Usage examples for earthwork:

• He straightway moved nearly his whole force over the eleven miles of dreadful roads, and on the 12th began investing the stronghold, an earthwork inclosing about 100 acres, with outworks on the land and water sides, and defended by more than 20, 000 men commanded by General Floyd, who had been President Buchanan's Secretary of War. "Ulysses S. Grant" – Walter Allen

• In some localities, where stone is abundant and the soil shallow, rude walls have been formed: the raths, however, are principally earthwork alone. "An Illustrated History of Ireland from AD 400 to 1800" – Mary Frances Cusack

• We worked during the whole night, expecting an attack on the right that night or the next morning, as the enemy were busy all day, throwing up an earthwork from Fort Wessels, which they had taken the night previous, running it parallel with our right towards the river. "In and Out of Rebel Prisons" – Lieut. A. [Alonzo] Cooper