Beachrock is a type of carbonate beach sand that has been cemented together by a process called synsedimentary cementation. Beachrock may contain meniscus cements or pendant cements. As the water between the narrow spaces of grains drains from the beachrock, a small portion of it is held back by
capillary forces, where meniscus cement will form. Pendant cements form on the bottom of grains where water droplets are held.
Carbonate hardgrounds are hard crusts of carbonate material that form on the bottom of the ocean floor, below the lowest tide level. Isopachous (which means equal thickness) cement forms in subaqueous conditions where the grains are completely surrounded by water. Carbonate cements can also be formed by biological organisms such as
Sporosarcina pasteurii, which binds sand together given organic compounds and a calcium source (Chou
et al., 2010). Cementing has significant effects on the properties and stability of many soil materials. Cementation is not always easily identified and its effects cannot be easily determined quantitatively. It is known to contribute to clay tenderness and may be responsible for an apparent preconsolidation pressure. The filtration of iron compounds from a very sensitive clay from Labrador, Canada, resulted in a 30 t/m reduction in apparent preconsolidation pressure. Coop and Airey (2003) show that for carbonate soils, cementation develops immediately after deposition and allows the soil to maintain a loose structure. Non-recognition of cementation has resulted in construction disputes. For example, a land on a major Project is marked as glacier on contract drawings. It was so hard that it had to be detonated. The contractor claimed that the soil was cemented during excavation as it was formed due to the clay matrix as well as the gravel. The owner concluded that this was due to the weathering of the pebbles. Proper evaluation of the material before the award of the contract could have avoided the problem. Clay particles adhere to the surfaces of larger silt and sand particles, a process called clay bonding. Eventually, larger grains are embedded in a clay matrix and their influence on geotechnical behavior is limited. The clay confinement maintains a large void ratio even at high effective stresses, allowing the interparticle forces to spring up. == References ==