4160V Primary Direct Burial Cable

Does a sheilded direct burial power cable meeting NEC 310.7 (Okonite CLX Okoguard 5KV), carrying 4160V at a burial depth of 30" minimum below grade as per NESC need to be encased in concrete or is a 4" all round cusioning bedding (sand) sufficient.

There is a difference of opinion with the code that I would like to clarify.

Thanks