Lohkokoosta

Lohkokoosta is a term used in geology, sedimentology, and civil engineering to describe the size distribution of rock fragments, or blocks, within a rock mass or debris material. The concept helps characterize fragmentation patterns resulting from natural weathering, seismic events, or mechanical excavation, and it informs decisions about excavation, slope stabilization, and foundation design.

Etymology: The word combines lohko (“block”) and koko (“size”) with the instrumental suffix -sta, reflecting its Finnish linguistic roots. In technical usage, lohkokoosta is often expressed as a distribution function or as a set of summary statistics describing fragment sizes.

Measurement and descriptors: Field and laboratory methods include sieving of rock samples, image analysis of exposed faces, and laser scanning. Descriptors commonly used are median size (d50), d84, d16, and the overall distribution shape, which is frequently modeled as log-normal or power-law. Size data may be presented as cumulative or volumetric distributions.

Applications and implications: Understanding lohkokoosta supports rock mass classification, blasting design, drainage assessment, and stability analyses for slopes and foundations. Coarser distributions tend to reduce packing efficiency and increase interlock, influencing shear strength and permeability, while finer distributions may enhance compaction and settlement.

See also: Particle size distribution, rock fragmentation, blocky rock, rock mass rating.