Glacial soils

The use of glacial soils in a reclamation area involves some specific issues and challenges  

Because of their unpredictable composition and mechanical properties, glacial soils are difficult to use as construction material. Also their presence in the subsoil underneath a land reclamation project may result in problems with foundation works and unexpected development of voids during or even after construction. 

There is a very large range of glacial soils. Their nature varies according to their constituents, the way of transport and the environment of deposition. Generally, two types of glacial soils can be discerned (Price, 1986)  

Tills are sometimes referred to as boulder clay although this does not always imply that these soils contain boulders or clay. Till is deposited by ice and characterised by the absence of both grain sorting and stratification. Tills are variable in nature and consequently also in their mechanical properties. In general they consist of an assortment of rock debris, ranging in size from rock flour (very fine) to boulders. Gap grading is usual. 

Fluvio-glacial soils have been transported and deposited by meltwater and are therefore more sorted and stratified than tills. Many of such deposits consist of gravel and sand characterised by low relative densities. Pockets of very low density can generate geotechnical problems in foundation works. Also voids may appear during or even after construction, possibly caused by melting of ice blocks that have been deposited within the gravel (Price, 1986). 

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Example 29.1 A thirty gallon shipping drum containing 215 pounds of picric acid is found half buried in glacial soil. Rather than move this material, it is decided to detonate it in place. What size crater will be formed ... 

Glacial soils are soils formed during the glacier era. These soils may extend to a depth of many kilometres they consist of boulders, cobbles, gravel, sand, silt and clay, and they are widely found in the Northern Hemisphere. 

Glacial soils may be characterised with respect to their content in inorganic materials. Soils in which the inorganic ingredients of mineral materials outclass the organic substances are called inorganic soils. Otherwise, they are called organic soils, which are characterised by their dark brown colour and their characteristic smell. 

Glacial Soil is transported to the area through glaciers. 

Voids in fluvio-glacial soils are difficult to locate, and this problem is usually anticipated and dealt with by assuming their presence and using compaction equipment before the start of construction. 

Glacial soils should be treated with great caution when used as fill material or when present in the subsoil underneath a reclamation site. Mechanical properties are difficult to predict and should therefore be analysed in the laboratory. The presence of gravel pockets and possible voids in the subsoil must be taken into account during the foundation design. 

The same is true of the geographical distribution of the uranium concentration in glacial till, the most common soil type in Finland (Geological Survey of Finland, 1985). The sometimes very large effect of ground permeability is the main reason that the details of the radon concentration distribution differ from the distribution of other radiation parameters. 

Much of the bedrock is covered with up to 3 m of a sandy till deposited during a southeast to northwest ice-flow event. Soil formed on the glacial sediment is typically a well-drained brunisol. 

A strong positive correlation exists between Cu, Ag, Co, Au, W, and Se in the B and C horizon soil and suggests that these elements are geochemical pathfinders for sulfide mineralization at the Shiko Lake mineral occurrence. Glacial dispersal of Cu and Co in C horizon soil samples is characterized by the shape of geochemical profiles. These typically... 

Kimberlite bodies can be identified at ground surface using soil geochemistry where 90 m of glacial sediment overlies a kimberlite. This is based on variations in element concentrations of pathfinder elements such as Ni, Mg, Co, K, and total REEs over versus off a kimberlite. 

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