We toured Lambeau Field last year and learned that they use a mix of real and fake grass. The field is about half and half of each. The fake grass is long, green polyester fibers, with several of them connected to a small spike deep in the soil, like 8 inches down. The real grass grows in and around those fibers and the fake fibers help strengthen the roots of the real grass.
Somehow the soil and the field drainage is set up so that they could get 4 inches of rain in an hour before any puddle would form on the field. Pretty impressive, I thought.
That's interesting. From all the comments about hardness under artificial turf, I was wondering if the problem is the medium it sits on. Soil vs. ground-up automobile tires, or whatever they use. What you describe sounds like an effort to combine the two, which will be great if it can be made to work.
As we know all too well, natural turf gets soggy and yucky with a lot of rain. But when conditions are right, what makes natural turf great is that it has roots that go down 12 inches in soil. That makes it flexible. If soil is kept well-aerated, it offers traction, and yet also has some give, and players get protection from vertical impact (concussion) and lateral stress (muscle pulls, ankle rolls, knee blowouts).