Can you please help me with these 1. A sand soil has a maximum dry density of 12

Question

Can you please help me with these

1. A sand soil has a maximum dry density of 120.0 pcf based on the modified proctor test. The project specifications require the sand soil to be compacted to 95% of the maximum dry density. A soil engineer tests a compacted lift of sand using a nuclear density gauge and the result shows a dry density of 112 pcf. Does this measured density test meet the specification and “pass”. SHOW WORK!

2. You are present on site during a proofroll test on the subgrade soils to be used for support of a new pavement section. You and the earthwork contractor observe the soil deflect down about 4 inches temporarily when the wheel of the tandem-axle truck is pressing down on the soils. Then, once the truck continues driving the soil “re-bounds” upward 4 inches back to the same elevation it began before the truck passed over. What is the name for this temporary deflection and rebound of the soils?

Explanation / Answer

Q.1 Maximum dry density = 120 pcf.

required 95% = 0.95*120 = 114 pcf.

but measured = 112 pcf, which is less than the requierd, so it does not meet the requirements.

Q.2 This elastic deflection and rebound is known as 'Pumping".

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