How did the qin terracotta warriors get burnt and destroyed?

When we found the warriors in 1974, they were buried 6-7 meters deep underground. Originally, there was a 3.5 meters high wooden ceiling which covered all of the warriors. The archaeologists think there are 3 meters of dirt on top of the ceiling. Furthermore the wooden ceiling was burnt 2,200 years ago and almost all the figures and horses were found broken.
Sima Qian’s “Records of History” indicates that Emperor Qin’s palaces were destroyed and burnt by the rebellions in 206 B.C. The archaeologists think that the rebels needed weapons ,so they opened the pits, took the weapons away, then set a fire and destroying them.
One question this begs is that if the wooden ceiling was buried three meters underground for many years,the wood would most likely be wet and/or rotten. How can you burn rotten and wet wood, especially underground where there is sure to be little if any oxygen?
My opinion is that the ground level here was much lower 2,200 years ago. The warriors, in my opinion, were buried half underground with the ceiling one meter above the ground in the open air. This would resemble a very normal house of the time. I furthermore believe that once the emperor was pronounced dead his son or some high-ranking official ordered the mausoleum to be burned.
In China, the oldest religious tradition, dating back even before the time of the First Emperor, is Daoism. According to Daoism, the only way to send objects to the dead is by burning them as a sacrifice.This tradition persists even today, as people continue to burn paper money, horses, cars, etc., as offerings to their loved ones who have passed away.
I think the same thing happened 2,200 years ago. The Emperor Qin had ordered more than one million people to work for nearly 40 years and spent a lot of money to build his underground army, surely he wanted to make sure that all this work would benefit him in the afterlife. The only way he could be sure, according to Daoism, was to burn everything that had been prepared. Many new pits such as the Stone Armor pit, Acrobats’ pit have all been found in this same burnt state. This leads me to believe that the pits in this whole area were burnt at the same time.
To the south of the mausoleum, there is a mountain. On this mountain there was once a forest.It is said that after the mausoleum was completed the forest in the mountain disappeared. This is primarily due to the fact that the trees from the mountain forest were the ones used to build the mausoleum. With no trees to help keep the soil on the
mountain in place, when the heavy rains came the water brought the mud down hill into the valley in which the mausoleum was built. The warriors were buried deeper and deeper, and the water made the section-earth-wall,which supported the wood ceiling, wet and soft. Eventually, the ceiling caved in and all the warriors were broken.
Almost all the warriors found here were broken into pieces, but the flank guards in pit 1 and the kneeling archers in pit 2 were intact. The flank guards were situated on the edges of the pit where the pressure would have been less intense. The kneeling archers, who sit lower than the rest of the army and may in fact have been already partially buried by flood material by the time they were buried were also in better shape upon discovery.
There are more than 7,600 warriors and horses in the three pits, only 2,200 had been excavated as well as over 40,000 bronze weapons, which means there are more than 5,400 warriors still buried with about one million weapons. If the pits had been opened during the rebellion, they would have looted all the weapons here. Therefore it doesn’t seem likely that they looted the pits.
The terrain around Xian is mostly loess, a special kind of silt or clay. People in this region have been living in the caves for several thousand years, and there are still more than 40 million people living in caves around Shaanxi province. I think the people who built the tomb lived in the caves as well. If the Emperor had indeed wanted the figures safely buried underground it would have been much more reasonable and secure to place them in caves rather than bury them under a wooden ceiling. Why did they build a wooden ceiling and not dig a cave which would have been cheaper, easier and would have lasted longer? Because the wood is the material to be burnt after the funeral.
According to my understanding of ancient Chinese religions, practices and historical traditions, it would seem to me that the Emperor ordered the complex to be burned as a rite to his spirit after his death, and the warriors were damaged by the ceiling collapsing.