4.帷幕灌浆，表层孔段的灌浆压力不宜小于(  )倍帷幕的工作水头。

、<span>1.6</span><span>～</span><span>2.0</span>

、<span>1</span><span>～</span><span>1.5</span>

、<span>2</span><span>～</span><span>3</span>