These rail maintenance problems became more serious as the duration of the war lengthened.
1. The US reduced the agricultural area of Virginia. That meant more food and forage had to be transported to the swollen population of Richmond, and the army.
2. Sherman's army gained on a position the railroad east of Atlanta. The Confederates tried to drive the US forces off, but the damage had been done, and the attempt was unsuccessful.
3. Farragut's flotilla closed Mobile Bay, and the work needed to tighten the blockade was simplified and made more efficient.
4. Grant designed an operation to get Warren's 5th corp onto the Richmond/Weldon railroad. The operation was successful and a horrific, but small battle followed to re-open this direct line south from Petersburg. The fact that is attempt was unsuccessful had to have a large impact on General Lee's appraisal of the continual viability of the Richmond as the Confederate capital.
5. Finally, General Sherman's high risk operation, to swing away from his railroad, though deep in Confederate territory, with Confederate cavalry still potentially active and able to raid his supply line, succeeded. And it so surprised the Confederates, that much of the rolling stock could not be evacuated and had to be destroyed.
Those were the major efforts. But there were also US cavalry raids both west and north of Richmond, to disrupt railroad traffic and test the repair capability of the Confederate railroad companies.