Li An has enough reason to believe that there must be a lot of mineral resources under the dense mountains ahead, but they have not yet been discovered, just like lime mines, if they are not discovered, it is a very ordinary mountain, and after they are discovered, they will become lime mines.

The mountain range itself is a treasure, even if there are no special mineral resources, but there are always earth, stones, and all kinds of trees and flowers that grow on the mountain, these are very important resources, and they are very useful.

After the discovery of the lime mine, nearly 100 people in charge of exploration did not stop, they also carried out detailed exploration of various resources in the nearby mountains, of course, there are also surveying and mapping tasks, terrain and roads in the mountains, the distribution of various animals and plants, these situations must be clarified in detail, because these places are now the land of Datang, and it is not very far from Anzhu City, if you don't figure it out, it would be too dereliction of duty.

As a very important transportation hub city in the future of Datang, all the conditions on the periphery of the city must be clearly figured out, so that we can have a clear idea and facilitate unified planning in the future.

Because the population of Anzhu City will definitely increase step by step, if the city content is not down, then it can only develop the land outside the city, and how can it be done without understanding the situation outside the city.

This temporary city wall is not very high, it is about the same as the city of ordinary prefectures and counties in the Tang Dynasty, the width of the top is two zhang, this is still the narrowest place, and the part of the width is three or four zhang, that is, on the basis of the city wall, it is distributed inside and outside the city wall for a distance, which is also for better defense.

For example, when the enemy runs under the city wall, the soldiers defending the city must poke their whole bodies out of the lookout to see the enemy below, and this is very dangerous, and it is easy to be shot by the besieging enemy.

This can be avoided by constructing small protruding sections of the wall, as the defenders can easily see the enemy running below the wall from the side and shoot them from the side, or tell the soldiers in front of them to accurately throw the rolling wood and stone to kill the enemy below the wall.

The outward protruding part can be used for defense, and the inward protruding part can be used to store all kinds of materials to defend the city, after all, the consumption of various materials in the city is very huge, in the face of the threat of the enemy, many materials must be transported from the city to the city wall, and the best place to place it is these small sections of the city wall that stretch out inward. It can only be properly practical if it is placed in a wide place.

Considering the importance of the future of Anzhu City, Li An also decided to deploy artillery at several city gates in this city, one city gate should be enough to deploy four gates, and the deployment position is in a prominent position on both sides of the city gate, such a location, the space is large enough, and there is a place for artillery ammunition and various maintenance tools, which is a very good location.

"You see it! In front of you is a flat road, if the enemy attacks, you only need to deploy four artillery pieces in these two positions on both sides, you can bomb the enemy on their backs, and there is no need to worry about how many enemies come. ”

Li An pointed to the two most suitable locations for deploying artillery, and spoke.

"What Li Shilang said is that these two positions are important positions for the Gongwei Gate, as long as they are equipped with artillery, they are enough to block the enemy from several miles away, so that the enemy cannot approach."

"With the power of Datang, where will there be an enemy who dares to be an enemy of Datang, unless he doesn't want to live."

The subordinates were all full of self-confidence, and one by one they were full of contempt for all possible foreign enemies.

Anzhu City is close to the territory of the Great Food Country, and the north gate is a hundred miles northwest of the country, which is the border city of the Great Food Country, however, although the Great Food Country is a bullish existence in Central Asia, but in the eyes of the Tang Empire, it is not a fart, it is not worth mentioning at all, and the Tang Empire only needs to move a finger to completely destroy this seemingly powerful power.

Therefore, in the eyes of the civil and military officials of the Tang Dynasty, the Great Food Country does not have the courage to provoke the powerful Tang Empire, and the rest of the small countries have no strength to be enemies of the Tang Empire.

Since the enemy did not dare to attack, the deployment of powerful artillery units seemed to be somewhat redundant and completely unnecessary.

But Li An didn't think so, because he was about to leave Anzhu City to go to Aden City, Aden City is a piece of land that the Tang Dynasty has a fancy for, and Aden City has belonged to the Great Food Country for a long period of time, if the Tang Empire takes possession of Aden City, will it cause extreme dissatisfaction among the nascent Apos Dynasty, and will they attack Anzhu City as a retaliation.

Although this is only a possibility, it must not be guarded against, at least, before the Tang Dynasty takes Aden City, the defense of Anzhu City must be paid attention to, and there must be no accidents.

If a city gate is to place four cannons, then, the five gates of Anzhu City need twenty cannons, and the defense of the port also needs a few, in addition, in addition to the city gate and the harbor, there are two gates on the northwest city wall, which are used for future trains, because the railroad tracks have not yet been laid, so the inside and outside of the door hole are sealed with two iron fence gates, and here is also the weaker part of the city wall, so it is also necessary to deploy heavy troops to protect it, and it is necessary to place four artillery, so count, At least 30 or so artillery units should be deployed in the entire Anzhu City, and if mobile fire reinforcements are added, a whole artillery brigade will be needed.

Li Feiyu led two standard corps, each of which was a standard of more than 3,000 people, each equipped with an artillery brigade, that is, fifty artillery pieces.

If an artillery brigade is left in Anzhu City, one regiment will lose artillery support, and the combat effectiveness will inevitably be greatly reduced.

With the support of the Celestial Brigade and the Chariot Brigade, no enemy would be an opponent, so why lead too many soldiers and horses to the city of Aden?

In addition, Li An drew a large amount of manpower from the surrendered pirates in the Malacca area, expanded the troops, and when fighting, let these troops rush to the front as cannon fodder, which can greatly reduce the death rate of the soldiers and horses brought from the capital, in short, as long as the Tang Dynasty soldiers and horses reach the level of 1,000 people, it is almost invincible.

"Let's go north."

Li An took the civil and military officials under his command and walked all the way north along the city wall, and the feeling of walking on flat ground was completely different from the feeling of walking on the city wall, that was because the vision was completely different, standing on the city wall, you could have a panoramic view of the entire Anzhu City, and the feeling was not ordinary comfort.

At the location of the doorway, the crowd stopped.

One is because this place is more special, there are two door openings below, which are used for the train in the future, and the other is because there is no good road ahead, the city wall is not completely completed, and the east city wall is not far from the door hole, and the wall of the east city wall has not been completed, not only is the top not laid bricks, the height is still a lot worse, the city wall must be built at the same height as the north city wall, the floor tiles can be laid, and finally the female wall and the inner wall can be laid.

In order to improve the defense of the female wall, the material of the female wall is not ordinary bricks, but concrete with higher strength, even if there is no role of steel bars, the structural strength of concrete is higher than that of ordinary bricks, and the flexibility of concrete is also better.

The general female wall thickness is the same, are made of two layers of bricks little by little, and the structure of the concrete female wall is more interesting, just like the city wall, every other distance to protrude a small piece, the protruding female wall part is thicker than the ordinary female wall, and there is no protruding part, the thickness of the female wall is thinner than the general brick wall, but even if it is a thinner part, the strength is stronger than the ordinary brick female wall, and the higher the thickness of the part, the strength is more powerful, It is impossible to destroy it with all cold weapons, and even if you use Datang's artillery weapons, it will take a lot of ammunition to completely destroy it.

Li Ang has great confidence in the women's wall he designed, whether it is the degree of beauty or defense, the new women's wall is much stronger than the old-fashioned women's wall, and from a distance outside the city, the new women's wall is very layered.

Ang Lee's feet are doorways, and there are two doorways, these two doorways are not far apart, and the width of each doorway is only two steps more than the width of the train, and the height is one person higher than the top of the train, so as to ensure the absolute safety of the train.

The reason why we chose to build two relatively small door openings instead of one door hole that is twice as large is naturally due to safety considerations.

Open a hole in the city wall, itself will reduce the defense of the city wall, if the two lanes are placed in a door opening, the door hole will be too wide, the arch at the top will also be very wide, the strength of supporting the bricks and soil above the city wall will be reduced, for a long time, under the action of stress, it is very likely that the accident of collapse will occur, and the two small door openings are different, because it is relatively narrow, the support force of the arch structure is greater, and it is less likely to collapse the accident, and the amount of work is relatively small.

In addition, in the event that one door hole is captured by the enemy, one large door hole is more conducive to the entry of enemy heavy equipment, while two small door holes are much less effective and easier to block.

Therefore, no matter what aspect you consider, it is better to build two relatively independent doorways than to build a single doorway.

Later generations of trains also follow this principle, when encountering mountains, the tunnels dug are only for the train to pass through alone, the round-trip train to go through the tunnel, sometimes the distance between the two tunnels is still relatively far, a few kilometers apart is normal.

This is because if the width is doubled, then the height should be doubled accordingly, so as to ensure that the semicircle above the head has enough amplitude to decompose the stress and protect the tunnel from collapsing, but if the width and height are doubled, the cross-sectional area will be increased by four times, that is, the earthwork of the excavation tunnel will be increased by four times, so that the amount of work is twice as high as digging two small tunnels alone, and the fool will choose to dig a big one?

Another point is that the later generations of tunnels are excavated with today's shield machine, that is, a cylindrical machine, the head of the machine is equipped with a lot of hard blades, can be excavated while traveling, the efficiency is much higher than manual excavation, but it is not easy to build a large shield machine, the technical requirements are very high, it is difficult enough to build a shield machine that can dig out a single train track, to build a shield machine with a double diameter, the difficulty will increase many times, and the cost and other aspects will increase, so it is not desirable.

With the current level of technology of the Tang Empire, it is impossible to build a shield machine, and it still takes manpower to excavate tunnels, but whether it is the use of manpower or the use of machines, the less earth and stone is the better, and the use of manpower to dig tunnels also requires digging two separate small tunnels.

There was a small staircase next to the doorway, and Li An and his military officials walked down the stairs and came to the side of the doorway.

Because the iron fence is locked, therefore, no one can enter and exit the city through the doorway, however, the defense of the iron fence is very limited after all, so, there are iron fences inside and outside the two places, in addition, there is a two-story small building on the side of the city near the doorway, which is enough to station thirty or fifty people, in the future, after the opening of this place, it is natural that this place needs to be guarded day and night, the doorway must be guarded inside and outside the city, and there must be guards above the city wall, so as to ensure safety, at least to prevent people from entering the doorway, Cause a certain danger.

The door opening will be opened with the opening of the railway track in a year or two at most, and then the iron fence will be removed, and there will be traffic near the door opening, as a transportation hub, in the future, there must be a lot of trains passing through this door hole, and it will be very frequent.

After lingering near the two gates for a while, Li An and his military officials did not rush back to the city gate, but walked along the inner city wall all the way to the south, and they had to walk around the city wall and inspect the entire city wall.

However, considering that the distance of the city wall is a little too far, and the officials are relatively old, it is natural that they cannot walk all the time, and horseback riding has become a very good choice.

Because there is a river near the city through Anzhu City into the sea, so, there is a river in the city of Anzhu City, and when the river enters Anzhu City, there must be a channel, the city wall will block the flow of water, so, in the position where the river passes, it is necessary to build an arched culvert, in order to ensure the solidity of the city wall, the larger river is built three culverts, each culvert is not very large, there are iron fences and wooden fences in the middle of the culverts, in order to prevent people and animals from entering and leaving the city.