tshark -i eth -b duration:10 -x > trial.txt

-w specifies a file to which to write packet metadata, and the raw packet data, in binary format, i.e. a capture file.
Running without -w will cause TShark to write packet summaries (without -V) or packet details (with -V), as well as packet hex data as text (with -x), to the standard output, so to get it into a file, redirect the standard output to that file.