How do you repair a broken sprinkler pipe that runs under a concrete w

Lots of videos here: I have use a garden hose myself with out adapters.

https://www.youtube.com/watch?v=3Kv9x8bAWVM

Start digging. I had this happen to me, luckily it was a short run.

Have you thought about attaching a garden hose fixture to a piece of PVC pipe, attach the garden hose; on the opposite end attach another fitting that will accept a brass tapered spray nozzle, adjust the nozzle opening to the desired setting, turn on the water & aim the nozzle at the soil where you want the new pipe to go; it should 'flush the soil' out of the way & create a new tunnel for the new pipe to go under the concrete walk way...granted...you will have water, but the rest of your lawn will probably like that!

To repair the pipe that was damaged...attach an 'adjustable connector' to the new pipe on one side, then slide the new pipe UNDER THE CONCRETE WALKWAY [AFTER you have bored the tunnel] & slide the adjustable piece [after applying the primer & sealant] onto the old piece of pipe that is buried. THEN attach the 2nd adjustable piece of pipe to the opposite end of the new pipe, cut the old pipe so that the adjustable piece will be able to 'slide onto it'...then prime & apply sealant & slide the adjustable piece onto the 2nd piece of old pipe [that is buried in the ground] & wait recommended amount of time & test with water pressure. Congratulations!!! You have now completed your project!