This is what I have in groovy:
sh 'echo "'+params.TEST+'"'
echo params.TEST
test.sh
#!/bin/bash
echo "'+params.TEST+'"
sh 'echo "'+params.TEST+'"'
echo params.TEST
sh './test.sh'
You can try passing it as an argument to the shell script eg.
sh 'echo "'+params.TEST+'"'
echo params.TEST
sh './test.sh "' +params.TEST + '"'
And use the argument in the shell script as
#!/bin/bash
echo $1