Let me translate the question from @linuslee0216 for other readers –
Why construction projects always delay?

My answer -
There are many different reasons may lead a construction project delays, for instance, inclement weather is the most common example, as many construction works cannot be done in heavy rainfall, like concreting. Other than that, unpredictable underground conditions always lead delay to a project, hence construction cost increased. This is commonly found in civil engineering works, as ground investigation technology cannot fully discover underground conditions so far, trial pit will be conducted for further investigation, underground utilities or obstacles may need to change of design and abortive works, hence, the project might delay.

其實有很多原因會導致建議項目延期，例如最簡單的天氣問題，因很多工序在暴雨的情況下是不能進行的，例如落石矢。另外一個比較常見的原因，尢其在大型基建項目會看到就是地底不能探測的障礙，現時的科技下還未能完全探測到地底的情況，需透過現場工地進行探坑，障礙物或是地底複雜的線路可能會引致建築設計需臨時改變，什至需重建等等，這都是其中一些會嚴重引起工程延期的例子。

希望這能解答你的問題:)