For every vibrating point, the vibration shall go on till free mortar appears on the concrete surface and not sinks any more, normally 20 ~ 30s.

每一振点的振捣延续时间应使混凝土表面呈现浮浆和不再沉落为止，约20 ~ 30s。

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Following years of lobbying by bricks-and-mortar stores, the US Senate is expected today to pass a bill that would help end tax-free online shopping.

经过实体商店多年的游说，美国参议院预计将在今日通过一项法案，将有助于终结网上购物免税的局面。

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Research indicates that mortar and soil could be pressured into a stable lining structure through explosive lining. Free face is one of the important factors influencing shape of the lining shell.

研究表明，爆炸衬砌可以使砂浆和土壤形成稳定的衬砌结构，自由面是影响砌体形状的一个重要因素。

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As a result, many online sales are essentially tax-free, giving Internet retailers a big advantage over brick-and-mortar stores.

NPR: Senate Bill Jeopardizes Tax-Free Online Shopping

There was a quiet respect for brick-and-mortar stores in the quaint nature of Cyber Monday: 20 percent off underwear and free shipping, but that was about it.

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