Can I fill a wet trench with concrete

[ukdodger]

when the bottom of the trench is wet and soft you are supposed to dig it out to dry and firm.

A spec I used to see for utility cabins said that if the bottom was damp after pumping out they would lay dry lean mix first and compress it well; it absorbs the moisture and gives a more firm surface that you can then pour you proper mix onto.

Is that what builders do? Getting down to dry and firm in this weather is nigh impossible yet there must be plenty of building still going on.