How to disable the use of shorthands in biblatex?

If you just want to get rid of the shorthand to make sure the label is just a normal numeric one, you can go with

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldset=shorthand, null]
    }
  }
}

This makes sure the shorthand is ignored by Biber before it comes to label generation. (An \AtEveryCitekey approach can not work here.)

MWE

\documentclass{article}

\usepackage{biblatex}
\addbibresource{biblatex-examples.bib}

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldset=shorthand, null]
    }
  }
}

\begin{document}
\cite{kant:kpv}
\printbibliography
\end{document}

If one does not want to use a sourcemap definition, it is possible to nullify the values of the shorthand (or other fields) using \DeclareFieldInputHandler

Here the value of the field is read from the .bbl file (so after it has been generated by biber)

\DeclareFieldInputHandler{shorthand}{\def\NewValue{}}