  Soar filament eruptions are often associated with solar flares and coronal
mass ejections (CMEs), which are the major impacts on space weather. However,
the fine structures and the trigger mechanisms of solar filaments are still
unclear. To address these issues, we studied a failed solar active-region
filament eruption associated with a C-class flare by using high-resolution
H$\alpha$ images from the New Vacuum Solar Telescope (NVST), supplemented by
EUV observations of the Solar Dynamical Observatory (SDO). Before the filament
eruption, a small bi-pole magnetic field emerged below the filament. And then
magnetic reconnection between the filament and the emerging bi-pole magnetic
field triggered the filament eruption. During the filament eruption, the
untwisting motion of the filament can be clearly traced by the eruptive
threads. Moreover, the foot-points of the eruptive threads are determined by
tracing the descending filament materials. Note that the filament twisted
structure and the right part of the eruptive filament threads cannot be seen
before the filament eruption. These eruptive threads at the right part of the
filament are found to be rooting in the weak negative polarities near the main
negative sunspot. Moreover, a new filament formed in the filament channel due
to material injection from the eruptive filament. The above observations and
the potential field extrapolations are inclined to support that the filament
materials were transferred into the overlying magnetic loops and the nearby
filament channel by magnetic reconnection. These observations shed light on
better understanding on the complexity of filament eruptions.
