A concrete wall was built to stop silt from leaking to the conservation land.一道水泥墙修筑起来，用以防止泥沙流进保留地。The concrete wall that used to divide this city has now all but gone.曾经将这座城市分隔开的混凝土墙现在已几乎不复存在。A workman was drilling through the concrete wall.一名工人正在水泥墙上钻孔。