Drilling Shaft Casing with Radial Fluid Injection
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Solution Overview
Problem
Existing methods for drilling shafts in ground layers of rock, clay, and related materials face inefficiencies due to ground material adhesion to the drill head and obstruction of discharged material, particularly in cohesive layers like clay and cracked rock, reducing drilling speed and efficiency.
Innovation Solution
A method involving a borehole casing that admits minimal water, a rotating drill string with cutting tools, and a water column to maintain flow, with high-pressure fluid injection through nozzles positioned radially outward to weaken the ground beneath the casing, reducing adhesion and the need for underreaming, and optionally using a second fluid with lower density to enhance flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If ground material is dislodged by cutting action of cutting tools in cohesive ground layers, then drilling progresses, but ground material adheres to the drill head impeding cutting action and obstructing discharge
Solution Approach 1:
The patent applies preliminary action by injecting fluid through nozzles positioned on the drill head to pre-weaken and fluidize the ground material before the cutting tools engage. This preliminary fluid injection reduces the adhesion of ground material to the drill head surface, preventing the harmful effect of material buildup that would otherwise impede cutting action and obstruct discharge, thereby maintaining drilling efficiency throughout the operation.
2Reliability
If borehole casing is used to contain drilling operation, then drilling can proceed in unconsolidated ground, but casing cannot move deeper without underreaming construction
Solution Approach 1:
The patent extracts the underreaming construction from the drilling system by using fluid injection through nozzles to create a fluidized zone beneath the borehole casing. This fluidized zone allows the casing to sink deeper into the ground without requiring mechanical underreaming devices, thereby removing the complex underreaming construction while maintaining the ability to drill in unconsolidated ground and achieve deeper penetration.
3Length of moving object
If high pressure fluid is injected radially outward to weaken ground beneath casing, then casing can move deeper and less deep drilling is necessary, but fluid injection system complexity increases
Solution Approach 1:
The patent applies universality by designing the fluid injection system with nozzles that serve multiple functions: they weaken the ground beneath the casing to enable deeper movement, reduce ground material adhesion to the drill head, and assist in dislodging and discharging cut material. This multi-functionality allows the system to achieve greater shaft depth without proportionally increasing complexity, as a single fluid injection system accomplishes multiple drilling objectives.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly increases drilling efficiency by reducing material adhesion and the need for underreaming, allowing deeper penetration with less drilling effort and minimizing the risk of drill head entrapment, while maintaining high-pressure fluid dynamics to enhance material removal.
Implementation Method 1
a first fluid is injected under a first pressure of at least 200 bar into the ground layers by means of one or more nozzles, the nozzles being positioned such that they inject the first fluid substantially radially outward into ground layers situated at a greater depth than the lower outer end of the borehole casing
Implementation Method 2
the radially outward directed first fluid jets do indeed ensure that the ground is at least partially removed or weakened at the position of the underside of the borehole casing
Implementation Method 3
ground material is dislodged by the cutting action of the cutting tools and is discharged using a flow maintained by the water column in the hollow drill string
Implementation Method 4
arranging a water column in the borehole casing... discharged using a flow maintained by the water column in the hollow drill string
Implementation Method 5
setting the drill string into rotation in the borehole casing so that ground material is dislodged by the cutting action of the cutting tools
Implementation Method 6
a second fluid is also injected under a second pressure into the hollow drill string at the position of the drill head. The second fluid preferably has a lower density than water, whereby this second fluid rises and expands in the drill string, thus further supporting the upward flow
Data Source
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AI summary
The invention relates to a method for drilling shafts (2) in ground layers (3). The method comprises of arranging a borehole casing (4) in the ground (3), lowering into the borehole casing (4) a hollow drill string (5) provided with a drill head (7) with cutting tools (8), arranging a water column (10) in the borehole casing (4), and then setting the drill string (5) into rotation (20) in the borehole casing (4) so that ground material (31) is dislodged by the cutting action of the cutting tools (8). At the position of the drill head (7) a first fluid (26) is injected under a first pressure into the ground layers (3) by means of one or more nozzles (25). The method has a higher drilling efficiency than the known method. The invention also relates to a device for performing the method, and a jack-up pontoon provided with the device.