Before the National Day, Shen Huan returned to Zhonghai.
Now the work of Jiangnan Changxing Shipbuilding Base is progressing in an orderly manner, and Shen Huan has also held a position in CSSC Changxing Construction and Development Co., Ltd., plus there is a pulsating production line in the base project, so he must participate in a lot of design demonstration work.
At the same time, the first phase of the Jiangnan Changxing Shipbuilding Base project building materials wharf has also started.
In order to complete the production task of ultra-long diameter pipe piles for building materials terminals, the entire Linhai Concrete Company of China Shipping Third Harbor Bureau has made concerted efforts from top to bottom to make a breakthrough in the production technology of PHC pipe piles, which is the longest and largest diameter in China.
In fact, with the development of domestic hydraulic construction, the length and diameter of a single section of PHC pipe piles are also getting larger and larger, which is mainly due to the influence of the piling stress transmission caused by the material difference between the splicing joint and the pile matrix on the integrity of the joint, and the length of the single section is designed to be longer and longer in order to pursue the integrity of the pile.
The increase of the diameter of the pipe pile is considered from the perspective of economy, and secondly, from the design point of view, the large diameter is more advantageous than the small diameter, especially for large water terminals.
Of course, it is not so easy to produce high-quality super-large diameter PHC pipe piles.
The Linhai Concrete Company of China Shipping Third Harbor Bureau also experienced several failures before finally completing this arduous task.
Li Fusheng also participated in the whole process of development, and his feelings were too deep.
If it weren't for an expert like Chief Engineer Duan, it is estimated that it would not have been possible at all.
Li Fusheng still remembers that during the first trial production, there was a problem with the positioning of the steel cage in the tube mold.
For this kind of extra-long PHC pipe pile, due to the concrete distribution, the tension force is insufficient to completely straighten the steel rod due to the falling pressure on the reinforcement cage.
At that time, everyone didn't know why or how to solve it.
Later, Chief Engineer Duan led everyone to do analysis, and through testing and calculation analysis, the problem was discovered.
Since the PHC pipe pile is made of high-strength concrete, the viscosity of the concrete is too large in the mixture stage, and when these high-viscosity and low-slump concrete are pressed against the steel rod, the steel rod cannot lift and straighten the concrete.
Even at the end of tensioning, the steel rod still cannot be straightened.
As a result, the tensile force is partially eliminated and the main reinforcement is now offset.
In the end, Chief Engineer Duan came up with a solution, that is, some specially shaped concrete cushion blocks were specially made to fix around the reinforcement cage, which could be regarded as solving this problem.
This is the same reason as when pouring concrete floor slabs on the construction site, a lot of small concrete cushion blocks are placed under the steel bars to control the thickness of the concrete protective layer.
It's a very earthy method, but it's very effective.
Of course, the failure is not only this time, after this problem is solved, a new problem has appeared, that is, the quality of the second pipe pile produced in trial production has not passed.
I don't know what the reason is, the mortar layer of the inner wall of the pipe pile is more than twice the normal value, in fact, it is not only that, after breaking the structure of the pipe pile, it is found that the concrete structure of the pipe pile wall has been layered.
This delamination is a relatively serious quality defect, which has seriously affected the actual strength and hammer resistance of the pile, so this pile is also a failed test product.
What is the reason for this?
Chief Engineer Duan once again led the personnel of the production technology system to conduct a careful analysis, generally speaking, the two biggest possibilities are the problems in the design and quality control of the concrete mix ratio, and the other is the problem of speed control of the pipe pile centrifuge.
Finally, the chief engineer decided to adjust the speed of the centrifuge and try production again, because the centrifugal parameter setting of pipe pile production is a very complex process, which requires theoretical calculation and practical experience to obtain the best parameters for speed and time control.
Of course, only Chief Engineer Duan personally did the matter of adjusting the centrifugal parameters, because others could not compare to him.
However, everyone knows that Chief Engineer Duan will leave Linhai Concrete Company of China Shipping Third Harbor Bureau in a few days and go to the concrete mixing plant of CSSC Jiangnan Changxing Shipbuilding Base, so during this time, Chief Engineer Duan is also trying his best to train a successor, this person is Lu Haichuan, the manager of the technical quality department.
To say that Lu Haichuan has been following Chief Engineer Duan for decades, but he hasn't learned much about Chief Engineer Duan's skills, probably this is a matter of people's qualifications.
But after Chief Engineer Duan is leaving, this position will definitely be Lu Haichuan's.
However, Li Fusheng was also fortunate to follow the two experts and learned a lot of secret techniques, such as the setting of centrifugal parameters.
Generally speaking, the centrifugal molding of concrete pipe pile is divided into three stages, the first stage is low-speed centrifugation, and the rotation speed of this stage is relatively slow, so that the concrete in the pipe mold is slowly distributed evenly.
The second stage is medium speed, in which the solid particles in the concrete will be distributed more evenly, which is equivalent to basic molding.
The third stage is the high-speed centrifugal stage, through higher speed, greater centrifugal force, so that the solid particles of concrete are more tightly combined, and at the same time, the excess free water will be thrown out and flowed away, which is similar to the washing machine to dry clothes.
This time, the super-large diameter pipe pile, because the wall thickness of the pipe pile has also increased, so it also led to the initial centrifugal parameter setting, because of the fear that the concrete can not be compacted, so the set high-speed centrifugal time is too long, which makes the concrete in the pipe mold delamination too large.
At the same time, due to the design of the concrete mixture, the problem of steel rod straightening is taken into account, and the sand rate is relatively increased, which in the centrifugal process, the lighter mortar is layered on the inner wall.
After the calculation and adjustment of the chief engineer of the section, the low-speed centrifugation time was extended and the high-speed centrifugation time was shortened, and the third super-large diameter PHC pipe pile test product finally solved this problem.
In terms of the design of the steaming and curing process, the final scheme was the first time that the process of non-high-pressure steaming and curing was adopted.
First, this time is an ultra-large diameter pipe pile, if the original high-pressure autoclave process is adopted, it will lead to the increase of brittleness of the high-strength concrete pile, and the second is the use of autoclave steaming, and the pipe pile is very difficult to cool down when the pipe pile is out of the kettle.
Of course, the most fundamental reason is that there is no autoclave more than 30 meters long in China now!
In September, the first batch of super-large diameter PHC pipe piles were lifted to the cargo ship parked on the dock after passing the factory inspection.
Li Fusheng felt that the harvest was too great, and it was a rare opportunity to participate in the R&D and production of the longest and largest PHC pipe pile in China, and more importantly, this time Duan Yongfu also gave him an important task, that is, to let him and Lu Haichuan jointly write a summary paper on the production technology of ultra-large diameter pipe piles.