2 sentences for 主干 (zhǔ​gàn)

1. 这棵古松的主干非常粗壮，需要两人合抱。

   zhè kē gǔ sōng de zhǔ​gàn fēi​cháng cū​zhuàng, xū​yào liǎng rén hé​bào.

   The main trunk of this ancient pine is very thick, requiring two people to encircle it.

   Source: Dong Chinese Dictionary

2. 这些经验丰富的工程师是整个项目的技术主干。

   zhè​xiē jīng​yàn fēng​fù de gōng​chéng​shī shì zhěng gè xiàng​mù de jì​shù zhǔ​gàn.

   These experienced engineers are the technical backbone of the entire project.

   Source: Dong Chinese Dictionary