The difficulty of building a concrete road is much lower than the difficulty of opening a road in the dense forest before. After all, it doesn't need to cut down trees. In fact, the amount of labor involved in cutting down trees is not very large. The really big amount of work is digging up the roots and transporting the trunks and roots.

In the tropical rainforest, there are many thousand-year-old trees, each of which is often tens of meters high, and the area of the roots is also extremely large. The older the tree, the thicker the roots, and the intertwined roots, the distribution area is quite large. The roots of these thousand-year-old trees are very widely dispersed, and they are all digging deep in the earth, which is extremely laborious to dig.

That's why it took so long for the Panamanian colonial team led by Gaurard to open up this path. In addition to cutting down trees, it is also necessary to consider drainage issues and choose a higher ground. Also, try to avoid rivers. After all, crossing one more river requires a bridge.

In this era, there was no construction machinery, and it was very troublesome to build bridges. For example, a small stone bridge takes many stonemasons months to build. And this time Ghoillard's report mentions that the road passes through 24 small rivers and 3 large rivers along the way...... The construction of these 27 bridges is no less troublesome than the entire cement road......

The construction of a concrete road is actually very simple, without a roller, Marin can ask the stonemasons to build a few more stones, and let a few black people pull together with a fiber rope to flatten the roadbed. Guffard now had more than 6,000 strong black slaves under his command, and as long as there were enough rocks, it was relatively easy to lay the roadbed.

After laying the roadbed, it is to lay the line with lime. This needs to be measured to ensure that the distance between the two lime lines is 3.5 meters or 4 meters. It's not difficult, just bring a ruler and measure it.

After that, it's time to erect bricks on both sides of the road......

The purpose of erecting bricks is simple, that is, to set boundaries for the cement poured on the cement pavement. At the same time, the height of the brick standing on the side is the thickness of the cement pavement. Therefore, the purpose of the side bricks, in addition to being a boundary, also has the meaning of a reference for pouring cement. At the same time, there are bricks to protect the sides, so that the cement will not leak to the outside. Of course, after the bricks are erected, you need to stir a part of the cement and apply it between the bricks to fix it.

After that, the biggest problem was the cement mixing. Cement mixing is a purely manual job, and it also requires technology. Because, in addition to the ratio of cement and sand and gravel needs to be mastered, it is also necessary to pay attention to the amount of water, which will affect the quality of cement. Therefore, this link requires the participation of professionals. At the very least, it is necessary to have a professional to guide the labor on how to stir it.

After mixing the cement, the rest is simple, directly let the young adults fill the mixed cement in a bucket and pour it between the bricks standing on both sides. Then, it is enough to pat and flatten it with a wooden plank. When I saw that it was almost pressed, I would use a long wooden board or a long stick to stick to the upper edge of the bricks on both sides and scrape it hard. By pressing, use a large wooden board to press on the road surface to make the road surface tight enough.

The last step is to cut the square and tie the line. The cutting side is that every other section of the cement road will be cut to make the road surface divided into pieces. In fact, this is to prevent cracks in the pavement caused by thermal expansion and contraction of the cement surface. The threading is to use a knife-edged wooden board to press a series of shallower lines on the cement surface. These shallow lines are designed to prevent the cement pavement from being too slippery on rainy days......

The pouring and post-treatment of cement pavement is not difficult, on average, hundreds of people can still do it by laying one kilometer a day. Ghoillard had more than 6,000 strong black slaves, and even if the blacks were not proficient in labor, they could still do it by laying a few kilometers a day. The premise is that Marin needs to send a group of craftsmen to guide them.

Finally, there is the problem of drying the cement pavement. This phase takes a long time, usually after a month (standard 28 days) before the cement road can be put into use. Until then, cement surfaces need to be maintained for maintenance. I am not afraid of drying and drying, and I am most afraid of rain halfway.

Therefore, during the drying period of cement appearance, it is necessary to prepare shelters. For example, straw mats, straw curtains, etc. Once it rains, cover the surface of the cement that has not yet dried, so as to avoid further moisture and prolong the drying time.

It is precisely because the drying period is too long, so the construction time of the general cement road, even a few kilometers of small cement road in the countryside, takes several months. It's not that it takes so long to build a cement road, but that it takes a month to dry a kilometer of cement road......

Therefore, as long as the materials are complete and there is the guidance of skilled craftsmen, the cement road can be repaired very quickly. But Marin didn't expect them to fix it fast, either. Why? Because the time to lay the roadbed is uncertain...... Modern rollers help and it takes a short time to lay the roadbed. And with Uncle Black pulling the stone stone to press the road, God knows how long......

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In fact, it was not very difficult to build a village-grade cement road as long as it was a way out, even in ancient times. However, the 24 small bridges and 3 bridges left Marin with a lot of headaches.

This era is not a later generation, with a large number of construction machinery. Marin remembers that in later generations, bridges could be built in as little as 5 minutes. Of course, it's that kind of little bridge. As long as the crane lifted a cement slab made of reinforced concrete (or simply an iron plate) across the banks of the creek, a proposed bridge was successful.

However, there are two prerequisites for this, that is, the strength of the cement board or iron plate is high enough. Because, this is to go through the carriage and horses, and the carrying capacity must be strong. In addition, this type of bridge is only suitable for narrow streams. A slightly larger river, it's not so easy. As long as it comes to the construction of bridge piers, it is not simple. If it is an arch bridge that does not use piers like Zhaozhou Bridge, the project is more difficult.

However, Marin does not have a high-strength cement slab in his hand now, and he will not be willing to make such a large iron plate to be used as a small bridge. Now that iron is so expensive, there is a chance that such a large iron plate will be stolen...... Moreover, before the stainless steel came out, the ordinary steel bridge, which was exposed to wind and rain, was easy to rust and then collapse...... Besides, even if there is stainless steel, you can't have the luxury of building a small bridge. At least, in this day and age, no fool would build a small bridge with a treasure like stainless steel......

However, if the bridge is built using traditional methods, a small stone bridge will require a large group of stonemasons and several months of labor to complete. There are 24 stone bridges, and many craftsmen are required, and the working hours are also very long. It is estimated that it will take more than two or three years to complete the construction of 24 small stone bridges.

This is still a small bridge, and the bridge is even more finished. In this era, there is no ability to build bridges. In the absence of cable-stayed technology, bridge piers must be used to build bridges. However, pier building is a technical job. The piers of the small bridge are easy to do, but the piers of the bridge are difficult to get. Because, to repair the piers, you have to drain the water first. Then, it will be possible to drive piles. Before piling, it is necessary to do a good job of calculation and site selection...... A whole set down, very troublesome...... With current technology, it is difficult to drain parts of large rivers or build large bridge piers.

Of course, it is a pity to learn from the Luding Bridge on the Dadu River, where the iron cable crosses the river and then lays wooden planks...... However, such a bridge is at most passable, and cannot be carried by horse-drawn carriages. But the concrete road that Marín built on the Isthmus of Panama was used to transport goods. In the future, horse-drawn wagons that may have been used to transport gold and silver from the Potosí silver mine must have been heavy. Such a cable-drawn bridge could certainly not be used to carry horse-drawn carriages laden with gold and silver......

If it is to fill in the river and build a bridge...... The bridges on the small rivers are okay, and it is certainly unrealistic for the three big rivers to fill the river and build bridges......

"Is it possible that the problem of crossing a large river can only be solved by ferry?" Marin scratched his head in the captain's room.

However, it is very troublesome to put a horse-drawn carriage full of gold and silver on the ferry, and it is easy to delay time. If there are bandits who take the opportunity to intercept them halfway, it will be very bad.

Annoyed, Marin went to rest on the deck and looked out to sea......

Walk on deck......

"Deck!" Marin shook his heart......

"It seems that we can build a pontoon bridge!"

When the army marched, pontoon bridges were often built. Generally, pontoon bridges are built with boats, rafts, etc., and can be used for temporary marching of large armies.

However, there is a problem with pontoons, and that is that they affect river navigation. If it is a temporary pontoon bridge, it is fine, but if a long-term pontoon bridge is built, then this pontoon bridge is equivalent to cutting off the navigation channel of the river. If the pontoon bridge is not removed, other ships will not think about passing it...... Then inland waterway navigation on this river was abolished......

So, in general, no one wants to build a permanent pontoon bridge over the river. Only when marching did a pontoon bridge be built improvisely.

Marin didn't bring a civil servant, and Schwartz wasn't there, so he didn't know who to talk to. So, he had no choice but to talk to Karn as if he were playing the harp.

As a result, Karn, who was battling a roast duck, asked curiously:

"Young master, what is inland waterway shipping? Why do you want to do inland waterway shipping in Panama? ”

Seeing Karn's curious look on his face, Marin was so depressed that he almost vomited blood. But suddenly, he reacted—

"yes, why should I think about the kernel shipping in Panama?"

Panama is a colony, and Marin doesn't want to develop there, so why bother with the problem of inland waterway shipping being affected? To put it mildly, there is no inland waterway shipping there at all. Perhaps, but it's just a Native American canoe. Even if you encounter a pontoon bridge that barrages the river, you can carry a canoe around it......

I was also stunned, and I considered the Panama region as a local. In fact, the only thing that works in the Panama area for Marin is the transit function. The rest, Marlin can not be considered......

After a sudden realization, Marin found that these 24 small bridges and 3 bridges seemed to be able to be replaced by pontoon bridges......

Marin first planned to send shipbuilders to Panama to make more inland river boats from locally harvested timber, and then line them horizontally on the river to make pontoon bridges.

However, it takes a long time to build a ship, and it is still a waste of materials...... Marin needs to open the Isthmus of Panama cement road as soon as possible so that he doesn't want to wait slowly......

After thinking about it, Marin suddenly found that the logs cut down from the tropical rainforest seemed to be directly tied into a super large raft across the river......

Logs are inherently floating, and the larger the log, the stronger the ability to float. A pile of felled logs tens of meters long is gathered and tied up across the river, and it is easy to form a pontoon bridge. Moreover, the load-bearing capacity is very high. At least, crossing the carriage is not a problem.

Even a large river (in fact, the great river in Panama is not very big) can cross the river if you get enough logs and tie or nail it into a faction.

There are so many pontoon bridges made of tens of meters long and very thick logs lined together, and it is not a problem to walk the carriage......

Moreover, Ghoillard and a few thousand blacks had just cut an 80-kilometer road out of the rainforest by cutting down trees, and halfway through it was littered with oversized logs that had been cut down. As long as a lot of manpower is used, these logs along the road are pushed down the river, and tied into a super-large raft, which can be crossed on the river, and can be made into a large pontoon bridge that can run horse-drawn carriages.

Because the source of logs is extremely abundant, it basically doesn't take much time to build a pontoon bridge like this. Even if there are 27 bridges, it is not very troublesome......

Of course, the life of this pontoon bridge made of oversized rafts will not be too long. But what Marlin needs is to get it into use quickly, and quick success is the most important thing. In the longer term, Marin will build a concrete bridge next to the pontoon bridge to replace the pontoon bridge made of logs. However, because there are pontoon bridges made of log rafts, the construction of cement bridges or stone bridges is not so nervous, and the log raft pontoon bridge is used first...... Later, when we have the energy and financial resources, we will build regular bridges to replace this temporary pontoon bridge......

It's just that the pontoon bridges on the 24 small rivers are easier to be replaced by concrete or stone bridges, but the bridges on the 3 big rivers are difficult to replace. After all, the river is too wide and the volume of water is too large, and with current technology, it is difficult to build a bridge across the river.

However, the good news is that the Panama region is very rich in logs, and you can cut them everywhere. It's a big deal, if it's broken, I'll cut down a few more trees to repair the three log pontoons......

Thinking of this, Marin immediately wrote a letter of order and sent someone to Panama:

"Giant logs cut down can be used to tie or nail giant rafts across the banks of the river to make bridges and keep the carriages unimpeded......"

Anyway, Marin's meaning is very clear - first use a pontoon bridge made of giant rafts to connect the road first. As long as this road is opened, whether it is to transport valuable goods from Daming on the Pacific route, or to transport silver from Peru and saltpeter from Chile, it will be able to start. With the profits in the account, it will be simple to withdraw funds to repair the bridge in earnest. Anyway, with the pontoon bridge, there is no need to rush to repair the regular bridge......

Even if the pontoon bridge is broken again, it can withstand it for several years. There is no sea maggot erosion in the Tamsui River, and the pontoon bridge can be maintained for several years or more than ten years. Before the life of the pontoon bridge expires, it is estimated that it is still possible to replace all 24 small bridges along the line with regular bridges. As for the bridges over those three great rivers, we can only say more. With the level of engineering and technology of this era, God knows when a regular bridge across a large river will be built......

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