15. 土石坝粘性土防渗体碾压部位的干密度、含水量取样次数为(  )。

、<span>1</span><span>次</span><span>/</span><span>（</span><span>100</span><span>～</span><span>200</span><span>）</span><span>m3</span>

、<span>1</span><span>次</span><span>/</span><span>（</span><span>200</span><span>～</span><span>400</span><span>）</span><span>m3</span>

、<span>1</span><span>次</span><span>/</span><span>（</span><span>400</span><span>～</span><span>600</span><span>）</span><span>m3</span>