This reminds me of one particularly intense semester I had at graduate school. Trying to get a design project completed, a lab partner and I spent three days straight at our campus.
At one point in time, the lab director (who liked to run a pretty "tight ship"), looked at our sundry items strewn messily across a table, and said with an annoyed and disgusted voice, "Gee, it looks like someone is living here!"
We were taking an exam at the time, but a friend overheard the remark, and came to our defense, answering, "Actually, sir, I think Greg and Jim haven't been home since Tuesday."
"Oh!" the director replied, "Well, if they are living here, then that's okay."
In any case, if I were describing that situation, I could say:
I had not been home since Tuesday.
or:
I had not gone home since Tuesday.
and either of those would be equally appropriate or correct.
"Been home" implies arriving at my house; "gone home" implies leaving the lab to go home. In this context, these both imply the same thing – leave the lab to go home – so I can say it either way.
I had left the train before my brother spoke.
not spoken
I had left the train before my brother spoken.
This is incorrect because it lacks an auxiliary verb.. Without the auxiliary verb, spoken takes on the form of an adjective.
The words are spoken
The spoken words were fantastic
To make your incorrect sentence correct, you simply need to add the verb to have
I had left the train before my brother had spoken.
In this example, we are using the past perfect tense of to have
My brother had spoken
[........] had eaten
[........] had fallen
[........] had jumped
[........] had unexpectedly lain an egg, like a chicken.
Your last sentence is also incorrect
I had left the train before my brother speak.
This makes no sense at all.
It needs to be in the past tense.
my brother speak[s]
my brother spoke
and it would then be correct.
Best Answer
There are so many things to say here that I may miss some.
First, "dam" needs to be preceded by "the."
Second, either The dam had been constructed before the flood or The dam was constructed before the flood are acceptable. A purist might say that only "had been constructed" is technically correct because the past perfect is the correct tense to indicate a past action that preceded a different past action. However, if the sequence of construction and flood was of little importance, "was constructed" would be used by many well spoken people. Notice that this question is about whether to use the simple past or the past perfect in the passive voice. Passives are constructed from a form of the verb "be" and a past participle.
Third has been constructing is in the past progressive tense in the active voice. Dams do not construct anything so the active voice is meaningless with this verb. If we were to re-write using the passive voice, we must use the past participle of "construct" rather than the present participle. If we want to make the tense past progressive, we must also use a present participle. In other words to get a past progressive tense in the passive voice we must write "was being constructed" using the present participle of "be" and the past participle of "construct."
Fourth, using the past progressive changes the meaning. The dam was being constructed before the flood strongly implies that construction was not completed before the flood.
I think you need to review the difference in meaning between active and passive voice, the differences in meaning among simple past, past progressive, and past perfect, and how to construct the perfect and progressive tenses in both active and passive voices. You seem to have all these admittedly tricky things a bit jumbled.