Are there any limitations on the depth at which PE pipe can be laid?
There are normally no depth limitations related to PE pipe material.
The depth limitation to which PE pipe can be laid is not governed by the material properties but by the site conditions, soil type, level of water table, etc. This is no different from other pipe materials. The pipe should be designed to resist any additional forces from soil loading associated with deep excavations.
Suitable precautions should be taken to prevent collapse of the trench walls for deep excavations and consideration should also be given to trench drainage if the pipe is to be laid below the water table. Reference should be made to health and safety legislation relating to deep excavations to prevent potential injury to operators.
PE pipe can be assembled at the surface and placed into a deep trench without site personnel being in the trench for long periods, or possibly not at all. This is a considerable safety benefit where stability of the trench may be a concern.