Bentonite mining technical conditions project Claim The minimum thickness of the layer mineral recoverable 1 to 2 m Minimum stone thickness Not less than 1 m Open pit mining elevation Generally not less than 50 m below the erosion reference plane Open stripping ratio Not more than 4:1 The final slope angle of the open-air deposits Generally 50~60o Open-pit mining final chassis minimum width Not less than 20 m 10 Subwoofer,8 Ohm Woofer,Best Subwoofer,Subwoofer Bass Ningbo Sonice Electroacoustic Science and Technology Co., Ltd. , https://www.secspk.com