How are modified proctors created?

• A. With a 5.5 lb hammer on a 12\" drop with 25 blows per layer and 3 layers total.
• B. With a 10 lb hammer on a 12\" drop with 60 blows per layer and 4 layers total.
• C. With a 5.5 lb hammer on a 18\" drop with 50 blows per layer and 2 layers total.
• D. With a 10 lb hammer (rammer) on a 18\" drop with 56 blows per layers with 5 layers in total.

Answer: (D)

Modified Proctor uses a higher-energy compaction effort than the standard method. To simulate dense fills, it uses a heavier rammer, a greater drop height, and more blows per layer across more layers. Specifically, the test is performed with a 10-pound rammer dropped from 18 inches, delivering 56 blows to each of five layers. This combination increases the energy input, helping achieve higher density and determine the optimum moisture content for soils expected to be densely compacted. The other options don’t fit because they mix incorrect hammer weight, drop height, blows per layer, or number of layers, which would not provide the intended energy level and layering pattern of the Modified Proctor.