There is known to be a big problem.
这个句子怎么样理解？
There is known to be…可以当作一种句型来看待吗？
你可以把 There is known to be…视为一种句型。如此用的Thereis known to be…句式可以看作是there be（有）与be known（被了解）的复合形式或混搭形式，其意为“据悉有……”“据了解有……”“大家了解有……”“大伙都了解有……”等。又如：
There isknown to be an engine fault. 据悉发动机有问题。
There areknown to be thousands of snakes on the island. 据悉，那座岛上有成千上万条蛇。
There areknown to be thousands of different species of beetles. 据了解有成千上万种不一样的甲虫。
顺便给出以下类似的使用方法及句式：
1. Thereappears to be…
Thereappears to be…句式是there be（有）与appear（好像）搭配而成的混搭形式，其意为“好像有……”“仿佛有……”。如：
Thereappears to be a mistake. 好像有一个错误。
Thereappears to be a problem with the oil pressure. 看来是油压出了问题。
类似的还有：There seems to be…（好像有……）。如：
Thereseems to be something wrong with me. 我好像有点不对劲。
There seemsto be every reason to believe that business will get better. 看来完全有理由相信买卖会转好。
注：there seems to be…结构中的to be有时也可以省略。如：
Thereseemed nobody about, so I went in. 附近好像无人，因此我就走了进来。
2. Thereis expected to be…
There is expected to be…句式是there be（有）与beexpected（被预计）的混搭形式，其意为“预计有……”“估计有……”。如：
There is expected to be a severe frost tonight.预计今晚会有紧急的霜冻。
There isexpected to be an announcement about the project next week. 预计下星期将宣布一件关于这项工程的事。
3. Thereis said to be…
There issaid to be…句式是there be（有）与be said（被说，据了解）的混搭形式，其意为“据了解有……”。如：
There issaid to be plenty of oil off our coast. 据了解国内沿海有很多的石油。
There is said to be alack of harmony within the government. 据了解政府内部有分歧。
4. There isbelieved to be…
There is believed to be…句式是there be（有）与be believed（被相信，据信，据了解）的混搭形式，其意为“据信有……”“据了解有……”。如：
There is believed tobe a number of wounded on both sides. 据信双方都有一些人受伤。
There are believed tobe over two hundred monkeys living in the valley. 据了解山谷里生活着200多只猴子。
5. Thereis supposed to be…
There issupposed to be…句式是there be（有）与be supposed to（应该）的混搭形式，其意为“应该有……”。如：
There issupposed to be a train at 12:37. 12点37分应该有一班火车。
There issupposed to be some trouble when he hears the news. 他听到这消息后应该有的麻烦。
6. Thereis sure to be…
There issure to be…句式是there be（有）与be sure（一定）的混搭形式，其意为“一定有……”“准有……”。如：
There’ssure to be a place for him somewhere. 在什么地方准有他的容身之地。
There issure to be trouble when she gets his letter. 当她收到他的信时，一定会有麻烦。
7. Therehappens to be…
Therehappens to be…句式是there be（有）与happen（碰巧）的混搭形式，其意为“碰巧有……”。如：
Therehappened to be a man walking by. 当时恰好有一个人从旁经过。
Therehappened to be a severe drought that year. 那年碰巧出现了大旱。
8. Thereused to be…
There usedto be…句式是there be（有）与used to（过去有）的混搭形式，其意为“过去有……”“过去有……”。如：
There are fewer applicants this year than there used to be. 今年的申请者比往年少。
There usedto be a small park just around the corner. 以前在那个拐角处曾有一个小公园。