A method for dynamic monitoring of a wharf backfill area based on stress measurement

Abstract

The application provides a kind of wharf backfill area dynamic monitoring method based on stress measurement, and the raw material of solid waste-based anti-explosion soil includes 82-92 parts by weight of solid waste base material, 5-12 parts of cementing material, 0.1-0.4 parts of light component, 0.2-0.6 parts of hybrid fiber, 1.5-3.5 parts of multi-scale elastic energy dissipation particle, and 0.5-5 parts of intelligent sensing and self-repairing functional component;The mass ratio of hybrid fiber and multi-scale elastic energy dissipation particle is 1:(4-8);Intelligent sensing component includes distributed optical fiber sensor, piezoelectric ceramic particle and conductive nanomaterial;Conductive nanomaterial is coated on the surface of hybrid fiber and forms a three-dimensional piezoresistive sensing network;Self-repairing component is a microcapsule containing a repairing agent or a microbial carrier with mineralization ability, and the microcracks generated by local strain trigger the rupture of self-repairing component, releasing the repairing agent or microorganisms.

Description

Technical Field

[0001] This invention relates to a stress measurement technology, and more particularly to a dynamic monitoring method for wharf backfill areas based on stress measurement. Background Technology

[0002] The overall stability and safety performance of wharf structures (especially gravity and sheet pile wharves) are highly dependent on the engineering mechanical properties of the backfill layer behind them. Traditional wharf backfilling projects generally use quarried stone, slag, or sand for layered compaction, aiming to maintain slope stability through the shear strength of the fill material. However, with the increasing demands for high protection, rapid response, and sustainability in modern hydraulic engineering, the deep-seated defects of traditional backfilling techniques are becoming increasingly prominent. First, there is a contradiction between structural load reduction and stability: the wet density of traditional fill material is usually as high as 18-22 kN / m³, and the huge active earth pressure can easily induce lateral displacement, overturning, or even overall instability of the wharf wall. Especially in areas with soft soil foundations, the additional settlement and backward tilting moment caused by the excess self-weight seriously threaten the structural safety and service life of the berthing shoreline. Second, there is a disconnect between the single structural function and the need for composite protection: existing backfill materials only have basic physical filling and resistance functions, lacking dynamic dissipation mechanisms against shock waves and explosive loads. When subjected to extreme dynamic loads, stress waves attenuate very slowly in dense fillers, and the dynamic load energy directly reaches the main structure of the wharf, easily causing irreversible structural damage. Furthermore, traditional materials lack damage sensing and in-situ repair capabilities, making post-disaster hazard investigation difficult. Third, there is an imbalance between resource and environmental burdens and supply chain resilience: large-scale quarrying not only leads to severe ecological damage, but also makes the sand and gravel supply chain easily restricted in emergency repairs or under special geographical conditions. At the same time, the large amount of solid waste generated during port construction, such as dredged sludge and demolition waste, is often difficult to utilize directly due to its high moisture content and low strength. Long-term stockpiling not only occupies land resources but also poses a risk of secondary environmental pollution.

[0003] In recent years, although some civil engineering projects have introduced foamed concrete or EPS granular lightweight soil, these materials generally suffer from mechanical defects such as high cost, polymer degradation and pollution, poor resistance to seawater corrosion, and susceptibility to brittle collapse under impact loads, making them unsuitable for the complex marine engineering environment of high salt spray and strong impact. Therefore, developing a new type of backfill material that can utilize solid waste resources on-site, and possesses significant structural load reduction, multi-scale dynamic load absorption, and intelligent damage self-healing functions, along with its dynamic monitoring method, has become a key technological direction for improving the comprehensive protection level of coastal engineering. Summary of the Invention

[0004] To address the above problems, this invention provides a dynamic monitoring method for wharf backfill areas based on stress measurement, comprising:

[0005] Step S100: Set part of the backfill area as a reference area, incorporate elastic energy dissipation particles into the backfill area, and bury distributed optical fiber sensors, piezoelectric ceramic particles, hybrid fibers coated with conductive nanomaterials and self-healing components at different depths.

[0006] Step S200: Collect the resistance signal of conductive nanomaterials in the backfill area affected by the dynamic impact load of the explosion source, combine the resistance signal of conductive nanomaterials in the reference area to perform environmental drift compensation to obtain the electrical signal caused by physical damage, and normalize the electrical signal to the resistance change rate.

[0007] Step S300: Collect the wavelength offset signal of the distributed optical fiber sensor in the backfill area. Based on the linear mapping relationship of the strain sensitivity of the optical fiber, the wavelength offset is converted into transient strain. The least squares method is used to fit the constructed spatial strain attenuation model in which the transient strain dissipates exponentially with depth, and the spatial strain attenuation coefficient is obtained by inversion.

[0008] Step S400: Capture the peak impact stress signals generated by the impact load on the piezoelectric ceramic particles at the closest and farthest ends of the backfill area from the explosion source, and use the difference between the two peak impact stress signals to obtain the global dynamic load energy absorption efficiency of the backfill area.

[0009] Step S500: Determine the damage level of the backfill area based on the global dynamic load energy absorption efficiency, spatial strain attenuation coefficient and resistance change rate, and determine whether to use a self-healing component self-healing scheme or an artificial reinforcement grouting scheme for damage repair based on the damage level.

[0010] In step S600, if a self-healing component self-healing scheme is adopted, an excitation pulse is applied to the repaired backfill area, and the degree of recovery of the backfill area is quantitatively verified by comparing the stress wave reduction rate and resistance repair rate before and after repair.

[0011] Furthermore, step S200 specifically includes:

[0012] Step S210: Simultaneously collect the working resistance of the backfill area affected by dynamic impact load and the reference resistance of the non-stressed reference area.

[0013] Step S220: Subtract the reference resistance from the working resistance to obtain the electrical signal caused by physical damage;

[0014] Step S230: Normalize the electrical signal to the rate of change of resistance.

[0015] Furthermore, in step S220, environmental interference is eliminated using a dual-path differential compensation formula to obtain a clean damage signal ΔR. pure ,

[0016] ΔR pure =R work - k·R ref ,

[0017] in, k R is the correction factor; work R is the working resistance. ref This is the reference resistor.

[0018] Furthermore, in step S230, the electrical signal ΔR pure Converted to the rate of change of resistance ΔR pure / R0, where R0 is the initial resistance.

[0019] Furthermore, in step S300, the wavelength shift signal is converted into transient strain using the fiber-based strain sensitivity linear mapping relationship described in the following formula. s ,

[0020] Δλ=Ke· s ,

[0021] Where Δλ is the wavelength offset and Ke is the strain sensitivity coefficient of the optical fiber.

[0022] Furthermore, the specific process of inverting the spatial strain attenuation coefficient using the least squares method in step S300 includes:

[0023] Step S320, with transient strain s The dependent variable is the backfill depth. z Using the independent variable, a spatial strain decay model exhibiting exponential dissipation is constructed. s ( z ),

[0024] s ( z )= s 0·e -αz ,

[0025] in, s 0 is z The initial strain peak value when = 0, where α is the spatial strain attenuation coefficient;

[0026] Step S330, combined with Δλ=Ke· s The corresponding transient strain is obtained based on the wavelength offset at different depths. s ( z The least squares method was used for nonlinear fitting, and the spatial strain attenuation coefficient α was obtained by inversion.

[0027] Furthermore, the specific process of step S400 includes: capturing the initial impact stress peak σ of the piezoelectric ceramic closest to the explosion source. source and the peak residual stress σ of the piezoelectric ceramic at the farthest point from the explosion source wall Obtain the global dynamic load energy absorption efficiency η.

[0028] η=(1-σ wall / σ source )×100%.

[0029] Furthermore, the damage gradient determination process in step S500 includes:

[0030] If the resistance change rate of the obtained conductive nanomaterial undergoes a step-like open circuit jump, or the global dynamic load energy absorption efficiency is between the first energy absorption threshold and the second energy absorption threshold, a repair scheme for the self-healing component to repair the backfill area is triggered; the self-healing component is a microcapsule containing a repair agent or a microbial carrier with mineralization ability. Microcracks generated by local strain trigger the self-healing component to rupture and release the repair agent or microorganisms.

[0031] If the global dynamic load energy absorption efficiency is lower than the first energy absorption threshold, or the spatial strain attenuation coefficient is lower than the preset explosion-proof design lower limit, the artificial reinforcement grouting repair scheme will be triggered.

[0032] Furthermore, step S600 specifically includes the following processes:

[0033] Step S610: Extract the resistance signal R when damaged. damaged Initial resistance R0 and the repaired resistance signal R healed Calculate the resistance repair rate η R ,

[0034] η R =[1-(R healed -R0) / (R damaged -R0)]×100%;

[0035] Step S620: Inject artificially simulated excitation pulses based on the inverted spatial strain attenuation coefficient α and the initial transient strain. s 0. Compute the energy dissipation rate evolution flux E on the depth path. dis ( z ),

[0036] E dis ( z )=α·s0·e -αz ，z This refers to the backfill depth.

[0037] Step S630: Extract the residual strain intensity after dissipation through the backfill zone. s (L wall ), calculate the stress wave attenuation rate η a ,

[0038] η a =[1- s (L wall ) / s0]×100%;

[0039] Step S640, if η R ∈[80%,100%] and η a If the residual stress of the piezoelectric ceramic at the farthest point from the excitation pulse rises to more than 90% of the initial design value, and is below the safety threshold, then the repair is considered successful.

[0040] Compared with the prior art, the present invention has the following technical advantages: (1) The present invention realizes the self-sensing of materials by intelligent sensing components, and integrates the resistive permeation network of conductive nanomaterials, piezoelectric ceramics and distributed optical fiber sensors to achieve all-round coverage from microsecond-level impact response to long-distance spatial strain; (2) The introduction of dual-path differential compensation algorithm eliminates the interference of high salt, high humidity and large temperature difference environment of the dock on the electrical signal, and ensures the authenticity of the damage signal; (3) Through resistive tomography and optical fiber wavelength offset, three-dimensional reverse precise positioning of the deep stress concentration or explosion source of the backfill body can be achieved; (4) The present invention can self-repair and actively evaluate the repair quality. By establishing quantitative indicators such as resistive repair rate and stress wave reduction rate, the dynamic secondary verification is used to ensure that the explosion resistance level after repair returns to the design requirements.

[0041] The present invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0042] Figure 1 This is a schematic diagram of the dynamic monitoring method for blast-resistant soil backfilled behind the wharf according to the present invention.

[0043] Figure 2 This is a schematic diagram of the structure of the solid waste-based blast-resistant soil of the present invention.

[0044] Figure 3 This is a typical cross-sectional schematic diagram of the solid waste-based blast-resistant soil of the present invention used for backfilling of gravity wharves.

[0045] In the figure, 1 is a concrete caisson, 2 is a concrete breast wall, 3 is surface concrete, 4 is a riprap prism, 5 is a riprap foundation bed, 6 is solid waste-based blast-resistant soil, 7 is a wharf sheet pile wall, 11 is solid waste-based material, 12 is elastic energy-dissipating particles, 13 is mixed fiber, and 14 is a self-healing component. Detailed Implementation

[0046] Combination Figure 2Figure 3 illustrates an embodiment of a solid waste-based blast-resistant soil 6 for use in wharf backfill areas. The raw materials for preparing the solid waste-based blast-resistant soil 6, by weight, include 82-92 parts of solid waste base material, 0.5-5 parts of intelligent sensing and self-healing functional components, a cementing and functional modification system, and additives. The cementing and functional modification system includes 5-12 parts of cementing material, 0.1-0.4 parts of lightweight components, 0.2-0.6 parts of hybrid fibers, and 1.5-3.5 parts of multi-scale elastic energy-dissipating particles. The intelligent sensing components include distributed fiber optic sensors, piezoelectric ceramic particles, and conductive nanomaterials. The conductive nanomaterials are coated on the surface of the hybrid fibers to form a three-dimensional piezoresistive sensing network, enabling real-time monitoring of the internal strain state of the solid waste-based blast-resistant soil by monitoring resistivity changes. The self-healing component is a microcapsule containing a repair agent or a microbial carrier with mineralization capabilities. Microcracks caused by localized strain trigger the rupture of the self-healing component, releasing the repair agent or microorganisms. Figure 1 Larger irregular particles represent solid waste substrate 11, perfectly round particles represent elastic energy dissipation particles of different sizes 12, long strips represent mixed fibers 13, and scattered small round particles represent self-healing components 14.

[0047] Combination Figure 3 The solid waste-based blast-resistant soil 6 described in this embodiment is used for backfilling behind a wharf. The wharf includes a concrete caisson 1, a concrete breast wall 2, a surface concrete layer 3, a riprap prism 4, and a riprap foundation bed 5. The concrete caisson 1 is the main structure of the wharf, providing a vertical embankment to withstand earth pressure and ship loads. The concrete breast wall 2 is located on top of the concrete caisson 1 and is used to install mooring bollards, fenders, etc., to transfer horizontal loads. The surface concrete layer 3 is the surface layer of the wharf, bearing vehicle and equipment loads and protecting the underlying backfill material. The riprap prism 4 is part of the traditional backfill material, a permeable structure close to the caisson, reducing earth pressure. The riprap foundation bed 5 is the foundation at the bottom of the caisson, diffusing the caisson load to the ground. The solid waste-based blast-resistant soil 6 is located behind the riprap prism 4, providing functions such as load reduction, blast resistance, and intelligent sensing. The wharf sheet pile wall 7 is located behind the concrete breast wall 2 and extends into the solid waste-based blast-resistant soil 6 to retain soil and enhance structural stability. Solid waste base materials include one or more mixtures of port dredging sludge (dehydrated to a moisture content of ≤60%), waste concrete and crushed brick aggregate (particle size ≤5mm), and industrial waste residue powder (such as blast furnace slag powder, steel slag powder, alkali slag, serpentine and magnesium oxide, etc., with a specific surface area ≥400m² / kg).

[0048] The cementitious material, lightweight components, hybrid fibers, and multi-scale elastic energy-dissipating particles constitute the cementitious and functional modification system. The cementitious material is one or more of sulfoaluminate cement, ordinary silicate cement, or alkali activators (such as water glass modulus 1.2-1.8); sulfoaluminate cement is preferred to meet the requirements of rapid hardening and resistance to seawater erosion. The lightweight component is a stable foam pre-foamed by a protein-based or composite foaming agent, with the dosage controlled to maintain the wet density of the mixture at 9-12 kN / m³. The hybrid fibers are a combination of polypropylene (PP), glass fiber (GF), or polyvinyl alcohol (PVA) fibers with a length of 6-12 mm; the multi-scale elastic energy-dissipating particles are rubber particles or elastic polymer microparticles with a particle size of 1-3 mm. The mass ratio of hybrid fibers to multi-scale elastic energy-dissipating particles is 1:(4-8). The hybrid fibers and rubber particles or elastic polymer microparticles work together to form an energy absorption network. At this ratio, the mesh skeleton formed by the overlapping of the hybrid fibers can stably wrap the multi-scale elastic energy-dissipating particles. The elastic energy-dissipating particles provide compressive damping, and the fibers provide tensile reinforcement. If the ratio is less than 1:4, too many elastic energy-dissipating particles will cause the hybrid fiber mesh to be broken up, and the material will produce discrete collapse damage when impacted. If the ratio is greater than 1:8, the hybrid fibers are too dense, which will cause the particles to be squeezed out and unable to form an effective damping layer.

[0049] Additives include water-reducing agents, foam stabilizers, and anti-corrosion agents (such as silane impregnating agents), which are added in appropriate amounts to optimize workability and durability.

[0050] The intelligent sensing and self-healing functional components include sensing components and self-healing components. Sensing components include distributed fiber optic sensors, piezoelectric ceramic particles, or conductive nanomaterials (such as carbon nanotubes) for real-time monitoring of stress, strain, temperature field, and damage evolution within the backfill layer. Self-healing components contain microcapsules of repair agents (wall material is urea-formaldehyde resin or gelatin, core material is epoxy resin or sodium silicate solution) or carriers of mineralizing microorganisms (such as Bacillus pasteurellii), used to automatically trigger the repair mechanism and restore the material's integrity when microcracks occur.

[0051] The parameters of each raw material are as follows: Waste concrete aggregate, after crushing and screening, is used to obtain particles with a particle size ≤2.36mm, and can be further ball-milled to a powder with a specific surface area ≥300m² / kg for use; the specific surface area of ​​slag powder should be ≥400m² / kg to meet the gelling activity requirements; PP fiber uses monofilament fibers with a diameter of 25-45μm, a length of 6-12mm, a tensile strength ≥560MPa, and a melting point of 160-180℃; carbon nanotubes are selected from single-walled carbon nanotube powder with a diameter of 1-3nm and a specific surface area of ​​360-460m² / g; microcapsules use a two-component system with urea-formaldehyde resin or gelatin as the wall material and epoxy resin or sodium silicate solution as the core material, with a particle size controlled at 100-150μm to achieve optimal repair efficiency; the microbial self-healing component uses... For *Pasteurella multocida*, the bacterial concentration should reach OD600≈1.0-1.2, and the urease activity should not be less than 28-32 mmol / min; for the fiber optic sensor, the DEUZEFDH series high-temperature resistant (-40 to +350℃) fiber optic sensor can be selected, with a fiber diameter of 1.0-1.4 mm; for the piezoelectric ceramic particles, lead zirconate titanate (PZT) ceramic can be selected, with a piezoelectric constant of 300-700 pC / N; for the rubber particles, waste tire rubber powder with a particle size of 1-3 mm is used; for the water-reducing agent, high-performance polycarboxylate water-reducing agent (such as SPC-100 standard type) is used, with a water reduction rate ≥25% and a solid content of 21.0±1.0%; for the protein foaming agent, animal protein foaming agent is used, with a dilution ratio of 1:20-1:60 and a foaming ratio of 20-30 times.

[0052] When an explosive shock wave occurs, the toughening and blast-resistant components first absorb most of the energy through deformation and energy dissipation. If the impact force exceeds the material's bearing capacity and causes internal damage, the intelligent sensing components immediately capture waveform data and locate the damage location. Subsequently, the self-healing components fill the resulting microcracks to prevent seawater corrosive media from entering through the cracks, thereby ensuring the long-term durability of the wharf after damage.

[0053] By adjusting the above proportions, the material of this invention achieves the following key properties: wet bulk density of 9-10.5 kN / m³, 28-day unconfined compressive strength of 2.0-2.8 MPa, and excellent impact energy dissipation capacity. Parameters such as wet bulk density, 28-day unconfined compressive strength, and lateral pressure coefficient are determined according to the "Standard for Geotechnical Testing Methods" GB / T50123-2019. Wet bulk density is determined using the ring sample method, weighing the sample mass and volume. For the 28-day unconfined compressive strength, Φ50mm×H100mm cylindrical specimens are prepared, cured for 28 days, and then pressurized to failure at an axial strain rate of 1% / min. More importantly, by introducing intelligent sensing and self-healing components, this material can be upgraded to a fourth-generation intelligent civil engineering material with structural health self-sensing and micro-damage self-healing capabilities, enabling real-time status assessment and lifespan extension of concealed works at wharves.

[0054] This embodiment also provides a construction method for solid waste-based blast-resistant soil used for wharf backfilling, including the following steps:

[0055] Step 1, Construction Interface Preparation and Foundation Pretreatment: Clean up the slag, silt and water in the land area to be backfilled behind the wharf; for structures such as sheet pile wharves, lay high-strength geotextiles as interface isolation layer and flexible buffer layer.

[0056] Step 2, Pre-fabrication of sensing functionalized hybrid fibers: Conductive nanomaterials (such as carbon nanotubes) are immersed in deionized water containing surfactants, and multi-stage dispersion is performed using high-energy ultrasound to obtain a stable and uniform conductive functional slurry; the hybrid fibers are immersed in the conductive functional slurry for impregnation treatment, and the conductive nanomaterials are firmly coated on the surface of individual fibers through electrostatic adsorption or physical deposition; after low-temperature drying at 60℃-80℃ or centrifugal dehydration, a continuous three-dimensional piezoresistive sensing sheath is constructed on the fiber surface;

[0057] Step 3, on-site preparation of solid waste-based blast-resistant soil: In a mobile mixing plant, pretreated solid waste base material, cementitious material, mixed fiber and elastic energy-dissipating particles are added sequentially according to the design ratio and dry-mixed evenly; then water and additives are added and stirred to form a uniform slurry; finally, pre-made stable foam is injected into the slurry and stirred at high speed until a fluid lightweight soil with good flowability is formed (slump should be greater than 200mm); if the design includes intelligent sensing and self-healing functions, distributed fiber optic sensors, piezoelectric ceramic particles and self-healing components are uniformly mixed in the later stage of mixing. Attention should be paid to controlling the mixing intensity and time to avoid damaging the microcapsules or microbial activity;

[0058] Step 4, Self-leveling Pumping and Dynamic Embedding Positioning: A dedicated pumping device continuously injects the mixture into the backfill area, utilizing the material's self-leveling and self-compacting properties to fill complex voids. During the pouring process, a distributed optical fiber guiding and laying device is simultaneously activated to ensure that the optical fiber sensor is embedded in the center of the mixture according to the designed trajectory and forms spatial coupling with the piezoresistive network constructed from the mixed fibers. For the underwater area on the sea side, a closed-loop pouring method is used to ensure that the duct depth remains below the surface of the mixture at all times.

[0059] Step 5, Layered Continuous Construction and Sensing Link Calibration: The thickness of a single layer should be 0.5-1.0m. The next layer can be poured continuously before the initial setting of the previous layer of material until the design elevation is reached. For layers with sensing functions, the electrical connectivity test of the sensing elements should be performed immediately before the initial setting of each layer of material, and the initial resistance value and initial wavelength reference should be recorded to complete the initial calibration of the structural health monitoring system.

[0060] Step 6, Curing and Surface Protection: After pouring, cover with geomembrane or spray with curing agent for water retention and curing for 3-7 days; for materials containing microbial self-healing components, provide a suitable temperature and humidity environment in the early stage of curing to activate microbial activity; on the seaside or top surface, a protective coating against chloride ion penetration can be sprayed.

[0061] Step 7, Intelligent Monitoring System Integration: After construction is completed, the embedded sensing elements will be connected to the external data acquisition and analysis system to establish an intelligent monitoring platform for the structural health of the wharf backfill layer, enabling real-time visual monitoring and early warning of the internal stress state, damage initiation and expansion of the backfill.

[0062] Combination Figure 1 This embodiment provides a dynamic monitoring method for backfill areas filled with the above-mentioned solid waste-based blast-resistant soil, including the following steps:

[0063] Step S1: Collect the resistance signal of conductive nanomaterials in the backfill area affected by the dynamic impact load of the explosion source, combine it with the resistance signal of conductive nanomaterials in the reference area to perform environmental drift compensation to obtain the electrical signal caused by physical damage, and normalize the electrical signal to the resistance change rate.

[0064] Step S2: Collect the wavelength offset signal of the distributed optical fiber sensor in the backfill area. Based on the linear mapping relationship of the strain sensitivity of the optical fiber, the wavelength offset is converted into transient strain. The least squares method is used to fit the constructed spatial strain attenuation model in which the transient strain dissipates exponentially with depth, and the spatial strain attenuation coefficient is obtained by inversion.

[0065] Step S3: Capture the peak impact stress signals generated by the impact load on the piezoelectric ceramic particles at the closest and farthest ends of the backfill area from the explosion source, and use the difference between the two peak impact stress signals to obtain the global dynamic load energy absorption efficiency of the backfill area.

[0066] Step S4: Determine the damage level of the backfill area based on the global dynamic load energy absorption efficiency, spatial strain attenuation coefficient and resistance change rate, and determine the repair plan based on the damage level.

[0067] Step S5: Apply an excitation pulse to the repaired backfill area. Quantitatively verify the degree of recovery of the backfill area by comparing the stress wave reduction rate and resistance repair rate before and after repair.

[0068] S1 specifically includes:

[0069] Step S11: Simultaneously collect the working resistance of the backfill area affected by dynamic impact load and the reference resistance of the non-stressed reference area.

[0070] Step S12: Subtract the reference resistance from the working resistance to obtain the electrical signal caused by physical damage;

[0071] Step S13: Normalize the electrical signal into the rate of change of resistance.

[0072] In step S12, environmental interference is eliminated using a dual-path differential compensation formula to obtain a clean damage signal ΔR. pure ,

[0073] ΔR pure =R work - k ·R ref ,

[0074] in, k R is the correction factor; work R is the working resistance. ref This is the reference resistor.

[0075] In step S13, the electrical signal ΔR pure Converted to the rate of change of resistance ΔR pure / R0, where R0 is the initial resistance.

[0076] In step S2, the wavelength shift signal is converted into transient strain using the fiber-based strain sensitivity linear mapping relationship described in the following formula. s ,

[0077] Δλ=Ke· s ,

[0078] Where Δλ is the wavelength offset and Ke is the strain sensitivity coefficient of the optical fiber.

[0079] The specific process of inverting the spatial strain attenuation coefficient using the least squares method in step S2 includes:

[0080] Step S21, with transient strain s The dependent variable is the backfill depth. z Using the independent variable, a spatial strain decay model exhibiting exponential dissipation is constructed. s ( z ),

[0081] s ( z )= s 0·e -αz ,

[0082] in, s 0 is z The initial strain peak value when = 0, where α is the spatial strain attenuation coefficient;

[0083] Step S22, combined with Δλ=Ke· s The corresponding transient strain is obtained based on the wavelength offset at different depths. s ( zThe least squares method was used for nonlinear fitting, and the spatial strain attenuation coefficient α was obtained by inversion.

[0084] The specific process of step S3 includes: capturing the initial impact stress peak σ of the piezoelectric ceramic closest to the explosion source. source and the peak residual stress σ of the piezoelectric ceramic at the farthest point from the explosion source wall Obtain the global dynamic load energy absorption efficiency η.

[0085] η=(1-σ wall / σ source )×100%.

[0086] The damage gradient determination process in step S4 includes:

[0087] If the resistance change rate of the obtained conductive nanomaterial undergoes a step-like circuit break jump, or the global dynamic load energy absorption efficiency is between the first energy absorption threshold and the second energy absorption threshold, the self-healing component repair scheme for the backfill area is triggered; if the global dynamic load energy absorption efficiency is lower than the first energy absorption threshold, or the spatial strain attenuation coefficient is lower than the preset blast-resistant design lower limit, the artificial reinforcement grouting repair scheme is triggered, and construction is carried out according to the construction method of solid waste base blast-resistant soil.

[0088] The specific process of step S5 includes:

[0089] Step S51, extract the resistance signal R when damaged. damaged Initial resistance R0 and the repaired resistance signal R healed Calculate the resistance repair rate η R ,

[0090] η R =[1-(R healed -R0) / (R damaged -R0)]×100%;

[0091] Step S52: Inject artificially simulated excitation pulses based on the inverted spatial strain attenuation coefficient α and the initial transient strain. s 0. Compute the energy dissipation rate evolution flux E on the depth path. dis ( z ),

[0092] E dis ( z )=α·s0·e -αz ;

[0093] Step S53: Extract the residual strain intensity after the backfill layer has dissipated. s (L wall ), calculate the stress wave attenuation rate η a ,

[0094] ηa =[1- s (L wall ) / s 0]×100%;

[0095] Step S54, if η R ∈[80%,100%] and η a If the residual stress of the piezoelectric ceramic at the farthest point from the excitation pulse rises to more than 90% of the initial design value, and is below the safety threshold, then the repair is considered successful.

[0096] The working principle of the repair judgment and repair described in steps S4 and S5 is described as follows.

[0097] (1) Self-repair startup

[0098] Physical triggering: When the blast-resistant soil is subjected to impact load, it generates local strain and generates microcracks. The stress concentration at the crack tip acts directly on the self-healing component.

[0099] Signal monitoring: At the monitoring level, the system acquires feedback from the internal three-dimensional piezoresistive sensing network in real time. When any of the following conditions are met, the repair mechanism is activated: First, the resistance change rate of the conductive nanomaterial undergoes a step-like open circuit jump, indicating that the conductive network is interrupted due to physical cracking; or second, the dynamic load energy absorption efficiency η in the entire time domain decreases and is between the preset first energy absorption threshold and the second energy absorption threshold.

[0100] (2) Repair process

[0101] Automatic filling: As microcracks expand, the microcapsule wall material encapsulating the matrix ruptures due to mechanical failure, and the repair agent stored inside automatically overflows and fills the microcracks; or mineral precipitation occurs through microbial mineralization mechanisms. The repair agent undergoes a physicochemical reaction within the cracks, re-bonding the damaged solid waste matrix. Along with the filling of the repair agent and the healing of the cracks, the fractured conductive nanomaterial network and hybrid fiber interface begin to re-contact and establish connections. The system tracks the repair progress in real time by collecting the resistivity curve as it falls from its peak.

[0102] Artificial reinforcement grouting: Carry out the work according to steps 1 to 7 of the construction method of solid waste base blast-resistant soil.

[0103] (3) Conditions for successful repair

[0104] Repair rate meets target: Repair rate η calculated based on the degree of resistance recovery. R Entering the preset qualified range [80%, 100%], this indicator reflects the degree of reconstruction of the internal conductive network (and the corresponding mechanical structure).

[0105] Dynamic performance recovery: The dynamic strain field of the blast-resistant soil recovers to a steady state, and the stress wave attenuation rate η a It has rebounded to over 90% of the initial design value.

[0106] Evaluation conclusion: When the resistivity and stress wave attenuation simultaneously meet the recovery threshold and the residual stress peak of the piezoelectric ceramic at the farthest point from the excitation pulse is below the safety threshold, the system determines that the area has been successfully repaired and re-enters the full-time domain monitoring state.

[0107] Example 1: This example is used for load reduction and reinforcement of the rear of a gravity wharf. A gravity wharf needs to be expanded and filled in the rear. The original design used sand and gravel backfill, but due to the soft soil, there were concerns that excessive soil pressure would affect the stability of the original wharf. Therefore, the material in this example is used for load reduction backfill.

[0108] Material Preparation: A mixture of dewatered sludge from the port area, crushed aggregate from waste concrete, and slag powder in a weight ratio of 5:3:2 was used as the solid waste base material. Based on 100 parts of the solid waste base material, 12 parts of sulfoaluminate cement, 0.3 parts of PP fiber, 2 parts of rubber granules, 0.5 parts of water-reducing agent, and 35 parts of water were added and stirred into a slurry. Finally, foam made from a protein foaming agent was added until the wet bulk density of the mixture reached 10.5 kN / m³ and the flow value was 220 mm. To enhance intelligent monitoring capabilities, 0.1 parts of carbon nanotubes (CNTs) and 0.5 parts of microcapsules encapsulating sodium silicate solution were uniformly incorporated during the later stages of mixing.

[0109] Construction: combined Figure 2 Figure 3 shows the excavation to the design elevation behind the completed riprap prism 4 behind the original wharf wall. Using pumping equipment, the prepared lightweight soil was continuously poured to the design height, forming the backfill layer 6. The continuous pouring thickness reached 2.5 meters per day. Reference electrodes were pre-embedded in key sections of the backfill layer for later inversion of internal stress distribution using resistivity tomography.

[0110] Results: Monitoring after backfilling showed that the lateral displacement of the wharf wall was far less than the design warning value. The material's 28-day strength reached 2.8 MPa, meeting the requirements for laying heavy transport roads later. Compared to the original scheme, the soil pressure on the original structure was reduced by approximately 40%. Through an integrated monitoring system, the resistance changes of the backfill layer could be acquired in real time, successfully identifying stress concentration areas caused by localized heavy equipment overload. Furthermore, the restoration of conductivity in the area after microcapsule rupture repair was observed, verifying the material's self-sensing and self-healing capabilities.

[0111] In this embodiment, to ensure that the CNTs are not disturbed or broken during the pouring of the fluid soil, a synchronous guiding constraint method is used to deploy the CNTs, as shown below:

[0112] In step S110, CNTs undergo surface functionalization treatment, such as acid treatment, and are ultrasonically dispersed in water for 20 minutes with 0.1 parts of a dispersant, such as sodium dodecylbenzene sulfonate, to form a uniform suspension.

[0113] Step S120: Add the CNT suspension along with the mixing water to the mixer; to achieve spatial positioning monitoring, embed stainless steel electrode pairs in the backfill area with a grid spacing of 0.5m × 0.5m.

[0114] Step S130: After construction is completed, the pre-embedded electrodes are connected through the electrical resistance tomography (ERT) system. When the wharf is subjected to overload impact or uneven settlement, the system monitors the voltage / current changes between different measuring points and inverts the strain inside the backfill. When the backfill layer experiences a local settlement of 0.5mm, the resistance change rate (ΔR / R0) of the corresponding area reaches more than 5%, thus achieving high-precision real-time monitoring of the deep stress of the backfill.

[0115] In step S110, the specific process of surface functionalization of CNTs is as follows: carbon nanotubes are immersed in a mixed acid solution of 65% concentrated nitric acid and 98% concentrated sulfuric acid (volume ratio 1:3) and continuously magnetically stirred and ultrasonically treated at 60°C for 4 hours; then, they are repeatedly filtered and washed with deionized water until the filtrate is neutral (pH≈7.0) to remove residual acid and excess ions, and dried in a vacuum drying oven at 80°C for later use; during dispersion, 0.1 parts of sodium dodecylbenzenesulfonate are used as a dispersant, and the mixture is dispersed for 30 minutes at a speed of 3000 r / min using a high-speed shear emulsifier.

[0116] In this embodiment, CNTs are used as stress-sensitive conductive networks, which form a permeable network through physical overlap in the lightweight soil of the solid waste base. When external loads (such as foundation settlement) are applied to the backfill, small strains occur inside the soil, causing changes in the contact spacing of the CNT overlap points, resulting in a nonlinear change in the overall resistance value. Using a four-electrode measurement method, and employing R=ρL / S, where ρ is the material resistivity, and L and S are the electrode spacing and the equivalent cross-sectional area of ​​the backfill, respectively, combined with electrical resistance tomography (ERT) technology, the electrical signal can be converted into a stress field distribution within the backfill layer. The stress field distribution is represented by horizontal coordinates (x, y) and depth coordinates z, with numerical dimensions including the resistance change rate ΔR / R0 and transient strain. s By deriving ΔR / R0≈Δρ / ρ+ΔL / L-ΔS / S through total differential, ΔL and ΔS are obtained using a displacement gauge (LVDT) and a transverse strain gauge, where ΔL and ΔS are the longitudinal deformation and cross-sectional area change of the CNT, respectively.

[0117] The self-healing criterion is based on the ΔR / R0 curve. When the solid waste-based blast-resistant soil undergoes deformation, the ΔR / R0 curve exhibits a sharp, step-like jump; after triggering the microcapsule / microbial response, the curve enters a period of high-level fluctuation; during the healing process, the ΔR / R0 curve gradually and smoothly declines from its peak; when the ΔR / R0 curve falls back to near its initial level, it indicates that the cracks have been densely filled and the conductive network has been largely rebuilt. The specific judgment process is as follows:

[0118] Phase 1, Linear Sensing Period: As the load increases, the CNT undergoes minute elastic deformation, and the monitoring system displays the rate of change of resistance ΔR / R0 as a function of transient strain. s It decreases linearly, and the sensitivity coefficient (GF) stabilizes between 15 and 20;

[0119] Stage 2, Damage Abrupt Change Period: When the load reaches 85% of the ultimate strength, visible microcracks appear on the CNT surface, the effective conductive cross section S decreases drastically, the ΔR / R0 curve jumps upward instantaneously, the amplitude surges from -5% to +450%, and the system automatically triggers a damage warning.

[0120] Phase 3, Repair Response Period: Stress concentration at the crack causes the epoxy resin-coated microcapsules to rupture, and the core material flows out under capillary action and fills the crack space. The monitoring curve shows that ΔR / R0 remains on a plateau for about 2 hours after reaching its peak, and then begins to slowly decline.

[0121] Phase 4, Performance Recovery Period: As the repair product solidifies, the conductive network is partially rebuilt, and the effective cross-sectional area S recovers; after 48 hours, ΔR / R0 drops back to around +12% and tends to stabilize.

[0122] Example 2: This example is used for the rapid repair and backfilling of a sheet pile wharf. In a simulation, a sheet pile wharf needs rapid repair of the backfill area damaged by an explosion, and the new backfill material must have a certain protective function. In this example, in addition to adding CNTs as in Example 1, fiber optic sensors and piezoelectric ceramic particles are added to the blast-resistant soil based on solid waste to calculate the degree of structural damage to the sheet pile wharf after the explosion. The piezoelectric ceramic particles utilize their microsecond-level response characteristics to first capture the peak pressure of the shock wave and activate the data acquisition system to collect data through instantaneous voltage pulses; the distributed fiber optic sensors utilize their advantages of long distance and spatial continuity to record the overall structural strain cloud map caused by the impact, and monitor the residual strain and settlement displacement of the structure after the explosion.

[0123] This implementation requires the execution of a manual reinforcement grouting repair process, which includes material preparation, construction, and results.

[0124] Material Preparation: To achieve rapid hardening and explosion resistance, an alkali-activated system was adopted. The solid waste base material consisted of brick and stone debris cleaned up on-site and steel slag powder from a nearby steel plant (7:3). Based on 100 parts of the base material, 8 parts of alkali activator (water glass and NaOH composite), 0.4 parts of PVA fiber, 3 parts of elastic polymer microparticles, and 30 parts of water were added. After foaming, the wet bulk density was controlled at 9.0 kN / m³, and the flow value at 180 mm. The initial setting time for this mix was approximately 45 minutes. To meet the needs of rapid assessment, 0.05 parts of a distributed fiber optic sensor and piezoelectric ceramic particles were incorporated as dynamic stress sensing elements.

[0125] Construction: Simple formwork was directly erected in the cleared damaged area. Lightweight soil was prepared and poured on-site using a pump truck equipped with a mixing function. Due to the material's self-compacting properties, it quickly filled the irregular pit. During pouring, quick-connect fiber optic cables with interfaces were simultaneously laid along the depth of the repair structure. A groove was pre-reserved at the top of the poured structure, which was later fitted with a precast concrete cover as a temporary pavement.

[0126] Results: Pedestrian access was possible after 6 hours, and light vehicle access was permitted after 24 hours. Subsequent testing showed that the material layer effectively attenuated the peak value of the explosive stress wave, and produced no sharp fragments after failure, achieving a 28-day strength of 2.0 MPa. During testing, embedded piezoelectric and fiber optic signals successfully captured and located the propagation path and peak stress region of the shock wave, providing precise data for assessing the repair effect and secondary reinforcement. The tests demonstrated that this material, while rapidly restoring functionality and improving protection levels, also enabled rapid perception and assessment of the engineering condition, significantly enhancing protection effectiveness.

[0127] The performance data achievable in this embodiment are shown in Tables 1, 2, and 3.

[0128] Table 1 Self-healing performance test conditions and indicators

[0129]

[0130] Table 2 Test conditions and indicators for intelligent sensing response performance

[0131]

[0132] Table 3 Material Cost and Economic Benefit Evaluation

[0133]

Claims

1. A dynamic monitoring method for wharf backfill areas based on stress measurement, characterized in that, include: Step S100: Set part of the backfill area as a reference area, incorporate elastic energy dissipation particles into the backfill area, and bury distributed optical fiber sensors, piezoelectric ceramic particles, hybrid fibers coated with conductive nanomaterials and self-healing components at different depths. Step S200: Collect the resistance signal of conductive nanomaterials in the backfill area affected by the dynamic impact load of the explosion source, combine the resistance signal of conductive nanomaterials in the reference area to perform environmental drift compensation to obtain the electrical signal caused by physical damage, and normalize the electrical signal to the resistance change rate. Step S300: Collect the wavelength offset signal of the distributed optical fiber sensor in the backfill area. Based on the linear mapping relationship of the strain sensitivity of the optical fiber, the wavelength offset is converted into transient strain. The least squares method is used to fit the constructed spatial strain attenuation model in which the transient strain dissipates exponentially with depth, and the spatial strain attenuation coefficient is obtained by inversion. Step S400: Capture the peak impact stress signals generated by the impact load on the piezoelectric ceramic particles at the closest and farthest ends of the backfill area from the explosion source, and use the difference between the two peak impact stress signals to obtain the global dynamic load energy absorption efficiency of the backfill area. Step S500: Determine the damage level of the backfill area based on the global dynamic load energy absorption efficiency, spatial strain attenuation coefficient and resistance change rate, and determine whether to use a self-healing component self-healing scheme or an artificial reinforcement grouting scheme for damage repair based on the damage level. In step S600, if a self-healing component self-healing scheme is adopted, an excitation pulse is applied to the repaired backfill area, and the degree of recovery of the backfill area is quantitatively verified by comparing the stress wave reduction rate and resistance repair rate before and after repair.

2. The method according to claim 1, characterized in that, Step S200 specifically includes: Step S210: Simultaneously collect the working resistance of the backfill area affected by dynamic impact load and the reference resistance of the non-stressed reference area. Step S220: Subtract the reference resistance from the working resistance to obtain the electrical signal caused by physical damage; Step S230: Normalize the electrical signal to the rate of change of resistance.

3. The method according to claim 2, characterized in that, In step S220, environmental interference is eliminated using a dual-path differential compensation formula to obtain a clean damage signal ΔR. pure , ΔR pure =R work - k ·R ref , in, k R is the correction factor; work R is the working resistance. ref This is the reference resistor.

4. The method according to claim 3, characterized in that, In step S230, the electrical signal ΔR pure Converted to the rate of change of resistance ΔR pure / R0, where R0 is the initial resistance.

5. The method according to claim 1, characterized in that, In step S300, the wavelength shift signal is converted into transient strain using the fiber-based strain sensitivity linear mapping relationship described in the following formula. s , Δλ=Ke· s , Where Δλ is the wavelength offset and Ke is the strain sensitivity coefficient of the optical fiber.

6. The method according to claim 5, characterized in that, The specific process of inverting the spatial strain attenuation coefficient using the least squares method in step S300 includes: Step S320, with transient strain s The dependent variable is the backfill depth. z Using the independent variable, a spatial strain decay model exhibiting exponential dissipation is constructed. s ( z ), s ( z )= s 0·e -αz ， in, s 0 is z The initial strain peak value when = 0, where α is the spatial strain attenuation coefficient; Step S330, combined with Δλ=Ke· s The corresponding transient strain is obtained based on the wavelength offset at different depths. s ( z The least squares method was used for nonlinear fitting, and the spatial strain attenuation coefficient α was obtained by inversion.

7. The method according to claim 1, characterized in that, The specific process of step S400 includes: capturing the initial impact stress peak σ of the piezoelectric ceramic closest to the explosion source. source and the peak residual stress σ of the piezoelectric ceramic at the farthest point from the explosion source wall Obtain the global dynamic load energy absorption efficiency η. η=(1-σ wall / s source )×100%.

8. The method according to claim 1, characterized in that, The damage gradient determination process in step S500 includes: If the resistance change rate of the obtained conductive nanomaterial undergoes a step-like open circuit jump, or the global dynamic load energy absorption efficiency is between the first energy absorption threshold and the second energy absorption threshold, a repair scheme for the self-healing component to repair the backfill area is triggered; the self-healing component is a microcapsule containing a repair agent or a microbial carrier with mineralization ability. Microcracks generated by local strain trigger the self-healing component to rupture and release the repair agent or microorganisms. If the global dynamic load energy absorption efficiency is lower than the first energy absorption threshold, or the spatial strain attenuation coefficient is lower than the preset explosion-proof design lower limit, the artificial reinforcement grouting repair scheme will be triggered.

9. The method according to claim 1, characterized in that, Step S600 specifically includes the following processes: Step S610: Extract the resistance signal R when damaged. damaged Initial resistance R0 and the repaired resistance signal R healed Calculate the resistance repair rate η R , η R =[1-(R healed -R0) / (R damaged -R0)]×100% Step S620: Inject artificially simulated excitation pulses based on the inverted spatial strain attenuation coefficient α and the initial transient strain. s 0. Compute the energy dissipation rate evolution flux E on the depth path. dis ( z ), E dis ( z )=α·s0·e -αz ，z This refers to the backfill depth. Step S630: Extract the residual strain intensity after dissipation through the backfill zone. s (L wall ), calculate the stress wave attenuation rate η a or a =[1- s (L wall ) / s 0]×100%; Step S640, if η R ∈[80%,100%] and η a If the residual stress of the piezoelectric ceramic at the farthest point from the excitation pulse rises to more than 90% of the initial design value, and is below the safety threshold, then the repair is considered successful.

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