Turf walls (and other forms of earthen ramparts) were often used for fortifications in the 1st century AD, particularly in Britain. They were employed for both auxiliary forts and legionary fortresses, and were standard for temporary camps used when on the march or on campaign. Vegetius describes how they were constructed. They were not commonly used for frontiers, however, Hadrian’s Wall being the first and the Antonine Wall the second, so far as we know.
Further reading: Milner 1995