The workers will go on digging until they hit a water pipe. Here the underlined part is -

• The workers will go on digging until they hit a water pipe. Here the underlined part is - Phrasal Verb.

• Phrasal Verb:
- বাক্যে Verb + preposition/adverb থাকলে সেটা Phrasal Verb হয়।
- যেমন - look down upon, give up, look after.
- তাই এখানে Phrasal Verb (verb + preposition) হচ্ছে phrasal verb.
- go on (go + on).

অন্যদিকে,
• Verb Phrase:
- যে phrase - verb এর কাজ করে সেটি Verb Phrase.