What is zavel?
Zavel is a soil type from the Dutch soil classification that sits between sand and clay: a clayey soil with a lutum content of 8 to 25 percent. Lutum is the finest mineral fraction of soil, with particles smaller than 2 micrometres. At 25 percent lutum or more the soil is called clay; below 8 percent it is a sandy soil. Zavel forms where layers of clay and sand were deposited alternately and became mixed, for example along rivers and in former sea areas. In English it is often loosely described as a sandy clay or light clay loam, but there is no exact equivalent because soil classification systems differ between countries.
Classification
- Light zavel: 8 to 12 percent lutum
- Moderately light zavel: 12 to 17.5 percent lutum
- Heavy zavel: 17.5 to 25 percent lutum
Properties
- The sandy part makes the soil easy to work and easy for roots to penetrate.
- The clayey part holds on to moisture and nutrients.
- The heavier the zavel, the more slowly water drains away and the more the soil behaves like clay.
Application
In construction you will come across zavel in Dutch borehole logs and site investigation reports. Its behaviour under load lies between that of sand and clay. Whether it is suitable for a shallow foundation is decided by a structural engineer based on a ground investigation, not by eye.
In the garden zavel is regarded as a pleasant soil that rarely needs improving.
Practical tips
- Always have the ground investigated before designing a foundation.
- Check whether softer layers such as peat or clay lie beneath the zavel.
- Do not dig or work heavy zavel when it is wet, as it smears and loses its structure.
Related terms
- Clay
- Silt
- Loam
- Soil type
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