Application of post-grouting technology of punching cast-in-place pile in high-rise building?

In recent years, with the rapid development of China's construction industry, technical requirements have become more and more stringent. Post-grouting technology of punching cast-in-place pile is a basic form under this background, which improves the bearing capacity of foundation, ensures the quality of construction personnel, saves the cost of building materials and reduces the project cost budget. Based on the development background of high-rise building industry, from the perspective of economic and social benefits, this paper understands the principle and characteristics of post-grouting technology of punching cast-in-place piles, and comprehensively analyzes its great value in the application of high-rise buildings, including putting forward countermeasures for the problems encountered in the application and what far-reaching impact it has on the development of high-rise building industry in the future.

With the development of modernization, people's economic level is advancing by leaps and bounds, and the requirements for quality of life are getting higher and higher. The housing problem has become an urgent concern of people. When the country began to solve the people's livelihood, it paid more and more attention to the development of the construction industry. However, the increase of population and the large-scale development of urban construction area make the urban land area increasingly tense. Faced with such a severe situation, China can only start from the technical aspect and strive to meet the largest building demand with the minimum land occupation cost.

Therefore, the research and development of cast-in-place pile technology has greatly made up for the requirements of the original building foundation bearing capacity, and has been widely and effectively applied in high-rise buildings, effectively solving this problem. With the continuous accumulation of construction experience, the technology has been further improved and perfected, which makes the post-grouting technology of punching cast-in-place pile more and more mature and widely used in the construction industry. Great economic and social benefits have been produced in the pile foundation construction of urban high-rise buildings and even super-high-rise buildings, and great contributions have been made to urbanization.

1 development background of high-rise building industry

With the continuous improvement of urbanization, population growth is increasing, per capita area is decreasing, and the demand for land use is getting higher and higher. The development of high-rise buildings, even super-high-rise buildings, and the transformation of old cities are all products of this economic background, but the original production technical conditions can not meet the requirements of high-quality buildings. A series of problems such as limited bearing capacity of foundation, serious noise pollution and high engineering cost all challenge the development status of high-rise buildings.

Facing the severe development situation, the construction industry must strengthen technical research and develop advanced technological achievements. As a technical achievement in this situation, the post-grouting technology of bored pile has a remarkable effect on improving the bearing capacity of pile foundation, and it is found that the shorter the pile length, the greater the increase, which will reduce the noise pollution caused to residents in the construction process, save the material cost, reduce the project cost, effectively alleviate various technical difficulties in the construction process, to a certain extent, not only improve the overall project quality control, but also provide a huge development prospect for the construction industry.

2. Analyze the principle, characteristics and advantages of post-grouting technology for punching cast-in-place piles.

2. 1 principle overview

Post-grouting technology of punching cast-in-place pile is an important part of construction industry. Generally speaking, with the aid of grouting pump, the cement with standard mixture ratio is poured into the inner conduit in the pile body, and then the cement is input into the surrounding medium on the basis of increasing the pressure. It can be divided into three types: end grouting, grouting around piles and combined grouting. Post-grouting technology of punching cast-in-place pile is to combine cement slurry with sediment, so that the formed cement solidified body can alleviate the different situations caused by sediment to some extent. This is beneficial to improve the bearing capacity and range of foundation piles, thus improving the compressive performance of pile foundations and greatly ensuring the high-quality completion of construction projects.

2.2 Process characteristics

First, in the process of high-rise building construction, the post-grouting technology of punching cast-in-place pile can reduce the construction noise and vibration. In contrast, it is beneficial to the production and life around the building and greatly reduces the scope of influence. Secondly, the post-grouting technology of punching cast-in-place pile is constantly innovated in practice, and the technical level is becoming more and more mature, which can speed up the completion of the project, be safe and reliable, and strictly control the engineering quality standards.

Thirdly, the post-grouting technology of punching cast-in-place pile has the characteristics of good reliability, simple operation and low additional cost. It is generally suitable for high-rise buildings and super-high-rise buildings, and can even be applied to the foundation construction of pile foundation in earthquake-prone areas, which can effectively fix the soil of pile foundation and improve the compressive performance and stability of pile foundation. Fourthly, the post-grouting technology of punching cast-in-place pile is flexible, widely used and requires high material quality. In high-rise buildings, the quality is difficult to control, and the construction quality has a great influence on the bearing capacity of pile foundation, which is easy to cause engineering failure.

2.3 Advantages of post-grouting technology for punching cast-in-place piles in high-rise buildings compared with traditional technology

In recent years, the post-grouting technology of punching cast-in-place pile has been widely used in high-rise buildings. Post-grouting technology has solved the weakness of insufficient bearing capacity caused by sediment at the bottom of punching cast-in-place pile and mud skin on the pile body due to hole-forming process defects, and strengthening pile foundation treatment has become an urgent problem for high-rise buildings. The traditional punching cast-in-place pile technology has two shortcomings: thick mud skin and more sediment. When the drilling range is less than 800 mm, the construction effect of punching pipe pile technology is better, but when the drilling range is larger, the mud circulation speed decreases, which leads to the weakening of slag discharge ability, the phenomenon of thick mud skin on the hole wall is serious, and even there is a high risk of instability and collapse.

From this point of view, the traditional punching cast-in-place pile technology can not completely solve the problems existing in these high-rise building projects. On this basis, through technical reform and innovation, a more perfect post-grouting technology is developed, which makes up for the shortcomings of traditional technology. Post-grouting technology of punching cast-in-place pile in high-rise building can be divided into three parts: post-grouting at pile end, post-grouting at pile side and post-grouting at pile end and pile side. During the project implementation, the grouting pipe shall be installed 200-500mm outside the reinforcing cage, and the grouting pipe shall be blocked 7-8 hours after the pile is completed. The interval of initial grouting should be controlled at 30-60 minutes, and the time for personal leave should not exceed 2 hours. Grouting should be carried out in stages, and the total grouting amount can reach 75% of the design value. In this way, mud with proper concentration can be injected to improve the sediment at the bottom of the pile and the mud skin of the pile body through physical and chemical action, so that its mechanical properties can be greatly improved. To some extent, the stability of pile foundation is strengthened and the bearing capacity of pile foundation is improved.

3 common problems and countermeasures of post-grouting technology of punching cast-in-place pile in high-rise building application

3. Common problems in the application of1in high-rise buildings

In the construction of high-rise buildings, the violent impact caused by post-grouting of punched cast-in-place piles can easily affect the foundation layer and reduce the bearing capacity of the foundation. Although the hole wall is protected from collapse, it has a negative impact on the horizontal movement of the pile foundation and the frictional resistance of the pile body, and it is easy to cause slurry leakage along the pile body or slurry plugging caused by technical reasons such as uneven concrete mix ratio.

3.2 Take effective measures to solve the problem.

In the process of construction, if there is slurry leakage and blockage, grouting can be reduced or terminated, or the grouting pipe can be washed with clean water and then grouted again. Grouting blockage can be solved by vibration dredging and adjusting the catheter. And through the establishment of effective management system, clear reward and punishment system, pre-construction training, strengthen construction management, improve the quality of construction projects. Pay more attention to construction technology;

(1) Adopt appropriate tool materials, such as preparing a grouting pipe with a diameter of 25.4m, accurately measure the aperture of 5mm, and ensure that there are no holes at the bottom of 25cm and the head of 50cm, so as to ensure the grouting quality is up to standard;

(2) During the punching construction of punching cast-in-place pile, pay attention to the secondary hole cleaning to reduce the occurrence of sediment, which is beneficial to the acceptance quality of the sediment thickness of pile foundation in high-rise buildings and meets the standards that the end bearing pile is less than 50 mm and the friction pile is less than 150 mm;

(3) In order to reduce the pressure loss caused by grouting distance in construction, the grouting pressure can be controlled within a reasonable range by using the pressure gauge at the pile hole;

(4) In the later stage of grouting, in order to ensure that the grouting quantity of each pile meets the design requirements, the water cement ratio should be strictly controlled according to the design requirements during grouting, and grouting should be carried out in turn. After the grouting pressure meets the design requirements, keep the pressure for 3-5 minutes to complete the grouting. Vigorously develop science and technology, cultivate outstanding talents in the construction industry, develop innovative post-grouting technology for punching cast-in-place piles, or introduce advanced foreign production technology to improve the quality of the project, so as to obtain economic benefits on the basis of establishing a sense of social responsibility.

It has a far-reaching impact on the development of high-rise building industry in the future.

In the process of socialist modernization in China, the degree of urbanization is getting higher and higher, and the development of high-rise buildings plays a great role in improving the land utilization rate in China. At the same time, high-rise buildings and even super-high-rise buildings, as well as the transformation of old urban areas, have increasingly strict requirements on the technical conditions of urban buildings. On the basis of meeting its requirements, the post-grouting technology of punching cast-in-place pile needs continuous development and innovation to better serve the development of construction industry.

Post-grouting technology of punching cast-in-place pile is a brilliant achievement of technological innovation in high-rise building industry. Fundamentally solved the problems faced by high-rise building projects. By strengthening the bearing capacity of pile foundation, expanding the bearing area of pile foundation, reducing the sinking of pile foundation and improving the quality of foundation, it is beneficial to meet the requirements of engineering quality. At the same time, the technical advantages are used to reduce the waste of materials, save the production cost, control the project cost within a reasonable range, and create greater economic benefits for the project. On the other hand, the improvement of engineering quality promotes the quality of finished products of high-rise buildings, ensures the safety of people's lives and property, and promotes social harmony and stability, which has great social benefits. More importantly, the development of post-grouting technology of punching cast-in-place pile provides a broad development prospect for high-rise building industry and even the national construction industry, which is of great significance.

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