In Mandarin if you use 地 to an adjective, it can change into an adverb. For example,
我真喜欢你健健康康地长大。
他舒服地躺在那里。
Now I wonder whether all adjectives can be transformed into adverbs in this rule. Is this assumption true? If not, how can I know if one adjective can be transformed into an adverb with 地?
Check out these dictionary entries for 地[de5]:
ABC
(adv.-forming, like English -ly)
很快地
hěn kuài de
very quickly
Oxford
AUXILIARY
[used with an adverb or adverbial phrase]
合理地安排和使用劳动力
dispose of available manpower rationally
应该历史地评价一个人。
We should judge a person from the historical point of view.
Oxford Pocket
<助> [used after an adjective, a noun or a phrase to form an adverbial adjunct before the verb]
狐狸偷偷地跑进果园
The fox sneaked into the orchard
他喝醉酒似地叫嚷
He shouted as if he were drunk
KEY
{grammar} (variant pronunciation of -dì) (forming an adverb from an adjectiv, e.g., gāoxìng 高興/高兴 "happy" + de 地 yields gāoxìngde 高興地/高兴地 "happily")
CC-CEDCIT
1 -ly
2 structural particle: used before a verb or adjective, linking it to preceding modifying adverbial adjunct
The simple answer to your question is: yes. The more complicated answer is that many things can be turned into an adverbial adjunct by adding 地[de5].
It depend on the property of the adjective. For example "不明的" means unknown, But if use "地" to replace it, it will be ridiculous.
If the meaning of the adjective is also suitable to verb or other adjective. It can be replaced to adverb, otherwise it can't.
It should be noticed that some word have a flexible meaning. Even if it both have form in adjective and adverb but there meanings are different. For example: 文明的 ---> 1,advanced development of knowledge;2, always behave gently 文明地 ---> gently
In Chinese, there is no such thing as an equivalent to adverb in English. Chinese basically and mainly use adjective, 形容词， to describe everything.
So the Sentence, <他舒服地躺在那里。>, can be rewritten as <他躺在那里很舒服。>， which means you don't need a 地 or 的 at all，which is sort of the -ly equivalent to English. You don't need that. Chinese grammar is easy and not as strict as English grammar. When it makes sense, then it's correct.
For instance：他在那里舒服的躺着躺着睡着了后慢慢的做了一个很长很长的关于爱情的美梦。
On the other hand: <他舒服地躺在那里。> translation to English would be < He is comfortably laying there.> or < He is laying comfortably there.> or < He is laying there comfortably.> While all the above three English sentences are correct, Chinese is not the same.
<他舒服地躺在那里。> Good
<他躺着舒服的在那里。> Weird
<他躺在那里很舒服。> Good
Why the second one is bad writing? Technically, it's okay, but it's bad. For instance, in English, a bad way to call 中国人 < Chinese > would be < the People of China >，or even worst, < People living in Mainland China >. Why would you use this awkward long phrase when there is a single simple word to describe the same thing?
I will give you another example why you should never use English Grammar as an analogy when trying to learn Chinese or any other Language. For instance, the word "Red", it's an adjective or a noun in English, but in Chinese， 红，can be used as everything.
她喜欢吃猪红。 Noun
她的脸红了。Verb
她爱带红花。Adjective
她在网上走红了。Adverb
的、得、地 are sharing a same meaning, but the way we use is quite different.
的, is used when there is a pronoun or a noun behind:
得，is used when there is an adjective behind:
地，is used when there is a verb behind:
It's not transformed to a adverb, but to an adverbial or adjective phrase.
It depends the word you want to modify upon. If the word to be modified is a noun, then it's an adjective phrase. And if it's a verb or adjective, then an adverbial phrase.
For example, in 舒服的躺着, 舒服的 is an adverbial phrase, while in 舒服的环境，it's an adjective phrase. It's because 躺 is a verb whilst 环境 is a noun.
By the way, in modern Chinese, 的 can replace 地 in this usage. However, 地 can not replace 的 in other usages. So, 的 will be correct most of time.
