Fiber Optic Soil Probe for Miniaturized Cone Resistance Measurement
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Solution Overview
Problem
Conventional cone penetration tests face challenges in miniaturizing sensors for soil property measurement without compromising sensitivity, as they require multiple wires and are sensitive to humidity and temperature changes, and are not compatible with harsh environments.
Innovation Solution
The use of fiber optic sensors, specifically Fiber Bragg Gratings, which are power-free, allow for multiplexing and remote measurement, providing high accuracy and resistance to harsh conditions, and are designed to distinguish between temperature and force responses using pairs of FBGs with similar or opposite responses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If electric strain gauges are used in the probe, then measurement capability is provided, but the probe size increases and sensitivity decreases
Solution Approach 1:
The patent replaces electric strain gauges with fiber optic sensors, specifically using optical fiber technology to measure strain and mechanical properties. This substitution eliminates the need for electrical components within the probe body, enabling miniaturization while maintaining or improving measurement sensitivity. The optical fiber sensors can detect mechanical deformations through optical property changes without requiring power or signal wires.
Solution Approach 2:
The patent extracts the electrical components (strain gauges, wiring, power sources) from the probe structure and replaces them with passive optical fiber sensors. This extraction allows the probe to be miniaturized significantly, as optical fibers have minimal diameter and do not require complex electrical connections or power supply systems within the probe body.
2Adaptability or versatility
If electric sensors are used in the probe, then measurement functions are enabled, but multiple wires are required increasing complexity
Solution Approach 1:
The patent employs fiber optic sensors that can measure multiple parameters (strain, temperature, pressure) using a single optical fiber medium. The same optical fiber infrastructure that provides sensing can also serve as the communication channel for data transmission, eliminating the need for separate wiring for power and signals. This multi-functionality significantly reduces the number of wires and connections required.
Solution Approach 2:
The patent merges the sensing function and communication function into a single optical fiber system. The optical fiber both detects physical parameters through optical property changes and transmits measurement data back to the surface equipment, consolidating multiple functions into one component and dramatically simplifying the probe structure.
3Measurement precision
If electric sensors are used in the probe, then measurement capability is provided, but sensitivity to humidity and temperature changes increases
Solution Approach 1:
The patent replaces electric sensors with optical fiber sensors that are inherently immune to electromagnetic interference and environmental factors like humidity. Optical fibers are made of dielectric materials (glass or plastic) that do not conduct electricity and are not affected by electromagnetic fields, making them ideal for harsh environments where electric sensors would fail or give inaccurate readings.
Solution Approach 2:
The patent creates an electrically inert environment within the probe by using optical fiber technology. The optical fiber sensors operate based on optical properties rather than electrical properties, making them insensitive to electromagnetic interference, humidity, and temperature variations that would affect conventional electric sensors. This inert optical environment ensures stable and reliable measurements in challenging subsurface conditions.
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 solution enables improved accuracy and reduced probe size with reduced electrical and communication lines, while being resistant to corrosion and electromagnetic interference, allowing for effective measurement of soil properties like cone resistance, sleeve friction, and pore water pressure in harsh environments.
Implementation Method 1
The at least one fiber optical sensor includes a Fiber Bragg Grating, FBG. An FBG comprises a fiber having a core including therein, over a certain distance, a periodic variation of the refractive index. This periodic variation forms a wavelength-specific dielectric mirror, wherein light in a specific (narrow) range around and including a certain wavelength is reflected.
Implementation Method 2
Fiber optic sensing provides remote measurement capability owing to the fact that long distance low-loss, interference free, high bandwidth signal transmission can be achieved with a low cost communication fiber.
Implementation Method 3
In optical fiber sensors an optical fiber is used as a sensing element. The optical fiber can be lit (e.g. by a laser), and a change in the fiber due to an external cause (dependent on the type of sensor) results in a measurable change in the optical signal transmitted by or received from the sensor.
Data Source
Figure 1
Figure 2A~2B
Figure 3A
AI summary
The invention relates to a probe arranged for subsurface penetration of a soil for measuring properties of the soil. The probe comprising a probe body and at least one fiber optical sensor. The at least one fiber optical sensor is arranged for measuring at least one of a cone resistance, sleeve friction, pore water pressure or inclination.