A filling body life cycle wave velocity monitoring and mechanical test device and a use method thereof

Abstract

The application provides a filling body life cycle wave velocity monitoring and mechanical test device and a use method, relates to the field of mine filling mining and geotechnical engineering material testing, and comprises a loading frame, an axial loading electric cylinder, a triaxial pressure chamber, a sound wave signal generation and collection instrument and a central controller. The upper and lower parts of a sample preparation barrel in the triaxial pressure chamber are respectively provided with an upper sound wave pressure head and a lower sound wave pressure head, and the upper sound wave pressure head and the lower sound wave pressure head are respectively electrically connected with an upper sound wave sensor and a lower sound wave sensor. The upper sound wave sensor and the lower sound wave sensor are configured to continuously collect the wave velocity of the filling body sample from the initial moment of filling slurry injection into the sample preparation barrel to the whole process of curing and the whole process of mechanical loading. The sound wave signal generation and collection instrument controls the sound wave sensor to switch between transmission mode, reflection mode and acoustic emission monitoring mode. The application realizes continuous monitoring of the wave velocity of the filling body from slurry state to failure, and establishes a wave velocity-intensity correlation model and a damage evaluation method.

Description

Technical Field

[0001] This invention relates to the field of mining backfilling and geotechnical engineering material testing technology, and more particularly to a device and method for monitoring wave velocity and conducting mechanical tests on the life cycle of backfill bodies. Background Technology

[0002] Backfill mining is one of the main mining methods. The backfill body in the stope is subjected to a complex physicochemical evolution process due to the coupled effects of heat, water, mechanical, and chemical fields. Accurately evaluating the integrity, uniformity, and solidification degree of the backfill body throughout the entire process from grout injection to hardening and bearing capacity is of significant engineering importance for stope stability assessment and backfill effectiveness evaluation.

[0003] Wave velocity, including longitudinal wave velocity (Vp) and transverse wave velocity (Vs), is an important non-destructive testing indicator for evaluating the integrity, homogeneity, elastic modulus, and curing degree of filling materials. The propagation speed of sound waves in filling materials is closely related to their density, porosity, and elastic modulus: the higher the density and the fewer the pores, the faster the wave velocity, and vice versa. By axially placing ultrasonic transmitting and receiving probes in the curing cavity of the filling material, wave velocity testing can be performed on the filling material. This allows for the acquisition of its internal structural information without damaging the specimen, and further, a correlation model between wave velocity and the compressive strength of the filling material can be established, enabling non-destructive prediction of the strength development of the filling material.

[0004] However, in existing technologies, wave velocity testing is separated from the curing and mechanical testing of the backfill. The conventional procedure is as follows: the sample is first cured in a curing chamber to a predetermined age (e.g., 7, 14, or 28 days), then removed and placed on a separate wave velocity meter for discrete time-point wave velocity measurements, before being transferred to a triaxial testing machine for mechanical testing. This model has the following fundamental drawbacks. First, wave velocity testing is only conducted at a few discrete time points, making it impossible to obtain a continuous evolution curve of wave velocity with curing age, resulting in an inability to accurately capture key wave velocity change nodes during the hydration reaction (such as initial setting, final setting, and peak hydration rate). Second, the sample is transferred multiple times between the curing chamber, wave velocity meter, and triaxial testing machine, interrupting wave velocity testing and potentially subjecting the sample to mechanical disturbance, failing to reflect the real-time initiation and propagation process of microcracks. Third, wave velocity testing is conducted under no confining pressure, which differs significantly from the actual stress state of the backfill in the mining area, limiting the applicability of the wave velocity-strength model. Fourth, wave velocity changes cannot be monitored synchronously during the mechanical testing phase, making it difficult to establish a quantitative relationship between wave velocity, stress, and strain. Wave velocity data is completely disconnected from the mechanical failure process.

[0005] Therefore, there is an urgent need for an integrated device that can continuously monitor the wave velocity of the filling material throughout its entire life cycle, from slurry injection to mechanical failure, within the same apparatus, in order to obtain the continuous evolution law of wave velocity over time and simultaneously establish the coupling relationship between wave velocity, stress, and strain during mechanical testing. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a device and method for monitoring wave velocity and conducting mechanical testing throughout the life cycle of filling materials. This invention continuously collects wave velocity data from the initial injection of the filling grout, throughout the entire curing and mechanical loading process, and supports switching between three acoustic wave monitoring modes: transmission, reflection, and acoustic emission.

[0007] To achieve the above objectives, the present invention provides a device for monitoring wave velocity and conducting mechanical testing on the life cycle of a filling material, comprising a loading frame, an axial loading mechanism mounted on the loading frame, at least one triaxial pressure chamber disposed within the loading frame, a confining pressure control system connected to the triaxial pressure chamber, and a temperature control system disposed on the triaxial pressure chamber. A sample preparation container is disposed inside the triaxial pressure chamber. An upper acoustic pressure head and a lower acoustic pressure head are respectively disposed at the upper and lower parts of the sample preparation container. The upper and lower acoustic pressure heads are electrically connected to an upper acoustic sensor and a lower acoustic sensor, respectively. The sample preparation container is used to contain a filling material sample. The device is characterized in that the upper and lower acoustic sensors are configured to continuously collect wave velocity data of the filling material sample throughout the entire curing and mechanical loading process, starting from the initial moment when the filling slurry is injected into the sample preparation container. The acoustic signal generator is configured to control the upper acoustic sensor and the lower acoustic sensor to switch between the following modes: In the transmission mode, one acoustic sensor acts as the transmitter and the other as the receiver, measuring the propagation time of the sound wave in the sample to calculate the wave velocity. Reflection mode, in which one acoustic sensor acts as both transmitter and receiver, receiving reflected signals from internal defects or the bottom of the sample; In the acoustic emission monitoring mode, both the upper acoustic wave sensor and the lower acoustic wave sensor serve as passive receivers, continuously recording acoustic emission events generated by micro-fractures inside the sample.

[0008] Furthermore, in the transmission mode, the acoustic signal generator generates longitudinal or transverse wave pulses through the upper or lower acoustic sensor, measures the longitudinal wave velocity Vp and the transverse wave velocity Vs respectively, and calculates the dynamic elastic modulus and dynamic Poisson's ratio of the filling sample based on Vp and Vs.

[0009] Furthermore, the device also includes a central controller configured to divide the maintenance process into stages based on the wave velocity change rate dv / dt.

[0010] Furthermore, the central controller also incorporates a wave velocity-intensity correlation model σc=a·Vp+b, where σc is the uniaxial compressive strength of the filling material, Vp is the longitudinal wave velocity, and a and b are regression coefficients calibrated through pre-tests. The central controller is configured to nondestructively predict the current strength of the filling sample based on the currently measured wave velocity value using the wave velocity-strength correlation model.

[0011] Furthermore, the central controller is also configured to perform multi-parameter collaborative fusion inference, with input data including wave velocity Vp(t), permeability K(t), displacement W(t), confining pressure P(t), temperature T(t), and acoustic emission event count AE(t); the multi-parameter collaborative fusion inference includes: When the wave velocity increases and the permeability decreases, it is determined that the pores are filled and the density increases. When the wave velocity increases but the permeability remains unchanged or increases, it is determined that the wave velocity test coupling is poor or there are defects inside the sample. When the wave velocity decreases and the permeability increases, it is determined to be microcrack propagation.

[0012] Furthermore, the central controller is also configured to: during the mechanical loading process, based on the acoustic emission events recorded in the acoustic emission monitoring mode, correlate with the synchronously acquired wave velocity data and stress-strain data, plot the wave velocity-acoustic emission-stress-strain synergistic curve, and identify the characteristic stress levels of crack initiation, propagation and penetration.

[0013] Furthermore, the central controller is also configured to calculate the wave velocity attenuation rate η = (Vp0 - Vp 破坏 The damage variable D = 1 - (Vp0 × 100%) is established based on the wave velocity attenuation rate. 破坏 / Vp0)², where Vp0 is the longitudinal wave velocity before destruction, Vp 破坏 The damage variable, representing the longitudinal wave velocity at failure, is used to quantitatively evaluate the degree of damage to the filling sample during triaxial mechanical loading.

[0014] Furthermore, the transmitting voltage of the acoustic signal generator is adjustable from 100V to 500V, the receiving gain is adjustable from 20dB to 60dB, the center frequency range is from 50kHz to 500kHz, and the sampling frequency is not less than 10MHz.

[0015] Furthermore, the filling sample is composed of cementitious material, aggregate and water, wherein the aggregate is sand or tailings; one side of the ultrasonic pressure head is provided with a curing sample air inlet connector, which is used to introduce nitrogen into the sample to perform in-situ permeability testing, or to introduce carbon dioxide gas to accelerate curing.

[0016] This invention also provides a method for using a device for monitoring the life cycle wave velocity and conducting mechanical tests on filling materials, applied to the aforementioned device, comprising the following steps: S1. Fill the prepared filling slurry into the sample preparation bucket, install the upper acoustic pressure head and the lower acoustic pressure head, and assemble the triaxial pressure chamber; S2. At the initial moment when the filling slurry is injected into the sample preparation bucket, the upper acoustic wave sensor and the lower acoustic wave sensor are turned on. Under the control of the acoustic wave signal generator and acquisition instrument, the wave velocity of the filling sample is continuously acquired in transmission mode. The continuous acquisition of wave velocity continues throughout the curing stage and the subsequent mechanical loading stage. S3. During the maintenance phase, the longitudinal wave velocity Vp and the transverse wave velocity Vs are continuously collected, the wave velocity change rate dv / dt is calculated, the maintenance phase is automatically divided based on the feature points of the wave velocity-time curve, and a wave velocity-intensity correlation model is established. S4. During the mechanical loading stage, the wave velocity is continuously acquired, and the upper acoustic wave sensor and the lower acoustic wave sensor are switched to acoustic emission monitoring mode to record acoustic emission events synchronously. The wave velocity data, acoustic emission event data and stress-strain data are analyzed in a coordinated manner to evaluate the damage evolution process of the filling sample until the sample is destroyed.

[0017] By adopting the above technical solution, the present invention has the following advantages compared with the prior art: 1. The present invention provides a device and method for monitoring and testing the wave velocity of a filling body throughout its life cycle. The wave velocity is continuously collected from the initial moment when the filling slurry is injected into the sample preparation tank, and is collected throughout the entire curing process and the entire mechanical loading process. This enables the continuous acquisition of the wave velocity evolution curve of the filling body from the slurry state to failure, overcoming the shortcomings of the prior art which can only acquire wave velocity data at discrete time points and cannot capture key nodes of the hydration reaction.

[0018] 2. The present invention provides a device and method for monitoring the wave velocity and mechanical testing of the life cycle of filling bodies, which integrates three acoustic wave working modes: transmission mode, reflection mode and acoustic emission monitoring mode. It can acquire longitudinal wave velocity Vp and transverse wave velocity Vs during the curing stage, evaluate the uniformity and internal defects of the sample, and passively record acoustic emission events during the mechanical loading stage to track the crack initiation and propagation process, thereby realizing the synchronous and coordinated acquisition of multi-mode acoustic wave information.

[0019] 3. The present invention provides a device and method for monitoring wave velocity and conducting mechanical tests on the life cycle of filling bodies. Based on the wave velocity change rate dv / dt, the device automatically divides the maintenance stages and establishes a wave velocity-intensity correlation model. By combining multi-parameter collaborative fusion reasoning, the device cross-validates wave velocity data with permeability, drainage volume and acoustic emission data, effectively eliminating false signals such as poor coupling and significantly reducing the intensity prediction error. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a cross-sectional view of the overall structure of the infill body life cycle wave velocity monitoring and mechanical testing device described in this invention; Figure 2 This is a schematic diagram of the overall structure of the infill body life cycle wave velocity monitoring and mechanical testing device according to the present invention; Figure 3 This is a triaxial pressure chamber cross-sectional view of a filling body life cycle wave velocity monitoring and mechanical testing device according to the present invention; Figure 4 This is a schematic diagram (II) of the overall structure of the infill body life cycle wave velocity monitoring and mechanical testing device described in this invention; Figure 5 This is a schematic diagram of the full life cycle wave velocity-time curve and maintenance stage division of the infill body life cycle wave velocity monitoring and mechanical testing device described in this invention; Figure 6 This is a curve fitting the wave velocity-strength correlation model of the infill life cycle wave velocity monitoring and mechanical testing device described in this invention; Figure 7 This is a multi-parameter collaborative monitoring curve (curing stage) of a filling body life cycle wave velocity monitoring and mechanical testing device described in this invention. Figure 8 This is a waveform diagram of wave velocity-acoustic emission-stress-strain synergy during the mechanical test of the infill body life cycle wave velocity monitoring and mechanical testing device described in this invention; Figure 9 This is a flowchart illustrating the usage method of the infill body life cycle wave velocity monitoring and mechanical testing device described in this invention.

[0022] In the diagram: 1. Sample preparation container; 2. Upper acoustic pressure head; 3. Lower acoustic pressure head; 4. Permeable stone slab; 5. Curing sample; 6. O-ring; 7. Air inlet connector for curing sample; 8. Base; 9. Cylinder; 10. Snap ring; 11. Locking pin; 12. Nitrogen and CO2 inlet connectors; 13. Nitrogen inlet connector; 14. Nitrogen outlet connector; 15. Temperature sensor; 16. Upper acoustic sensor; 17. Lower acoustic sensor; 18. Heating coil; 19. Top cover; 20. Self-balancing piston; 21. Pressure pad; 22. Sensor pressure pad; 23. Axial loading electric cylinder; 24. Upper crossbeam; 25. Lower crossbeam; 26. Adapter; 27. Two-way ball valve; 28. Collection bottle; 29. ​​Column; 30. Profile frame assembly; 31. Fuma wheel. Detailed Implementation

[0023] It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other. The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0025] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0026] Unless otherwise specifically stated, the relative arrangement, numerical expressions, and values ​​of the components and steps set forth in these embodiments do not limit the scope of the invention. It should also be understood that, for ease of description, the dimensions of the various parts shown in the drawings are not drawn to actual scale. Techniques, methods, and devices known to those skilled in the art may not be discussed in detail, but where appropriate, such techniques, methods, and devices should be considered part of the specification. In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not as limitations. Therefore, other examples of exemplary embodiments may have different values. It should be noted that similar reference numerals and letters in the following drawings denote similar items; therefore, once an item is defined in one drawing, it need not be further discussed in subsequent drawings.

[0027] In the description of this invention, it should be understood that the orientation or positional relationship indicated by directional terms such as "front, back, up, down, left, right", "horizontal, vertical, horizontal" and "top, bottom" is generally based on the orientation or positional relationship shown in the accompanying drawings, and is only for the convenience of describing this invention and simplifying the description. Unless otherwise stated, these directional terms do not indicate or imply that the device or element referred to must have a specific orientation or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the scope of protection of this invention. The directional terms "inner" and "outer" refer to the inner and outer contours relative to the outline of each component itself.

[0028] For ease of description, spatial relative terms such as "above," "on top of," "on the upper surface of," "above," etc., are used herein to describe the spatial positional relationship of a device or feature as shown in the figures to other devices or features. It should be understood that spatial relative terms are intended to encompass different orientations in use or operation beyond the orientation of the device as described in the figures. For example, if the device in the figures were inverted, a device described as "above" or "on top of" other devices or structures would subsequently be positioned as "below" or "under" other devices or structures. Thus, the exemplary term "above" can include both "above" and "below." The device may also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein will be interpreted accordingly.

[0029] Furthermore, it should be noted that the use of terms such as "first" and "second" to define components is merely for the purpose of distinguishing the corresponding components. Unless otherwise stated, the above terms have no special meaning and therefore should not be construed as limiting the scope of protection of this invention.

[0030] Example This embodiment describes one working unit of the device as an example. The operation steps of the other working unit are exactly the same, and it can be operated synchronously or independently, or it can be used as a comparative test channel. The core of this invention is that continuous wave velocity acquisition begins from the initial moment when the filling slurry is injected into the sample preparation tank, throughout the entire curing process and the entire mechanical loading process, and the integration of full life cycle wave velocity monitoring and mechanical testing is achieved by switching between three sound wave modes: transmission, reflection and acoustic emission.

[0031] like Figure 1 , Figure 2 and Figure 4 As shown in the figure, this embodiment provides an integrated device for continuous monitoring of wave velocity and mechanical testing throughout the entire life cycle of a filling body, including a loading frame, an axial loading electric cylinder 23, a triaxial pressure chamber, a confining pressure control system, a temperature measurement and control module, a wave velocity testing module, a permeability testing module, a drainage collection module, an acoustic signal generator and acquisition instrument, and a central controller.

[0032] The loading frame is a four-column structure, consisting of an upper crossbeam 24, a lower crossbeam 25, and a middle load-bearing crossbeam. Four columns 29 are vertically connected by bolts and support the upper crossbeam 24 and the lower crossbeam 25, forming a closed, high-rigidity loading space. The upper crossbeam 24, the lower crossbeam 25, and the columns 29 are all made of high-strength alloy steel and have undergone heat treatment to improve rigidity and fatigue resistance.

[0033] The loading frame is placed on the profile frame assembly 30. The profile frame assembly 30 is made of aluminum alloy profiles spliced ​​together using angle brackets and T-bolts, possessing good rigidity and lightweight characteristics. A caster wheel 31 is bolted to each of the four lower corners of the profile frame assembly 30. The caster wheel 31 serves both as a movement wheel and a fixing foot: when the device needs to be moved, the foot is screwed up, allowing for flexible movement using the casters; upon reaching the test position, the foot is screwed down and locked, ensuring the device is stably fixed to the ground.

[0034] The device includes two independent axial loading electric cylinders 23 and two triaxial pressure chambers, symmetrically arranged on the left and right sides of the loading frame. The loading path, confining pressure parameters, and temperature parameters of the left and right working units can be set independently without interference.

[0035] like Figure 3 As shown, the triaxial pressure chamber includes a curing sample assembly. The curing sample assembly consists of a sample preparation container 1, an upper acoustic pressure head 2, a lower acoustic pressure head 3, a permeable stone slab 4, a curing sample 5, an O-ring 6, and a curing sample air inlet pipe connector 7.

[0036] The sample preparation container 1 is made of stainless steel, with an inner diameter of 50 mm and a wall thickness of 5 mm. The inner wall is polished. The upper part of the sample preparation container 1 is connected to the upper acoustic pressure head 2 with a clearance fit and sealed with an O-ring 6, and the lower part is connected to the lower acoustic pressure head 3 with a clearance fit and sealed with an O-ring 6. A permeable stone slab 4 is placed above the lower acoustic pressure head 3. The permeable stone slab 4 is made of porous ceramic material and has a thickness of 5 mm. The space between the permeable stone slab 4 and the upper acoustic pressure head 2 is filled with the curing sample 5. In this embodiment, the curing sample 5 is prepared by mixing cementitious material, aggregate, and water in a mass ratio of cement:tailings:water = 1:4:0.5, wherein the cementitious material is P·O42.5 ordinary Portland cement, and the aggregate is mine tailings with a particle size of less than 2 mm. Two O-rings 6 are installed between the upper acoustic pressure head 2, the lower acoustic pressure head 3, and the inner wall of the sample preparation container 1. The O-rings 6 are made of fluororubber and have a temperature resistance range of -20°C to 200°C. A curing sample inlet pipe connector 7 is installed on one side of the upper acoustic pressure head 2 via a threaded connection. This connector is used to introduce nitrogen gas into the sample to perform in-situ permeability testing, or to introduce carbon dioxide gas to accelerate curing.

[0037] The acoustic pressure head 3 at the bottom of the curing sample assembly is fixedly connected to the base 8 by bolts. The base 8 is made of stainless steel and serves as the bottom support for the entire triaxial pressure chamber. The upper outer part of the base 8 is sealed to the cylinder 9 by a retaining ring 10 and a locking pin 11. The retaining ring 10 is a split steel retaining ring used for radially locking the cylinder 9; the locking pin 11 consists of multiple internal hexagon head screws evenly distributed along the circumference for axial fixation.

[0038] The upper part of the base 8 is equipped with nitrogen and CO2 inlet connectors 12, nitrogen inlet connector 13, nitrogen outlet connector 14, temperature sensor 15, upper acoustic sensor 16, and lower acoustic sensor 17. Each connector is fixed to its corresponding interface on the base 8 via threaded connections. The nitrogen and CO2 inlet connector 12 is a multi-functional composite interface, connected to the curing sample inlet connector 7 via an external pipeline. The nitrogen inlet connector 13 is connected to a nitrogen source via a pipeline, used to introduce the confining pressure medium into the triaxial pressure chamber. The nitrogen outlet connector 14 is used to discharge nitrogen that permeates the sample during permeability testing; its outlet is connected to a gas flow meter via a quick-connect fitting.

[0039] Temperature sensor 15 is a Pt100 platinum resistance temperature sensor, which is threaded onto base 8. The probe extends into the triaxial pressure chamber and is located near the curing sample 5.

[0040] The upper acoustic wave sensor 16 and the lower acoustic wave sensor 17 are threaded onto the base 8. The upper acoustic wave pressure head 2 is electrically connected to the upper acoustic wave sensor 16 via a coaxial cable, and the lower acoustic wave pressure head 3 is electrically connected to the lower acoustic wave sensor 17 via a coaxial cable. The upper acoustic wave sensor 16 and the lower acoustic wave sensor 17 are electrically connected to the acoustic wave signal generator and acquisition instrument via a coaxial cable.

[0041] A heating coil 18 is installed in the middle of the outer side of the cylinder 9. The heating coil 18 is made of flexible silicone heating tape and is fixed tightly to the outer wall of the cylinder 9 with stainless steel cable ties. The outer layer is covered with 20mm thick aluminum silicate fiber insulation material. The maximum heating power of the heating coil 18 is 500W, which can provide a temperature control range from room temperature to 80°C.

[0042] A top cover 19 is bolted to the top of cylinder 9. The lower part of the self-balancing piston 20 passes through the top cover 19 and the central hole at the top of cylinder 9, achieving a dynamic seal with the top cover 19 via an O-ring. The self-balancing piston 20 employs a constant-volume piston design, ensuring that the volume of the piston rod immersed in the pressure chamber remains constant during axial loading. The top of the self-balancing piston 20 is connected to the pressure pad 21 via multiple circumferentially distributed hexagonal head screws, and the pressure pad 21 is connected to the sensor pressure pad 22 in the same manner. The sensor pressure pad 22 contains a spoke-type axial force sensor.

[0043] An axial loading electric cylinder 23 is installed above the sensor pressure pad 22. The axial loading electric cylinder 23 is a servo electric cylinder with a rated thrust of 50kN, and is fixed to the upper crossbeam 24 by bolts. The base 8 is placed on the lower crossbeam 25 and is positioned and centered with the lower crossbeam 25 by a locating pin.

[0044] The center hole below the base 8 is connected to an adapter 26 via a thread. Below the adapter 26, a two-way ball valve 27 is connected via a thread. Below the two-way ball valve 27, a collection bottle 28 is connected via a thread. The collection bottle 28 is made of transparent glass and has graduations marked on its outer wall.

[0045] Two sets of axial loading electric cylinders 23 are independently controlled by two fully digital servo controllers in a closed-loop manner. Each controller has a built-in 32-bit DSP processor, a sampling frequency of 5kHz, and a control accuracy better than 0.5%. A test force sensor is installed at the front end of each electric cylinder to detect its output force in real time. The controller compares this value with the set target value and outputs the corrective force to the servo motor via PID control. This closed-loop servo control can achieve three loading modes: force control, displacement control, and strain control. The piston displacement of the electric cylinder is measured using a rotary encoder built into the servo motor, with a resolution of 20 bits and a measurement accuracy of ±0.001mm. All measurement data is transmitted in real time to the central controller via the RS485 communication protocol. The central controller is an industrial control computer running dedicated test control software.

[0046] The triaxial pressure chamber is used to apply confining pressure to the filled specimens. The pressurizing medium is nitrogen, with a maximum confining pressure of 5 MPa. The confining pressure is controlled by a digital pressure controller with a built-in high-precision pressure sensor, achieving an accuracy of ±0.1% of full scale. Operators set the target pressure and pressurization time via the central controller's testing software. The controller automatically adjusts the inlet valve opening to ensure a smooth pressure rise to the set value and maintain stability, with pressure fluctuations less than ±0.01 MPa. Due to the constant-volume design of the self-balancing piston 20, axial loading and confining pressure loading do not interfere with each other.

[0047] The temperature measurement and control module consists of a heating coil 18, a temperature sensor 15, and a temperature controller. The temperature sensor 15 monitors the temperature around the sample in real time and feeds the temperature signal back to the temperature controller. The temperature controller uses a PID algorithm and controls the on / off duty cycle of the heating coil 18 through a solid-state relay based on the deviation between the sensor feedback signal and the set value, so that the temperature quickly reaches the set value and stabilizes, with a temperature control accuracy of ±0.5°C.

[0048] The device supports in-situ permeability testing of filling samples, based on the differential pressure method. During testing, the multi-functional composite interface of the nitrogen and CO2 inlet connector 12 is used. This connector is connected to the curing sample inlet connector 7 via an external pipeline, allowing nitrogen gas to be introduced into the curing sample 5. The nitrogen outlet connector 14 is connected to a gas flow meter to measure the flow rate of nitrogen permeating the sample per unit time. Permeability testing can be performed at multiple time points during the curing phase without disassembling the pressure chamber.

[0049] The wave velocity testing module is the core module of this invention, including a sound wave signal generator and acquisition instrument, an upper sound wave sensor 16, and a lower sound wave sensor 17. The sound wave signal generator and acquisition instrument has an adjustable transmission voltage of 100V to 500V, an adjustable receiving gain of 20dB to 60dB, a center frequency range of 50kHz to 500kHz, and a sampling frequency of not less than 10MHz, in order to accommodate both weak signal acquisition during the slurry stage and strong signal acquisition after hardening.

[0050] The acoustic signal generator is configured to control the upper acoustic sensor 16 and the lower acoustic sensor 17 to switch between the following three modes: (1) Transmission mode: The upper acoustic wave sensor 16 serves as the transmitter, and is excited by the acoustic wave signal generator to generate ultrasonic pulses. Longitudinal or transverse wave excitation modes can be selected, with the center frequency typically set to 100kHz. The acoustic wave is transmitted to the curing sample 5 via the upper acoustic wave indenter 2, and after propagating within the sample, it is received by the lower acoustic wave sensor 17 via the lower acoustic wave indenter 3. By measuring the propagation time t of the acoustic wave in the sample, combined with the sample height L (100mm in this embodiment), the longitudinal wave velocity Vp=L / t and the transverse wave velocity Vs=L / t are calculated respectively. Based on Vp and Vs, the dynamic elastic modulus and dynamic Poisson's ratio of the filling sample are further calculated. The function of this mode is to obtain the average wave velocity of the entire sample, reflecting the macroscopic elastic properties and density changes of the sample.

[0051] (2) Reflection Mode: The upper acoustic wave sensor 16 serves as both the transmitter and receiver, emitting ultrasonic pulses and receiving reflected echo signals from internal defects, delamination, or the bottom of the sample. By analyzing the arrival time and amplitude variations of the reflected waves, the internal uniformity of the sample is evaluated, and the location and size of internal discontinuous interfaces are detected. This mode is used during the hardening stage after the initial setting of the sample, when the sample has sufficient acoustic impedance differences to generate identifiable reflected signals.

[0052] (3) Acoustic emission monitoring mode: During the mechanical test, both the upper acoustic wave sensor 16 and the lower acoustic wave sensor 17 are switched to passive receiving ends to continuously record acoustic emission events generated by micro-fractures inside the cured specimen 5. The acoustic wave signal generator continuously acquires acoustic emission waveforms at a sampling frequency of 10MHz, extracts the characteristic parameters of each acoustic emission event, including arrival time, amplitude, duration and rise time, and locates the source position of the acoustic emission event through a planar positioning algorithm to study the damage evolution process of the filling body during loading and identify the characteristic stress levels of crack initiation, propagation and penetration.

[0053] like Figure 9 As shown, this embodiment also provides a method for using the infill life cycle wave velocity monitoring and mechanical testing device. The method of using the present invention includes the following four steps: S1. Sample preparation and pressure chamber assembly First, fill the prepared filling grout into sample preparation container 1, install the upper acoustic pressure head 2 and the lower acoustic pressure head 3, and assemble the triaxial pressure chamber. The specific operation is as follows.

[0054] Weigh the cementitious materials, aggregates, and water according to the mass ratio of cement:tailings:water = 1:4:0.5, and mix them thoroughly to prepare the filling grout. Install the ultrasonic down-pressure head 3 at the bottom of the sample preparation container 1, and embed an O-ring 6 between the ultrasonic down-pressure head 3 and the inner wall of the sample preparation container 1 to form a seal. Place a permeable stone slab 4 above the ultrasonic down-pressure head 3, ensuring that the permeable stone slab 4 is in close contact with the ultrasonic down-pressure head 3 to ensure a stable propagation path for the ultrasonic waves. Fill the sample preparation container 1 with the filling grout in layers, each layer about 2cm to 3cm thick. After each layer is filled, vibrate it 10 to 15 times with a tamping rod to remove air bubbles. Repeat the operation until the grout fills the sample preparation container 1. Press the ultrasonic up-pressure head 2 into the upper part of the sample preparation container 1 and seal it with an O-ring 6. Place the assembled curing sample assembly on the base 8, and fix the ultrasonic down-pressure head 3 to the base 8 with bolts. Connect the upper acoustic sensor 16 to the upper acoustic pressure head 2 via a coaxial cable, and connect the lower acoustic sensor 17 to the lower acoustic pressure head 3 via a coaxial cable. Fit the cylinder 9 onto the upper outer side of the base 8, radially locking it with the retaining ring 10 and axially fixing it with the locking pin 11. Install the heating coil 18, upper cover 19, and self-balancing piston 20 in sequence, connecting the self-balancing piston 20 to the pressure pad 21 and sensor pressure pad 22 with hexagonal head screws. Connect the adapter 26, two-way ball valve 27, and collection bottle 28 in sequence, and close the two-way ball valve 27. Connect the nitrogen and CO2 inlet connectors 12 to the curing sample inlet connector 7 via external pipelines, connect the nitrogen inlet connector 13 to the confining pressure gas source, and connect the nitrogen outlet connector 14 to the gas flow meter. Fix the axial loading electric cylinder 23 to the upper crossbeam 24 with bolts, with its lower end contacting the sensor pressure pad 22. Turn on the acoustic signal generator and acquisition instrument, set the transmission voltage to 300V, the receiving gain to 40dB, and the center frequency to 100kHz, and perform a system self-test to confirm that the upper acoustic sensor 16 and the lower acoustic sensor 17 are transmitting and receiving normally.

[0055] S2, Continuous acquisition of wave velocity starting from the initial moment At the initial moment of filling the slurry into the sample preparation container 1, the upper acoustic wave sensor 16 and the lower acoustic wave sensor 17 are activated. Under the control of the acoustic wave signal generator and acquisition instrument, continuous wave velocity acquisition of the curing sample 5 begins in transmission mode. This continuous wave velocity acquisition continues throughout the entire curing stage and the subsequent mechanical loading stage. The specific operation is as follows.

[0056] Once the filling grout is injected into sample container 1 and the acoustic pressure head 2 is installed, an excitation pulse is immediately emitted in transmission mode and the received signal is acquired via an acoustic signal generator. During the curing phase, the wave velocity acquisition interval is set to once every 10 minutes to capture the abrupt changes in wave velocity during the initial and final setting processes with sufficient resolution. During the mechanical loading phase, the wave velocity acquisition interval is shortened to once every 5 seconds to capture the wave velocity changes caused by the generation and propagation of microcracks during loading. All wave velocity data—including longitudinal wave velocity Vp and transverse wave velocity Vs—are transmitted in real time to the central controller for storage and display.

[0057] S3. Continuous acquisition and data analysis of wave velocity during the maintenance phase During the maintenance phase, the longitudinal wave velocity Vp and the transverse wave velocity Vs are continuously collected using an acoustic signal generator. The wave velocity change rate dv / dt is calculated, and the maintenance phase is automatically divided based on the characteristic points of the wave velocity-time curve. A wave velocity-intensity correlation model is then established. The specific operation is as follows.

[0058] The curing parameters are set via the central controller: confining pressure is set to 1 MPa, and temperature is set to 35°C. The confining pressure control system and temperature control system are then activated. Throughout the curing process, the acoustic signal generator continuously collects wave velocity data in transmission mode.

[0059] like Figure 5 As shown, the central controller automatically identifies and marks the following curing stages based on the wave velocity-time curve: Stage 1 (initial slurry stage): The filling slurry is in a flowing state, with a low wave velocity (in this embodiment, the initial Vp is approximately 800 m / s to 1000 m / s), and the wave velocity signal is weak; Stage 2 (rapid wave velocity increase stage): The wave velocity increases significantly in a short period of time, corresponding to the initial setting of the slurry. The hydration products begin to form a continuous solid skeleton, and the sound wave propagation path changes from a liquid medium to a solid-liquid mixed medium. The wave velocity change rate dv / dt reaches its maximum value, and the central controller automatically marks this wave velocity abrupt change point as the initial setting point; Stage 3 (slow wave velocity growth stage): After final setting, the wave velocity enters a slow growth period, and the wave velocity growth rate gradually slows down and approaches a stable value (in this embodiment, the wave velocity Vp is approximately 2450 m / s after 28 days), marking the hydration reaction entering a stable stage. The central controller automatically marks the final setting point and the peak point of the hydration reaction based on the characteristic inflection point where the wave velocity change rate dv / dt changes from a rapid increase to a slow increase.

[0060] In addition, the reflection mode can be switched as needed during the curing phase to evaluate the internal uniformity of the sample.

[0061] At multiple time points during the curing phase (e.g., day 3, day 7, and day 14), in-situ permeability tests were performed: the inlet pipe connector 7 of the curing sample was switched to an N2 gas source, and nitrogen gas was introduced into the curing sample 5 through the pipeline using nitrogen and CO2 inlet connectors 12. The pressure difference was set to 0.3 MPa, and the permeation flow rate was recorded through the gas flow meter connected to the nitrogen outlet connector 14 to calculate the permeability K. The drainage volume W was recorded simultaneously, and the amount of water seeping out during the curing process was read from the scale of the collection bottle 28.

[0062] like Figure 6 As shown, after curing to the specified age (e.g., 28 days), the central controller performs regression analysis on the full life-cycle wave velocity data and the compressive strength data obtained from the calibration tests conducted concurrently, establishing a wave velocity-strength correlation model σc = a·Vp + b, where σc is the uniaxial compressive strength of the filling material (MPa), Vp is the longitudinal wave velocity (m / s), and a and b are regression coefficients. The empirical formula established in this embodiment is σc = 0.0025·Vp - 1.2, with a correlation coefficient R² = 0.96. After this model is established, subsequent tests only require wave velocity testing to non-destructively predict the current strength of the filling material.

[0063] like Figure 7 As shown, the central controller performs multi-parameter collaborative fusion of wave velocity data Vp(t) with permeability data K(t), displacement data W(t), confining pressure P(t), and temperature T(t), plotting a multi-parameter collaborative monitoring curve and executing collaborative fusion inference. The inference logic is as follows: when wave velocity increases and permeability decreases, it is determined that pores are filled and density increases; when wave velocity increases but permeability remains unchanged or increases, it is determined that wave velocity testing coupling is poor or there are defects inside the sample; when wave velocity decreases and permeability increases, it is determined that microcracks are propagating. This collaborative inference method reduces the intensity prediction error from approximately ±15% of the single wave velocity model to approximately ±8%.

[0064] S4. Coordinated monitoring and damage assessment of wave velocity and acoustic emission during mechanical loading phase During the mechanical loading phase, wave velocity is continuously acquired, and the upper acoustic sensor 16 and lower acoustic sensor 17 are switched to acoustic emission monitoring mode to synchronously record acoustic emission events. Wave velocity data, acoustic emission event data, and stress-strain data are then analyzed collaboratively to assess the damage evolution process of the filling sample until the sample fails. The specific operation is as follows.

[0065] The mechanical loading parameters are set via the central controller: displacement control mode is selected, and the loading rate is 0.1 mm / min. The axial loading electric cylinder 23 is activated to apply an axial load to the curing specimen 5. During loading, the acoustic signal generator acquires wave velocity data at a frequency of once every 5 seconds (transmission mode), and simultaneously passively records acoustic emission events generated by micro-fractures inside the specimen in acoustic emission monitoring mode during mechanical loading.

[0066] like Figure 8 As shown, the central controller plots the wave velocity-acoustic emission-stress-strain synergistic curve in real time. The horizontal axis represents time or axial strain, the left vertical axis represents axial stress σ, and the right vertical axis represents the longitudinal wave velocity Vp and the cumulative number of acoustic emission events. In the initial loading stage (elastic stage), the wave velocity remains relatively stable or increases slightly (pore compaction effect), and acoustic emission events are extremely rare. When the stress approaches approximately 60% to 70% of the peak intensity, the wave velocity begins to decrease, and the number of acoustic emission events increases significantly. This point is identified as the stress level at which crack initiation occurs. In the post-peak stage, the wave velocity drops sharply, and a large number of acoustic emission events occur. This stage is identified as the crack propagation and penetration stage.

[0067] The central controller calculates the wave velocity attenuation rate η = (Vp0 - Vp) 破坏 ) / Vp0×100%, and establish the damage variable D=1-(Vp) based on the wave velocity attenuation rate. 破坏 / Vp0)², where Vp0 is the longitudinal wave velocity before destruction, Vp 破坏 The longitudinal wave velocity at failure is denoted by ...

[0068] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A device for monitoring wave velocity and conducting mechanical testing on the life cycle of filling materials, comprising a loading frame, an axial loading mechanism mounted on the loading frame, at least one triaxial pressure chamber disposed within the loading frame, a confining pressure control system communicating with the triaxial pressure chamber, and a temperature control system disposed on the triaxial pressure chamber, wherein a sample preparation container is disposed inside the triaxial pressure chamber, and an upper acoustic pressure head and a lower acoustic pressure head are respectively disposed at the upper and lower parts of the sample preparation container, the upper acoustic pressure head and the lower acoustic pressure head being electrically connected to an upper acoustic sensor and a lower acoustic sensor respectively, and the sample preparation container being used to contain filling material samples, characterized in that, The upper acoustic wave sensor and the lower acoustic wave sensor are configured as follows: From the initial moment when the filling slurry is injected into the sample preparation bucket, the wave velocity of the filling body sample is continuously collected throughout the entire curing process and the entire mechanical loading process. The acoustic signal generator is configured to control the upper acoustic sensor and the lower acoustic sensor to switch between the following modes: In the transmission mode, one acoustic sensor acts as the transmitter and the other as the receiver, measuring the propagation time of the sound wave in the sample to calculate the wave velocity. Reflection mode, in which one acoustic sensor acts as both transmitter and receiver, receiving reflected signals from internal defects or the bottom of the sample; In the acoustic emission monitoring mode, both the upper acoustic wave sensor and the lower acoustic wave sensor serve as passive receivers, continuously recording acoustic emission events generated by micro-fractures inside the sample.

2. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of filling materials according to claim 1, characterized in that, In the transmission mode, the acoustic signal generator generates longitudinal or transverse wave pulses through the upper or lower acoustic sensor, measures the longitudinal wave velocity Vp and the transverse wave velocity Vs respectively, and calculates the dynamic elastic modulus and dynamic Poisson's ratio of the filling sample based on Vp and Vs.

3. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of filling materials according to claim 1, characterized in that, The device also includes a central controller configured to divide the maintenance process into stages based on the wave velocity change rate dv / dt.

4. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of an infill body according to claim 3, characterized in that, The central controller also has a built-in wave velocity-strength correlation model σc=a·Vp+b, where σc is the uniaxial compressive strength of the filling body, Vp is the longitudinal wave velocity, and a and b are regression coefficients calibrated by pre-tests. The central controller is configured to nondestructively predict the current strength of the filling sample based on the currently measured wave velocity value using the wave velocity-strength correlation model.

5. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of an infill body according to claim 3, characterized in that, The central controller is also configured to perform multi-parameter collaborative fusion inference, with input data including wave velocity Vp(t), permeability K(t), water displacement W(t), confining pressure P(t), temperature T(t), and acoustic emission event count AE(t). The multi-parameter collaborative fusion inference includes: When the wave velocity increases and the permeability decreases, it is determined that the pores are filled and the density increases. When the wave velocity increases but the permeability remains unchanged or increases, it is determined that the wave velocity test coupling is poor or there are defects inside the sample. When the wave velocity decreases and the permeability increases, it is determined to be microcrack propagation.

6. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of an infill body according to claim 3, characterized in that, The central controller is also configured to: during mechanical loading, based on the acoustic emission events recorded in the acoustic emission monitoring mode, correlate with the synchronously acquired wave velocity data and stress-strain data, plot the wave velocity-acoustic emission-stress-strain synergistic curve, and identify the characteristic stress levels of crack initiation, propagation and penetration.

7. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of an infill body according to claim 6, characterized in that, The central controller is also configured to calculate the wave velocity attenuation rate η = (Vp0-Vp) 破坏 ) / Vp0× 100%, and based on the wave velocity attenuation rate, establish the damage variable D = 1-(Vp) / Vp0× 100%. 破坏 / Vp0)², where Vp0 is the longitudinal wave velocity before destruction, Vp 破坏 The damage variable, representing the longitudinal wave velocity at failure, is used to quantitatively evaluate the degree of damage to the filling specimen during triaxial mechanical loading.

8. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of filling materials according to claim 1, characterized in that, The transmitting voltage of the acoustic signal generator is adjustable from 100V to 500V, the receiving gain is adjustable from 20dB to 60dB, the center frequency range is from 50kHz to 500kHz, and the sampling frequency is not less than 10MHz.

9. The device for monitoring wave velocity and conducting mechanical testing on the life cycle of an infill body according to claim 1, characterized in that, The filling sample is composed of cementitious material, aggregate and water, wherein the aggregate is sand or tailings; one side of the ultrasonic pressure head is provided with a curing sample air inlet connector, which is used to introduce nitrogen into the sample to perform in-situ permeability testing, or to introduce carbon dioxide gas to accelerate curing.

10. A method of using a device for monitoring the life cycle wave velocity and conducting mechanical testing of an infill body, applied to the device according to any one of claims 1 to 9, characterized in that, Includes the following steps: S1. Fill the prepared filling slurry into the sample preparation bucket, install the upper acoustic pressure head and the lower acoustic pressure head, and assemble the triaxial pressure chamber; S2. At the initial moment when the filling slurry is injected into the sample preparation bucket, the upper acoustic wave sensor and the lower acoustic wave sensor are turned on. Under the control of the acoustic wave signal generator and acquisition instrument, the wave velocity of the filling sample is continuously acquired in transmission mode. The continuous acquisition of wave velocity continues throughout the curing stage and the subsequent mechanical loading stage. S3. During the maintenance phase, the longitudinal wave velocity Vp and the transverse wave velocity Vs are continuously collected, the wave velocity change rate dv / dt is calculated, the maintenance phase is automatically divided based on the feature points of the wave velocity-time curve, and a wave velocity-intensity correlation model is established. S4. During the mechanical loading stage, the wave velocity is continuously acquired, and the upper acoustic wave sensor and the lower acoustic wave sensor are switched to acoustic emission monitoring mode to record acoustic emission events synchronously. The wave velocity data, acoustic emission event data and stress-strain data are analyzed in a coordinated manner to evaluate the damage evolution process of the filling sample until the sample is destroyed.

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