Gophers are remarkably industrious diggers, but they can't move enough dirt to derail a train. The problem occurs when runoff water finds the gopher tunnel, then starts cutting and digging as it pipes through the embankment. Where I live we're forever patching up canal breaks started by gopher holes. Last spring, the pesky critturs tunneled clear under a paved county road, then some farmer's irrigation runoff found the tunnel and dug out a regular cavern. The unsupported asphalt collapsed and we had a huge sinkhole across both lanes. Now back to trains...
J