glancing at the bits of wood and metal that lay around him

glancing at the bits of wood and metal that lay around him
1.lay around him
2.glancing at 是动名词做主语吗?
it crashing into the courtyard below 为什么crashing加ing不加不可以吗？

您的提问不是一个句子,而是句中的的一个成分（即一部分）.从互联网上搜索,得到全句：Glancing at the bits of wood and metal that lay around him,the man sadly picked up the mattress and carried it into his house.
意思是：他瞥了一眼周围的木块和金属块后,无可奈何地搬起垫子并拿到屋里.
1、 lay around him 是放置在他周边的.这里,lay是动词lie的过去式.意思是：摆放,位于；处于……,that lay around him是定语从句,修饰the bits of wood and metal
2、glancing at the bits of wood and metal that lay around him是一个分词短语做状语,表示时间.
3、it crashing into the courtyard below出自：
A gust of wind swept the bed off the roof and sent it crashing into the courtyard below.
意思是：一阵风把床从屋顶吹下来,掉到了下面的院子里
分词短语crashing into the courtyard below 在句中表示方式或伴随情况,做状语,不可用动词原形.