“Taking full advantage of the topographical conditions to build forts and passes”, means that the construction of the Great Wall had taken full advantage of the natural terrain environment. “In line with the terrain”referred to carrying out the construction work according to the terrain conditions,and fully utilizing the local natural resources as well as choosing the appropriate building materials. “Controlling the strategic position relying on the inaccessible terrain”referred to using the geographic natural barrier guarding against the enemy.This principle was conducive to defense,and could also save a lot of building materials.
To sum up,the Great Wall constructed by the various dynasty before the Northern Wei(386-534)Dynasty was mainly built with rammed earth by using wooden planks as moulds.The Great Wall of brick masonry structure emerged in the Northern Wei Period.The building methods by laying bricks or stones or both stones and bricks were widely used in the Ming Great Wall.The construction required a huge amount of materials,so being in line with the local conditions,most of the materials were taken from local resources in light of the local circumstances.In the mountain areas,the mountain was blasted for rocks to build the wall;in the loess zone,the soil was taken for ramming the wall;in the desert,reeds or willow twigs were being used and replenished with sand layers upon layers.In addition,the materials used for building the wall,such as bricks,titles,lime and timber,etc. were supplied by a special department set up by the local authorities apart from building kilns to fire bricks or cutting trees for timber on the spot.
The Rammed Earth Wall Built with Wooden Moulds
The Wall Built with Adobes
The Grey-brick Wall
The Wall Built with Stone Slabs
The Wall Built with Both Bricks and Stones