Drainage Layer for Pavement

Depends on what type of pavement. Concrete or Asphalt? What its going to be used for. (Type of Traffic?) And types of soil you will be building on. And natural drainage in the area. Here in St. Louis Missouri we tend to use: 4" Type C Asph Concrete on 8" Type 1 Aggregate (for Heavy traffic) 4" Type C Asph. Concrete on 6" Type 1 Aggregate (Lt Traffic) or 8" Portland Cement Concrete (4000 psi) on 4" Type 1 Aggregate for parking Lots. We also use Drainage Fabric Material under the Aggregate on some jobs

Then our State and various County Highway Departments have there own standards for the streets under their jurisdictions.

I would check with your Local Highway Dept and see what they use. If the pavement will hold up to the heavy traffic of highway use it will hold up to just about anything.

Depends on application, drainage of site, type of subgrade soils, etc. Typical AASHTO granular base is 2" (50mm) 100% passing, 1" (25 mm) 95-100% passing, 3/8" (9.5 mm) 30-65% passing, No. 4 (4.75 mm) 25-55% passing, No. 10 (2.00 mm)-15-40% passing, No. 40 (8-20% passing, No. 200 (0.075mm) -2-8% passing. Soundness-max. 50% loss LA abrasion test. Amount passing No. 200 should not exceed 2/3 the amount passing the No. 40. The fraction passing the No. 40 should have max LL=25, IP=6. For strength at least 75% of the plus 3/8" (9.5 mm) material shall have at least two fractured faces. If frost is a consideration, the IP should be no more than 4 and the minus 200 fraction should be lowered slightly. A geotextile can reduce the amount of granular sub-base required and improve the performance of the pavement structure, especially if the soils are fine grained and/or with poor subgrade drainage. 3/4" minus runnercrush (quarry crusher-run stone that all passes the 3/4" (37.5 mm) and has a little dust) is also good,and has a lot of strength. If you are in the US, check local State Department of Transportation materials specifications as they have standard items that are good for this purpose.

DAS geotechnical engineer

Not enough information. What is your average rainfall?, what is the grade of the pavement and surrounding area. Is the pavement raised or at ground level. Are frost heaves an issue?

Not a civil engineer but I've lived where 72 inches of rain a year is normal and where 7 inches is normal. The freeze depth at the 7 inches per year was much deeper but 400 miles closer to the equator(4,000 ft higher elevation). Your local conditions and laws/guidelines should be of help.

Brad