Introduction to Full Casing Technique
The Full Casing Technique, also known as the Benoto method, is a pivotal method in pile foundation construction. This technique involves the use of a full casing or 'full follow-up casing' to ensure the stability and integrity of the borehole during the drilling process. It's known for its minimal environmental impact, high reliability, rapid boring efficiency, and excellent quality, making it a preferred method for various geotechnical conditions.
Advantages of Full Casing Technique
Full casing offers several significant advantages over traditional drilling methods. It reduces pollution by containing displaced soil and groundwater within the casing, ensuring a cleaner worksite and minimal environmental disruption. The technique's high reliability and quick boring efficiency mean that projects can be completed swiftly, with fewer delays and reduced costs. Additionally, its adaptability to various soil conditions, from clay and sand to gravel and karst formations, makes it a versatile solution for complex geotechnical challenges.
Application 1: Urban Engineering Projects
In densely populated urban areas, construction projects often face strict environmental regulations and space constraints. Full casing construction becomes the go-to method in such scenarios, providing a clean and efficient solution. For instance, the 2009 project at Beijing's Liuliqiao area utilized a rotary drilling rig with a full casing to construct pile foundations amidst high-rise buildings and near subway stations, demonstrating its effectiveness in sensitive urban environments.
Application 2: Dealing with Unstable Soil Layers
Soil layers like backfill, silt, marine clay, and quicksand pose significant challenges due to their tendency to collapse or shrink during drilling. The full casing technique supports the borehole walls, preventing collapse and ensuring continuous drilling to the desired depth. Projects in Zhejiang's power plant and a residential construction site in Fujian exemplify the technique's role in ensuring smooth drilling in unstable soils.
Application 3: Karst Terrains and Unpredictable Geology
Karst terrains and areas with unpredictable geological features like boulders or soft spots are particularly challenging. The full casing technique provides a stable environment for drilling, even in the presence of soluble rocks, boulders, and varying soil hardness. The Guangzhou project involving limestone and soluble rocks and the Liuzhou Liujian River project are testaments to the technique's ability to maintain borehole integrity in complex geologies.
Application 4: Deep Foundation and Subway Projects
For deep foundation and subway projects that require robust load-bearing capacity, lateral support, and waterproofing, the full casing technique offers an efficient solution. The precision and strength provided by the full casing are crucial for the construction of tongue groove piles and other complex foundation structures. Shenzhen and Shanghai projects illustrate the method's effectiveness in achieving waterproof, tight-fitting piles essential for structural integrity.
Application 5: Slanted Piles for Horizontal Loads
Slanted or inclined piles are often used to counteract large horizontal loads in structures like bridges, docks, and large-scale transmission lines. The full casing technique facilitates the construction of these slanted piles by ensuring the borehole remains stable and aligned, despite the challenging angles and loads involved. This application showcases the technique's adaptability to various construction needs, including those with significant technical demands.
The Full Casing Construction Technique with a rotary drilling rig is a testament to modern engineering's ability to solve complex construction challenges. Its applications in urban engineering, unstable soils, unpredictable geologies, deep foundations, and slanted piles demonstrate its versatility and efficiency. As construction continues to evolve, the full casing technique will undoubtedly remain a staple in ensuring the safety, reliability, and speed of foundational works.
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Table of Contents
- Introduction to Full Casing Technique
- Advantages of Full Casing Technique
- Application 1: Urban Engineering Projects
- Application 2: Dealing with Unstable Soil Layers
- Application 3: Karst Terrains and Unpredictable Geology
- Application 4: Deep Foundation and Subway Projects
- Application 5: Slanted Piles for Horizontal Loads