1. 1 research background and motivation

With the continuous development of China's economy and urbanization, bridge engineering is not only a simple means of transportation, but also an important symbol to measure a country's modernization and technical strength. Every towering bridge carries people's yearning for a better life and the pursuit of scientific and technological progress. However, in order to build a beautiful, safe, economical and durable bridge, the stability of pile foundation is an essential link.

As the key to ensure the stability of bridges, pile foundation reinforcement technology has been developed for hundreds of years. However, under the changeable geographical environment and climatic conditions in China, the traditional pile foundation technology faces many challenges. For example, how to ensure the stability of pile foundation under complex geological conditions such as soft soil, swamp and rock fault zone; How to design a pile foundation that can resist earthquake impact in earthquake-prone areas; How to ensure the durability of pile foundation in saline-alkali soil and corrosive environment is an urgent problem for engineers at present.

Therefore, both academic circles and engineering practice circles have invested huge R&D efforts to explore new materials, new technologies and new methods. Innovative methods such as high performance concrete, carbon fiber composite materials and prestress technology are gradually introduced into the design and construction of pile foundation to better adapt to various complex engineering conditions and meet increasingly strict design requirements.

With the development of digital and information technology, how to monitor and diagnose the health of pile foundation in real time by using advanced technologies such as big data, Internet of Things and artificial intelligence has become a new direction of pile foundation research. This can not only improve the safety of pile foundation, but also provide strong technical support for the maintenance and management of pile foundation, thus prolonging its service life and reducing maintenance costs.

To sum up, the research and application of pile foundation reinforcement technology in China is at a historic turning point. At the intersection of traditional technology and new technology, practical experience and innovative thinking, the future of pile foundation reinforcement technology is full of infinite possibilities and opportunities.

1.2 research purpose and problem statement

The purpose of this study is to explore the new progress of pile foundation reinforcement technology in bridge engineering construction, especially the performance and application of high performance concrete piles and carbon fiber composite piles. This study will try to answer the following questions:

What are the advantages of high performance concrete pile and carbon fiber composite pile compared with traditional pile foundation?

How to design and construct these new pile foundations correctly to ensure their performance and stability?

How to choose and apply suitable pile foundation reinforcement technology under complex geological conditions?

Overview of research methods and structure of 1.3

In this study, the methods of literature review, experimental analysis and case study are used to discuss the above problems. First of all, through literature review, understand the development history and present situation of pile foundation reinforcement technology, especially the research progress of new material piles. Then, the performance of piles made of different materials is analyzed and compared through experiments to verify its superiority and application prospect. Finally, the application and effect of pile foundation reinforcement technology in practical engineering are deeply discussed through cases.

The structure of this paper is as follows: The second chapter is literature review, the third chapter introduces the pile foundation reinforcement technology in bridge engineering in detail, the fourth chapter discusses the design and analysis of pile foundation reinforcement technology, the fifth chapter shows the case analysis of pile foundation reinforcement engineering, the sixth chapter summarizes the innovation and practical value of the research, and finally the conclusion and reference.

2 Literature review

2. 1 related theories and concepts

As a deep foundation technology, pile foundation is a traditional and commonly used foundation form in civil engineering. Its goal is to transfer the load of the superstructure to the soil layer or rock stratum with deep underground and good bearing capacity. The working mechanism of pile foundation can be divided into friction pile and end-bearing pile. The former mainly relies on the friction between pile and soil to provide bearing capacity, while the latter mainly relies on the contact between pile tip and hard soil or rock stratum to provide bearing capacity.

In recent years, with the progress of science and technology and the change of engineering requirements, new pile foundation materials and construction technologies are constantly emerging. Through special material selection and mix design, high performance concrete piles have higher strength and better durability. At the same time, carbon fiber composite pile has been paid more and more attention by civil engineering because of its advantages such as portability, high strength and excellent corrosion resistance.

Pile foundation reinforcement technology is a technical means for existing buildings or foundation soil when there is insufficient settlement, displacement or stability. It usually includes piling under or around the original foundation to increase its bearing capacity and stability. This technology is especially critical in complex geological conditions, earthquake-prone areas or important projects.

In the design of pile foundation, the characteristics of foundation soil, load type, pile material and construction technology should be fully considered to ensure the safety, stability and economy of pile foundation. In addition, with the enhancement of environmental awareness, the environmental friendliness and sustainability of pile foundation have been paid more and more attention.

In a word, pile foundation reinforcement technology plays an irreplaceable role in civil engineering, and the emergence of new materials and technologies provides more possibilities and application prospects for it.

2.2 Research status at home and abroad

As the core technology in civil engineering, pile foundation reinforcement technology has experienced decades of development. Since 1970s and 1980s, the United States, Britain, Canada and other western countries began to systematically study this technology. At first, the research focused on traditional concrete piles and steel piles, and discussed their design principles, construction strategies and performance. With the rapid development of materials science, new materials such as high performance concrete and carbon fiber composite materials have gradually attracted researchers' interest. These materials not only significantly improve the overall performance of the pile, especially the compressive strength, tensile strength and durability, but also show excellent adaptability under complex geological conditions such as earthquakes and soft soil.

With the rapid development of infrastructure construction, China began to explore pile foundation technology extensively in the 1990s. Domestic scholars have conducted in-depth research on concrete piles and steel piles, covering design, construction and performance analysis. In recent years, with the introduction of new material technology and domestic research and development, domestic researchers have also begun to explore the application of high-performance concrete piles and carbon fiber composite piles. These studies not only focus on the performance and characteristics of new materials, but also further investigate their implementation effects and economic benefits in practical engineering projects. In view of China's vast territory and diverse geological conditions, scholars have also made special research on the application of pile foundation in various special geographical environments, such as soft soil areas, rock formations and earthquake-prone areas.

Generally speaking, pile foundation reinforcement technology has shown its unique activity and great development prospect in both international and domestic fields. With the emergence of new materials and technologies, the research in this field will continue to deepen, providing more solid and advanced technical support for modern civil engineering.

2.3 literature blank and research significance

Although the pile foundation reinforcement technology has been widely studied, there are still some literature gaps and areas that have not been fully explored. First of all, most of the existing research focuses on traditional concrete piles and steel piles, while the research on new material piles, such as high-performance concrete piles and carbon fiber composite piles, is relatively rare. Secondly, although the application of pile foundation under complex geological conditions has been studied to some extent, how to optimize the design and construction of pile foundation with new materials and technologies is still a problem to be solved. In addition, the research on the long-term performance and durability of pile foundation reinforcement technology, especially in extreme environmental conditions, such as saline-alkali soil, high temperature and freeze-thaw cycle, is not sufficient.

These blank documents provide important research significance for this study. The purpose of this study is to provide a more reliable, economical and lasting pile foundation solution for bridge engineering through in-depth discussion on the performance and application of new material piles and the optimal design and construction of pile foundation under complex geological conditions. In addition, this study also expects to provide theoretical support and practical guidance for the development and innovation of pile foundation technology, so as to promote the technical progress and improve the engineering quality in the field of civil engineering.

3. Pile foundation reinforcement technology in bridge engineering

3. 1 Basic principles of pile foundation reinforcement

Pile foundation reinforcement technology is a method to improve the bearing capacity and stability of foundation by inserting piles into soil. The basic principles of this technology include the following:

Load transfer: The main function of pile foundation is to transfer the load of superstructure to deeper and stronger soil or rock. In this way, even if the bearing capacity of the surface soil is low or unstable, the bridge or building can be stably supported.

Friction and end bearing: There are two main bearing mechanisms of piles in soil: friction and end bearing. Friction mechanism refers to the friction between the pile and the surrounding soil supporting the pile. The end-bearing mechanism refers to the direct contact between the pile bottom and hard soil or rock, so that the load can be effectively transmitted.

Improving soil quality: In the process of pile foundation construction, the vibration of construction machinery and the insertion of pile body can improve the surrounding soil to a certain extent, increase its compactness, and thus improve the bearing capacity of soil.

Limit the settlement of foundation: In some cases, the introduction of pile foundation can effectively limit the uneven settlement of foundation. When the pile foundation is evenly distributed and reasonably designed, the load can be evenly shared, thus reducing the risk of uneven settlement.

Provide lateral stability: When bearing lateral load or earthquake, the pile foundation can provide additional lateral resistance and enhance the stability of the structure.

Generally speaking, pile foundation reinforcement technology provides an effective method to improve the bearing capacity and stability of foundation, especially in areas with complex geological conditions or poor soil quality.

3.2 Traditional pile foundation reinforcement technology

3.2. 1 Design and construction of concrete piles

Concrete pile is a common pile type in pile foundation reinforcement, mainly made of concrete, with good compressive performance and long service life. The design of concrete piles first needs to determine the diameter, length and spacing of piles, usually according to the bearing capacity of soil, the load of superstructure and other related factors. The cross-sectional shape of the pile can be round, square or other shapes, and the specific choice depends on the construction conditions and design requirements. The concrete mixture ratio and strength of concrete piles should also be selected according to the engineering needs.

In terms of construction, concrete piles can be prefabricated or cast on site. Precast concrete piles are prefabricated in the factory, then transported to the site and driven underground with a pile driver. On-site pouring of concrete piles is carried out directly on site. First, drill a soil sample on the ground with a drill bit, and then pour concrete into the borehole. No matter which method is adopted, it is necessary to ensure the verticality of the pile, the pouring quality of concrete and other related parameters in the construction process.

The connection of concrete piles is also an important link in design and construction. When the length of piles exceeds the limit of prefabrication or transportation, connectors or other methods must be used for connection. In addition, the pile top usually needs to be connected with the superstructure to ensure the effective transmission of load.

In a word, the design and construction of concrete piles is a multi-step and multi-technology process, which needs reasonable selection and optimization according to specific engineering conditions and requirements.

3.2.2 Design and construction of steel piles

Steel pile is made of high-strength steel, which has excellent bearing capacity, construction efficiency and adaptability, and has become one of the first choices for pile foundation engineering. When designing steel piles, important factors include their cross-sectional shape, size, length and material selection, among which H-shaped, U-shaped and tubular cross-sections are the most common. Correct selection of section and size is the basis to ensure its optimal bearing capacity and economy. In addition, the length selection of steel piles is usually closely related to the characteristics of underground soil, the depth of bearing layer and the design load of the project.

In the construction stage, steel piles are usually installed with the help of pile drivers or vibrating hammers. Because of its inherent high strength and rigidity, steel piles can easily penetrate hard soil or other underground obstacles. In the installation process, it is very important to ensure the verticality and accurate position of the pile, which needs real-time monitoring and adjustment. For pile connection, welding and bolt connection are two mainstream methods, and which one to choose depends on the specific type of pile and engineering requirements. Considering that steel is easy to be corroded, anti-corrosion coating or other protective measures are usually applied to the surface of steel piles.

Steel piles are favored not only because of their fast construction speed and strong adaptability, especially when they encounter hard soil or urgent construction period, but also because of the instability of steel prices and its potential corrosion risk, and their long-term maintenance costs and economic benefits should also be deeply considered. To sum up, the design and construction of steel piles should be carried out on the basis of fully weighing the engineering requirements, geological conditions and economic considerations.

3.3 New pile foundation materials and technologies

3.3. 1 high performance concrete pile

High-performance concrete piles with high-performance concrete as the core material have brought a technological innovation to the field of pile foundation engineering. High-performance concrete not only has high strength that traditional concrete does not have, but also its compactness of microstructure endows it with extraordinary durability and impermeability. This characteristic mainly benefits from special cement, preferred coarse and fine aggregates, mineral admixtures such as silica fume and fly ash, and chemical admixtures such as superplasticizer and air entraining agent.

In the design of pile foundation, high-performance concrete pile has the characteristics of high strength and good durability, which gives engineers greater flexibility in design. For example, it can be designed as a thin pile, but it can still bear a large load, which not only reduces the use of materials, but also facilitates the construction in a narrow construction space. Its excellent durability also means that high-performance concrete piles can show long-term stability in harsh environments, such as salt spray erosion and acid-base geological conditions.

In the construction process, although the construction technology of high-performance concrete piles is similar to that of traditional piles, due to the particularity of HPC, the construction team needs more accurate operation control to ensure that every step is accurate, and its characteristics need to be fully exerted from concrete mixing, transportation to pouring. This also means that builders need to receive stricter training and supervision.

To sum up, as a cutting-edge pile foundation technology, high-performance concrete piles not only provide solid support for important structures such as bridges and buildings, but also bring technical and economic advantages to the field of civil engineering. With the continuous progress of technology and increasing attention to environmental and economic benefits, it is expected that high-performance concrete piles will be more widely used and developed in the future.

Carbon fiber composite pile

The appearance of carbon fiber composite pile is a great innovation to traditional pile foundation materials. In many complicated geological conditions and harsh environments, CFRP piles show superior performance that other materials can't match. For example, in areas with frequent earthquakes, the high strength and stiffness of CFRP piles can provide better support for the superstructure and reduce the damage caused by earthquakes; In coastal and saline-alkali areas, its excellent corrosion resistance ensures the long-term stability of pile foundation.

CFRP piles also have good fatigue resistance. Traditional steel bars and concrete are prone to fatigue cracks under long-term load cycle, but CFRP still maintains good performance under repeated loads because of the uniform distribution of fibers and the bonding effect of resin. This characteristic is especially suitable for high-speed railways, long-span bridges and other projects, which can greatly reduce the maintenance cost and prolong the project life.

CFRP piles also have good environmental protection performance in the construction process. Compared with traditional concrete and steel, the production and construction of CFRP have a lower carbon footprint, which is more in line with the current concept of green building and sustainable development. In addition, CFRP materials can be recycled to further reduce the impact on the environment.

However, although CFRP piles have many advantages, they still face some challenges in practical application. Firstly, the manufacturing cost of CFRP piles is relatively high, which limits its application in large-scale projects to some extent. Secondly, because CFRP pile is a relatively new material, many designers and construction units are not familiar with it and need further training and promotion. In addition, although CFRP piles have good corrosion resistance and fatigue resistance, their long-term performance under extreme temperature, humidity and load conditions still needs further study and verification.

In order to popularize the application of CFRP piles, researchers and engineers are trying to solve the above problems. For example, by improving the production process and material formula, the manufacturing cost of CFRP can be reduced; Carry out a large number of tests and practical engineering applications, accumulate experience, and formulate relevant design and construction specifications; At the same time, it is also strengthening international exchanges and cooperation, absorbing advanced technology and experience, and promoting the rapid development of CFRP pile technology.

In a word, as a new pile foundation material, carbon fiber composite pile has great development potential and application prospect. With the progress of technology and market recognition, it is believed that CFRP piles will be widely used in more projects in the near future.

3.4 Pile foundation reinforcement technology under complex geological conditions

Complex geological conditions such as soft soil, staggered rocks, seismically active areas and groundwater-rich areas put forward higher requirements for pile foundation reinforcement technology. Under this condition, the pile foundation should not only bear the load of the superstructure, but also deal with complex external influences such as soil instability and ground movement.

Soft soil area: The low bearing capacity and high compressibility of soft soil make the design and construction of pile foundation in this kind of area more complicated. Usually, the pile foundation needs to reach a deeper bearing layer, such as hard clay layer or rock layer, in order to ensure stability. In addition, the consolidation and compression of soil and possible lateral displacement should be considered during pile foundation construction.

Rock staggered area: In the rock staggered area, the pile foundation may need to pass through multiple layers of rocks and soil layers, which poses a challenge to the design and construction of pile foundation. Usually, this requires the use of special drilling rigs and piling methods to ensure that the pile foundation can penetrate the rock stratum smoothly and reach the required depth.

Seismic activity area: In the seismic activity area, the pile foundation should not only bear the static load, but also deal with the dynamic load caused by the earthquake. This requires the pile foundation to have good seismic performance, such as sufficient strength, stiffness and toughness. In addition, the arrangement and connection of pile foundation also need special design to ensure the stability of the whole structure.

Groundwater-rich areas: In groundwater-rich areas, pile foundation construction may encounter groundwater erosion and erosion. This not only increases the difficulty of construction, but also may affect the stability and durability of pile foundation. Therefore, measures should be taken in pile foundation construction, such as setting enclosure, underwater construction or pumping method, to ensure construction safety and quality.

In a word, pile foundation reinforcement technology under complex geological conditions is a highly specialized field, which needs to comprehensively consider geological, engineering and construction factors to ensure the performance and stability of pile foundation.

Design and analysis of pile foundation reinforcement technology

4. 1 Design principles and methods of pile foundation reinforcement

The design principle and method of pile foundation reinforcement is to ensure the solid foundation of bridge and other structural projects to meet various engineering needs. In the design of pile foundation, we should not only consider the bearing capacity of soil, the load of superstructure and geological conditions, but also carefully evaluate the influence of external factors such as groundwater level, seasonal variation and earthquake. All these may affect the stability of pile foundation, so they should be fully considered in the design.

The material selection of pile foundation is also an important aspect in design. Different materials, such as concrete, steel or composite materials, have their unique performance characteristics and application scenarios. Choosing suitable materials can ensure the best performance of pile foundation under specific engineering conditions. In addition, the construction methods of pile foundation, such as piling, rotary excavation or static pressure, also need to be selected according to the design requirements and site conditions.

In the process of pile foundation design, it is also necessary to pay attention to the coordination with other engineering elements, such as pier, foundation slab and underground structure. The interaction between these elements and pile foundation may affect the overall stability and bearing capacity. Therefore, the design of pile foundation is not only a single engineering problem, but also needs to comprehensively consider various factors to ensure the safety and stability of the whole project.

With the development of science and technology, modern pile foundation design is no longer limited to traditional methods and concepts. New design ideas, materials and construction techniques are constantly emerging, which brings more possibilities for the design and construction of pile foundation. Such as prestress technology, monitoring technology and intelligent materials, all provide new ideas and methods for the design of pile foundation.

To sum up, the design principle and method of pile foundation reinforcement is a complex and diverse system engineering, which needs to combine all kinds of knowledge and experience to ensure the expected performance under various engineering conditions. With the continuous progress of technology and materials, we have reason to believe that the future of pile foundation design will be broader and more colorful.

4.2 Calculation and analysis of bearing capacity of pile foundation

As a core concept in civil engineering, the calculation and analysis of pile foundation bearing capacity involves many factors, which interact to form a complex system. In order to ensure the safety and economy of pile foundation, engineers must conduct comprehensive and in-depth research when calculating and analyzing the bearing capacity of pile foundation.

Firstly, soil condition is the main factor affecting the bearing capacity of pile foundation. Different types of soils have different frictional resistance, compressibility and cohesion. For example, clay has greater friction than sand, but it is also more compressible. Therefore, when calculating the bearing capacity of pile foundation, it is necessary to investigate and classify the soil in detail, determine its engineering properties, and choose the appropriate calculation method according to these properties.

The material and size of the pile also have an important influence on the bearing capacity. For example, due to different materials, concrete piles and steel piles have different compressive, flexural and torsional capacities. The diameter, length and shape of pile will also affect its contact area and distribution with soil, thus affecting its bearing capacity.

In addition, the installation methods of piles, such as piling, bored grouting or rotary excavation grouting, will affect the contact state and friction between piles and soil. For example, piling will squeeze the soil and increase its density, thus improving the friction of the pile; However, drilling and grouting may loosen the soil around the pile hole and reduce its friction.

When bearing load, pile foundation not only bears vertical load, but also horizontal load, torque and eccentric load. These loads will lead to bending, torsion and lateral displacement of the pile, thus affecting its bearing capacity. Therefore, these complex stress conditions must be considered when analyzing the bearing capacity of pile foundation.

The influence of long-term load, cyclic load and earthquake load on pile foundation can not be ignored. These working conditions may lead to changes in soil properties, or cause fatigue, creep and fracture of piles, thus reducing their bearing capacity.

To sum up, the calculation and analysis of pile foundation bearing capacity is a highly complicated work, which needs to be studied in detail by using advanced theories and methods in combination with the actual engineering situation. Only in this way can we ensure that the bearing capacity of pile foundation not only meets the design requirements, but also has enough safety reserves to provide reliable guarantee for the long-term stability and safety of the project.

4.3 Pile Foundation Reinforcement Construction Technology and Quality Control

The success of pile foundation reinforcement construction depends not only on the construction technology and quality control, but also on the management and coordination of the construction site. In the process of construction, in order to ensure safety and efficiency, every link needs careful organization and coordination. For example, drilling pile holes is very important for the prediction and treatment of unknown underground obstacles. In complex geological conditions, such as rock formation or hydrological changes, more accurate drilling technology and equipment may be needed.

At the same time, the environmental protection and governance of the construction site is also very critical. For example, preventing concrete overflow, mud leakage and noise control are all necessary measures to ensure the smooth construction. This is not only related to the construction quality, but also a responsible attitude towards the surrounding environment and community.

In addition, coordination with other projects is also an indispensable part of construction management. As a part of the whole project, the construction progress and quality of pile foundation reinforcement directly affect the superstructure and other related projects. Therefore, the formulation and adjustment of construction scheme, the supply of materials and equipment, the training and management of workers, etc. , all need careful planning and efficient implementation.

With the development of science and technology, the application of digital and intelligent technology in pile foundation construction is increasing. For example, GPS positioning, drone inspection, intelligent construction log system and so on. All these provide more possibilities for the accuracy and efficiency of construction. These technologies not only improve the construction efficiency, but also provide more means and tools for quality control.

To sum up, pile foundation reinforcement construction is not only a technical and quality control problem, but also a comprehensive system engineering. It involves many factors such as design, materials, construction, management, technology and so on, and needs all-round and multi-angle thinking and practice. Only in this way can we ensure the quality and effect of the pile foundation reinforcement project and lay a solid foundation for the success of the whole project.

5 case analysis of pile foundation reinforcement project

5. 1 typical bridge engineering pile foundation reinforcement case

Take Yangming Bridge as an example. This bridge is located in a complex geological area where earthquakes are active and rivers meet. During the construction of the original bridge pile foundation, it was found that there were unknown weak rock-soil staggered layers underground, which increased the difficulty of pile foundation reinforcement.

Project Description: Yangming Bridge is a cable-stayed bridge with a span of 800 meters and a main tower height of 150 meters. Connecting the two major transportation hubs in the city, it is estimated that the daily average flow will be 654.38+10,000 vehicles.

Problem: During the construction, it was found that there was a large area of soft soil and rock staggered in the pile foundation of the north tower of the bridge, which made the original design of the pile foundation unable to meet the bearing requirements.

Solution:

Construction of deep foundation pit: In order to ensure that the pile foundation can reach the hard rock stratum, the construction method of deep foundation pit is determined. First, block the working area with a retaining wall, and then excavate to a depth of 50 meters.

High-performance concrete piles: Considering the complexity of geological conditions and the importance of bridges, we decided to adopt high-performance concrete piles. This kind of pile has high strength and good durability, and can effectively bear the load of the superstructure.

Carbon fiber composite pile: in order to further improve the bearing capacity and seismic performance of pile foundation, it is decided to adopt carbon fiber composite pile in key parts.

Pile foundation connection: high-strength bolts and special connection design are adopted to ensure the effective connection between pile foundation and superstructure.

Results: After redesign and construction, the pile foundation of Yangming Bridge was successfully reinforced. Subsequent quality inspection and static load test show that the bearing capacity and stability of pile foundation meet the design requirements. Yangming Bridge was successfully opened to traffic within the planned time, becoming a new landmark and traffic artery of the city.

This case shows how to combine modern technology and experience to successfully complete the reinforcement of bridge pile foundation under complex geological conditions. It provides valuable experience and reference for similar projects.

5.2 Application cases of pile foundation reinforcement in geological disaster areas

"Xishi Mountain Road" is located in a mountainous city and passes through a landslide area with unstable geology. In recent years, cracks and local collapse have appeared many times in this section, posing a threat to public safety. In order to solve this problem, it is decided to use pile foundation reinforcement technology to reinforce the landslide area and restore the road.

Project Description: Shixishan Road is about 3km long and15m wide, which is the main road connecting the urban area and the mountainous area. The landslide is about 500 meters long, 50 meters wide and 20 meters deep.

Problem: Due to continuous rainfall and weak geological structure, the soil in the landslide area gradually loses stability, resulting in cracks and collapses on the pavement. In addition, the river below also poses a threat to the stability of the landslide area.

Solution: It is decided to adopt pile foundation reinforcement technology to reinforce the landslide area. First, a detailed geological survey is conducted to determine the scope and depth of the landslide. Then the concrete pile net is designed, and the piles are driven into the hard stratum to provide stable support. According to the shape and size of landslide, optimize the layout and depth of pile foundation. In order to improve the stability and bearing capacity of pile foundation, high performance concrete and carbon fiber composite reinforced cages are adopted. The upper part of the pile foundation is connected with the pavement to form an integral structure, which effectively disperses and transmits the load. In addition, in order to reduce the impact of rain, a drainage system was installed in the landslide area.

Results: The pile foundation reinforcement was successfully completed and Shixishan Road was restored. Follow-up monitoring data show that the stability of landslide area has been obviously improved, and cracks and collapse have been controlled. The traffic safety and function of roads have been restored, which has provided convenience for local residents and tourists. This case shows the successful application of pile foundation reinforcement technology in geological disaster areas and provides valuable experience for similar projects.

6 innovation and practical value of the paper

6. 1 Innovation and contribution of research

This study has made many innovations and contributions in the field of pile foundation reinforcement technology. Firstly, the application of high performance concrete pile and carbon fiber composite pile is deeply studied. The application of these two new pile materials in bridge engineering is relatively rare, and this study provides theoretical and practical basis for their application in complex geological conditions. Secondly, aiming at the pile foundation reinforcement technology under complex geological conditions, this study puts forward a complete set of design, construction and quality control schemes, which provides reliable technical guidance for engineering practice. In addition, the calculation and analysis method of pile foundation bearing capacity is optimized, and the accuracy and reliability of calculation are improved.

In practical engineering application, the research results have been verified and popularized. Such as Yangming Bridge, Shixishan Road and other typical projects, the pile foundation reinforcement scheme proposed in this study successfully solved the engineering problems under complex geological conditions, and provided a guarantee for the smooth completion and safe operation of the project.

Generally speaking, this study has put forward many innovations and contributions in the field of pile foundation reinforcement technology, and provided strong technical support for the design, construction and management of civil engineering such as bridges. At the same time, these research results also provide new ideas and directions for academic research and technological development in related fields.

6.2 Practical value and application prospect

The practical value of this study is obvious, which provides a complete, scientific and efficient technical scheme for pile foundation reinforcement of bridge engineering and other civil engineering. Under the background of vigorously promoting infrastructure construction in China, the application demand of pile foundation reinforcement technology is increasing day by day. The research results just meet this market demand and provide a solid technical guarantee for engineering construction. Especially in mountainous areas, river junctions, earthquake zones and other areas with complex geology and great engineering difficulties, the pile foundation reinforcement scheme in this study has obvious technical and economic advantages.

From the perspective of application, with the continuous development of new materials, new technologies and new equipment, pile foundation reinforcement technology will also usher in greater development space. The high-performance concrete piles and carbon fiber composite piles mentioned in this study are expected to be applied in more projects in the future, especially in large-scale projects such as long-span bridges and high-rise buildings. In addition, with the application of digital and intelligent technology, the design, construction and management of pile foundation reinforcement will be more accurate, efficient and intelligent, providing more powerful technical support for engineering construction.

In addition, the research results can also provide technical guidance and reference for related fields, such as foundation treatment, tunnel engineering and underground engineering. In the future, pile foundation reinforcement technology is expected to be combined with other technologies and methods, such as foundation reinforcement, soil nailing wall, anchor cable and so on. , form a more perfect and efficient basic engineering technology system.