create foundations, typically constructed underwater or in areas with high water tables.

load-bearing capacity: The maximum load that a foundation or structural element can safely support without failure.