Design of Pre-Bored Socketed Steel H-Pile - Deep Foundation Design -KEEP edX

Steel H-Pile Selection and Safety Factors
🏗️ Typical steel H-piles in Hong Kong are selected based on specific load-bearing requirements and installation methods like jacking or pre-boring.
⚖️ For these installation methods, a factor of safety of 2 is applied, effectively reducing the allowable stress of the steel to half of the yield strength ($f_y$).

Socket Length Design and Bond Friction
📏 The required socket length for H-piles typically ranges between 5 to 7 meters, designed to meet structural integrity needs.
⛓️ Bond friction calculations involve the interaction between the H-pile and the grout, as well as the grout and the surrounding rock.
📊 Per the foundation code, the allowable bond stress between steel and grout is set at 400 kPa to ensure structural stability.

Rock Socket and Grout Specifications
🪨 When dealing with category 1C rock, designers use an allowable bond friction of 700 kPa for compression and 350 kPa for tension.
🕳️ Pre-bored hole diameters are generally kept between 550 mm and 600 mm to facilitate pile insertion.
🛡️ A minimum grout cover of 40 mm must be maintained around the pile, making the 550 mm pre-board hole the most economical choice.

Key Points & Insights
➡️ Structural Efficiency: Designing the socket length requires balancing bond resistance from both the steel-to-grout interface and the grout-to-rock interface.
➡️ Compliance Standards: Always refer to the specific tables within the foundation code to determine allowable bond friction values based on rock quality.
➡️ Cost Optimization: Selecting the smallest compliant hole diameter (e.g., 550 mm) while maintaining the 40 mm grout cover provides the best balance between technical requirements and project costs.

📸 Video summarized with SummaryTube.com on Apr 07, 2026, 04:44 UTC