Micropiles - A Story of Success-Paper

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Micropiles are small-diameter foundation elements, defined by European Standard EN 14199 as bored piles up to 300 mm in diameter or displacement piles up to 150 mm. Although pile foundations have ancient roots, modern injected micropiles became widely used in Europe from the mid-20th century. Improved compact drilling equipment later expanded their use in restricted-access and difficult terrain.<br /><br />Under European practice, design follows Eurocode 7 and execution standards, using partial safety factors. Micropiles may rely on end bearing or skin friction; European designs commonly use friction. Because they are slender, they have limited resistance to bending and horizontal loads, and buckling is a concern in soft ground. Careful pile layouts—often using piles battered in different directions—can reduce bending. Corrosion protection, ground conditions, installation quality, supervision, and maintenance must also be addressed.<br /><br />Micropiles can be installed as cased bored piles or hollow-bar injection piles. Grouting is critical: appropriate methods, pressure, and materials can improve soil contact and bearing capacity. Casing helps control pile diameter but may be difficult or costly to install and can reduce side friction in some soils.<br /><br />The paper presents applications including stabilizing a landslide-threatened coastal road, supporting a reinforced-soil embankment on a creeping alpine slope, stabilizing a riverbank after flooding, founding tall ropeway towers in congested ground, and supporting a deep excavation where neighbouring property could not be anchored. These projects demonstrate micropiles’ versatility in foundations, underpinning, slope stabilization, soil reinforcement, and anchoring.<br /><br />The authors conclude that micropiles are adaptable and can be installed with lightweight equipment in challenging conditions. Their successful use depends on recognizing their structural limitations and carefully coordinating design, pile arrangement, execution, and quality control.
Keywords
micropiles
foundation elements
Eurocode 7
EN 14199
bored piles
displacement piles
grouting
slope stabilization
soil reinforcement
corrosion protection