The idea of building a railway to the Western Regions has to be said to be very bold and difficult.

Just from Chang'an to Yumen Pass, this route is more than 3,000 miles, and from Yumen Pass, to the farthest Julan City that Datang can influence, it is about more than 4,000 miles.

The newly built section has a total length of more than 7,000 miles, and if you add the section from Chang'an to Haizhou, this railway properly exceeds the length of 10,000 miles.

Many people are persuading that so far, there is no need to build a railway to the Western Regions.

Although trade with the Western Regions has brought a lot of benefits to Datang, compared to a railway of more than 7,000 miles, this benefit is obviously not enough.

Instead of having this effort and funds, it is better to invest these in the territory, radiate to more people as soon as possible, and bring more radical changes to Datang.

But Li Yuanji didn't care, the economy is only one aspect of it, and what he attaches more importance to is political significance.

This is a railway that can allow the Central Plains Dynasty to control the region for a long time, and this is a railway that can provide great help to the Tang Dynasty in many aspects, whether it is economic, political, or military.

We all know that the plateau railway is difficult to repair, which is a problem all over the world, but Huaxia still repairs it.

Since the founding of the People's Republic of China, the Chinese people have been thinking about building the railway, but there are too many problems of all kinds, and there is not enough technology to support them to complete the construction of this railway, so they can only give up temporarily, wait for the opportunity, and wait for the solution that can solve the problem.

In a later war, it was obviously won, but because the materials could not keep up, the troops had to be withdrawn.

Although the battle was won, it also made people know that Huaxia could not fight for a long time and could not support more troops to come here.

So there was provocation after provocation.

Then, after half a century and several generations of painstaking efforts, China finally overcame these global problems and built this plateau railway.

So, when the border beacon fire was ignited again, although it didn't really start, but this time, it was not us who retreated, but the opponent.

Therefore, the significance of the railway is here, and it cannot be considered purely from an economic point of view, especially at the national level.

Therefore, when the problem of the bridge was never solved, Li Yuanji once again took action.

This time, he came up with a completely new design idea.

Well, that's an unbelievable train of thought.

Drawbridge.

With the current technical level of Datang, it is too difficult to construct in the water surface, and the quality of the piers may not be guaranteed, so the safety of the bridge can only be ensured by increasing the density of the piers and deepening the depth of the piers.

But in this way, the water blocking area will increase, and the quality of the bridge itself will be difficult to guarantee.

When encountering a wider river, there is no way, but the kind of river surface that is tens of meters wide also has to build a bridge pier every four or five meters on average, which is still relatively luxurious in Li Yuanji's opinion.

So, there is this model that is now in front of everyone.

This model is five meters long and half a meter wide, and you can see a river passing through it, and if you compare it with the real thing, you will find that this is actually the location of the bridge site east of Xianyang.

There are four relatively large piers in the whole bridge, the one with a strange appearance, and the middle part is no different from the normal pier.

From here, the river is divided into two sections, with an island of about 100 meters in the middle, and on both sides of the river are marked with a 50-meter-high holding pillar, which is also two and a half meters long at the narrowest point, and this is still at the very top.

A finger-thick rope passes through the top of the pier, pulling one end of the bridge and the other end, the tail reaching deep into the ground.

Well, this bridge is actually a suspension bridge that can be seen everywhere in later generations, Li Yuanji is not an engineer and has never built a bridge, but he has seen it, so he knows some general things.

Then there is the current suspension bridge, in fact, the suspension bridge is more technically difficult, and if the relevant technical reserves are not up to standard, it is best not to play the suspension bridge.

Li Yuanji also knows this, but judging from the current situation, Datang can't even reach the technology of continuously hitting bridge piers on the water, so there seems to be no better choice except for the suspension bridge.

It took four years for the construction of a Yellow River bridge to be opened to traffic, and there is no need to say how difficult the process is, even so, when the train passes here, it can only slow down, and even limit the weight of the body.

Freight cars are only allowed to pass three cars at a time, passenger cars are only allowed to pass four cars at a time, the locomotive and the coal and water carriage pass alone, and the rest are towed by light locomotives at the bridge station.

This result is actually quite good, and in the late Qing Dynasty and early Republic of China, the passing rate of the Yellow River Bridge was even more annoying.

Only one car can pass at a time, and the speed must not exceed five kilometers, and it often takes more than an hour for a train to pass here, and if you are unlucky, it will be difficult to pass half a day.

Train queues have become the norm.

Although the whole vehicle can't pass at one time now, but it can't stand Li Yuanji's confidence, and it can't pass at one time, then build more ferry locomotives, and split the train in the station, one after another, so now through the Yellow River Bridge, it only takes about 20 minutes to be enough, which refers to the time from dismantling to assembling and leaving on its own.

Well, back to the suspension bridge.

The moment Li Yuanji's model was taken out, it attracted the attention of many designers.

After a short while, many questions were raised.

For example, the steel rope could not provide such a large pulling force, and there was a big problem just holding up the bridge, and they were really worried about the safety of the bridge if they were passing through the train.

The collapse of the bridge is a trivial matter, in case a person also goes down, then it will be blind, there is water below, people are in the train, once the bridge collapses, you can't run away, with the train sinking to the bottom, I am afraid that even the body will be difficult to salvage.

"Okay, just try it!" In this regard, Li Yuanji scoffed.

"Your Majesty, how can you try this? In case the bridge collapses......"

"That is, the distance of more than 30 meters is actually not too long, and it is a big deal to increase the diameter of the bridge."

Li Yuanji was a little speechless, these people's arithmetic was simply in vain.

Although physics has not yet become a regular subject, there is also corresponding physics knowledge in the textbook.

"Just take this model as the main one, build it one to one, and then test its maximum passing weight, and after the test results are obtained, wouldn't it be nice to scale up the standard in equal proportions?" Li Yuanji was a little speechless.

Is it difficult? It's not difficult, it's the way of thinking.

Is this an accurate experiment? Not necessarily, but it's not completely impossible.

It seems small, but the standards used are also small, as long as there is a result, then everything is easy to say, isn't it?

The pressure that one chopstick can withstand is different from that of two chopsticks, such a simple truth.

……

There was no way, the emperor gave an order, and the designers had to do such a test in the courtyard of the Ministry of Works.

The bridge is five meters long, and the highest place is about two meters, in fact, the entire bridge deck is only half a meter high from the ground.

The test bridge was built very quickly, because it was small, a two-meter-deep foundation pit was dug in the ground, and then the piers were started.

In less than ten days, the bridge was completed.

As for the test, this one is much simpler, with the heaviest steel, put it on top, install a small pulley underneath, pull it with a tractor at one end, and watch the changes in the bridge deck.

After continuous testing, the results finally came after half a month, but it was an embarrassing result.

The bridge did not collapse, and the fixed lock rope was not broken, but this is only half a month's test results, and the test environment is different from the real use environment, so this result can only have a certain reference value for the load-bearing capacity of the bridge, and the reference significance is not great in other aspects.

But even so, after a series of tests and calculations, it was concluded that this kind of bridge can support the normal passage of trains without considering the aging of the bridge.

So, the tests began to move on to the next stage.

Scaled up, but also on land, but the location was changed to the test site.

This time, the bridge was large enough for a locomotive to pass through a coal-fired water wagon, and it was also a two-lane one.

A month later, the second test bridge was completed and began to enter the practical testing phase.

This time, something was wrong, and when the locomotive just went up, the bridge could be seen shaking.

Can the bridge still be shaking? Are you sure it's not the bridge that's about to collapse?

However, the train passed smoothly, the bridge did not collapse, and a test did not find any problems, and then the test continued.

Later, the test of speeding up or decelerating the train began, and the result was that the faster the train, the greater the amplitude of the bridge shaking, and the slower the speed, the smaller the magnitude of the shaking.

However, after the same scale of the bridge, there are still no problems.

As a result, the Ministry of Engineering decided to put the construction plan of the Weishui Bridge on hold for the time being, and let the engineers first repair other land bridges, which they would need to test for a long time to determine whether it was feasible.

In this regard, Li Yuanji has no other expression.

It's not wrong to be cautious about bridges, but even if the bridge is repaired?

And you can't let the whole process open to traffic immediately, is there any difference between an earlier day and a day later?

Moreover, Xianyang is not far from Chang'an, even if the bridge is not repaired, after the train arrives in Xianyang, it will be transported to Chang'an by truck. It's a bit of a hassle, but it's better than taking risks, right?