<p> 设土颗粒体积为1<br> 由<img src="http://que-oss.fenziquan.com/web/akimg/asource/2014091715553776002.jpg">得<img src="http://que-oss.fenziquan.com/web/akimg/asource/2014091715554627083.jpg"><br> <img src="http://que-oss.fenziquan.com/web/akimg/asource/2014091715561033653.jpg"></p>