Rotary drilling has long been the standard method for deep foundations, but it comes with its challenges. This is where fully cased methods prove invaluable.
When the formations being drilled cannot maintain an open hole, installing casing provides stability and reduces risk. Various drilling tools are used to install casing, which then secures the drilled shaft and serves as a conduit for installing the rebar cage and pouring concrete to complete the operation.
Today’s blog focuses on the benefits of oscillators, rotators, and the Fully Cased Method. Let’s start with an in-depth look at the various methods and their pros and cons.
What is the Fully Cased Method?
The Fully Cased Method involves installing casing along the entire length needed to avoid shaft collapse. Four commonly used methods include:
- Drill rig installation
- Drive casing
- Casing oscillator
- Casing rotator
How it works
In the drill rig installation, an adapter is attached to the Kelly stub, with arms that engage the casing. These arms can be 2, 3, or 4 in number. The casing is fabricated with J-locks or receivers for the arms. The casing is then attached to the adapter and drilled down to the required depth, with multiple casing sections potentially used in a telescoping manner to reach the desired depth. The rebar and the concrete must be added while the casing is in place. Then, the casing is removed.
Driving casing requires an attachment from a crane to grip and either hammer or vibrate the casing into position at the required depth. The drill rig is used to clean out the spoils inside the casing, completing the shaft in the usual manner. The vibro or hammer is then used to extract the casing after installing the rebar cage and pouring the concrete.
Casing oscillators are employed for both permanent and temporary casing. Temporary casing features mechanical connections (male and female) secured with bolts to lock the casing sections together. A casing shoe with carbide bits ensures the casing can penetrate desired formations and cut through challenging ground. The oscillator clamps onto the casing and oscillates it while applying downforce.
Casing rotators function similarly to oscillators, but spin the casing 360 degrees and utilize a different style of tooth on the casing shoe. Rotators are typically used when the formation needs to be cut rather than merely penetrated.
Key casing installation equipment
Size and type
Drilling rigs come in various sizes, affecting the maximum diameter for drilled shafts and casings based on the rig’s capacity. Casing driving equipment also varies in capacity, enabling vibration or hammering to install the necessary casing.
Casing oscillators are available in different diameter selections. They feature key components such as upper and lower clamping jaws and lifting cylinders located between the jaw frame to facilitate pushing or pulling the casing.
Control systems
Today’s casing installation methods utilize cutting-edge control systems, enhancing drilling accuracy and ensuring the equipment remains on track. Many systems are equipped with built-in safety features that reduce the risk of accidents during operation.
Durability
Fully Cased Method machines are designed to withstand harsh conditions. Constructed from high-quality materials, they perform reliably under the intense demands of foundation drilling.
Choosing the right equipment involves understanding your project’s needs and the capabilities of the tools available. With advancements in technology and design, modern casing installation equipment is better equipped than ever to address the complex challenges of building foundations.
How to perform the Fully Cased Method
Project teams meticulously plan and execute casing installation methods for deep foundations to ensure precision and safety at every step.
Site assessment and planning
Before drilling begins, conduct a comprehensive ground survey to analyze soil composition, identify potential obstacles, and assess groundwater conditions. These insights will help determine the most suitable method for effectively addressing the project’s specific challenges.
Setting up
When the equipment arrives on-site, carefully mount it onto a crane or drilling rig. Perform a thorough check of the entire setup to ensure stability and operational readiness. Properly preparing the equipment is essential for safety and efficiency.
Initiating drilling
Once everything is set, drilling commences. The chosen equipment secures the casing and applies vibration, hammering, or rotational force, allowing the casing to be installed into the ground. This applied motion helps the casing move through dense layers and obstacles effectively.
Continuous monitoring
Constant monitoring is essential during drilling. Utilize sensors and visual inspections to ensure the process remains on track and address any irregularities or challenges. Ongoing vigilance is key to maintaining the integrity of the drilled shaft and preventing issues.
Extracting soil
As drilling progresses, it is necessary to remove the soil inside the casing. Tools like clamshell buckets or augers can be used to clear out soil, keeping the drilled shaft clean and free from blockages.
Completion
Drilling ceases once the desired depth is reached. Depending on the project’s needs, the next steps may involve adding reinforcing bars, pouring concrete, or other foundational work.
Retrieval
If required, carefully withdraw the casing from the borehole by reversing the installation method.
Each step of this process demands careful attention to detail, underscoring the need for expertise and experience in using these proven methods for foundation construction.
Benefits of using the Fully Cased Method for difficult ground conditions
Penetrate dense strata and obstructions
The unpredictable composition of the earth often presents challenges for drillers. Mechanical action allows them to easily slice through tough materials, streamlining the drilling process and enhancing efficiency.
Minimize vibrations
Drilling vibrations and hammering are often restricted in residential areas due to potential damage to adjacent structures. Casing oscillators and rotators, which utilize a rotational method, generate significantly fewer vibrations than traditional drilling techniques.
Maintain stability in loose soils
Traditional drilling methods risk borehole collapse in loose or poorly compacted soil. Casing oscillators and rotators drill and case simultaneously, providing immediate support that enhances safety and efficiency.
Control groundwater intrusion
Groundwater poses a significant challenge during foundation construction, especially in areas with high water tables. The risk of water infiltrating the borehole can weaken its structural integrity. Fully Cased Methods are designed to prevent groundwater issues, forming a watertight seal that effectively blocks water from entering the borehole.
Get your Fully Cased Method tools and equipment at Western Equipment Solutions
Are you looking for reliable solutions to your foundation drilling challenges? Acquire your drilling rigs, hammers, vibros, segmental casing, casing oscillators, and casing rotators from Western Equipment Solutions. Our Soilmec drilling rigs, Junttan hammers, PTC vibros, and Leffer casing equipment provide the precision, power, and protection you need to effectively handle tough terrains and groundwater issues.
Don’t compromise on the quality of your foundation work. Choose Soilmec and Leffer for drilling equipment that ensures durability and safety at your work site.
Contact Western Equipment Solutions today to learn more about our Fully Cased Method tools and equipment and discover how they can enhance your construction projects. Equip your site with the best — start with Western!
