In the railway construction, the roadbed treatment of this aspect, has been the hardest hit area of the railway project, how many railways are completed, because the roadbed as a whole sinks, resulting in the destruction of the line type, and finally can only be repaired all year round, due to the disease on the foundation, no matter how to repair the roadbed as a whole or the ballast, there is no way to cure the key point. Pen ~ fun ~ pavilion www.biquge.info

In fact, in the process of emergency repair, the most commonly used method is to increase the thickness of the ballast, many railway sections, the thickness of the ballast is more than one or two meters, which is not uncommon, and the thickness of the 45 cm ballast designed by the railway is too high!

With the increase of railway speed, the requirements for the roadbed are getting higher and higher, and the roadbed treatment has become one of the main factors affecting the speed of domestic trains.

In order to get rid of the disease caused by the road foundation, the easiest way is to build bridges, replace roads with bridges, increase the cost of construction, and avoid large-scale renovation construction after completion.

However, in the eighties of the last century, the state was unable to build bridges on a large scale due to economic and financial reasons, and replaced roads with bridges, which eventually led to the running speed of railway trains not being able to be improved.

In order to solve this problem, in the early nineties, the Ministry of Railways specially convened the first, second, fourth and other domestic design institutes to carry out a series of studies on the treatment of the roadbase foundation, and finally found several solutions after a long period of practice.

In order to keep Qiao Tianhong in his design company, Chu Jianghe can only use these killer features to attract Qiao Tianhong's attention, and while retaining Qiao Tianhong, he can also do his part for the domestic railway industry.

Chu Jianghe vaguely felt that once he came up with this method and put it into practice, there would definitely be a qualitative leap in the speed of domestic trains, but by adopting this method, the construction cost would not increase much, which was just suitable for the country's current economic conditions.

"Yes, after all, I have more front-line construction, this method, I have no opinion to find, I think this method, to solve the weak foundation, should be feasible. "The Chu River channel.

"Is that the new type of pile you are talking about?" Qiao Tianhong asked.

Seeing Chu Jianghe nodding, Qiao Tianhong continued: "Tell me what your specific measures are?"

"My method is actually very simple, like bridge construction, many designs do not have pile foundations, the bottom of the use of caissons, such as the Jingtan Railway is this design, but into the eighties began, bridge pile foundation application more and more, because the pile foundation is long enough, can fully support the force on the foundation, to ensure that the bridge does not sink. Even if the bearing layer is not reached, the pile group relies on friction, and the sinking amount of the bridge is limited. Chu Jianghe explained to Qiao Tianhong step by step, Qiao Tianhong understood these contents better than Chu Jianghe, Chu Jianghe still recounted it, and continued: "And the foundation treatment of the roadbed, my method is also to use the pile foundation, but compared with the pile foundation of the bridge, the pile foundation of the roadbed is different in the following aspects. ”

The construction of the Jingtan Railway began in 84 years, but the preliminary survey and design and construction of the railway was carried out before 80 years, and the planning, approval and survey, design, and finally entered the construction state, less than three or four years, and more than decades.

Like the first high-speed railway in China after 20 years, the Beijing-Tianjin intercity high-speed railway, 05 years of construction, 08 years into operation, the early survey, design, in 97 years began to carry out, after a long period of preliminary survey and design, only the completion of this high-speed railway.

80 years ago, the bridge pile foundation has not been fully promoted, and the foundation of some bridges is the use of caisson foundation.

Hearing Chu Jianghe say this, explaining like an expert, Qiao Tianhong showed a strong interest, and he suddenly found that Chu Jianghe, a kid, knew a lot about the railway industry.

"First of all, the pile foundation of the roadbed from the depth point of view, I don't think it needs to be too long, the length of 6 meters to 10 meters is appropriate, the diameter does not need to reach one meter, 50 centimeters I think it is about the same, in addition, the distance between the pile and the pile, I think this requirement should be stricter, the distance between the pile center is kept at about 60 centimeters, which should be able to meet the requirements. Chu Jianghe said, adding: "Of course, the specific situation has to go through mechanical calculations, I don't understand this aspect, these data are just my ideas." ”

Although Chu Jianghe said so, these data are all commonly used values in design thirty years later, and Chu Jianghe is basically handy, quite handy.

"Xiao Chu, you have to know that the foundation width of the roadbed, even if there is no filling height, is calculated with a double line spacing of 5 meters and the center of the line is 3 meters from the shoulder, and the width of the 11 meters is 11 meters, how much does it cost to arrange the pile foundation according to your density?" Qiao Tianhong quickly realized the shortcomings in Chu Jianghe's words, from beginning to end, Qiao Tianhong considered the problem from the perspective of the budget, if the budget was not considered, the bridge could be used across the line, and there was no such situation.

Just like the high-speed railway in China, in order to prevent geological problems, viaducts are set up in most areas, which is one of the reasons.

For example, a bridge pier, there are 8 pile foundations under the piers, each pile foundation is 40 meters, so calculated, it is only 320 meters of pile foundation, 85 years, the general bridge span is 16 meters, very few bridge spans use 24 meters, and there has never been a 32-meter bridge.

However, even so, in the case of bridges, a 320-meter-long pile foundation with a diameter of 1 meter is used for 16 meters. If it is a roadbed, 11 meters wide roadbed, transverse need to arrange 18 piles with a diameter of 50 centimeters, the depth is calculated according to the shortest 6 meters, a cross section, it takes 108 meters, 16 width range, a total of 26 rows, the length of the pile foundation is 2808 meters, compared with the 320 meters of the bridge pile foundation, the gap is not small, even if the pile diameter of the roadbed is only 50 centimeters, the length is half of the pile foundation is far more than 320 meters.

Obviously, as long as people who have studied mathematics, they will know that the method proposed by Chu Jianghe will not work, and the amount of concrete used for the pile foundation will far exceed the amount of concrete used for the bearing platform and pier, and even the amount of concrete for the bridge is enough.

If there is such a price, it is enough to simply build a bridge, so why bother to deal with the foundation and then fill in the roadbed?

"Dean Qiao, if the concrete is used to pour these pile foundations, it is definitely not cost-effective, another difference I want to say next, is the use of raw materials, I propose this kind of pile, I call it cement mixing pile, to put it bluntly, I just want to rely on the mixed cement slurry, to meet a certain specific gravity, and then find a way, and the foundation of the soil mixed together, so that the soil and cement slurry fused together, set up a complete pile. For the use of materials, only cement is needed, and I have roughly calculated that a bag of cement can almost meet the requirements for each meter of cement mixing pile. "The Chu River channel.

"Cement mixing pile?" For this title, Qiao Tianhong has been working in the railway industry for so long, and it is the first time he has heard of it.

For Chu Jianghe's method, especially the pile foundation does not need to be drilled, but uses soil and cement slurry to fuse together, Qiao Tianhong is very puzzled.

"That's right, this name is given by me, because this kind of pile, is the use of cement slurry and soil mixed together, after solidification, into the form of a pile, has a good reinforcement effect on the weak foundation, after a large area of construction, the formation of a group of piles, together to support the road base and the load generated by the train, to ensure that the roadbed does not sink!"

"Xiao Chu, you speak slowly, your explanation is a little messy, now I ask you a few questions, and you answer me one by one. Qiao Tianhong still didn't quite understand what Chu Jianghe meant, and stopped Chu Jianghe from continuing.

Chu Jianghe was stunned for a moment, and then smiled slightly, all along, he has always regarded Qiao Tianhong as a person who understands cement mixing piles, and when asked by Qiao Tianhong, Chu Jianghe felt that his explanation was indeed too far-fetched, even if Qiao Tianhong was an old expert in railways, it was inevitable that he would be confused.

"Okay, Dean Qiao, you ask. Chu Jianghe nodded.

"First of all, the first one, and what I am most puzzled about, you said that you don't need to drill holes, so at least 6 meters deep, how do you ensure that the injected cement slurry can form a complete pile foundation, and without extracting the soil, inject the cement slurry?" Qiao Tianhong thought about it and decided to ask this most doubtful question first.

Qiao Tianhong's meaning is obvious, for example, a 6-meter pile foundation, you want to inject cement slurry, how to inject to this depth, and ensure that the cement slurry and soil are fused together?

"Dean Qiao, I'll draw you an imaginary picture first. Chu Jianghe decided that this method still needs to be explained more clearly in the form of pictures and texts.

Chu Jianghe roughly drew a diagram, on the diagram, a drill pipe is fixed vertically by a machine, the top of the drill pipe, and then a pipe, connected to another machine, in the lower part of the drill pipe, there are four curved steel blades, at the same time in the lower part of the drill pipe, also set up two small holes.

After the painting, Chu Jianghe explained to Qiao Tianhong: "After we set the drilling rig in position, we use the machine to rotate the drill pipe, and at the same time, the four blades rotate together, and as the drill pipe is driven into the soil, the four blades will cut the soil while rotating, which is equivalent to breaking the soil loose." ”

The place where the cement mixing pile is used is loose soil, therefore, after the drill pipe rotates, the blade is easy to cut the soil, after four times of cutting, although it cannot be said that there is no dead angle, at least most of the soil is loose.

"In the process of drilling down the drill pipe, we can determine the depth of the drill pipe according to the mark of the drill pipe, so that we can know whether the drill pipe has been drilled to the designed elevation. Once the drill is in place, the rig begins to rotate in the opposite direction, lifting the drill pipe upwards, and in the process of lifting the drill pipe, the grouting hole below begins to spray a certain specific gravity of cement slurry. "The Chu River channel.

"Can this cement slurry shoot into the soil?" Qiao Tianhong asked with a frown.

"It should be fine, it's like when we shoot water into the soil, it depends on the pressure, and the higher the pressure, the deeper the soil penetrates. Because the pipeline connected above the drill pipe is connected to the cement slurry production pool, when the cement slurry is needed, the cement slurry is pressed into the pipeline by high pressure, and then shot out of the sprinkler, we can determine the pressure according to the diameter of the mixing pile, so that the entire pile foundation can be filled with cement slurry. Chu Jianghe said this, paused, and continued: "And when the drill pipe is sprayed with cement slurry, the four blades are still cutting the soil, which is equivalent to loosening the soil again to ensure that the soil is loose, so that the cement slurry is easier to shoot into the soil." ”

Listening to Chu Jianghe's explanation, Qiao Tianhong fell into contemplation for a while, he took Chu Jianghe's sketch, compared it to it, and kept listing formulas and calculated numbers.

Soon, Qiao Tianhong put down the pen and nodded slightly: "Xiao Chu, you are right, if the pressure reaches a certain level, it can indeed press the cement slurry into the soil layer!"

"Dean Qiao, in fact, this is the same as our water shooting soil, and I also got the inspiration from the water shooting into the soil. "The Chu River channel.

"Well, if the amount of cement slurry injected in one injection is not enough, you can also carry out a second operation. This time, Qiao Tianhong helped Chu Jianghe speak.

"Yes, that's what I mean, so that the quality of the cement mixing pile can be ensured. "The Chu River channel.

"Well, if there is really this kind of machinery, the construction of a large area of the roadbed pile foundation, to prevent the foundation from sinking, can indeed play a certain role, but the specific situation, still needs to be discussed, after all, these are just the results of your imagination, the specific situation still needs to pay for practice. Qiao Tianhong looked at the sketch and said.

"Of course, even for this method of reinforcing the weak foundation, whether it is feasible or not, still needs to be calculated by Dean Qiao, and after the pile foundation is constructed, I think that pouring a square concrete block with a thickness of 20 cm on the top of the pile foundation can better ensure that the foundation does not sink. Chu Jianghe continued.

Qiao Tianhong's eyes flickered, Chu Jianghe proposed this method, he was indeed moved, for Chu Jianghe's proposal, although Qiao Tianhong has not practiced, but as the retired vice president of the Huangjia Design Institute in China, the perennial design experience tells him that this method has a certain feasibility.

If the pile foundation and the pile cap can really be combined, then the stress area is increased, which is equivalent to this large piece of cement mixing pile, which bears the dynamic load brought by the road base and the train driving process together, and the feasibility of foundation sinking is very small.

"That's a good idea, but even if I join your design company, I can't do research on it alone. Qiao Tianhong glanced at Chu Jianghe and sighed.

Qiao Tianhong said this, indicating that Qiao Tianhong had agreed in disguise.

Chu Jianghe hurriedly hit the railway while it was hot: "Dean Qiao, don't worry, in addition to you, I will also invite some other experts from the Third Design Institute to join, and some old experts who are retired at home, I hope Dean Qiao will also come forward to help, see if they can be invited out of the mountain, presumably these old experts are also very happy to see that China's railway industry can develop rapidly and embark on the generation of high-speed railways as soon as possible!"