Conventional gob-side entry retaining technology has some limitations

such as mining speed restriction and risks of working in the goaf. In this study

we proposed a modified gob-side entry retaining technology named pier column reserving technology in the wide roadway. First

a wide roadway is excavated

and a row of pier columns are established in the middle of the roadway. One side of pier columns is the conveyance roadway of the working face

and the other side is the rail roadway of next working face. Then the rail roadway with the support of pier columns can be retained to use for the next working face. The results show that the pier columns can maintain the stability of surrounding rock during roadway drivage. Meanwhile

the safety is improved greatly by avoiding working behind the working face. During the roadway excavation

the technology of roadway secondary excavation and the bolt-column combined support are used to guarantee the roadway stability. At the stage of gob-side entry retaining

the high strength pier columns have great performance on roof cutting and supporting. When the distance between pillars is 1.5 m

the required pressure of pier column for roof cutting is 21.53 MPa

which is lower than the compression strength of pier columns. The bearing capacity of the pier column meets the requirements of gob-side entry retaining. The relative displacement of the top and bottom plates is 652 mm

and the maximum convergence of pier column is 164 mm. The pier column can play a certain role in relieving pressure and has good support to the roof

which can be well adapted to the roof activity law of gob-side entry retaining.