They either pass by mountains and build roofs above them to form “Ming Dong” (Peng Dong is a special kind of tunnel
. 
The running speed and transportation efficiency were far from enough Climbing predetermined elevation, often by extending the line to achieve the purpose of slow climbing, such a railway is called “line development”.
. 
Take Baoji Chengdu Railway built in the 1950s as an example, which connects Baoji in Shaanxi Province in the north and Tianfu Chengdu in the south
. 
This is not a traditional railway, but a trans provincial “subway” (tunnel along the Guiyang Guangzhou high-speed railway, photographer @ Liu shenku)
. 
80% of the whole line is high mountains
. 
Later, they invented a clever new technology
. 
At present, the total mileage of these tunnels ranks first in the world (this paper only discusses railway and highway tunnels in mountainous areas, not urban tunnels and underwater tunnels)
. 
It is also the most common entrance
. 
First, people cut a passage through the mountain by drilling, blasting and digging, and the rock drilling jumbo with several “arms” drills holes in the tunnel like “three heads and six arms” for safety Blasting (blasting construction is the most widely used and mature method in mountain tunnels at present
. 
Workers first drove bolts into the rock mass of the tunnel and then laid them A circle of steel mesh is set up, and finally a layer of concrete is sprayed, so that the deformation of surrounding rock mass can be controlled, so as to play a supporting role (this tunnel construction method was first proposed by the Austrian scholar labsevich, and later officially named as the new Austrian tunnel construction method by the International Conference on soil mechanics, referred to as the new Austrian method for short)
. 
It is the first railway trunk line connecting northwest and southwest
. 
In the 1970s, this method began to be introduced into China and was widely used in tunnel construction in China (please see the horizontal screen, the ladder type rock drilling jumbo in the bailuoshan tunnel
. 
If we drive at the speed limit of 70km / h, we need to travel underground for 15 minutes to pass through (please watch the cross screen, Qinling tunnel group composed of three tunnels, photographer @ Wei) @ @ @ when we stand in Guizhou, more than 1400 tunnels almost drive through Guizhou Province under our feet More than half of the 857km long Guiyang Guangzhou high-speed railway from Guizhou to Guangzhou runs underground
.
When we look at the whole China, you can’t imagine that there are more than 35000 seats under the land of 9.6 million square kilometers, with a total length of about 37000km Equatorial tunnels are passing day and night, building a very convenient super channel network for the passenger and freight flows from south to North and from east to west, and most of these tunnels have been built in just 40 years after the reform and opening up
.
The following figure shows the thermal distribution of highway tunnels across the country, drawing @ Chen Zhihao & Wang Shenwen / planet Research Institute) @ @ from the Loess Plateau to Taihang Mountain Area (the freight train on Jingyuan line is passing through Shidu tunnel 2, photographer @ Wang Weiguang) @ @ from the Qinghai Tibet Plateau to Tianshan mountain area (please watch the horizontal screen, hashilegen tunnel on Duku highway, photographer @ Shen Longquan) @ @ the tunnel is changing the situation How did the Chinese dig through all these mountains? 01 the birth of tunnels in China there are many kinds of tunnels
.
Generally, the walls of the entrances are upright and rough (an upright wall is the entrance, which is called the end wall type entrance
.
The rock drilling jumbo with three drilling arms is shown in the figure below, which is located in Luojiashan tunnel of Zhengzhou Wanzhou high-speed railway
.
The following picture shows the tunnels along the Chengdu Kunming railway
.
Photo source @ Vision China) @ @ the precision controlled “blasting” can blast the rock according to the preset profile, and the rock wall after blasting can be described as quite flat (the flat rock wall after blasting, in which the blast mark In the past, people used wood or steel to support the excavated tunnel directly
.
Photographer @ Li Changhua)} the “luxurious” entrance is added with columns on both sides The columnar portal is beautiful and more stable (the columnar portal at the Badaling tunnel entrance, photographer @ Zhao Bin)} the best integration with the environment is the bamboo cutting portal, which is like a section of bamboo pole being cut along the hillside, with a clean shape (Xinjiang Sailimu Lake highway tunnel, photographer @ Shen Longquan)} there is a more special shape, which is distributed at the entrance of the high-speed railway tunnel When the train passes through the tunnel at high speed, the compressed air will produce a strong impact pressure, which will cause noise and discomfort of passengers
.
Only through 304 tunnels can the railway passage pass through Qinling Mountains, changing the difficult situation of Shu Road However, due to the technical level at that time, the length of tunnels along Baoji Chengdu Railway was mostly less than 1000 meters, and the longest tunnel was only 2300 meters
.
One after another, short tunnels formed a spectacular tunnel group, while trains could only climb slowly on the “Panshan Railway” composed of tunnels and Exhibition lines
.
How many workers are there? Photographer @ Niu Rongjian)} of course, in addition to stabilizing the rock structure, a water resisting layer is also needed in the tunnel for waterproofing (the water resisting layer in Ning county tunnel of Qingyang section of YinBai expressway, photographer @ Jin Xi)} finally, for the third time, people set up a “formwork car” in the tunnel, and then poured concrete between the wall and the “formwork car”, just like casting metal in the mold for reinforcement This is the “secondary lining” (the formwork trolley in Luojiashan tunnel of Zhengzhou Wanzhou high speed railway and the leveled tunnel with secondary lining, photo source @ Vision China) @
.
The following picture shows the Peng Dong along the Chengdu Kunming railway, photographers @ Zhang Puchao)} or hang on the cliff and open “sky windows” every other section to form a wall hanging highway (Guoliang wall hanging highway in South Taihang, photographers @ Shi Yaochen)} or along the mountain The slope sometimes disappears when it hovers, and sometimes appears when it drills into the mountain, forming a pan mountain road like a ladder (please watch the horizontal screen, Yuntai Mountain Diecai Cave Tunnel in Jiaozuo City, Henan Province
.
With ventilation, lighting and other necessary facilities, a complete tunnel was born (celebration ceremony after the opening of qixingfeng tunnel of Mujia Passenger Dedicated Line, photographer @ Wang Li) The tunnel connects the world on both sides of the mountain and promotes mutual communication and exchange
.
When we stand in Qinling Mountains, seven tunnels with a length of more than 10km run through the mountains under our feet, and the longest highway tunnel is 18km long
.
The bell shaped tunnel portal can play a buffer role (through the Taihang Mountain high-speed railway tunnel, photographer @ Tian zhuoran)} when we enter the tunnel through the tunnel portal, it is an unobstructed channel, no matter it is darkļ¼ The train passes through the railway tunnel, photographer @ Li Changhua) or the lights are bright (the car passes through the highway tunnel, photographer @ Shenshao)} behind the smooth passage of these tunnels, there are actually several “changes”
.
How many tunnel openings are there in the picture? Photographer @ Shen Longquan)} but most of the time, they are hidden in the mountains, only showing narrow entrances and exits
.
