Introduction

 

China's social and economic level and science and technology are in a stage of continuous development, and the construction industry is likewise developing continuously. However, because China's construction industry started relatively late, the requirements for project quality have always been very high, and as an important part of industrial and civil building projects, the quality of pile foundation works is held to even stricter standards, so building high-quality pile foundation works is crucial. Only by strictly controlling the quality of pile foundation construction technology and construction schemes can we build high-quality construction projects and enable China to rank among the forefront of the world's construction industry.

 

I. Classification of Pile Foundation Construction Technologies

 

1. Grouting construction technology

 

Grouting reinforcement technology mainly refers to using a drilling rig to drill holes in the foundation at pre-selected drilling positions, with the drilling depth required to reach into the reinforced soil layer; in addition, the interior of the holes must be cleaned. After the above work is completed accurately, a sufficient amount of prepared cement chemical grout is injected into the soil layer using high-pressure grouting equipment. Under the splitting and squeezing action of the high-pressure grouting equipment, the grout and the soil layer quickly bond together, greatly improving the structure and performance of the entire pile foundation soil layer, enhancing the strength of the entire pile foundation soil layer, and making the soil layer strength meet the requirements of industrial and civil building projects.

 

2. Cast-in-place pile construction technology

 

Cast-in-place pile construction technology mainly includes two aspects: first, construction using bored cast-in-place piles. Before construction, holes must first be drilled in the foundation at pre-selected drilling positions, and the mud therein must be cleaned up. The mud is mainly discharged into a mud pit, and the specific gravity of the mud must meet the needs of pile foundation construction. Once residue is found inside the hole, it must be dealt with promptly. Only when the above work has been carried out accurately can concrete pouring proceed. Second, construction using excavated piles. There are two construction methods for this type of pile: manual excavation and mechanical excavation. When manual excavation reaches a depth of about one meter, concrete wall protection must be poured; then, when the hole depth meets the construction requirements, the hole is enlarged; finally, construction personnel must install reinforcing steel inside the protective wall and pour concrete.

 

3. Static pressure pile construction technology

 

Static pressure piling mainly uses the load-bearing capacity of the building's load-bearing columns to press precast piles into the soil layer. This method is more environmentally friendly than other pile foundation construction technologies, effectively improving the surrounding environment of the building and also effectively preventing noise pollution. In practice, static pressure pile construction technology generally requires segmental prefabrication, pressing in, and section-by-section splicing. However, this pile foundation construction technology has significant limitations; it is usually only suitable for soft soil environments, and other special environments require investigation.

 

II. Application of Pile Foundation Construction Technology in Industrial and Civil Buildings

 

1. Preparations for pile foundation technology construction

 

First, the hydrological conditions and environmental conditions of the construction site must be investigated. Environmental investigation mainly involves analyzing the topography and geology, soil hardness and properties, and climatic conditions of the project location; hydrological investigation mainly involves measuring the lowest groundwater level and comprehensively analyzing the investigation results to predict the possibility and frequency of natural disasters in the area. In addition, the lighting conditions, heights, and underground pipelines of surrounding buildings must also be investigated to avoid damage to underground pipe piles. Second, preparations for construction equipment must be made. A detailed construction plan should be formulated, including equipment use plans and supporting equipment. The functions of mechanical equipment should be fully utilized, with attention to equipment characteristics and scope of use, so that equipment is used properly and at the right time to maximize efficiency. Third, preparations for construction technology must be made. A complete construction plan should be formulated, protective measures for underground pipelines should be taken, and specific parameters in construction should be determined.

 

2. Setting-out and positioning and construction site cleanup

 

Setting-out and positioning means fixing all pipe piles so that they do not deviate from their alignment. This project used the grid reset method, arranging lines into square grids to adjust the positions of the pipe piles. Because the heights of the pipe piles are not completely uniform, benchmarks must be set to determine the range and positions of the pipe piles. Cleaning the construction site requires a thorough cleanup before the pipe piles are fixed, keeping construction site supplies neatly arranged and removing irrelevant items. This project adopted the cast-in-place pile construction method, and the focus of cleanup was the pile holes; both the interior and surroundings of the pile holes had to be cleaned thoroughly.

 

3. Civil engineering pile foundation construction

 

3.1 Precast piles. Precast piles refer to pipe piles of different forms and materials made at the construction site, which are pressed, vibrated, or driven into the soil layer using deep pile sinking. Precast piles are usually of two types: steel piles and concrete piles. Concrete piles can bear relatively large building loads and have the characteristics of rapid construction and durability, so they are widely used, but they have a relatively large impact on the surrounding environment. When making precast piles, the pile tip orientation must be clarified according to the piling sequence, and pouring proceeds from the pile top to the pile tip. Commonly used precast pile construction methods include hammer-driven pile sinking, static pressure pile sinking, vibratory pile sinking, and water-jet pile sinking. Among these, water-jet pile sinking is used more often in sandy soil layers. During pile sinking construction, soil squeezing may occur and damage the soil layer, so the spacing and number of pile foundations within the civil construction scope must be scientifically planned. At the same time, attention should be paid to continuity of operation to ensure that the pipe piles are solid.

 

3.2 Cast-in-place piles

 

During cast-in-place pile construction, the construction method should be selected according to the hole-forming method of the pile foundation technology, mainly including dry-operation hole forming, impact hole forming, driven-casing hole forming, and mud-wall-protected hole forming. Among these, impact hole forming is used more often in soft soil layers, and mud-wall-protected hole forming is used more often in muddy soil layers. When making cast-in-place piles, the strength of the pile body must be considered, as this affects the service life of the pile. At the same time, attention should be paid to the quality of the concrete to prevent the pile casing from being buried or blocked. In addition, attention should also be paid to the depth to which the pile body sinks into the soil layer, so as not to affect the bearing capacity of the pile.

 

III. Control of Key Technical Points in Pile Foundation Construction in Industrial and Civil Buildings

 

1. Control of key technical points in the construction preparation stage

 

To ensure the quality of pile foundation construction in modern industrial and civil building projects, work in the construction preparation stage must first be done well. The professional level and overall quality of construction workers have an important impact on project quality. Before construction, technical briefings and safety education should be provided to operators, requiring them to strictly follow technical specifications during construction to ensure the quality of pile foundation construction. In pile foundation construction, large-scale mechanical operations are widely used, which can effectively shorten the construction period, reduce labor intensity, and improve work efficiency. Before using mechanical equipment, a comprehensive inspection and timely maintenance and repair must be carried out, and preparations before mechanical operations must be properly made. The construction site must be leveled and compacted in advance to prevent accidents such as mechanical equipment tipping during construction. Before construction, for mechanical equipment and other processes requiring electricity during operations, good insulation protection measures for electrical lines must be ensured; for the metal parts of electrical equipment, grounding protection measures must be taken to prevent electric leakage during use from causing safety accidents and affecting project progress and construction quality.

 

2. Control of key technical points during pile foundation construction

 

During pile foundation construction, the travel paths of piling machinery must be level and solid to ensure equipment safety. When lifting piles into position, the lifting speed should be slow and uniform, and the tail rope should be held to prevent the pile head from striking the pile frame, ensuring the safety of the pile body. In pile foundation construction, piling and fixed-hammer pile lifting are key points of construction technology control. During piling, the technical essentials of heavy hammer and low blow and low lift and heavy driving should be followed. When the pile begins to be driven into the ground, the drop distance of the pile hammer should be low, generally 50–80 cm, so that the pile can sink normally into the foundation. When the pile has sunk to a certain depth in the foundation, and on the premise that the pile tip does not deviate, the drop distance of the pile hammer may be appropriately increased to continue hammering. When the pile tip encounters a boulder or passes through a hard interlayer, to prevent the pile tip from cracking, the drop distance of the pile hammer must not exceed 80 cm. In addition, when using excavated cast-in-place piles, during drilling operations between 4 and 10 m, the pile hole diameter shrinkage is serious, and the pile hole is prone to collapse during pile formation.

 

Engineering and technical personnel have found through long-term construction that, in addition to controlling the drilling speed and the lifting speed of the rotary bucket as key technical points, the proportioning of static mud and the structure of the drilling tools are also important technical points. During drilling rig construction, mud can prevent hole wall collapse, effectively suppress groundwater and suspended drill cuttings, and form a thin mud cake on the hole wall that acts as wall protection, preventing water from seeping from inside to outside or from outside to inside. Therefore, the proportioning of mud is very important. Controlling the specific gravity of the mud, improving the quality of the mud powder, and adding treatment agents to increase the viscosity, lubricity, and cohesion of the mud can provide good protection for the hole wall. After the pile hole is formed, indicators such as the embedded depth of the pile hole, the strength of the foundation rock layer, the thickness of sediment, and the verticality of the pile hole should be checked, and all data should meet the design requirements.

 

Conclusion

 

Pile foundation works are an important part of industrial and civil buildings, and pile foundation construction technology is an important foundation for the entire industrial and civil building project. To better apply pile foundation construction technology, further discussion of pile foundation construction technology in industrial and civil buildings is still needed. Therefore, only by ensuring the stability and high quality of pile foundation works can the overall quality of industrial and civil building projects be guaranteed, while also achieving better social and economic benefits and eliminating some later hidden dangers and repair problems.