I don't know where to find data supporting it but my hunch is there is not a great divide between women and men employed as janitors (aka custodial workers).
Granted it's usually less labor intensive than some custodian duties.
As far as construction, land scaling and mining well for the most part it's due to sexual dimorphism.
The average women has considerably lower upper body strength than they average man.
Jobs that involved throwing 60lbs bags of cement or fertilizer over ones shoulder aren't going to bode well for most women.
If a women isn't a CEO or engineer, we assume women are unfairly being discriminated against. If a women isn't a low value job, we assume they aren't biologically ideal for it.
That said it doesn't mean there is no discrimination either.