Phosphogypsum solid waste filling process for phosphorite goaf

Abstract

This invention relates to the field of mine backfilling technology and discloses a process for backfilling phosphogypsum solid waste in phosphate mine goafs. The process includes: erecting a wavy backfilling pipeline along the base plate, consisting of alternating uphill and downhill pipe sections; pumping prepared phosphogypsum slurry into the pipeline for transport; as the slurry flows through the uphill pipe section, its own weight increases the axial extrusion pressure, driving free water to seep into the pipe wall to form a boundary liquid film; as it flows through the downhill pipe section, its own weight reduces the extrusion pressure, generating negative pressure to draw the boundary liquid film back into the slurry; by alternating pipe sections, a periodic seepage and backflow cycle of free water is established, transporting the slurry to the goaf for consolidation. This invention utilizes the undulation of the pipeline to induce stress alternation in the slurry, spontaneously constructing a lubricating liquid film regeneration mechanism, blocking liquid phase dissipation, eliminating the need for additional components, reducing friction along the route, and ensuring stability during long-distance transport.

Description

Technical Field

[0001] This invention belongs to the field of mine backfilling technology, and particularly relates to a process for backfilling solid waste phosphogypsum in phosphate mine goaf areas. Background Technology

[0002] Currently, preparing high-concentration slurries from bulk industrial solid wastes such as phosphogypsum and pumping them to in-situ backfilling in goaf areas is the mainstream method for controlling rock movement and treating surface solid waste. During long-distance pipeline transportation, high-concentration slurries exhibit non-Newtonian fluid characteristics. Maintaining the boundary lubricating film between the slurry plunger and the pipe wall becomes the core mechanism for reducing frictional resistance along the pipeline and maintaining the rheological stability of the pipeline network. As the mining direction extends and the transportation distance of the horizontal backfilling pipeline increases, the surface lubricating film continuously undergoes physical shear dissipation during long-distance horizontal sliding of the slurry and gradually dries up due to the osmotic pressure balance of the internal solid skeleton, causing a surge in frictional resistance in the later section of the pipeline network. If the initial water content of the slurry is simply increased during the ground preparation stage to compensate for water loss along the pipeline, the excess free water will cause overall water bleeding after the slurry is discharged into the goaf area, resulting in an early decrease in the consolidation strength of the backfill and damage to the overall mechanical stability of the stope retaining wall.

[0003] To achieve in-line regeneration of liquid films under extremely low water-to-solid ratio conditions, existing technologies typically incorporate spiral guide strips or static flow-blocking blades on the inner wall of the pipeline. These rely on internal mechanical components to agitate the flow and force internal moisture to migrate towards the boundary. However, high-concentration solid waste slurries inherently constitute highly abrasive, flexible cutting bodies, exposing fundamental structural flaws in these internal flow guidance schemes. Besides improvements to the pipeline hardware structure, methods for controlling the rheological properties of the slurry also have shortcomings. For example, Chinese invention patent application CN1821547A discloses a method for filling phosphogypsum into underground goaf areas to form a solidified filling body. Although optimizing the relationship between cement, fly ash, and phosphorus... The chemical formulation of gypsum, with the addition of sodium sulfate at a specific concentration, improves the initial fluidity and later hardening strength of the slurry. However, this type of scheme is a static formulation optimization. In actual long-distance transportation, relying solely on chemical formulation cannot counteract the dehydration and dissipation of the liquid film caused by continuous physical shear between the slurry and the pipe wall. It is also difficult to suppress the eccentric sedimentation of solid particles under the horizontal gravitational field. This static formulation control approach causes the slurry to become rheologically unstable after crossing the depletion threshold of long-distance transportation. The above-mentioned physical dissipation process shows that the transportation method that relies on the introduction of internal mechanical components to counteract the dissipation along the way has structural unreliability under the high-load continuous operation conditions in deep mines.

[0004] Therefore, how to construct a liquid film regeneration and dynamic homogenization mechanism without internal physical intervention based on the smooth boundary of the entire cross-section of the pipeline network has become the technical problem to be solved by this invention. Summary of the Invention

[0005] This invention discloses a process for backfilling solid waste from phosphogypsum in phosphate mine goaf areas, comprising the following steps:

[0006] Step 101: Install support pipe racks at intervals along the bottom plate of the mine roadway, and install a corrugated filling pipeline consisting of alternating uphill and downhill pipe sections on the support pipe racks. To ensure the linear stability of the corrugated pipeline when conveying high-pressure slurry, the support pipe rack adopts an integrated welded steel structure, with the base anchored in the rock strata of the roadway bottom plate. An adjustable height U-shaped bracket is installed at the top to lock the geometric undulations of the pipe section. A high-elasticity rubber pad is installed between the pipeline and the bracket to absorb the axial vibration caused by the fluctuation of the slurry pumping pressure. At the same time, by constraining the horizontal lateral displacement of the pipeline, the thermal stress and internal pressure stress caused by the deformation of the pipe diameter are limited to within the preset 1mm, ensuring that the geometric tolerance of the corrugated topology meets the expected rheological control accuracy.

[0007] Step 102: Mix the cementitious material with the original phosphogypsum solid waste to prepare a phosphogypsum slurry with a yield stress greater than the hydrostatic pressure, and pump the phosphogypsum slurry into a corrugated filling pipeline for transportation.

[0008] Step 103: When the phosphogypsum slurry flows through the uphill pipe section, the axial extrusion force inside the phosphogypsum slurry is increased based on the self-weight component of the phosphogypsum slurry, which compresses the spacing between solid particles in the phosphogypsum slurry and drives free water to seep radially into the inner wall of the wavy filling pipe, forming a boundary liquid film on the inner wall.

[0009] Step 104: When the phosphogypsum slurry with boundary liquid film flows through the connected downhill pipe section, the axial extrusion force inside the phosphogypsum slurry is reduced based on the self-weight component of the phosphogypsum slurry, causing the pores inside the phosphogypsum slurry to expand and generate negative pressure, and the boundary liquid film is drawn back into the phosphogypsum slurry based on the negative pressure.

[0010] Step 105: Relying on the continuous alternating structure of the uphill and downhill pipe sections in the wavy filling pipeline, a periodic cycle of free water seepage and backflow is established to transport the phosphogypsum slurry to the goaf for hardening and consolidation.

[0011] Preferably, in step 101, the central axis of the corrugated filling pipeline is a sine curve; the ratio of the inner diameter of the corrugated filling pipeline to the axial spacing of the support pipe rack is constant, so as to limit the radial displacement of the corrugated filling pipeline within a preset deformation tolerance.

[0012] Preferably, in step 101, the vertical height difference between the top of the uphill pipe section and the bottom of the downhill pipe section satisfies the following formula with respect to the wavelength of the sine curve: H=α×λ, where H is the vertical height difference, λ is the wavelength, and α is the fluctuation coefficient determined based on the yield stress of the phosphogypsum slurry and the friction coefficient of the pipe wall, and the value of the fluctuation coefficient is 0.02 to 0.08.

[0013] Preferably, step 102, the step of preparing phosphogypsum slurry, specifically includes: step 401, obtaining untreated undisturbed phosphogypsum solid waste and cementing material; step 402, adding water to the undisturbed phosphogypsum solid waste and cementing material and mixing and stirring, applying mechanical shear force through mixing and stirring to peel off the insoluble calcium salt precipitates generated on the surface of the cementing material; step 403, maintaining mechanical shear force while stirring until the yield stress of the obtained phosphogypsum slurry is greater than the hydrostatic pressure.

[0014] Preferably, in step 103, the step of driving free water to seep into the inner wall of the radially wavy filling pipe includes: step 501, using increased axial compressive force to overcome the skeleton yield strength of the phosphogypsum slurry and compress the pore volume between solid particles; step 502, the pressurized free water seeps into the inner wall along the pore channels; step 503, the seeped free water converges between the outer surface and the inner wall of the phosphogypsum slurry to form a boundary liquid film.

[0015] Preferably, in step 104, the step of drawing the boundary liquid film back into the phosphogypsum slurry based on negative pressure includes: step 601, releasing the elastic strain energy accumulated when the axial compressive force decreases; step 602, the release of elastic strain energy causes pore expansion and generates negative pressure; step 603, drawing the boundary liquid film distributed on the inner wall into the pores of the phosphogypsum slurry based on negative pressure.

[0016] Preferably, in step 105, the step of establishing a periodic cycle of free water seepage and reabsorption includes: step 701, after experiencing multiple alternations of uphill and downhill pipe sections, making the free water content on the outer surface of the phosphogypsum slurry fluctuate with alternating peaks and troughs; step 702, setting the overall length of the wavy filling pipeline according to the spatial location of the goaf, so that the end of the wavy filling pipeline is the bottom of the downhill pipe section, thereby making the free water on the outer surface of the discharged phosphogypsum slurry in a trough distribution state.

[0017] Preferably, after step 102, the method further includes: step 801, obtaining solid phase concentration distribution data characterizing the phosphogypsum slurry on the cross-section of the corrugated filling pipeline; step 802, when the solid phase concentration distribution data indicates that the difference between the concentration at the bottom and the concentration at the top of the cross-section is greater than the concentration difference threshold, increasing the initial flow rate of the phosphogypsum slurry pumped into the corrugated filling pipeline; step 803, using the alternating shear force generated by the increased initial flow rate coupled with the continuous alternating structure of the uphill and downhill pipe sections, redispersing the solid particles enriched at the bottom to the central region of the cross-section.

[0018] Preferably, the method further includes: step 901, acquiring real-time monitoring data characterizing the fluid velocity inside the pipe at the end node of the corrugated filling pipeline; step 902, calculating the actual pressure loss gradient based on the real-time monitoring data; and step 903, increasing the pumping pressure at the feed end of the pumped phosphogypsum slurry when the actual pressure loss gradient is greater than the pressure loss reference value, so as to maintain the pressurized state inside the phosphogypsum slurry.

[0019] Preferably, step 105, the step of transporting phosphogypsum slurry to the goaf for hardening and consolidation, includes: step 1001, discharging the phosphogypsum slurry flowing out of the corrugated filling pipeline into the goaf; step 1002, utilizing the overall three-dimensional stress release generated after the phosphogypsum slurry is freed from the constraints of the corrugated filling pipeline to promote the hydration reaction of the cementing material on the surface of the undisturbed phosphogypsum solid waste; and step 1003, relying on the self-leveling properties of the phosphogypsum slurry to fill the goaf and complete the hardening and consolidation within the goaf.

[0020] Compared with existing technologies, the phosphogypsum solid waste backfilling process for phosphate mine goaf of the present invention has the following advantages:

[0021] 1. In the backfilling of phosphogypsum solid waste in phosphate mine goaf areas, by constructing a wave-topology pipeline structure with alternating undulations, the spatial geometry of the transport path is transformed into an alternating stress loading source for the pressurized solid skeleton. During the flow of slurry through the uphill and downhill pipe sections, the axial component of gravity periodically induces axial compression and tensile deformation of the solid skeleton, thereby relying on the Poisson's ratio effect of the material to drive deep pore water to continuously seep out and be drawn back to the pipe wall boundary. The regeneration process of the boundary lubricating film is reconstructed from physical intervention that relies on internal mechanical components to disturb the flow field to spontaneous regulation that relies on external spatial layout to change the internal pore pressure, eliminating the root cause of concentrated cutting wear of highly abrasive slurry on the internal flow-obstructing components of the pipeline, and establishing the physical compatibility of pipeline drag reduction and system wear resistance while maintaining the smoothness of the entire cross-section of the pipeline inner wall.

[0022] 2. This process utilizes the variation of gravity components in the wave-topology pipeline to establish a relay regeneration and dynamic homogenization network of lubricating fluid film along the pipeline network. The radial extrusion stress generated in the uphill pipe section forces the precipitation of pore water to replenish the physical dissipation of the boundary fluid film, while the internal negative pressure generated in the downhill pipe section drives the surface water and frictional rock debris to be drawn back into the skeleton. This reciprocating flow of pressure and permeation, coupled with the total amount of water carried by the initial slurry and the gravitational potential energy, completes the self-sufficient turnover of the interfacial liquid phase. From a mechanical evolution mechanism perspective, this blocks the physical trend of unidirectional drying of the lubricating fluid film due to friction along the pipeline, and improves the rheological stability of the system across the depletion critical point of ultra-long-distance transport. Attached Figure Description

[0023] Figure 1 This is a flow chart of the phosphogypsum solid waste backfilling process using the corrugated pipeline of the present invention.

[0024] Figure 2 This is a schematic diagram of the stress on the slurry and the dynamic evolution of the liquid film within the uphill and downhill pipe sections of the present invention. Detailed Implementation

[0025] 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.

[0026] It should be noted that all directional and positional terms used in this invention, such as: up, down, left, right, front, back, vertical, horizontal, inner, outer, top, bottom, transverse, longitudinal, center, etc., are only used to explain the relative positional relationship and connection between components in a specific state (as shown in the accompanying drawings). They are only for the convenience of describing this invention and do not require that this invention be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting this invention. In addition, the descriptions of "first," "second," etc., in this invention are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated.

[0027] In the description of this invention, unless otherwise explicitly specified and limited, the terms installation, connection, and linking should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections; they can refer to direct connections or indirect connections through an intermediate medium; they can refer to the internal connection of two components. For those skilled in the art, the specific meaning of the above terms in this invention can be understood in conjunction with the specific circumstances.

[0028] In the description of this specification, references to the terms "an embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example, and the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0029] A process for backfilling phosphogypsum solid waste in phosphate mine goaf includes the following steps:

[0030] Step 101: Install support pipe racks at intervals along the bottom plate of the mine roadway, and install a corrugated filling pipeline consisting of alternating uphill and downhill pipe sections on the support pipe racks. To ensure the linear stability of the corrugated pipeline when conveying high-pressure slurry, the support pipe rack adopts an integrated welded steel structure, with the base anchored in the rock strata of the roadway bottom plate. An adjustable height U-shaped bracket is installed at the top to lock the geometric undulations of the pipe section. A high-elasticity rubber pad is installed between the pipeline and the bracket to absorb the axial vibration caused by the fluctuation of the slurry pumping pressure. At the same time, by constraining the horizontal lateral displacement of the pipeline, the thermal stress and internal pressure stress caused by the deformation of the pipe diameter are limited to within the preset 1mm, ensuring that the geometric tolerance of the corrugated topology meets the expected rheological control accuracy.

[0031] Step 102: Mix the cementitious material with the original phosphogypsum solid waste to prepare a phosphogypsum slurry with a yield stress greater than the hydrostatic pressure, and pump the phosphogypsum slurry into a corrugated filling pipeline for transportation.

[0032] Step 103: When the phosphogypsum slurry flows through the uphill pipe section, the axial extrusion force inside the phosphogypsum slurry is increased based on the self-weight component of the phosphogypsum slurry, which compresses the spacing between solid particles in the phosphogypsum slurry and drives free water to seep radially into the inner wall of the wavy filling pipe, forming a boundary liquid film on the inner wall.

[0033] Step 104: When the phosphogypsum slurry with boundary liquid film flows through the connected downhill pipe section, the axial extrusion force inside the phosphogypsum slurry is reduced based on the self-weight component of the phosphogypsum slurry, causing the pores inside the phosphogypsum slurry to expand and generate negative pressure, and the boundary liquid film is drawn back into the phosphogypsum slurry based on the negative pressure.

[0034] Step 105: Relying on the continuous alternating structure of the uphill and downhill pipe sections in the wavy filling pipeline, a periodic cycle of free water seepage and backflow is established to transport the phosphogypsum slurry to the goaf for hardening and consolidation.

[0035] Preferably, in step 101, the central axis of the corrugated filling pipeline is a sine curve; the ratio of the inner diameter of the corrugated filling pipeline to the axial spacing of the support pipe rack is constant, so as to limit the radial displacement of the corrugated filling pipeline within a preset deformation tolerance.

[0036] Preferably, in step 101, the vertical height difference between the top of the uphill pipe section and the bottom of the downhill pipe section satisfies the following formula with respect to the wavelength of the sine curve: H=α×λ, where H is the vertical height difference, λ is the wavelength, and α is the fluctuation coefficient determined based on the yield stress of the phosphogypsum slurry and the friction coefficient of the pipe wall, and the value of the fluctuation coefficient is 0.02 to 0.08.

[0037] Preferably, step 102, the step of preparing phosphogypsum slurry, specifically includes: step 401, obtaining untreated undisturbed phosphogypsum solid waste and cementing material; step 402, adding water to the undisturbed phosphogypsum solid waste and cementing material and mixing and stirring, applying mechanical shear force through mixing and stirring to peel off the insoluble calcium salt precipitates generated on the surface of the cementing material; step 403, maintaining mechanical shear force while stirring until the yield stress of the obtained phosphogypsum slurry is greater than the hydrostatic pressure.

[0038] Preferably, in step 103, the step of driving free water to seep into the inner wall of the radially wavy filling pipe includes: step 501, using increased axial compressive force to overcome the skeleton yield strength of the phosphogypsum slurry and compress the pore volume between solid particles; step 502, the pressurized free water seeps into the inner wall along the pore channels; step 503, the seeped free water converges between the outer surface and the inner wall of the phosphogypsum slurry to form a boundary liquid film.

[0039] Preferably, in step 104, the step of drawing the boundary liquid film back into the phosphogypsum slurry based on negative pressure includes: step 601, releasing the elastic strain energy accumulated when the axial compressive force decreases; step 602, the release of elastic strain energy causes pore expansion and generates negative pressure; step 603, drawing the boundary liquid film distributed on the inner wall into the pores of the phosphogypsum slurry based on negative pressure.

[0040] Preferably, in step 105, the step of establishing a periodic cycle of free water seepage and reabsorption includes: step 701, after experiencing multiple alternations of uphill and downhill pipe sections, making the free water content on the outer surface of the phosphogypsum slurry fluctuate with alternating peaks and troughs; step 702, setting the overall length of the wavy filling pipeline according to the spatial location of the goaf, so that the end of the wavy filling pipeline is the bottom of the downhill pipe section, thereby making the free water on the outer surface of the discharged phosphogypsum slurry in a trough distribution state.

[0041] Preferably, after step 102, the method further includes: step 801, obtaining solid phase concentration distribution data characterizing the phosphogypsum slurry on the cross-section of the corrugated filling pipeline; step 802, when the solid phase concentration distribution data indicates that the difference between the concentration at the bottom and the concentration at the top of the cross-section is greater than the concentration difference threshold, increasing the initial flow rate of the phosphogypsum slurry pumped into the corrugated filling pipeline; step 803, using the alternating shear force generated by the increased initial flow rate coupled with the continuous alternating structure of the uphill and downhill pipe sections, redispersing the solid particles enriched at the bottom to the central region of the cross-section.

[0042] Preferably, the method further includes: step 901, acquiring real-time monitoring data characterizing the fluid velocity inside the pipe at the end node of the corrugated filling pipeline; step 902, calculating the actual pressure loss gradient based on the real-time monitoring data; and step 903, increasing the pumping pressure at the feed end of the pumped phosphogypsum slurry when the actual pressure loss gradient is greater than the pressure loss reference value, so as to maintain the pressurized state inside the phosphogypsum slurry.

[0043] Preferably, step 105, the step of transporting phosphogypsum slurry to the goaf for hardening and consolidation, includes: step 1001, discharging the phosphogypsum slurry flowing out of the corrugated filling pipeline into the goaf; step 1002, utilizing the overall three-dimensional stress release generated after the phosphogypsum slurry is freed from the constraints of the corrugated filling pipeline to promote the hydration reaction of the cementing material on the surface of the undisturbed phosphogypsum solid waste; and step 1003, relying on the self-leveling properties of the phosphogypsum slurry to fill the goaf and complete the hardening and consolidation within the goaf.

[0044] Example 1: In the filling of deep phosphate mine goaf areas with a strike length exceeding 3000 meters and including horizontal roadways, high-concentration phosphogypsum slurry experiences surface lubricant film drying and eccentric sedimentation under low water-to-solid ratio conditions, leading to increased frictional resistance in the downstream section of the pipeline network. When using homogenized slurry preparation and adding static flow-blocking components to deal with highly abrasive slurries, there are problems of component cutting and wear failure and local rheological instability. Simply relying on internal fluid disturbance to separate the liquid phase is insufficient to overcome the eccentric sedimentation tendency of the solid skeleton caused by horizontal gravity. A phosphogypsum slurry with a yield stress greater than the hydrostatic pressure is prepared by mixing cementing materials and uncalcined undisturbed phosphogypsum solid waste. Support pipe racks are laid at intervals along the bottom plate of the mine roadway, and a corrugated filling pipeline consisting of alternating uphill and downhill pipe sections is erected on the support pipe racks. The phosphogypsum slurry is pumped into the corrugated filling pipeline for transportation, and the slurry flows through the uphill and downhill pipe sections in a plunger flow form.

[0045] When the phosphogypsum slurry flows through the uphill pipe section, the axial extrusion pressure increases due to the slurry's own weight. This increased axial extrusion pressure overcomes the skeletal yield strength of the phosphogypsum slurry, compressing the pore volume between solid particles. Pressurized free water seeps directionally into the inner wall along the pore channels and converges between the outer surface and inner wall of the phosphogypsum slurry to form a boundary liquid film. When the phosphogypsum slurry flows through the downhill pipe section, the axial extrusion pressure decreases due to the slurry's own weight. The decrease in axial extrusion pressure releases the elastic strain energy of the phosphogypsum slurry, causing the pores between solid particles to expand and generate negative pressure. This negative pressure draws the boundary liquid film back into the phosphogypsum slurry. The solid-phase skeleton formed by flocculation and cross-linking within the concentrated phosphogypsum slurry exhibits an elastic mechanical response similar to that of a porous sponge. When the downward gravity component partially offsets the pumping thrust, causing a decrease in the local macroscopic axial compressive pressure, the microscopic pore throats within the solid-phase skeleton, which were originally compressed and closed, undergo elastic rebound. This local expansion of the skeleton's volume induces a sudden drop in local pore water pressure within the closed, incompressible fluid matrix, thereby establishing a negative pressure gradient greater than the interfacial capillary resistance between the pipe wall lubrication layer and the central slurry plunger. This forces free water to overcome surface tension and flow back into the slurry. At the microscale, this elastic rebound process corresponds to the volume increase between the solid particles. ,in The initial porosity, This represents the stress unloading amplitude caused by changes in the gravitational component. This represents the equivalent compressive modulus of the slurry skeleton. Due to the non-Newtonian properties of the fluid matrix in high-concentration slurries, which possess extremely high apparent viscosity, the pressure changes induced within the pores by the instantaneous volume expansion mentioned above... ; A transient negative pressure gradient is created to enhance the pore fluid modulus, which can overcome the capillary resistance provided by interfacial tension within microseconds. Thus, under the stable shear background of the macroscopic pumping flow field, the boundary liquid film is spontaneously regenerated through this local micro-region negative pressure swallowing effect, maintaining the rheological stability of long-distance transportation; the squeezing seepage of the uphill pipe section and the negative pressure back suction of the downhill pipe section work synergistically, the uphill pipe section provides lubricating medium for the pipe wall, and the downhill pipe section prevents unidirectional loss of the boundary liquid film and homogenizes the water distribution around the solid skeleton; the spatial geometry of the corrugated filling pipeline establishes a periodic seepage and back suction cycle of free water along the pipeline network; the vertical height difference between the top of the uphill pipe section and the bottom of the downhill pipe section satisfies the following formula H=α×λ, where H is the uphill... The vertical height difference between the top of the pipe section and the bottom of the downhill pipe section, λ is the wavelength of the wavy filling pipe, and α is the dimensionless fluctuation coefficient determined based on the yield stress of the phosphogypsum slurry and the pipe wall friction coefficient, with a value ranging from 0.02 to 0.08. During the system calibration phase, the control unit has a built-in fluctuation coefficient mapping model. This model divides the obtained yield stress value of the phosphogypsum slurry by the pipe wall friction coefficient and multiplies it by a dimensionless scaling constant based on the pipe diameter calibration, thereby quantitatively calculating the geometric fluctuation ratio guiding the spatial configuration, thus avoiding the blindness of empirical estimation. The setting of this value range is based on the critical seepage instability limit determination; when At this time, the axial component of gravity is insufficient to drive free water to overcome the shear strength of the particle skeleton, resulting in a seepage pressure difference below the critical peeling threshold, thus preventing the formation of a continuous liquid film; when At this point, the local shear stress at the trough exceeds the yield stress of the slurry itself. This can lead to local disintegration of the plunger flow at the trough; through pressure loss tests along the pipe at various solid concentrations of slurry under different pipe diameters, and under the premise of ensuring dynamic balance between friction and fluid weight within the pipe, the confidence interval of the calculated fluctuation coefficient is: This ensures the stability of the seepage mechanism over a wide range of load fluctuations.

[0046] The corrugated filling pipeline regulates the boundary liquid film by altering the internal pore pressure, maintaining a smooth inner wall across the entire cross-section. This reduces pipeline friction while preventing abrasion from internal flow-obstructing components. The overall length of the corrugated filling pipeline is determined based on the spatial location of the goaf, ensuring the end is at the bottom of a downhill section, minimizing the free water distribution on the outer surface of the discharged phosphogypsum slurry. After the phosphogypsum slurry enters the goaf, it releases three-dimensional stress by escaping the constraints of the filling pipeline, relying on its self-leveling properties to fill the goaf and harden within it. As the constraint pressure inside the pipe drops from several megapascals to atmospheric pressure, the pore water inside the slurry undergoes rapid microscopic pressure relief and expansion. This fluid dynamic impact caused by macroscopic stress release directly tears apart the semi-permeable, difficult-to-re-adhere material surface that had reattached during the smooth sliding phase of pipeline transport. A passivating film made of soluble calcium salts allows pore water to instantly wet the fresh active sites of the cementitious material, thereby opening up the physicochemical channel for the transformation from macroscopic mechanical unloading to microscopic hydration ion diffusion, significantly accelerating the nucleation reaction of hydrated calcium silicate gel. Uncalcined virgin phosphogypsum solid waste is transported under low water-to-solid ratio conditions within the boundary of a smooth conveying pipeline network. The phosphogypsum slurry flowing out of the discharge port relies on initial cohesion to support the surrounding rock of the goaf. The elevation difference of the wavy filling pipeline is converted into the driving force for maintaining the circulation of the boundary lubricating fluid film. The stress alternation cycle of the high-concentration fluid is controlled by the geometry of the pipeline path. To achieve effective transmission of macroscopic elevation difference to microscopic pore stress, this invention constructs a decoupled mapping interface between fluid mechanics and skeletal mechanics. The wavy path causes a periodic change in macroscopic hydrostatic pressure. It is directly mapped to the normal compressive stress of the solid skeleton through the fluid-structure interaction boundary. In this mapping path, the slurry skeleton structure is equivalent to an isotropic porous elastic medium, utilizing the force transmission coefficient. By quantifying and allocating macroscopic pressure fluctuations, the periodic fluctuations of macroscopic hydrostatic pressure are made completely synchronized with the frequency of changes in the pore volume of the microscopic framework, thus achieving a physical consistency transformation from geometric configuration to rheological regulation.

[0047] Example 2: Addressing the engineering phenomenon of increased resistance during long-distance transport of high-concentration phosphogypsum slurry, a full-scale pipeline transport physical simulation platform was constructed to determine the correlation mechanism between the fluctuation coefficient α and the pressure loss along the pipeline and the boundary liquid film thickness. This physical simulation platform includes a 20m³ stirred slurry tank, a filling industrial pump with a rated discharge capacity of 120m³ / h, and a 500m long, 150mm inner diameter seamless steel pipe transport loop. High-frequency dynamic pressure transmitters with a measurement accuracy of 0.1kPa and a sampling frequency of 500Hz are deployed along the transport loop. Simultaneously, axial pressure transmitters are arrayed on the outer wall of the pipeline. An ultrasonic probe with a distance of 10m was used to detect the thickness of the liquid film. Solid phase concentration distribution data was acquired using four sets of 2.5MHz ultrasonic transducers installed on the cross-section of the corrugated pipe at the trough. The sensor array emitted pulse signals at a frequency of 1000Hz and received echoes. The solid phase distribution was reflected by comparing the amplitude attenuation energy difference between the top and bottom probes within a 20ms sliding window. The control unit extracted the energy values ​​of specific frequency bands from the raw echo signals using a fast Fourier transform and introduced a scattering attenuation correction coefficient based on the Lambert-Beer law to construct a solid phase concentration distribution calculation model. In the formula, The solid concentration difference between the upper and lower parts of the cross section. The acoustic scattering coefficient is pre-calibrated based on the slurry rheology. This serves as the baseline value for environmental noise compensation. By solving this model, the concentration field distribution matrix of each quadrant of the cross-section is obtained in real time, and the deviation between the centroid of the matrix and the central axis of the pipeline is used as a quantitative indicator for judging the eccentric settling of particles. The acoustic energy attenuation rate of the ultrasonic signal when penetrating the slurry is strictly positively correlated with the volume concentration of solid particles along the propagation path. The control unit has a built-in concentration conversion algorithm based on transmission acoustic theory that is pre-calibrated. By directly multiplying the percentage difference in amplitude attenuation energy acquired in real time by the preset solid particle size attenuation constant, the concentration attenuation rate at the bottom and top of the pipeline can be quantitatively calculated. The actual solid concentration difference value of the cross-sectional area; when the deviation of the echo energy difference between the bottom and top from its reference mean is greater than 15%, the system automatically triggers an abnormal concentration distribution alarm. The test material is uncalcined industrial by-product hemihydrate phosphogypsum, with 5% silicate cement added as a cementing material, and water is added to prepare a phosphogypsum slurry with a solid mass concentration of 78%. The initial yield stress of the phosphogypsum slurry was measured to be 150 Pa. This initial yield stress is greater than the hydrostatic pressure of the fluid in the test pipeline. To introduce engineering environmental disturbance, in The hydraulic drive end of the filling industrial pump actively superimposes a low-frequency pulsating signal with an amplitude of 5% of the rated pressure to simulate the pumping pressure fluctuation noise in the industrial field. The core of the wavy filling pipeline lies in setting a reasonable fluctuation coefficient α. The setting of this parameter depends on the balance between two physical constraints: the axial component of gravity needs to overcome the yield stress of the solid skeleton to squeeze out free water, and the avoidance of excessive slip shearing of the slurry in the downhill section, which would lead to the disintegration of the plunger flow. When the fluctuation coefficient α is too low, the component of gravity cannot squeeze out free water on the pipe wall; when its value is too high, the slurry will be squeezed out at the trough. Solid-liquid separation was achieved. The experimental wavelength λ was fixed at 50m. The vertical height difference H between the top of the uphill pipe section and the bottom of the downhill pipe section was determined according to the formula H=α×λ. A control group with a straight pipe laid in an absolutely horizontal manner and four experimental groups with corrugated filling pipes were set up. The fluctuation coefficients α of the four experimental groups were set to 0.01, 0.05, 0.08 and 0.12, respectively. The filling industrial pump was started to continuously inject phosphogypsum slurry into the pipe network at a constant flow rate. After the flow field in the pipe reached a steady state circulation, the friction loss and boundary liquid film thickness data of each sample group were extracted.

[0048] The measured data of the control group showed that the friction loss in the horizontal straight pipe reached 5.2 MPa / km. When executing the dynamic homogenization logic, if the solid concentration difference continues to exceed 15% for more than 30 seconds, the control unit sends a frequency increase command to the inverter of the filling industrial pump, increasing the operating frequency at a slope of 0.5 Hz per second until the initial flow velocity fed back by the electromagnetic flowmeter increases from 1.2 m / s to a high-velocity flushing range of 1.8 m / s to 2.1 m / s. The fluid kinetic energy, combined with the alternating shear force of the pipeline, resuspends the deposited particles. The boundary liquid film thickness detected by the ultrasonic probe gradually decreases with the conveying distance. At a depth of 300m, the liquid film thickness dropped below 0.11mm, and the pressure transmitter recorded continuous irregular fluctuations. In the first test group, with an fluctuation coefficient α set to 0.01, the pressure loss along the pipe was measured to be 4.82MPa / km, and the average liquid film thickness was 0.23mm. The low-amplitude axial component of gravity did not exceed the yield stress limit of the solid skeleton, and the free water seepage at the pipe wall was insufficient. In the second test group, with an fluctuation coefficient α set to 0.05, the liquid film thickness on the uphill section increased to 1.25mm, while the liquid film thickness on the downhill section decreased to 0.62mm with no liquid film drying. The pressure loss along the pipe in this group decreased to 2.15MPa / km. At a pressure of 5% pumping pressure fluctuation noise, the output flow fluctuation rate remained below 1.4%, demonstrating that alternating squeezing seepage and negative pressure backflow cycles established a steady-state fluid self-lubricating layer. In the third test group with an fluctuation coefficient α set at 0.08, the peak liquid film thickness in the uphill pipe section reached 1.84 mm, and the pressure loss along the pipe was measured at 2.08 MPa / km. The slurry skeleton structure did not undergo shear failure. In the fourth test group, when the fluctuation coefficient α increased to 0.12, the local pumping pressure in the uphill pipe section exceeded the system's set threshold, and the liquid film thickness in the downhill pipe section expanded to over 4.55 mm. The ultrasonic echo characteristics showed... The plunger flow of the slurry disintegrates and transforms into a heterogeneous two-phase flow. Solid particles segregate and settle at the troughs, causing pipeline blockage. Test data confirms that the fluctuation coefficient α in the range of 0.02 to 0.08 is the parameter boundary for maintaining radial water leakage lubrication of the pipe wall and the stability of the internal solid skeleton structure. The wavy filling pipeline relies on the periodic seepage and backflow network formed by the internal free water under the action of gravity to replace the mechanical shear viscosity reduction method. This spatial topology configuration enables the high-concentration phosphogypsum slurry to maintain a stable plunger flow pattern in the conveying network without additional drag-reducing agents or internal flow-blocking components, and suppresses the nonlinear growth of frictional resistance along the pipeline.

[0049] Example 3: In the surface slurry preparation stage of the deep phosphate mine goaf filling process, soluble impurities associated with the uncalcined virgin phosphogypsum solid waste preferentially adsorb onto the surface of cementitious materials such as silicate cement, forming dense, insoluble calcium salt precipitates. These precipitates hinder the nucleation and growth of hydration products, resulting in a low yield stress of the phosphogypsum slurry prepared under conventional stirring methods. This fails to meet the load-bearing requirements of the corrugated filling pipeline for the solid skeleton strength. Slurry preparation is performed using a co-rotating twin-screw high-shear slurry mixer with a built-in dynamic torque sensor. The virgin phosphogypsum solid waste and cementitious materials are obtained and water is added before being injected into the slurry mixer. The spindle speed of the slurry mixer is controlled to produce a shear rate between 150s. -1 up to 250s -1 The mechanical shear force at the fluid interface overcomes the interfacial adhesion energy, stripping away the insoluble calcium salt precipitates on the surface of the cementitious material, exposing fresh active sites to stimulate hydration crosslinking reactions, and maintaining the mechanical shear force in this region for operation. Fresh active sites refer to the original hydrated calcium silicate nucleation sites exposed on the surface of the cementitious material particles after the calcium salt passivation film is stripped away. By comparing the hydration heat release curves of the slurry before and after shear treatment, the exposure efficiency of these sites can be quantitatively evaluated. Under a specific shear rate, these sites can shorten the interfacial resistance of hydration ion diffusion during the induction period, increasing the coverage of hydration products on the surface of undisturbed phosphogypsum solid waste to over 85%, thus macroscopically manifesting as yield stress. A significant increase; when the shear rate is below 150 s. -1 At that time, the physical peeling kinetic energy is insufficient to break the calcium salt coating; when the shear rate is higher than 250s... -1 At that time, excessive fluid shear stress severs the initially formed hydrated calcium silicate gel network structure.

[0050] Maintaining the mechanical shear force within the aforementioned range during continuous stirring, the real-time torque value of the pulper spindle is simultaneously acquired via a dynamic torque sensor. As insoluble calcium salt precipitates peel off and initial hydration products form, the solid particles within the phosphogypsum slurry undergo flocculation and cross-linking, causing an increase in the real-time torque value. The control unit continuously calculates the real-time yield stress of the phosphogypsum slurry based on the acquired real-time torque value, using the following formula: ,in M represents the real-time yield stress, M represents the real-time torque value, and ω represents the angular velocity of the pulper spindle. The control unit calculates the real-time yield stress based on the dimensionless constants calibrated according to the geometry of the pulper blades. The pressure is compared with the preset hydrostatic pressure, which is determined by the product of the maximum single-segment vertical drop of the corrugated filling pipeline and the slurry density. It characterizes the minimum cohesive force of the slurry resisting the segregation and sedimentation of solid particles in a static pump-stopped state. When the real-time yield stress is monitored... When the static pressure of the fluid exceeds the specified value, the control unit outputs a shutdown signal to terminate the mixing and agitation, and pumps the prepared phosphogypsum slurry into the corrugated filling pipeline for delivery. This quantitative monitoring procedure establishes the evaluation criteria for the end point of the stripping reaction, providing a structurally stable initial solid framework for the phosphogypsum slurry to undergo extrusion seepage and negative pressure backflow circulation within the corrugated filling pipeline. During the preparation of the phosphogypsum slurry, a mixer equipped with a dynamic torque sensor is used to obtain the real-time yield stress. Compare the hydrostatic pressure determined by the maximum single-section vertical drop of the corrugated filling pipeline; adjust the proportion of cementitious material to make... Maintaining the slurry within 1.2 to 1.5 times the hydrostatic pressure, the slurry is supported to maintain the plunger flow skeleton. A monitoring device is installed at the end node to obtain flow velocity data and calculate the pressure loss gradient. When the actual pressure loss gradient is greater than the reference value, the pumping pressure at the feed end is increased. The reference value of the pressure loss is based on the hydraulic calculation model of clear water under the same pipeline layout as the initial baseline. The theoretical friction head loss along the pipe is measured by injecting the rated flow of clear water into the pipe in advance. Then, the loss value is multiplied by the solid-liquid two-phase flow resistance amplification factor calibrated in the laboratory to calculate the result. This is used as an objective judgment boundary for evaluating whether the lubricating film inside the long-distance pipeline is intact. Stress alternation is generated by the undulation of the pipeline to establish the periodic seepage and backflow circulation of free water. The slurry carries free water to reduce resistance and transport it within the boundary of the fully smooth pipeline.

[0051] Example 4: In the pre-construction commissioning phase of deploying corrugated filling pipelines on the mine roadway floor, a standard rheological test fluid with a pre-calibrated yield stress is injected into a co-rotating twin-screw high-shear slurry mixer with a built-in dynamic torque sensor; the slurry mixer spindle is driven to run continuously under a preset angular velocity gradient sequence, and the steady-state torque value corresponding to the angular velocity is synchronously collected using the dynamic torque sensor; based on this, the control unit receives the aforementioned steady-state torque value, angular velocity data, and the constant yield stress of the standard rheological test fluid, and then, according to the formula... The dimensionless constants specific to the current pulper blade geometry and flow channel boundary dimensions are calculated using the least squares fitting algorithm. ,in The constant yield stress is given by M, the steady-state torque is given by ω, and the angular velocity is given by ω. The control unit will calculate the dimensionless constant. The data is written into the storage register to form a benchmark transformation model for calculating the real-time yield stress of phosphogypsum slurry.

[0052] Before preparing phosphogypsum slurry from raw phosphogypsum solid waste and cementing materials, the control unit reads the coordinates of various elevation nodes along the wavy filling pipeline from the mining area spatial mapping database; calculates the elevation difference between the top of the adjacent uphill pipe section and the bottom of the downhill pipe section, and selects the maximum single-segment vertical drop; based on this, it retrieves the initial slurry mixing density fed back by the density transmitter in the pipeline inlet area, calculates the product of the maximum single-segment vertical drop, the initial slurry mixing density, and the gravitational acceleration, and outputs a quantitative comparison threshold characterizing the hydrostatic pressure of the fluid; the control unit sets this quantitative comparison threshold as the criterion for triggering the shutdown electrical signal, limiting the solid skeleton strength of the phosphogypsum slurry discharged into the wavy filling pipeline to be greater than the segregation shear stress generated by the ultimate drop of the pipeline network, and the slurry flows through the uphill and downhill pipe sections in a plunger flow form, maintaining the boundary liquid film circulation.

[0053] Example 5: In the pre-calibration stage of deploying corrugated filling pipelines for undulating mine floor conditions, the physical process of phosphogypsum slurry permeating from its internal pores to the pipe wall and forming a boundary liquid film under pressure exhibits a time lag. If the spatial wavelength of the pipeline does not match the pumping velocity of the fluid, the slurry may cross the wave crest and enter the downhill pipe section before fully expelling free water, leading to boundary liquid film rupture and increased frictional resistance. To determine the spatial wavelength parameter suitable for the specific rheological properties of the slurry, a pre-prepared phosphogypsum slurry sample was extracted and injected into a pressure-bearing filtration test cylinder. A step constant pressure equivalent to the axial component of gravity in the uphill pipe section was applied to the sample, and the measurement accuracy was measured to be 0.1 mL. A volumetric flow meter is used to monitor the cumulative volume of free water seeping through the bottom filter in real time. The time span from the application of pressure to the point where the rate of change of the cumulative volume of free water approaches zero is recorded. This time span is output as the seepage time constant, which characterizes the water transport response of the phosphogypsum slurry. The quantitative criterion for the seepage time constant is determined as follows: under a constant extrusion pressure of 1.5 MPa, the amount of free water seeping out is collected every 10 seconds using a flow meter with an accuracy of 0.01 mL. When the cumulative increase in seepage volume is less than 0.1 mL within 180 seconds, it is determined that the seepage process has reached physical equilibrium. The total time from the start of pressure application to this moment is recorded as the seepage time constant.

[0054] The rated flow rate for goaf backfilling operations is retrieved, and the average sliding velocity of the slurry within the pipeline is calculated based on the internal cross-sectional area of ​​the corrugated backfilling pipeline. The control unit receives the aforementioned seepage time constant and average sliding velocity, and calculates the average sliding velocity according to the formula... The spatial wavelength of the wavy filling pipe is calculated, where λ is the spatial wavelength of the wavy filling pipe and v is the average slip velocity of the slurry. The seepage time constant is To compensate for the edge effect of the flow field, a dimensionless geometric coefficient is used, with a value ranging from 1.2 to 1.5. The spatial wavelength data output from the solution guides the interval layout of the support pipe racks on the mine roadway floor, limiting the residence time of the slurry flowing through a single uphill pipe section to be greater than the time required for radial infiltration of free water. This avoids phase misalignment between the alternation period of pore pressure and the water transport period within the fluid, ensuring that the phosphogypsum slurry maintains a continuous boundary liquid film in the transport network. When determining the spatial parameters, a phosphogypsum slurry sample is placed in a pressure filtration device, simulating the axial extrusion pressure generated by the uphill pipe section and applying a constant pressure. The cumulative volume of free water seepage is monitored over time using a flow meter, and the time span during which the cumulative volume change rate tends to stabilize is recorded to determine the seepage time constant. ; To determine the time required for free water to radially migrate to the pipe wall, the spatial wavelength λ is set by adjusting the axial spacing of the support pipe racks, taking into account the average slurry flow velocity v. The dimensionless geometric coefficient ks not only compensates for edge effects but also incorporates a kinetic correction term that converts the static constant-pressure filtration time into the dynamic shear bleeding time. This correction term quantifies the radial stretching effect of the pipe wall shear band on the interparticle pore channels, thereby eliminating the boundary condition differences between the unidirectional static pressure test environment and the three-dimensional rheological environment inside the pipe. This ensures the applicability of the equivalent substitution of static test constants in the dynamic transport equation, satisfying the relational expression... The slurry is allowed to remain in a single section for a certain period of time to complete the lubricating film seepage; the vertical height difference H is determined by selecting the fluctuation coefficient α based on λ; the value of α ranges from 0.02 to 0.08; the pressure loss along the pipeline is monitored using a pressure transmitter, and when the measured pressure loss is greater than the reference value, α is increased to enhance the self-lubrication of the uphill pipe section.

[0055] 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 phosphogypsum solid waste filling process for phosphorite mined-out area, characterized in that, Includes the following steps: Step 101: Install support pipe racks at intervals along the bottom plate of the mine roadway, and install a corrugated filling pipeline consisting of alternating uphill and downhill pipe sections on the support pipe racks. To ensure the linear stability of the corrugated pipeline when conveying high-pressure slurry, the support pipe rack adopts an integrated welded steel structure, with the base anchored in the rock strata of the roadway bottom plate. An adjustable height U-shaped bracket is installed at the top to lock the geometric undulations of the pipe section. A high-elasticity rubber pad is installed between the pipeline and the bracket to absorb the axial vibration caused by the fluctuation of the slurry pumping pressure. At the same time, by constraining the horizontal lateral displacement of the pipeline, the thermal stress and internal pressure stress caused by the deformation of the pipe diameter are limited to within the preset 1mm, ensuring that the geometric tolerance of the corrugated topology meets the expected rheological control accuracy. Step 102: Mix the cementitious material with the original phosphogypsum solid waste to prepare a phosphogypsum slurry with a yield stress greater than the hydrostatic pressure, and pump the phosphogypsum slurry into a corrugated filling pipeline for transportation. Step 103: When the phosphogypsum slurry flows through the uphill pipe section, the axial extrusion force inside the phosphogypsum slurry is increased based on the self-weight component of the phosphogypsum slurry, which compresses the spacing between solid particles in the phosphogypsum slurry and drives free water to seep radially into the inner wall of the wavy filling pipe, forming a boundary liquid film on the inner wall. Step 104: When the phosphogypsum slurry with boundary liquid film flows through the connected downhill pipe section, the axial extrusion force inside the phosphogypsum slurry is reduced based on the self-weight component of the phosphogypsum slurry, causing the pores inside the phosphogypsum slurry to expand and generate negative pressure, and the boundary liquid film is drawn back into the phosphogypsum slurry based on the negative pressure. Step 105: Relying on the continuous alternating structure of the uphill and downhill pipe sections in the wavy filling pipeline, a periodic cycle of free water seepage and backflow is established to transport the phosphogypsum slurry to the goaf for hardening and consolidation.

2. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, In step 101, the central axis of the corrugated filling pipeline is a sine curve; the ratio of the inner diameter of the corrugated filling pipeline to the axial spacing of the support pipe rack is constant, so as to limit the radial displacement of the corrugated filling pipeline within the preset deformation tolerance.

3. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 2, characterized in that, In step 101, the vertical height difference between the top of the uphill pipe section and the bottom of the downhill pipe section satisfies the following formula with respect to the wavelength of the sine curve: H = α × λ, where H is the vertical height difference, λ is the wavelength, and α is the fluctuation coefficient determined based on the yield stress of the phosphogypsum slurry and the friction coefficient of the pipe wall, and the value of the fluctuation coefficient is 0.02 to 0.

08.

4. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, In step 102, the specific steps for preparing phosphogypsum slurry include: step 401, obtaining untreated undisturbed phosphogypsum solid waste and cementing material; step 402, adding water to the undisturbed phosphogypsum solid waste and cementing material and mixing and stirring, applying mechanical shear force through mixing and stirring to peel off the insoluble calcium salt precipitates generated on the surface of the cementing material; step 403, maintaining mechanical shear force while stirring until the yield stress of the obtained phosphogypsum slurry is greater than the hydrostatic pressure.

5. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, In step 103, the step of driving free water to seep into the inner wall of the radially wavy filling pipe includes: step 501, using increased axial compressive force to overcome the skeleton yield strength of the phosphogypsum slurry and compress the pore volume between solid particles; step 502, the pressurized free water seeps into the inner wall along the pore channels; step 503, the seeped free water converges between the outer surface and the inner wall of the phosphogypsum slurry to form a boundary liquid film.

6. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, In step 104, the step of drawing the boundary liquid film back into the phosphogypsum slurry based on negative pressure includes: step 601, releasing the elastic strain energy accumulated when the axial extrusion pressure decreases; step 602, the release of elastic strain energy causes pore expansion and generates negative pressure; step 603, drawing the boundary liquid film distributed on the inner wall into the pores of the phosphogypsum slurry based on negative pressure.

7. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, In step 105, the steps to establish a periodic cycle of free water seepage and reabsorption include: Step 701, after experiencing multiple alternating uphill and downhill pipe sections, the free water content on the outer surface of the phosphogypsum slurry is distributed in a fluctuating pattern of alternating peaks and troughs; Step 702, the overall length of the wavy filling pipeline is set according to the spatial location of the goaf, so that the end of the wavy filling pipeline is the bottom of the downhill pipe section, thereby ensuring that the free water on the outer surface of the discharged phosphogypsum slurry is in a trough distribution state.

8. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, After step 102, the method further includes: step 801, obtaining solid phase concentration distribution data characterizing the phosphogypsum slurry on the cross-section of the corrugated filling pipeline; step 802, when the solid phase concentration distribution data indicates that the difference between the concentration at the bottom and the concentration at the top of the cross-section is greater than the concentration difference threshold, increasing the initial flow rate of the phosphogypsum slurry pumped into the corrugated filling pipeline; step 803, using the alternating shear force generated by the increased initial flow rate coupled with the continuous alternating structure of the uphill and downhill pipe sections, redispersing the solid particles enriched at the bottom to the central region of the cross-section.

9. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, It also includes: step 901, acquiring real-time monitoring data characterizing the fluid velocity inside the pipe at the end node of the corrugated filling pipeline; step 902, calculating the actual pressure loss gradient based on the real-time monitoring data; step 903, increasing the pumping pressure at the feed end of the pumped phosphogypsum slurry when the actual pressure loss gradient is greater than the pressure loss benchmark value, so as to maintain the pressure state inside the phosphogypsum slurry.

10. The phosphogypsum solid waste filling process for phosphorite mined-out area according to claim 1, characterized in that, Step 105, the step of transporting phosphogypsum slurry to the goaf for hardening and consolidation, includes: Step 1001, discharging the phosphogypsum slurry flowing out of the corrugated filling pipeline into the goaf; Step 1002, utilizing the overall three-dimensional stress release generated after the phosphogypsum slurry is freed from the constraints of the corrugated filling pipeline to promote the hydration reaction of the cementing material on the surface of the undisturbed phosphogypsum solid waste; Step 1003, relying on the self-leveling properties of the phosphogypsum slurry to fill the goaf and complete the hardening and consolidation within the goaf.

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