What are the foundation treatment techniques in building infrastructure construction?

Recently, with the continuous acceleration of urban infrastructure construction, various infrastructure projects such as roads, bridges, municipal pipelines, and industrial plants have been steadily advancing. As the core bearing part of building infrastructure, the stability and bearing capacity of the foundation directly affect the construction quality, structural safety, and service life of the entire project. However, in the actual construction process, many project sites have problems such as insufficient foundation bearing capacity, excessive settlement, and uneven soil layers. If not treated scientifically, it can easily lead to safety hazards such as building cracking, deformation, and even collapse.
The foundation treatment in the construction of building infrastructure refers to the use of various technical means to improve the physical and mechanical properties of the foundation soil, enhance the bearing capacity of the foundation, reduce foundation settlement, and enable the foundation to meet the bearing requirements of the infrastructure structure, laying a solid foundation for subsequent construction of the project. Industry experts say that foundation treatment should follow the principle of "adapting measures to local conditions and implementing policies according to needs", combined with the geological conditions, engineering purposes, and design requirements of the project site, and select appropriate treatment technologies in a targeted manner to avoid blind construction and ensure stable and reliable foundation treatment effects.

The replacement cushion layer method is one of the widely used and technically mature foundation methods in the treatment of building infrastructure foundations. It is mainly suitable for areas with low foundation bearing capacity and soft soil layers, such as silty soil, silty soil, and miscellaneous fill soil. This technology excavates the poor soil layer within a certain depth range below the foundation bottom and replaces it with high-quality filling material with high strength, good stability, and strong permeability. After layer by layer rolling and compaction, a cushion layer that meets the requirements is formed, thereby improving the foundation bearing capacity and reducing foundation settlement.

Common fillers include graded sand and gravel, lime soil, plain concrete, etc. The specific selection needs to be determined based on engineering requirements. For example, in the treatment of municipal road subgrade, graded sand and gravel are often used as fillers, with reasonable particle size distribution and high compactness after rolling, which can effectively improve the bearing capacity of the subgrade and prevent settlement and cracking in the later stage of the road; In the treatment of industrial plant foundations, if high requirements are placed on the bearing capacity of the foundation, a plain concrete cushion layer can be used to enhance the overall integrity and bearing capacity of the foundation. The thickness of the replacement cushion layer should be reasonably controlled according to the thickness of the poor soil layer and the requirements of the foundation bearing capacity, generally 0.5-2.0 meters. During the rolling process, the compaction degree should be strictly controlled to ensure that the cushion layer is dense and uniform, and to avoid problems such as layering and looseness.

The compaction method is mainly used to improve the bearing capacity of shallow foundations. Through mechanical or manual compaction, the soil porosity is reduced, the soil compactness is increased, thereby enhancing the bearing capacity of the foundation and reducing its settlement. This technology is divided into two types: heavy hammer compaction and dynamic compaction, each with its own specific application scenarios. The heavy hammer compaction method is suitable for handling shallow silty soil, silt, miscellaneous fill soil, etc. The compaction depth is generally 1.5-3.0 meters. During construction, the impact force generated by the free fall of the heavy hammer is used to compact the foundation soil and improve the soil structure; The dynamic compaction method is suitable for dealing with deep soft foundations, such as deep silt, silty soil, etc. The compaction depth can reach 3-10 meters. A large heavy hammer (usually 10-40 tons) is used to freely fall from a height of 8-20 meters, generating strong impact and vibration forces to compact the deep soil and greatly improve the bearing capacity of the foundation.

In the foundation treatment of large squares, parking lots and other infrastructure, dynamic compaction method is widely used. It not only has good treatment effect, but also has high construction efficiency, which can effectively shorten the construction period. It should be noted that before the compaction method construction, a trial compaction should be carried out to determine a reasonable number of compaction times, compaction spacing, and compaction depth, to avoid excessive or insufficient compaction affecting the treatment effect. At the same time, settlement observation during the construction process should be done well, and construction parameters should be adjusted in a timely manner.

Squeezing method is a treatment technique that involves driving piles or injecting filling materials into the foundation soil to compact the surrounding soil and improve its bearing capacity. Common methods include vibration compaction, sand and gravel pile compaction, and lime soil compaction. The vibration compaction method is suitable for treating liquefiable soil layers such as sand and silt. Through the vibration and water flushing of the vibration device, the sand is liquefied and filled with fillers such as sand and gravel to form sand and gravel piles, which compress the surrounding soil and enhance the anti liquefaction and bearing capacity of the foundation; The sand and gravel pile compaction method is mainly used to treat miscellaneous fill soil, silty soil, etc. The sand and gravel are filled into the foundation through sinking pipes, vibration, and other methods to form sand and gravel piles, which compact the surrounding soil and improve the foundation structure.

In the foundation treatment of urban rail transit infrastructure, the compaction method is widely used, which can effectively treat weak soil layers along the line, prevent uneven settlement of the track in the later stage, and ensure the safety of rail transit operation. In addition, the lime soil compaction method is suitable for treating collapsible loess foundations. By driving lime soil piles and compacting the loess layer, the collapsibility of the loess can be eliminated, and the bearing capacity of the foundation can be improved to avoid later settlement due to water immersion.

The drainage consolidation method is mainly suitable for treating saturated soft soil foundations, such as silt, silty soil, and backfill soil. These soil layers have high moisture content, large porosity, and low bearing capacity, and are prone to significant settlement if directly constructed. This technology accelerates the drainage of water in the foundation soil by installing drainage systems such as sand wells and plastic drainage boards, gradually consolidating the soil and improving its bearing capacity, thereby reducing settlement.

During construction, drainage channels are first set up at certain intervals in the foundation, and then pressure is applied through methods such as preloading and vacuum preloading to promote drainage and consolidation of the foundation soil. For example, in the treatment of bridge pile foundation, for saturated soft soil sections, plastic drainage boards combined with preloading can be used to accelerate the consolidation of soft soil, ensure the quality of pile foundation construction and the stability of the bridge in the later stage; The vacuum preloading method is widely used in the foundation treatment of port and dock infrastructure, which can effectively shorten the consolidation time of soft soil, improve the bearing capacity of the foundation, and meet the requirements of heavy load operations at the dock.

In addition, with the development of high-rise and large-scale building infrastructure construction, the application of composite foundation treatment technology is becoming increasingly widespread. Composite foundation refers to a treatment technology that enhances the bearing capacity of the foundation and reduces settlement by setting reinforcement bodies (such as cement soil mixing piles, CFG piles, gravel piles, etc.) in the foundation to jointly bear the load with natural foundation soil. Among them, cement soil mixing piles are suitable for treating soft soil foundations such as silt and silty soil. By using mixing machinery to evenly mix cement with the foundation soil, cement soil piles are formed to enhance the overall integrity of the foundation; CFG piles (cement fly ash gravel piles) are suitable for treating various soil layers such as cohesive soil, loess, and sandy soil, with high bearing capacity and convenient construction. They are widely used in foundation treatment of high-rise buildings, municipal bridges, and other infrastructure.

The reporter learned that the detection of the effectiveness of foundation treatment is an important part of building infrastructure construction. After the foundation treatment is completed, the construction unit will comprehensively test the bearing capacity, settlement, compactness and other indicators of the foundation through static load tests, dynamic testing methods, geotechnical tests and other methods to ensure that they meet the design requirements before entering the subsequent construction process. Industry experts remind that foundation treatment is a key process in the construction of building infrastructure. In the future, it is necessary to carry out foundation settlement observation and maintenance work, timely discover and deal with various hidden dangers, and ensure the long-term safe and stable operation of infrastructure.

With the continuous advancement of construction technology, the foundation treatment technology of building infrastructure is also constantly upgrading, paying more attention to efficiency, greenness, and refinement. In the future, more new foundation treatment technologies will be applied to infrastructure construction, combined with intelligent monitoring methods to further improve the quality and efficiency of foundation treatment, providing strong support for the high-quality development of urban infrastructure and helping to create a safe, durable, and efficient urban infrastructure system.