Utilities usually bury directly here. Cable, then sand, then bricks, then marker tape or 4mm(?) sheet plastic (yellow, with warnings printed on), then more sand and finally gravel or soil. Seen it quite often during the last few years... in 1991 we got all new phone lines in the street, a few years after cable TV (fiber optical) was installed, then we got a new power feeder... and last year when they replaced the gas mains some cable protection showed too. In case of the PVC gas lines they even poured concrete atop of the pipes, down in the trench and then backfilled with soil.
