Acoustic Emission Sensor Waveguide for Underground Collapse Prediction
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Solution Overview
Problem
Existing methods for predicting underground collapse, such as displacement and stress measuring techniques, face challenges in detecting early signs of collapse due to small variance and non-homogeneous material changes during grouting, leading to unreliable acoustic emission signal transfer.
Innovation Solution
A device using a pillar-shaped waveguide rod with adhered acoustic emission sensors and a homogeneous acoustic emission generating layer, secured by a grouting layer, to enhance signal transfer and reliability by minimizing material sieving and ensuring consistent material homogeneity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a waveguide is spaced apart from the inner wall of the borehole, then installation is easier, but the change of ground stress is not sufficiently transferred to the waveguide
Solution Approach 1:
The patent introduces a grouting layer as an intermediary substance between the waveguide and the borehole wall. This grouting layer fills the gap and enables effective stress transfer from the ground to the waveguide while still allowing for relatively easy installation. The grouting material acts as a mediator that transmits the mechanical stress changes without requiring direct contact between the waveguide and borehole wall.
2Strength
If cement is used for grouting, then the waveguide is secured, but non-homogeneity of materials increases due to cement sieving
Solution Approach 1:
The patent uses a composite grouting material composed of multiple components including cement, water, and specific additives in controlled proportions. This composite formulation maintains the securing strength of cement while reducing the sieving effect and improving material homogeneity. The composite nature allows optimization of both mechanical properties and flow characteristics.
Solution Approach 2:
The patent specifies precise parameter changes in the grouting material composition, including water-cement ratio, particle size distribution, and additive concentrations. By controlling these parameters, the grouting material achieves both adequate strength for securing the waveguide and improved homogeneity by minimizing sieving effects during installation.
3Measurement precision
If displacement or stress measuring methods are used, then ground behavior can be measured, but early signs of collapse are difficult to detect due to small variance
Solution Approach 1:
The patent replaces traditional mechanical displacement and stress measurement systems with an acoustic emission-based detection system. Acoustic emission sensors detect high-frequency elastic waves generated by micro-fractures and stress changes in the ground, providing earlier and more sensitive detection of collapse precursors compared to mechanical measurement methods. This substitution enables detection of subtle ground behavior changes before macroscopic displacement occurs.
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
The device effectively predicts underground behavior and collapse possibilities by accurately capturing and transmitting acoustic emission signals, improving reliability and reducing errors associated with material non-homogeneity.
Implementation Method 1
The acoustic emission sensor uses a microscopic breaking sound generated inside an object at an early stage that the object is broken as a signal. The acoustic emission (AE) is an elastic wave generated when deformation energy accumulated in materials is suddenly emitted.
Implementation Method 2
a waveguide rod (120) having an elongated shape to be inserted into the borehole (B)
Data Source
Figure 1~2
Figure 3(a)~3(f)
Figure 4
AI summary
Provided is a device for predicting an underground behavior by using an acoustic emission (AE) sensor, including: a waveguide rod having an elongated end to be inserted in a borehole; a plurality of acoustic emission sensors mounted on different positions of the waveguide rod; a wrapping layer configured to cover a circumferential surface of the waveguide rod such that a gap is formed between the waveguide rod and the wrapping layer; an acoustic emission generating layer filled into the gap and being homogeneous along a direction of the waveguide rod; and a grouting layer configured to fix the waveguide rod in the borehole.