Travel is the most exciting thing for me. By traveling around, I have increased my knowledge and made me healthy and strong. Here I want to talk about one of my favorite scenic spots, which is called the Great Wall.
Why build the Great Wall? The construction of the Great Wall began in the Warring States Period in the 7th century BC, with a history of more than 2,500 years. At that time, it was the Warring States Period in ancient China. Many vassal states built city walls in central China to protect themselves from mutual attacks and Mongolian "barbarians". These walls were built in Qi, Chu, Yan, Han, Zhao, Wei and Qin. At that time, the Great Wall was only a regional project to resist the enemy in the north. However, in the Qin dynasty, these separated city walls were connected and extended from east to west for about 5 million kilometers. The Great Wall was further extended and strengthened in the subsequent dynasties. Especially in the Ming dynasty, the nomadic people in the north became very powerful, and the emperor ordered the renovation of the Great Wall many times, with a total length of 6,700 kilometers.
It is so incredible, and then you may ask, "What is the Great Wall made of?" In the Qin Dynasty (22 BC1-206 BC) or earlier or later, the Great Wall was basically built of rammed earth, because the skills of weapons such as swords and spears were very low. No fortress was built on the wall, and no brick was used to build the gate of the pass. During this period, the city wall was made of multi-layer rammed earth. The part that remains in Gansu Province today is a typical example. Scientists found that the foundation consists of a layer of raw soil, with 1.5 meters thick at the bottom and loess about 3 meters thick on it. The wall was built on a compacted soil foundation. The process of tamping soil begins with a simple wooden frame. Workers fill the frame with loose soil and then tamp it into a dense layer with a thickness of 4 inches. This process was repeated layer by layer, and the wall slowly rose four inches at a time. So you can imagine how long it will take to build a seven-meter-high wall. Gravel mixed into the wall to make it stronger.