( )是地下建筑物周边构筑的永久性支护结构。主要作用:承重、围护、环保与美观。 衬砌分为5种:模筑式衬砌、离壁式衬砌、装配式衬砌、锚喷式衬砌、复合式衬砌
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
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