Question

13. A field technician shows up at your site to test the in-place soil density of the soil you have just compacted. Your project specification calls for the soil to be compacted to at least 95% Standard density. The field technician tells you that the layer you just compacted fails to achieve the specified density because the values he measured were 107%, 109%, 103 % and 101 % of the Standard density a. Question 1: Can the soil be compacted to values greater than 100% Standard Density? If your answer is yes, explain why. b. How would you handle this situation?

Answer 1

a. Yes, the soil can be compacted to values greater than 100 percent. Because the maximum dry density generally we obtain in the lab is not the actual field density of the soil. Proctor dry density of 100 percent means maximum dry density achieve by the soil in the lab by its ideal or optimum moisture content. Though, in Standard (2.5 kg of rammer, height of drop is 310mm, 25nos of blow in 3layers) and Modified Proctor test ( 4.9kg o rammer , height of drop is 450 mm , 25nos of blow in 5layers) the weight and blow of the compacting equipment is different,there is a chance to achieve different dry density of the same sample. If it is 100 percent in the Standard proctor test, it will be generally 100-115 percent in the Modified proctor test.

b. To handle the situation, i need to less the compacting effort and compacting force on the soil to reach to the desirable standard dry density. In this situation, i will prefer Standard proctor test rather than Modified proctor test to achieve the Standard dry density of 95 -100 percent.