Pålgrund

Pålgrund is a form of deep foundation used to transfer loads from buildings or structures through weak surface soils to deeper, more stable layers. The term is common in Scandinavian engineering, where it refers to a system of piles driven or drilled into the ground and connected by a pile cap. In English, the same concept is usually called a pile foundation or piles.

A pile foundation consists of slender load-bearing members, typically made of concrete, steel, or timber, driven or excavated into the ground. Load transfer occurs mainly through end bearing at the tip, through skin friction along the shaft, or a combination of both. A pile cap ties the piles together and distributes the superimposed load to the individual piles.

Design of a pålgrund requires geotechnical investigation to determine soil profile, bearing capacity, settlement criteria, and groundwater conditions. Engineers select pile type and length to achieve adequate capacity, minimize settlement, and resist lateral loads. Piles may be end-bearing on a hard stratum or rely on friction along their surface. Material durability and scour protection are also considered.

Installation methods vary: driven piles installed with impact or vibration; bored or drilled piles created by concrete or steel casings; and soil displacement approaches. Quality assurance includes static load tests, dynamic tests, and non-destructive pile integrity tests to verify capacity and integrity before construction is completed.

Pålgrund foundations are used in soft or compressible soils, near water or in areas with variable groundwater, in buildings, bridges, and offshore structures. They offer advantages in reducing settlement and allowing support on unsuitable surface soils, but they can be more expensive and require specialized equipment and skilled execution.