Calcium carbonate cementation of sand: A method for producing artificially cemented samples for geotechnical testing and a comparison with natural cementation processes

Abstract

The experience of Dutch dredging companies is that cemented layers in Holocene calcareous sands are much more frequent than expected. In an effort to alleviate this problem a method for producing slightly calcium carbonate cemented sand is presented, these samples being used to better constrain the geotechnical parameters of slightly cemented carbonate sands when assessing dredging conditions. The most important environments where early marine cementation (mainly by high-magnesian calcite and aragonite) occur, are intertidal beaches and tidal flats, subtidal sandflats and reefs. Each environment has its typical occurrence and dimension of cemented layers and a characteristic form and distribution of cementing materials within the sandstone. It is, therefore, expected that sandstones from each environment will have a distinct set of geotechnical properties. Important factors controlling calcium carbonate cementation are the chemistry of the seawater (the source of the cementing material) the physical conditions, in terms of hydraulic energy, sedimentary parameters such as permeability, texture and composition of the sand, and an initially stabilizer of the loose sediment. All these factors and the way in which they relate to each other explain large variability in marine cement forms and the variability of the geotechnical properties of the cemented calcareous sediments. The factors controlling early cementation in the shallow-marine environment are discussed in order to evaluate the boundary conditions for a laboratory model used to produce artificially cemented and by simulating natural subtidal cementation processes. The resulting cemented sands are shown to be comparable with natural sandstones and to exhibit similar behaviour during strain tests. For the purposes of assessing dredging conditions these artificial samples have advantages over natural samples.