16.Through to introduce equipments of vertical shaft the cautery ,compendiary introduce insufficiency of electricity-arc spray-paint to prevent cauterization.
18.The technical measures and structure,applied principles of blastproof of ventilation shaft at excavating face,specific operational method and prospective effect are described.
20.As to the profile shapes of ground collapse, they are approximately divided into vertical shaft, butterfly, funnel, ampulliform in shapes and so on.