Applications of Rock Penetration H Pile for Deep Excavation Retaining System-Paper

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The paper presents the design and use of Rock Penetration H-piles (RPH piles) as a temporary retaining system for the Mumbai Metro Line 3 SEEPZ station launching shaft. Because land acquisition delays prevented installation of a conventional secant pile wall across the full excavation, RPH piles were installed approximately 30 m from the existing wall to enable construction within the available site.<br /><br />Each bored pile contained a structural steel H-beam socketed into rock. The beam carried the earth, water and surcharge loads, while low-strength M10 concrete filled the space around it. The system was supported by struts, ground anchors, and rock bolts as excavation progressed. PLAXIS 2D finite-element analysis modelled the ground–wall interaction and staged construction, and was used to assess structural forces, stability and displacement. At the critical stage, predicted lateral displacement was 9.5 mm, below the contractual limit of 15 mm. The wall was built in varying depths, with at least 1 m of socketing into Grade III rock, and enabled the timely lowering of the tunnel-boring machine.<br /><br />A key advantage of RPH piles is that they can be installed and dismantled quickly. Once the temporary wall is no longer needed, the concrete can be chipped away and the steel beams removed for reuse. Compared with conventional reinforced secant piles, the system can reduce construction time and cost, simplify connections for walers, and accommodate constrained sites, including areas with incomplete land acquisition or nearby utilities.<br /><br />The authors conclude that RPH piles performed effectively under the project’s ground and site constraints, providing a practical, economical alternative for temporary deep-excavation support.

Keywords

Rock Penetration H-piles

RPH piles

temporary retaining system

Mumbai Metro Line 3

SEEPZ station

deep excavation support

PLAXIS 2D analysis

socketed into rock

temporary retaining wall

lateral displacement