Process for filling coal gangue pre-treated into a molding

Abstract

The present application relates to coal gangue forming technical field, disclose a kind of for filling pretreatment coal gangue forming process, comprising: injection graded coal gangue mixture into forming mould cavity;First preset pressure is applied by pressure head and intermittent high-frequency excitation is applied, so that mixture is compacted under the action of gravity and pressure;The pressure is lifted to second preset pressure by controlling pressure head, the pressure is reduced after pressure maintaining and low-frequency mechanical wave exhaust is applied, and the second preset pressure is re-pressured;Second preset pressure is maintained to be pressure maintaining and demoulding, the present application utilizes intermittent high-frequency vibration to break down the mechanical bridge between coarse particles and avoid particle segregation, simultaneously rely on pressure reduction and low-frequency vibration to synergistically suck deep stagnation air pocket, eliminate internal tensile microcracks and anisotropy defects, effectively improve the density of forming body and early bearing strength.

Description

Technical Field

[0001] This invention belongs to the field of coal gangue forming technology, and particularly relates to a coal gangue forming process for filling pretreatment. Background Technology

[0002] Currently, in the pre-treatment of coal gangue in mine filling, the process of mixing graded and discrete coal gangue aggregates with cementitious materials and applying external loads to press them to obtain a molded body with early load-bearing strength is a basic process commonly used in the industry. With the increasing demands for reliability standards of the molded body structure in filling operations, the physical properties of coal gangue particles, which are sharp-edged and have irregular geometric shapes, lead to insurmountable mechanical constraints in the conventional static unidirectional pressing process. Because coarse particles are very easy to interlock with each other in the upper part of the mold cavity to form a rigid mechanical bridging structure, the rigid skeleton constructed by this structure not only consumes the pressing load and generates a stress shielding effect, but also seals the air inside the skeleton, causing the molded body to exhibit a density gradient imbalance state with a dense upper part and a loose lower part.

[0003] Existing technologies focus on forcibly disrupting mechanical bridging by improving the physical hardware structure of the molding device. For example, Chinese invention patent CN114801114B discloses an anti-bridging extrusion cylinder. This cylinder adds dispersing blades, connecting pins, and a screen, utilizing physical impact and discrete screening to prevent bridging. However, this type of rigid hardware intervention suffers from severe mechanical wear when dealing with highly abrasive coal gangue materials with large gradation spans. Physical disturbances easily induce large-scale particle convection during fluidization, leading to particle segregation and deep-seated cavitation during high-pressure consolidation. The lack of means to eliminate residual elastic stress, coupled with the lack of precise control of the timing coupling of pressure field and excitation energy during the molding process, makes it impossible to solve the problems of internal defects and density uniformity of the molded body from the physical root. Simply increasing the pressing load will instead strengthen the interlocking force of the mechanical bridging structure, solidify the air-encapsulated state and increase the residual elastic stress inside the system. Introducing conventional continuous high-frequency vibration as an alternative path to fluidize materials will stimulate convection circulation inside the granular body under continuous mechanical wave injection, causing segregation phenomena of coarse aggregate floating and fine powder deposition, destroying the spatial interlocking uniformity of the particle skeleton.

[0004] Therefore, the technical problem to be solved by this invention is how to reconstruct the force field application sequence during the pressing process while maintaining the inherent geometric shape of coal gangue material, dismantle the mechanical bridging effect during the forming process, avoid particle segregation caused by continuous vibration, and eliminate encapsulation porosity and residual stress gradient. Summary of the Invention

[0005] To address the problems mentioned in the background art, the technical solution of the present invention is as follows: A coal gangue molding process for pre-filling treatment, comprising the following steps:

[0006] Step 101: Inject graded coal gangue mixture into the molding cavity;

[0007] Step 102: Apply a first preset pressure to the graded coal gangue mixture through the pressure head, and apply a mechanical wave of the first frequency to the forming mold cavity using the first excitation device; divide the operating state of the first excitation device into alternating excitation time periods and vibration stop time periods according to the time axis, output the mechanical wave of the first frequency during the excitation time period, and stop outputting the mechanical wave of the first frequency during the vibration stop time period.

[0008] Step 103: Control the pressure head to increase the pressure from the first preset pressure to the second preset pressure, and after maintaining the second preset pressure for a preset holding time, control the pressure head to perform a pressure reduction and excitation operation; the pressure reduction and excitation operation includes: controlling the pressure head to reduce the pressure from the second preset pressure to the third preset pressure, and within a preset unloading time of maintaining the third preset pressure, using the second excitation device to apply a mechanical wave of the second frequency to the molding cavity, and controlling the pressure head to restore the pressure to the second preset pressure;

[0009] Step 104: Maintain the second preset pressure for pressure holding and solidification, and demold to obtain the coal gangue molded body.

[0010] Preferably, step 102 includes: step 201, obtaining the maximum aggregate particle size and fineness modulus of the graded coal gangue mixture, and obtaining the wave velocity of the mechanical wave of the first frequency in the graded coal gangue mixture; step 202, calculating the duration of the excitation time period based on the maximum aggregate particle size, fineness modulus, and wave velocity, and introducing the following formula: ,in, The duration of the excitation period. For the maximum aggregate particle size, For wave speed, For fineness modulus, The preset reference coefficient with time dimension is used; step 203, control the first excitation device to output a mechanical wave of the first frequency within the excitation time period according to the duration.

[0011] Preferably, the first frequency in step 102 and the second frequency in step 103 satisfy the following conditions: the first frequency is greater than or equal to 100Hz and less than or equal to 200Hz; the second frequency is greater than or equal to 20Hz and less than or equal to 50Hz.

[0012] Preferably, before step 101, a gradation construction step is included: Step 601, the raw coal gangue ore is crushed and screened to separate coarse aggregate components and fine powder components; Step 602, cement-based cementitious materials and activators are added to the fine powder components and dry-mixed to obtain mixed cementitious powder; Step 603, the coarse aggregate components and mixed cementitious powder are mixed in a mass ratio, and activated water is added and stirred to obtain graded coal gangue mixture.

[0013] Preferably, the third preset pressure is 50% to 70% of the second preset pressure, and the first preset pressure is 20% to 30% of the second preset pressure.

[0014] Preferably, the depressurization excitation operation includes performing at least three depressurization excitation cycles consecutively; each depressurization excitation cycle includes: controlling the pressure head to reduce the pressure to a third preset pressure, applying a mechanical wave of a second frequency, and restoring the pressure to a second preset pressure; the time interval between two adjacent depressurization excitation cycles maintaining the second preset pressure decreases in an arithmetic sequence.

[0015] Preferably, the process of controlling the pressure head to increase the pressure from the first preset pressure to the second preset pressure in step 103 includes: step 901, controlling the pressure head to increase the pressure at a constant first pressurization rate; step 902, when the pressure reaches the arithmetic mean of the first preset pressure and the second preset pressure, reducing the pressurization rate from the first pressurization rate to the second pressurization rate, and increasing the pressure at the second pressurization rate until the second preset pressure is reached.

[0016] Compared with existing technologies, the coal gangue molding process of this invention for filling pretreatment has the following advantages:

[0017] 1. In the coal gangue molding process, a mechanical intervention mechanism is constructed that combines low-pressure high-frequency fluidization with high-pressure low-frequency venting. Under the closed constraint of the first preset pressure, continuous vibration at the first frequency is applied to the mold cavity, converting mechanical vibration energy into the kinetic energy of granular particles to overcome the initial static friction force. This causes local fluidization of the coal gangue base material and guides fine particles to seep and fill the pores of coarse particles. When the transmission pressure at the bottom of the mold cavity reaches the fluidization threshold, the pressure head is controlled to output a second preset pressure higher than the first preset pressure. Simultaneously, continuous vibration at the second frequency lower than the first frequency is switched, causing relative slippage of the particle skeleton under strong compaction to squeeze out the internal closed gas. In the early stage, high-frequency fluidization uses a smaller constraint force to achieve spatial interlocking of material particles, avoiding the original mechanical bridging and stress shielding effects caused by direct high pressure. In the later stage, high-pressure low-frequency intervention forces the material to solidify on the basis of optimal particle arrangement. This sequential process opens up the venting channels inside the base material and eliminates the encapsulating pores, reducing the density difference between the upper and lower parts of the molded body.

[0018] 2. Establish a duty cycle-interrupted transient start-stop fluidization rearrangement mechanism. By applying alternating excitation activation and excitation dormancy windows to the molding cavity, the first frequency vibration waveform is output within the excitation activation window to break the mechanical bridging between material particles. Within the excitation dormancy window, the vibration output source is forcibly braked to maintain the set dormancy time. The transient energy cutoff operation in the time domain restricts the rheological motion of material particles to the local pore scale. The locally fluidized material particles that have temporarily lost excitation energy undergo transient gravity self-locking and mutual wedging under the combined downward pressure of gravity and top pressure. The above-mentioned specific time sequence physical intervention means cut off the kinetic energy accumulation path of large-scale convection circulation inside the granular body, avoiding the particle segregation and coarse aggregate floating phenomenon that are prone to occur in wide-graded aggregates during continuous vibration fluidization. The isotropy and structural cohesion of the molded body are established from the topological root of particle arrangement.

[0019] 3. A micro-unloading induced exhaust mechanism is introduced. During the exhaust process of applying a second preset pressure and continuous vibration at a second frequency, the pressure head is controlled to cyclically unload and repressurize, reducing the pressure from the second preset pressure to a third preset pressure greater than the first preset pressure, and maintaining the preset unloading time before returning to the second preset pressure. The periodic pressure reduction action causes the surface dense air barrier layer to expand its pores due to elastic recovery. Combined with the continuously input low-frequency mechanical wave, a dynamic negative pressure exhaust channel is constructed in the longitudinal direction of the material. The repressurization action provides the physical driving force to squeeze the closed microbubbles and deep pore water upward. This mechanism dynamically disintegrates the physical locking effect of the surface dense air barrier layer and eliminates the pressure of deep stagnant air cavities and pore water. Based on the longitudinal density uniformity of the molded body, it blocks the mechanical damage path of transverse fracture of the molded body induced by the expansion of internal air cavities during the demolding stage. Attached Figure Description

[0020] Figure 1 This is a flowchart of the coal gangue forming process combining multi-stage voltage transformation and alternating vibration of the present invention.

[0021] Figure 2 This is a diagram of the multi-sensor feedback compression-vibration coordinated control and signal interaction of the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of this application will be clearly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this application are within the scope of protection of this application.

[0023] A coal gangue molding process for backfill pretreatment includes the following steps:

[0024] Step 101: Inject graded coal gangue mixture into the molding cavity;

[0025] Step 102: Apply a first preset pressure to the graded coal gangue mixture through the pressure head, and apply a mechanical wave of the first frequency to the forming mold cavity using the first excitation device; divide the operating state of the first excitation device into alternating excitation time periods and vibration stop time periods according to the time axis, output the mechanical wave of the first frequency during the excitation time period, and stop outputting the mechanical wave of the first frequency during the vibration stop time period.

[0026] Step 103: Control the pressure head to increase the pressure from the first preset pressure to the second preset pressure, and after maintaining the second preset pressure for a preset holding time, control the pressure head to perform a pressure reduction and excitation operation; the pressure reduction and excitation operation includes: controlling the pressure head to reduce the pressure from the second preset pressure to the third preset pressure, and within a preset unloading time of maintaining the third preset pressure, using the second excitation device to apply a mechanical wave of the second frequency to the molding cavity, and controlling the pressure head to restore the pressure to the second preset pressure;

[0027] Step 104: Maintain the second preset pressure for pressure holding and solidification, and demold to obtain the coal gangue molded body.

[0028] Preferably, step 102 includes: step 201, obtaining the maximum aggregate particle size and fineness modulus of the graded coal gangue mixture, and obtaining the wave velocity of the mechanical wave of the first frequency in the graded coal gangue mixture; step 202, calculating the duration of the excitation time period based on the maximum aggregate particle size, fineness modulus, and wave velocity, and introducing the following formula: ,in, The duration of the excitation period. For the maximum aggregate particle size, For wave speed, For fineness modulus, The preset reference coefficient with time dimension is used; step 203, control the first excitation device to output a mechanical wave of the first frequency within the excitation time period according to the duration.

[0029] Preferably, the first frequency in step 102 and the second frequency in step 103 satisfy the following conditions: the first frequency is greater than or equal to 100Hz and less than or equal to 200Hz; the second frequency is greater than or equal to 20Hz and less than or equal to 50Hz.

[0030] Preferably, before step 101, a gradation construction step is included: Step 601, the raw coal gangue ore is crushed and screened to separate coarse aggregate components and fine powder components; Step 602, cement-based cementitious materials and activators are added to the fine powder components and dry-mixed to obtain mixed cementitious powder; Step 603, the coarse aggregate components and mixed cementitious powder are mixed in a mass ratio, and activated water is added and stirred to obtain graded coal gangue mixture.

[0031] Preferably, the third preset pressure is 50% to 70% of the second preset pressure, and the first preset pressure is 20% to 30% of the second preset pressure.

[0032] Preferably, the depressurization excitation operation includes performing at least three depressurization excitation cycles consecutively; each depressurization excitation cycle includes: controlling the pressure head to reduce the pressure to a third preset pressure, applying a mechanical wave of a second frequency, and restoring the pressure to a second preset pressure; the time interval between two adjacent depressurization excitation cycles maintaining the second preset pressure decreases in an arithmetic sequence.

[0033] Preferably, the process of controlling the pressure head to increase the pressure from the first preset pressure to the second preset pressure in step 103 includes: step 901, controlling the pressure head to increase the pressure at a constant first pressurization rate; step 902, when the pressure reaches the arithmetic mean of the first preset pressure and the second preset pressure, reducing the pressurization rate from the first pressurization rate to the second pressurization rate, and increasing the pressure at the second pressurization rate until the second preset pressure is reached.

[0034] Example 1: In the molding process of pre-processed materials for mine filling at a depth of 1000m, the system faces the task of densifying wide-grade coal gangue solid waste. This batch of coal gangue raw material aggregate has sharp edges and unevenly adhered liquid moisture on its surface. Under static unidirectional compression, the coarse particles rapidly interlock in the upper part of the mold cavity to form a rigid mechanical bridging skeleton. This skeleton generates a stress shielding effect, blocking the load from being transferred to the lower layers, and encapsulates a large number of irregular closed air pockets inside the skeleton. This results in the final molded body exhibiting a density gradient imbalance, with a dense upper part and a loose lower part. This structural defect makes the demolded block extremely brittle. Tensile fracture occurs along the density-weak zone; the coal gangue molding process for filling pretreatment injects graded coal gangue mixture into the molding cavity, and uses a pressure head to apply a first preset pressure to the material surface to establish a physical sealing boundary; under the constraint of maintaining the first preset pressure, the control system synchronously uses a first excitation device to apply a mechanical wave of the first frequency to the molding cavity, which is converted into the kinetic energy of the granular particles to overcome the initial static friction between irregular aggregates, causing the coal gangue matrix to undergo local fluidization, guiding the fine powder component to seep downward and fill the pores of coarse particles, and dynamically disintegrating the nascent mechanical bridging structure.

[0035] To capture the disintegration state of the material skeleton, the control system synchronously collects the real-time value of the first preset pressure output by the pressure head and the real-time value of the transmitted pressure at the bottom of the forming mold cavity, and calculates the stress transmission difference between the two. When the stress transmission difference decreases within three consecutive 50ms preset sampling periods and converges to a stable difference range of 5kPa to 8kPa, the control system determines that the internal stress shield of the material has been broken and a preset fluidization threshold has been reached. The control logic triggers a process switch, and the pressure head instantaneously outputs a second preset pressure greater than the first preset pressure. Simultaneously, a second frequency mechanical wave less than the first frequency is applied to the forming mold cavity using a second excitation device. The high pressure condition forcibly reduces the physical distance between material particles. The low-frequency, large-amplitude mechanical wave causes relative slippage of the particle skeleton under strong compaction. This slippage gap is used to expel the deep air trapped during the fluidization rearrangement process from the material system in a peristaltic manner. Specifically, the depressurization excitation operation includes continuously executing at least three depressurization excitation cycles, wherein the time interval for maintaining the second preset pressure between two adjacent depressurization excitation cycles decreases in an arithmetic progression. In this invention, the first maintenance time is set as follows: The tolerance of this arithmetic sequence is determined by the initial setting time of the cementitious material in the mixture and the rate of bubble peristalsis discharge under high pressure. The tolerance is calculated by determining the attenuation slope of the gas flow meter in the pre-calibration test, and its fixed value range is strictly limited to [value missing]. And the duration of maintenance when decreasing to the last term is not less than By using this arithmetic progression sequence, a longer pressure stabilization and venting window is provided when there is more air trapped inside the material and the gas discharge path is longer in the early stage, while the interval is shortened in the later stage when the material tends to be dense and the residual amount of bubbles is reduced, so as to improve molding efficiency and ensure the compactness and efficiency of the multi-stage pressure reduction and venting action.

[0036] A time-series control mechanism that combines low-pressure high-frequency fluidization with high-pressure low-frequency exhaust decouples and recombines the densification kinetic energy of mechanical waves with the consolidation potential energy of hydraulic loads. The first-frequency mechanical wave provides a high-quality topological arrangement prerequisite for eliminating the rigid skeleton in the physical consolidation at the second preset pressure. The second-frequency mechanical wave, combined with the second preset pressure, solidifies the fluidized rearrangement state and removes residual cavities, resolving the technical contradiction in traditional molding processes where simply increasing the pressing force strengthens the skeleton interlocking and reinforces the air-encapsulated state. The control system continuously extracts the pressure increase and downward displacement increase of the pressure head according to a preset sampling period and dynamically outputs the ratio of the two as a compaction stiffness parameter. As the free microbubbles and excess pore water inside the material are completely squeezed out, the solid aggregate particles directly... The interlocking and dense interlocking across scales cause a sharp increase in the system's stiffness against microscopic volumetric strain. When the system detects that the compaction stiffness parameter exceeds the preset stiffness threshold calculated based on 15% of the target compressive strength of the batch of filled material for three consecutive sampling cycles, it can be determined from a physical perspective that the material's degassing and consolidation evolution stage has reached its limit, and the decompression excitation operation can be actively stopped. Specifically, the preset stiffness threshold calculated based on 15% of the target compressive strength is determined through a pre-established multi-scale constitutive mapping relationship between unconsolidated granular compaction stiffness, microscopic solid contact strain, and long-term hydration consolidation compressive strength. In coal gangue mixtures, the transient compaction stiffness of early wet materials is manifested as the skeletal resistance under relative strain increments. The compressive strength of the later-cured body depends on the cementitious shear stress exerted on the aggregate interface by the hydration products of cement-based cementitious powder. By conducting triaxial compression tests and compressive strength tests at curing ages on calibrated samples, the transient tangential stiffness when the granular skeleton is completely tightly interlocked and the pores are completely emptied at a specific moisture content is extracted. This limiting tangential stiffness is numerically expressed as 15% of the final target compressive strength scalar value. Its dimensional conversion relationship is balanced and corrected by the inherent cross-sectional area of ​​the frame and the strain normalization coefficient matrix. The control system incorporates this conversion mechanism into the threshold discrimination module of the field controller. When the ratio of the increase in pressure monitored online to the increase in downward displacement crosses the calculated stiffness threshold for three consecutive sampling cycles, it indicates that there is no longer any intergranular bonding. The compressed cavitation and fluid barrier enable precise back-calculation and dynamic closed-loop control of the subsequent solid mechanical strength from the online bulk rheological state. After maintaining the second preset pressure for solidification for the preset holding time, the system controls the pressure head to depressurize at a given rate and execute the demolding procedure. The produced coal gangue molded body eliminates internal encapsulation pores, and the longitudinal density difference between the upper and lower end faces decreases to less than 5% of the reference parameter. The material particle level exhibits a dense and isotropic spatial interlocking structure. This physical state is based on the compressive strength of the molded body that meets the early bearing standard of mine backfill. This indicates that the system, by reconstructing the temporal boundary of the force field, avoids the traditional path of relying on increasing the ultimate load to resist stress shielding, and completes the bottom-level topological reshaping of discrete solid waste through dynamic mechanical intervention.

[0037] Example 2: In the mine filling material preparation system, the wide-graded water-containing coal gangue generates stress transmission resistance in the molding cavity. To verify this molding process, a press system was constructed, including a dual-channel servo hydraulic control module and a full-band mechanical excitation output module. It integrates a pressure head displacement sensor and a bottom array-type thin-film pressure sensor, with a pressure measurement range covering 0 to 50 MPa. The dynamic sampling frequency was set to 10 kHz. To address the viscous resistance introduced by the adhering liquid water in the graded coal gangue mixture at the mine site and the wide-band noise generated by the equipment's mechanical harmonics, the control system connected a low-pass hardware filter module with a cutoff frequency of 250 Hz in series in the data acquisition link. A moving average filtering algorithm was used to extract the stress transmission difference, avoiding interference from transient high-frequency noise on the judgment logic. The excitation time duration was set to balance the process requirements of fluidization and arch breaking while avoiding particle segregation. Too short a duration would result in the static friction of the coarse aggregate not being completely eliminated across the cross-section, while too long a duration would cause excessive sedimentation and secondary segregation of the fine powder components. The control unit determined the duration based on the formula... Calculate the duration; where, The duration of the excitation period. The maximum aggregate particle size of the graded coal gangue mixture is given. The wave velocity of the first frequency mechanical wave in the graded coal gangue mixture. As a reference coefficient with the dimension of time, For the fineness modulus, under the gradation conditions of a maximum aggregate particle size of 25.0 mm, a wave velocity of 1500 m / s, and a fineness modulus of 3.2, and based on the reference coefficients obtained from calibration, the control system calculates the duration of the output excitation time period to be 125 ms. (Reference coefficients are also mentioned.) Pre-calibration tests were conducted, selecting three coal gangue mixture samples with different fineness moduli gradients. Under the condition of maintaining a first preset pressure, a first frequency mechanical wave was applied, and the duration for which the ratio of the pressure output from the pressure head to the pressure transmitted at the bottom of the mold cavity reached a steady state of 0.85 to 0.90 was recorded. The slope was extracted by linear fitting of the duration and the fineness modulus and used as a benchmark coefficient. wave speed The sound velocity was obtained by installing an ultrasonic transducer at the end of the pressure head and a receiving probe at the bottom of the mold cavity. After the material stabilized under pressure, the time difference of the pulse penetrating the material layer was measured, and the sound velocity was calculated by combining the material height feedback from the displacement sensor. When performing this calculation, the input sound velocity parameter was strictly limited to the static ultrasonic transmission velocity of the material before it initially experienced the first preset pressure but before large-scale particle rheology occurred, in order to avoid nonlinear fluctuations caused by the densification process of the skeleton. At the same time, the formula used a reference coefficient with time dimension as a mapping bridge to physically and substantially transform the dimensionless fineness modulus parameter, which belongs to the statistical characteristics of macroscopic granular materials, into the particle components overcoming the initial viscous resistance in the local sound field energy. The microsecond-level hysteresis time increment required for the force establishes a fundamental quantitative correlation between the transient dynamic beam intervention period and the inherent geometric gradation distribution of the solid waste mixture. Specifically, to cooperate with the duty cycle-truncated transient start-stop fluidization rearrangement mechanism, the duration of the vibration cessation period must be strictly defined. The preset gravity settling time of the graded coal gangue mixture refers to the Stokes settling time required for fine powder particles in a locally fluidized suspension state to move downwards under their own gravity and complete the local gap filling under the current liquid phase viscous resistance constraint after the first frequency mechanical wave stops being injected. In the multiphase mixture system of this invention, its time range is determined by triaxial settling calibration. .

[0038] To test the adaptability of the process to different liquid bridge viscosity forces, three groups of raw material moisture contents with problem strength gradients were selected for the experiment: 4.0%, 8.0%, and 12.0%, respectively. Taking the graded coal gangue mixture with 8.0% moisture content as an example, when the pressure head outputs a first preset pressure of 10.0 MPa, the initial average pressure collected by the bottom array thin-film pressure sensor is 2.1 MPa, and the initial stress transmission difference reaches 7.9 MPa, indicating the existence of a rigid skeleton stress shielding phenomenon. The experiment constructed multiple control systems. The experimental group adopted the above molding process, selected 150 Hz as the first frequency, and selected 30 Hz as the second frequency. The partially missing control group cut off the output of the excitation equipment and applied only two-stage static pressure. For the out-of-range control group 1, the first frequency was set to 80Hz, and for the out-of-range control group 2, the first frequency was set to 250Hz. After applying a mechanical wave at a first frequency of 150Hz and a first preset pressure of 10.0MPa, the stress transmission difference in the test group converged to 6.5kPa, indicating that the mechanical bridging of the coarse aggregate had disintegrated. In the out-of-range control group 1, when an 80Hz mechanical wave was applied, the stress transmission difference remained at 3.2MPa, the vibration energy did not exceed the static friction threshold between particles, and fluidization rearrangement did not occur. In the out-of-range control group 2, when a 250Hz mechanical wave was applied, the stress transmission difference dropped to 5.0kPa, but after demolding, the longitudinal density difference between the upper and lower end faces reached 12.5%, indicating that the load was excessive. Residual kinetic energy causes fine-particle powder to deposit and undergo secondary segregation at the bottom of the mold cavity. In the experimental group, after process switching, a second frequency mechanical wave of 30Hz and a second preset pressure were applied. The control unit set the mechanical wave amplitude based on a volume expansion of 3.5mm to extrude deep cavities. The final measured top density of the demolded body in the experimental group was 2.15 g / cm³, the bottom density was 2.12 g / cm³, the longitudinal density difference was 1.4%, and the compressive strength reached 15.4 MPa. The partially missing control group had a top density of 2.20 g / cm³, a bottom density of 1.65 g / cm³, and fractured along the loose area in the lower middle section during demolding, with a compressive strength of 3.6 MPa. Furthermore, at 4.0% and 12... Under a 0.0% moisture content gradient, the longitudinal density difference of the molded bodies produced in the experimental group remained at 1.1% and 1.8%, respectively, and the compressive strength reached 16.2 MPa and 14.8 MPa, respectively. The data showed a stable monotonic correlation change, confirming that the process parameter system is adaptable within a wide moisture content fluctuation range. The temporal synergistic effect of the first frequency mechanical wave, the second frequency mechanical wave, and the step pressure disintegrates the rigid force chain under static compression and eliminates stagnant air cavities. This molding process separates the kinetic energy intervention and the static pressure solidification mechanism, changes the frictional resistance state and volume compression path of the granular material, and outputs a molded body with uniform density distribution under varying moisture content conditions, so that its early bearing strength meets the technical requirements of mine filling operations.

[0039] Example 3: When the mine backfill material preparation system deals with coal gangue raw materials with variable gradation characteristics, the system faces technical problems such as high-frequency excitation harmonic interference stress state determination and lack of adaptive adjustment benchmark for low-frequency exhaust amplitude. Before the formal execution of the main molding process of the coal gangue molding process used for backfill pretreatment, the control system starts parameter calibration and signal processing procedures for batch material characteristics. The control unit collects pressure signals through the pressure head displacement sensor and the bottom array thin film pressure sensor. The raw signal contains hydraulic servo fluctuations and periodic mechanical harmonics induced by the first excitation device. The control system intercepts the raw pressure signal sequence within a continuous sampling period and constructs a sliding sampling window with a time length that is an integer multiple of the reciprocal of the first frequency. The control unit calculates the arithmetic mean of the pressure data within the sliding sampling window to filter out the zero-mean periodic mechanical harmonics and outputs the smoothed real-time value of the pressure head output and the real-time value of the transmitted pressure at the bottom of the molding cavity. The control unit performs differential calculation on the above two real-time values ​​to generate a stress transmission difference value to avoid misjudgment of the fluidization threshold caused by high-frequency broadband noise.

[0040] To establish a deterministic control basis for the output amplitude of the second excitation device during depressurization excitation, the system performs calibration of the preset expansion coefficient, injects a calibrated mass of graded coal gangue mixture sample into the molding test cavity, and applies a mechanical wave of the first preset pressure and first frequency until the stress transmission difference converges to a stable difference range; the pressure head is unloaded to the third preset pressure, and the first downward displacement of the pressure head is recorded simultaneously. The actual volume expansion of the sample is calculated based on the cross-sectional area of ​​the molding test cavity and the first downward displacement; the system applies a test mechanical wave of the second frequency, and gradually increases the test amplitude of the test mechanical wave using an incremental step size method, while simultaneously monitoring the fluid overflow status of the material vent and the internal residual porosity. When continuously monitoring the internal residual porosity, the system control unit pre-acquires the dry basis mass of the material fed into the mold cavity and the true density parameters of the coal gangue components, and then calculates the theoretical skeleton volume of the batch of material in an absolutely dense state. Subsequently, the current downward stroke depth is collected by the pressure head displacement sensor and multiplied by the cross-sectional area of ​​the mold cavity to obtain the real-time apparent volume. The difference between the real-time apparent volume and the theoretical skeleton volume is divided by the real-time apparent volume, thereby converting the invisible pore state in the closed environment into an indirect physical parameter based on the quantitative calculation of external mechanical displacement. When the residual porosity drops to the calibration threshold and no powder is ejected with the gas, the current test amplitude is locked as the target amplitude. The control unit then calculates the target amplitude according to the formula. Calculate and store the preset expansion coefficient; where, The preset expansion coefficient, To lock onto the target amplitude, This represents the actual volume expansion. A dimensionless scaling constant is used to match the production mold cavity size with the test mold cavity size.

[0041] During the formal molding stage, when entering the decompression and vibration process, the control system acquires the first downward displacement of the pressure head and calculates the volume expansion of the material in the current molding cavity. The control system extracts the calibrated and stored preset expansion coefficient, multiplies the volume expansion with the preset expansion coefficient, and determines the amplitude command of the second frequency mechanical wave output by the second excitation device. This calibration and calculation logic establishes a linear correspondence between the energy injection amplitude of low-frequency excitation and the macroscopic expansion state after the disintegration of the granular skeleton. The skeleton disintegration state caused by the first frequency mechanical wave is reflected by the volume expansion represented by the first downward displacement. The control system matches the output amplitude of the second frequency mechanical wave to provide the exhaust creep stroke matching the deep decoupled particle spacing. This mechanism adjusts the densification energy according to the mapping logic of the underlying physical parameters, solving the engineering contradiction of insufficient exhaust under high expansion state or secondary particle segregation under low expansion state with fixed amplitude. During the decompression and vibration operation, the amplitude control logic is executed through real-time feedback of the material volume expansion. During the process of reducing the pressure from the second preset pressure to the third preset pressure, the displacement sensor acquires the first downward displacement of the pressure head, and calculates the material volume expansion by combining it with the cross-sectional area of ​​the mold cavity. , with the pre-stored preset expansion coefficient The product operation determines the target amplitude of the second frequency mechanical wave output by the second excitation device. Preset expansion coefficient The calibration results are derived from samples with different moisture contents. The calibration process includes monitoring the fluid overflow pressure from the vent holes within the test mold cavity, recording the ratio of amplitude to volume expansion at the point of highest venting efficiency, and generating a table corresponding to moisture content and expansion coefficient for instruction retrieval. During the calculation... For the determined target amplitude, The calculated volume expansion amount, To correspond to the preset parameters for the moisture content range, specifically, the displacement sensor establishes a linear position coordinate system with the top of the mold cavity as the zero point and the downward direction as the positive direction. During the micro-unloading stage, when the pressure decreases from the second preset pressure to the third preset pressure, the volume expands upward due to the elastic recovery of the enclosed air inside the granular material. The pressure head is pushed back upward by the material, resulting in an upward rebound. At this time, the real-time position coordinate value of the pressure head read by the displacement sensor shows a monotonically decreasing value in the positive direction. The first downward displacement refers to the absolute value of the difference between the maximum compaction depth coordinate of the pressure head under the second preset pressure and the depth coordinate at any instant during the decompression process. By multiplying this positive coordinate reduction by the cross-sectional area of ​​the mold cavity, the real-time apparent volume expansion released due to the rebound expansion of the material can be accurately calculated. This eliminates the apparent physical contradiction between the macroscopic direction of motion and the computational description caused by the coordinate system's defined direction.

[0042] Example 4: Before deploying the coal gangue molding process for pre-filling in the mine filling operation site, an initial calibration procedure for the mechanical transmission characteristics of graded coal gangue mixtures in different underground mining areas is performed to determine the stable difference range required for fluidization state determination. The system injects the batch of graded coal gangue mixture to be processed into the molding test cavity, applies a first preset pressure using a pressure head, and starts the first excitation device to output a mechanical wave of the first frequency. The stress transmission difference between the pressure output by the pressure head and the pressure transmitted at the bottom of the molding cavity is monitored in real time. The control unit records the evolution curve of the stress transmission difference as the excitation time increases. When the mechanical bridging structure inside the graded coal gangue mixture collapses, the stress transmission difference shows a non-linear drop and tends to stabilize. The system extracts the average value of the stress transmission difference for 5 consecutive sampling periods within this stable stage and defines it as the fluidization determination benchmark for the current batch of material. And according to the formula Establish a stable difference interval; among which, To stabilize the difference range, The fluidization criterion is Δp, which is a preset pressure tolerance constant.

[0043] To address the mechanical damping offset that occurs in the molding cavity during long-term operation, the system executes a baseline calibration procedure for the displacement detection link to ensure consistent feedback in the volume expansion calculation. When the molding cavity is unloaded, the pressure head is controlled to descend to the zero-point position at the bottom of its stroke. The control unit reads the output value of the pressure head displacement sensor and stores it as the sensor's zero-point offset. The system loads a rigid calibration block of standard volume into the molding cavity. The pressure head descends and contacts the upper surface of the calibration block. The displacement increment fed back by the displacement gauge is compared with the nominal height of the calibration block after zero-point offset correction. If the deviation exceeds a preset threshold of 0.05mm, the proportional conversion coefficient of the displacement gauge is updated. The calibrated displacement feedback data serves as the input for calculating the first downward displacement, enabling the quantitative calculation of volume expansion to eliminate sensor drift caused by ambient temperature and cumulative gap interference from the mechanical transmission chain. This pre-calibration and calibration process establishes a mapping relationship from material mechanical properties to system execution parameters, improving the stability of the densification degree of the molded body under varying working conditions.

[0044] Example 5: In processing coal gangue raw materials originating from different geological strata with varying strength coefficients, the system, to adapt general process parameters to the mechanical transmission characteristics of a specific batch of material, executes an adaptive calibration process for the pressure tolerance constant Δp. The control unit injects a graded coal gangue mixture sample into the molding cavity and applies a unidirectional static pressure load, simultaneously collecting pressure values ​​at different longitudinal depths within the cavity to record the pressure distribution gradient. To achieve stable data extraction at different longitudinal depths, the system embeds multiple sets of miniature piezoresistive side pressure sensors at equal intervals along the longitudinal axis on the pressure-bearing sidewall of the molding test cavity. The detection pressure-bearing end faces of all types of sensors are precisely machined flush with the inner wall of the cavity, effectively avoiding mechanical interference with the vertical downward displacement of large-diameter coarse aggregates while also preventing the sensor probes from being directly suspended and buried inside the highly abrasive mixture. The risk of pressure-limited stress shear failure is addressed by directly extracting the normal expansion stress transmitted from the surrounding material to the sidewall as a characterization benchmark for the longitudinal stress attenuation gradient. The control unit calculates the effective stress transmission coefficient η of the current batch of material based on the dispersion of the pressure distribution. The system first extracts the real-time pressure values ​​fed back by all sidewall sensor nodes within the same sampling period to form a multi-dimensional data sample, calculates the standard deviation of this sample set to quantify the overall distribution dispersion, then extracts the initial static input value of the first preset pressure at the top and subtracts the attenuated transmission pressure at the bottom of the mold cavity to obtain the total longitudinal stress loss of the system. Finally, the ratio of the total longitudinal stress loss to the standard deviation of the pressure distribution is calculated and output as the effective stress transmission coefficient η. This dimensionality reduction algorithm rigorously maps and converges the discrete stress matrix characterizing the spatial gradient into a scalar parameter that can directly evaluate the momentum barrier characteristics of the system; according to the formula... Determine the pressure tolerance constant that matches the current material properties; where Δp is the pressure tolerance constant. The uniformity pressure benchmark is preset for the molded body, where η is the effective stress transmission coefficient and e is the base of the natural logarithm. The preset equipment stiffness compensation factor, the reference coefficient Dimensionless scaling constant and equipment stiffness compensation factor As the core calibration constant in this molding process control network, its quantization boundary and determination method have clear physical mechanisms and engineering basis; among them, the benchmark coefficient The physical meaning is the fluidization boundary time increment per unit fineness modulus. Its value is determined by linear fitting of the stress reconstruction rate of samples with different gradations in a standard fluidization test. In this embodiment, its value range is limited to [value missing]. If the mass is below this lower bound, the viscous resistance of the liquid bridge between fine particles cannot be overcome; if it is above this upper bound, excessive convection of the aggregate will occur. (Dimensionless scaling constant) The equivalent conversion is then performed based on the geometric similarity ratio between the production mold cavity volume and the calibration mold cavity volume, as well as the acoustic impedance conduction attenuation rate, to correct for the energy density deviation caused by the scale effect. In this embodiment, the value is taken as [value missing]. Equipment stiffness compensation factor It is a reverse correction coefficient derived by applying a step load to the hydraulic system under no-load conditions, collecting the springback displacement of the press head, and substituting it into the structural stiffness matrix equation. This coefficient is used to eliminate parasitic interference caused by the macroscopic elastic deformation of the press frame and mold cavity sidewalls under ultimate stress on the transient strain measurement of the material. Its value range is within... This provides closed-loop engineering data support for high-precision calculation of various formulas under varying working conditions.

[0045] When the molding process is in the online operation stage and it is necessary to determine whether the material has reached the fluidization state, the control unit executes the process switching decision through a discretization discrimination algorithm. The control system continuously acquires real-time data of stress transmission difference at M sampling points with a period of 50ms, and calculates the variance of the data sequence. With the mean μ, when the mean μ enters the stable difference interval determined by the previous calibration, and the variance value... Below the preset smoothness threshold When the control unit determines that the internal displacement of the material has stopped, it outputs a switching command to the second preset pressure. If the control system fails to capture the convergence signal of the mean μ within the preset timeout period, it activates the power compensation operator of the first excitation device to increase the energy output of the first frequency mechanical wave. The dynamic monitoring mechanism of this quantitative criterion, together with the pre-calibration process, maintains the stability of the density of the molded body under the gradation fluctuation condition.

[0046] The embodiments of this application have been described above with reference to the accompanying drawings. Unless otherwise specified, the embodiments and features in the embodiments of this application can be combined with each other. This application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit of this application and the scope of protection of this invention, and all of these forms are within the protection scope of this application.

Claims

1. A coal gangue molding process for pre-treatment filling, characterized in that, Includes the following steps: Step 101: Inject graded coal gangue mixture into the molding cavity; Step 102: Apply a first preset pressure to the graded coal gangue mixture through the pressure head, and apply a mechanical wave of the first frequency to the forming mold cavity using the first excitation device; divide the operating state of the first excitation device into alternating excitation time periods and vibration stop time periods according to the time axis, output the mechanical wave of the first frequency during the excitation time period, and stop outputting the mechanical wave of the first frequency during the vibration stop time period. Step 103: Control the pressure head to increase the pressure from the first preset pressure to the second preset pressure, and after maintaining the second preset pressure for a preset holding time, control the pressure head to perform a pressure reduction and excitation operation; the pressure reduction and excitation operation includes: controlling the pressure head to reduce the pressure from the second preset pressure to the third preset pressure, and within a preset unloading time of maintaining the third preset pressure, using the second excitation device to apply a mechanical wave of the second frequency to the molding cavity, and controlling the pressure head to restore the pressure to the second preset pressure; Step 104: Maintain the second preset pressure for pressure holding and solidification, and demold to obtain the coal gangue molded body; In step 102, the first frequency and in step 103, the second frequency respectively satisfy the following conditions: the first frequency is greater than or equal to 100Hz and less than or equal to 200Hz; the second frequency is greater than or equal to 20Hz and less than or equal to 50Hz. The third preset pressure is 50% to 70% of the second preset pressure, and the first preset pressure is 20% to 30% of the second preset pressure.

2. The coal gangue molding process for pre-treatment filling as described in claim 1, characterized in that, Step 102 includes: Step 201, obtaining the maximum aggregate particle size and fineness modulus of the graded coal gangue mixture, and obtaining the wave velocity of the mechanical wave of the first frequency in the graded coal gangue mixture; Step 202, calculating the duration of the excitation time period based on the maximum aggregate particle size, fineness modulus, and wave velocity, and introducing the following formula: ,in, The duration of the excitation period. For the maximum aggregate particle size, For wave speed, For fineness modulus, The preset reference coefficients have a time dimension. The range of values ​​is Step 203: Control the first excitation device to output a mechanical wave of the first frequency within the excitation time period according to the duration.

3. The coal gangue molding process for pre-treatment filling as described in claim 1, characterized in that, Before step 101, the process also includes a gradation construction step: Step 601, crushing and screening the raw coal gangue ore to separate coarse aggregate components and fine powder components; Step 602, adding cement-based cementitious materials and activators to the fine powder components and dry mixing to obtain mixed cementitious powder; Step 603, mixing the coarse aggregate components and mixed cementitious powder according to the mass ratio, adding activated water and stirring to obtain graded coal gangue mixture.

4. The coal gangue molding process for pre-treatment filling as described in claim 1, characterized in that, The depressurization excitation operation includes performing at least three depressurization excitation cycles consecutively; each depressurization excitation cycle includes: controlling the pressure head to reduce the pressure to a third preset pressure, applying a mechanical wave of a second frequency, and restoring the pressure to a second preset pressure; the time interval between two adjacent depressurization excitation cycles maintaining the second preset pressure decreases in an arithmetic sequence.

5. The coal gangue molding process for pre-treatment filling according to claim 1, characterized in that, The process of controlling the pressure head to increase the pressure from the first preset pressure to the second preset pressure in step 103 includes: step 901, controlling the pressure head to increase the pressure at a constant first pressurization rate; step 902, when the pressure reaches the arithmetic mean of the first preset pressure and the second preset pressure, reducing the pressurization rate from the first pressurization rate to the second pressurization rate, and increasing the pressure at the second pressurization rate until the second preset pressure is reached.

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