The sizes of cross-section are related to the drivage costs , maintenance costs and ventilation electric costs .
井巷断面大小直接关系到掘进费、维护费和通风电费。
Stress is laid on analyais of main factors affectomg development of roadheaders in china , and problems existing in the fields of integration of drivage and bolting , randomized water-spraying dust suppression , improvement of hydraulic system and operating reliability of medium aed small-sized roadhead ers .
