Stability analysis of roadside backfill body at gob-side entry retaining under combined static and dynamic loading

The applications of gob-side entry retaining (GER) techniques tends to
increase over time as it can increase the minerals recovery rate and
reduce the output of the waste. In the literature, only the performance of
the roadside backfill body (RBB) at gob-side entry retaining under static
loading has been investigated. However, failure mechanisms of the RBB
under dynamic loading with various roof cutting angles have not been
addressed. This study presented a numerical simulation of the fracture
propagation and distribution in the roadside backfill body along the
gob-side under combined static and dynamic loadings using the Trigon model
built in UDEC (Discrete element methods) software. The influence of the
roof cutting angles on the behavior of the RBB was also discussed. The
input parameters were determined by back analysis with the field data.
Results of the model show that static loading is a bigger contributor to
the failure of the RBB compared to the dynamic loading. Several clear
fractures were observed at top left and bottom right of the RBB and the
fracture was more intensive at top left. In addition, it was found that if
the roof cutting angle is 70°, the influence of the dynamic loading on the
RBB is minimum, and the area and severity of the shearing failure in the
RBB is minimum as well. As a result, it was determined the optimal roof
cutting angle was 70° and a combined support measure of “roof cutting +
roof support above RBBs + RBB reinforcement” is proposed. The application
of roof cutting in gob-side entry retaining (RCGER) techniques in the
Lingzhida coal mine indicates that deformation of the surrounding rocks
can be effectively controlled.