Method and system for tracking grout diffusion by integrating optical fiber sensing and electrical resistance tomography

A method for tracking grout diffusion by integrating optical fiber sensing and electrical resistance tomography, comprising:

• conducting geological exploration of an area to be grouted;
• identifying an area with highly complex geological conditions in the area to be grouted based on a geological exploration result of the area to be grouted;
• acquiring electrical resistivity data in real time through an electrode network uniformly arranged across an entire surface of a tunnel face, and acquiring global electrical resistivity change data in a grouting process using electrical resistance tomography;
• acquiring, for the area with highly complex geological conditions, optical fiber sensing data in real time using optical fiber sensing arranged in a grouting borehole to further acquire local strain, temperature and pressure data;
• performing data fusion and calculation analysis on the acquired global electrical resistivity change data and the local strain, temperature and pressure data, acquiring a change rate of data through calculation, defining a point as an abnormal change point when the change rate exceeds a predefined critical value, extracting the abnormal change point, and projecting the abnormal change point on an optical fiber sensing path onto resistivity imaging to determine a grout front position;
• acquiring a deformation magnitude of a grout diffusion boundary through calculation, and projecting the deformed boundary position onto resistivity imaging to determine a grout diffusion boundary;
• and
• determining a grout diffusion range according to the resistivity imaging with the determined grout front position and grout diffusion boundary to capture a grout diffusion process, wherein the data fusion analysis constructs the grout diffusion range based on a data analysis approach, specifically:
• determining an area with significant electrical resistivity reduction based on preprocessed global electrical resistivity change data to acquire an approximate diffusion range in correspondence to a grout injection area and a grout diffusion range;
• extracting an abnormal change point of the strain, temperature and pressure based on preprocessed local strain, temperature and pressure data, judging the precise grout front position and grout diffusion boundary in combination with a grouting theory, and refining the approximate diffusion range;
• performing data analysis on the extracted strain, temperature and pressure monitoring change data along a grouting path and the extracted abnormal change point, identifying an area with large strain change on a strain gradient of strain data, performing data normalization processing on parameters, comprising surrounding rock permeability and elastic modulus along optical fiber layout acquired from preliminary geological exploration, and assigning a weight to each data type according to a weighted calculation formula:
• W
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• E
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• ;
• wherein, Wtotal representing a final weighted value, Eϵ representing the normalized strain, EK representing the normalized permeability, EE representing the normalized elastic modulus, and wϵ, wK, and wE respectively representing weights of the strain, the permeability and the elastic modulus;
• establishing a physical deformation model:
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• ϵ
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• wherein, ΔX representing a deformation magnitude of the diffusion boundary, and f(ϵ, σ, K, E) representing a deformation function of the strain, the stress, the permeability, and the elastic modulus;
• determining the deformed boundary position:
• X
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• wherein, Xold representing a position of an original diffusion boundary, and Xnew representing the deformed boundary position;
• projecting the deformed boundary position onto resistivity imaging to determine the precise grout diffusion boundary;
• and
• determining a diffusion path at a certain time point based on the determined grout front position and grout diffusion boundary, and accumulating the diffusion path over time to acquire a final diffusion range and precisely capture the grout diffusion process.