Continue outside and engage the enemies. Past the big rock are two paths. The path to the left leads to the upper path through the bridge and to another short tunnel while the path straight ahead is the fastest and shortest. Take the longer path so you can easily take out the enemies from above. Be careful of the brute that will appear along the way.
Continue through the tunnel and breach two doors until you reach the mine shaft entrance. Take out the guards on the generator room across the bridge and start up the generator. The mine shaft gate will open and more armored thugs will exit. Take them out then enter the shaft to complete the section.