'great thickness' is a correct and usable phrase in written English.
You can use it in instances when you are describing a physical item with a large measurement. For example, "The wall had a great thickness of two feet".
On one hand, with great thickness comes great durability.
Though the walls and piers are beautiful, the mortar was not good, and only great thickness made the masonry strong.
To the southwest the rocks of the massif are overlain by a great thickness of limestones (causses) from the Jurassic Period (about 200 to 145 million years ago).
Many lignite beds lie close to the surface and are of great thickness, sometimes greater than 30 m (about 100 feet); they are easily worked, and the cost of production is low.
It's a very homely affair: stewed fruit cooked in a "dough of great thickness" according to one 1859 reference – though whether the name comes from the bumpy top resembling cobblestones, a cob loaf or even, in particularly tragic cases, shoe leather, we'll never know.
Although the existence of permafrost had been known to the inhabitants of Siberia for centuries, scientists of the Western world did not take seriously the isolated reports of a great thickness of frozen ground existing under northern forest and grasslands until 1836.
Great thicknesses of lava flows also occur; it has been estimated that about 100,000 cubic kilometres (24,000 cubic miles) of lava were produced.
The wood is placed in a press between two metal plates to which the power is applied; great thicknesses of wood can be dried evenly by this method.
The Nile trough possesses the more complete record of the quaternary in Egypt, where the sediments assume great thicknesses.
The evidence of the caldera collapse is that great thicknesses of Gwangju porphyritic granite erupted through ring fractures rather than central vents.
Below the Sublett Mountains the Phosphoria Formation, a basal phosphorite overlain by a thick sequence of chert and cherty sandstone, reaches its greatest thickness.
