fall down   
phrasal verb with fall verb uk/fɔːl/ us/fɑːl/ fell | fallen
  (FALL)         
 B1 倒下,倒地
to fall to the ground
  Our apple tree fell down in the storm. 我们的苹果树在暴风雨中被刮倒了。 
 He stumbled and fell down. 他绊了一下,摔倒在地。 
  (建筑物)坍塌,垮掉
If a building is falling down, it is in a very bad condition and there is a risk that it will break into pieces and drop to the ground.
  Many buildings in the old part of the city are falling down. 老城区的许多建筑都快坍塌了。 
 - More examples
- I'm looking for a doings to hold up a curtain rail that's fallen down.
- The scaffolding prevents the building from falling down.
- A new steeple was built after the old one fell down.
- One of the their players fell down every time someone tried to tackle him.
- She fell down to her knees and prayed.
  (FAIL)      
 UK失败 
to fail
  Where do you think the plan falls down? 你认为这个计划的失败之处在哪里?