Underground Cable

Can you say: What is direct burial cable?

Depth depends on many factors, code is one.

Short answer is yes, but...

Longer answer is that it is preferreable to run any cable in conduit if you intend burying it.

It is preferable to bury the cable at least 30cm/1' deep This is of course dependant on what your local regulations decree.

By Low Voltage AC, do you mean 12/24 volts or 110/120/220 volts? There is a big difference, and it does cause some minor confusion between certain trades.

If this wiring for fairy lights in the garden which are normally 12 volts AC? Then yes you can bury the cable without conduit, but you must make an accurate map of your wiring so you don't go chopping it out when you put more plants in your garden.

→ British Standard 7671.

how about wikipedia?

Non armoured low voltage cable are not recommended to be buried under ground to supply AC low voltage load. Non armoured cables are usually run on cable tray, cable addle and trunking. Non armoured cables are subject to damages due stress and vehicle passing and pressing the underground buried cables.

The armoured cables are design for mechanically protection such as stress, protection against vehicle pressing on it and others. Standard buried depth is about 1 meter deepth. Cables are protected by GI pipe on all crossing under the ground.