Quantization method for rheological dynamic characteristics of plume in deep sea mining area

Abstract

The invention belongs to the technical field of deep-sea mining, and discloses a deep-sea mining area plume rheological dynamic characteristic quantification method which comprises the following steps: preparing a sample of a target research area, carrying out physical property test, and carrying out plume rheological test on the tested sample by adopting an indoor test method to quantify the plume rheological dynamic characteristic of the deep-sea mining area. The method comprises the following steps: acquiring a change rule of shear strength and dynamic viscosity within a certain shear rate range, finally fitting rheological test data according to different rheological models, determining rheological parameters of sediment plumes with different physical properties, and then quantifying the influence of the physical property change of the plumes on the rheological characteristics of the plumes based on a data fitting method. According to the method, the plume rheological model considering the physical property change is established, the influence of the physical property change on the low-density polymetallic mine area sediment plume is quantified, and the method has important guiding significance for optimizing deep-sea mining operation, reducing the environmental influence and formulating a scientific ocean management strategy.

Description

Technical Field

[0001] The present invention belongs to the technical field of deep-sea mining, and in particular relates to a method for quantifying rheological dynamic characteristics of plumes in deep-sea mining areas. Background Art

[0002] Deep-sea mining sediment plumes are primarily composed of tiny particles resulting from excavation, cutting, drilling, mining equipment movement, and ore collection losses during the mining process. The spatial distribution of these plumes is crucial for predicting their spread. To understand the changing properties of sediment plumes during their propagation, existing techniques often involve conducting large-scale in-situ deep-sea mining simulation experiments, providing valuable data for subsequent laboratory experiments and numerical simulations.

[0003] However, most existing studies simplify sediment plumes as low-concentration Newtonian fluids (Jankowski et al., 1996; Gillard et al., 2019), ignoring the complex rheological properties of deep-sea sediments. Based on numerous engineering geological surveys, deep-sea surface sediments in mining areas are typically highly viscous, exhibiting extremely high water content and thixotropy, resulting in complex static and dynamic properties. When disturbed by mining equipment, sediments undergo a transition from a solid to a fluid state, resulting in drastic changes in their physical and mechanical properties. Furthermore, the resulting sediment plume involves the evolution of both non-Newtonian and Newtonian fluids, further complicating the quantitative description of its rheological properties. More importantly, the rheological behavior of deep-sea mining sediment plumes is influenced by a complex and diverse set of factors, including plume sediment concentration, sediment particle size distribution and mineral composition, as well as seawater pH, temperature, and salinity. This results in complex, nonlinear, and time-dependent rheological properties during plume diffusion.

[0004] Although in-situ monitoring can be used to obtain the physical and mechanical properties of deep-sea mining sediment plumes, it is difficult to quantify the changes in rheological properties during their propagation. Among the existing technologies, although some technologies can be used to measure the changes in physical parameters of sediment plumes with a high density (1.5 g / cm 3 ) The influence of the rheological properties of homogeneous sediment plumes has been quantified, but the evolution of the rheological properties of low-density, heterogeneous sediment plumes in deep-sea mining areas still needs further exploration.

[0005] Therefore, in order to accurately characterize the rheological properties of deep-sea mining sediment plumes, it is necessary to establish a more sophisticated rheological model that is adapted to the characteristics of the deep-sea environment, thereby providing a scientific basis for the environmental impact assessment of deep-sea mining. Summary of the Invention

[0006] The technical solution of the present invention can overcome the above technical defects and provide a method for quantifying the rheological dynamic characteristics of deep-sea mining plumes. It solves the problem of inaccurate rheological parameter testing of low-density sediment plumes under low shear rate conditions, and innovatively considers the change in density into the construction of the rheological model, which can realize the quantification of the rheological characteristics of low-density sediment plumes under low shear rate conditions.

[0007] To achieve the above objectives, the present invention is implemented by adopting the following technical solutions: a method for quantifying the rheological dynamics characteristics of plumes in deep-sea mining areas, Step A: Project requirements analysis: Determine the target deep-sea mining area and its geological conditions based on project requirements, investigate relevant environmental regulations for deep-sea mineral development, and the collection, transportation, and detection systems for deep-sea mineral development; Based on the above information, we further analyze the plume type, formation mechanism and plume distribution; Through the above analysis, the density dependence of sediment plume rheological parameters is further analyzed; Step B: Engineering geological survey: Investigate the environmental parameters of the target deep-sea mining area and obtain test samples from the target deep-sea mining area; Step C: Sample indoor test: Based on the rheometer, shearing is applied to the test sample to obtain the variation pattern of shear strength and dynamic viscosity of the test sample within a certain shear rate range. The concentration of the test sample is determined based on the physical properties of the sediment sample, as follows: (1) Determine the density, natural water content, liquid limit and plastic limit of sediment samples; (2) Preliminary judgment of the state of sediments in their natural state by comparing the natural water content with the liquid limit; (3) Based on the liquid limit, convert the mass ratio of the solid phase to the liquid phase in the sediment and estimate the mass concentration of the sediment-water mixture under this water content condition. In this way, the configuration concentration of the sediment plume is determined, and the maximum concentration is required not to exceed the sediment concentration under the liquid limit condition; Step D: Rheological model construction: Obtain viscosity data of low-shear-rate, low-density sediment plumes, fit the rheological test data according to different rheological models, determine the rheological parameters of sediment plumes with different physical properties, and establish a plume rheological model: (1) Based on the power law model, the variation of shear strength with shear rate is quantified by data fitting, thereby determining the rheological parameters of the plume under different density conditions; (2) Constructing the relationship between the rheological parameters of the plume and its density; ;

[0008] Among them, K(ρ) is the consistency coefficient, n(ρ) is the flow index, is the fitting constant, reflecting the trend of sediment plume consistency coefficient and flow index with density, and quantifying the effect of plume density on rheological parameters k and n; 、 are the plume density and b k 、b n power; (3) Establish a plume rheological model that takes into account changes in physical properties: ; in, is the shear strength, is the shear rate.

[0009] The present invention addresses the lack of research in the prior art on the rheological properties of low-density, heterogeneous deep-sea mining sediment plumes, and proposes a method for quantifying the rheological dynamics of low-density deep-sea mining plumes under low shear rate conditions. The target study area is determined by analyzing engineering requirements, the environmental parameters of the study area are obtained, and the required sediment samples and seawater samples are collected. Using indoor test methods, basic geotechnical tests are first carried out on sediment samples, and plume samples are prepared according to the physical properties of the sediment samples. The rheological properties of the plume samples are then tested. The rheological parameters of sediment plumes of different densities are determined by comparing the applicability of different classical rheological models. By coupling, a plume rheological model that takes into account changes in physical properties is established to quantify the impact of changes in physical properties on low-density polymetallic mining sediment plumes under low shear rate conditions.

[0010] The present invention has carried out low shear rate (0 ~ 25 s -1 ) low density (1.035 ~ 1.2343 g / cm 3 ) sediment plume rheological test, based on the power law model, the rheological parameters of sediment plumes with different densities under low shear rate conditions were determined. The relationship between density and rheological parameters ( The mathematical relationship between η and n is then introduced into the power law model, thereby constructing a rheological model of deep-sea mining sediment plume that takes density changes into account.

[0011] Compared with the prior art, the advantages and positive effects of the present invention are:

[0012] This project focuses on the rheological and dynamic characteristics of low-density, heterogeneous deep-sea mining sediment plumes under low shear rate conditions. Using indoor experimental methods, plume rheological tests are performed on test samples. The rheological test data are then fitted according to different rheological models to determine the rheological parameters of sediment plumes with different physical properties. The impact of changes in the physical properties of the plume on its rheological characteristics is quantified based on the data fitting method, and a plume rheological model that takes into account changes in physical properties is established. This project quantifies the impact of changes in physical properties on sediment plumes in low-density polymetallic mining areas, which has important guiding significance for optimizing deep-sea mining operations, reducing environmental impacts, and formulating scientific ocean management strategies. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic flow chart of a method for quantifying rheological and dynamic characteristics of plumes in deep-sea mining areas according to an embodiment of the present invention; Figure 2 The results of the rheological properties test of the West Pacific sediment plume in the embodiment of the present invention are as follows: (a) Shear strength changes with shear rate; (b) Dynamic viscosity changes with shear rate; Figure 3 This is the fitting curve of the rheological test data of the Western Pacific sediment plume according to the embodiment of the present invention; Figure 4 The variation of rheological parameters of the West Pacific sediment plume with density in the embodiment of the present invention is shown in FIG. (a) Relationship between consistency coefficient and density, (b) Relationship between flow index and density. DETAILED DESCRIPTION

[0014] In order to more clearly understand the above-mentioned objects, features and advantages of the present invention, the present invention is further described below with reference to the accompanying drawings and embodiments. In the following description, many specific details are set forth to facilitate a full understanding of the present invention. However, the present invention can also be implemented in other ways than those described herein. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0015] This example proposes a method for quantifying the rheological dynamics of sediment plumes in deep-sea mining areas. Based on rheological theory and combined with the actual environment of deep-sea mining, the rheological characteristics of sediment plumes and the influence of plume physical parameters on their rheological characteristics are systematically studied. Figure 1 Said method comprises the following steps: Step A: Project requirements analysis: Determine the target deep-sea mining area and its geological conditions based on project requirements, investigate relevant environmental regulations for deep-sea mineral development, and the collection, transportation, and detection systems for deep-sea mineral development; Based on the above information, we further analyze the plume type, formation mechanism and plume distribution; Through the above analysis, the density dependence of the sediment plume rheological parameters is further analyzed; Step B: Engineering geological survey: Investigate the environmental parameters of the target deep-sea mining area and obtain test samples from the target deep-sea mining area; Step C: Sample indoor test: Based on the rheometer, shearing is applied to the test sample to obtain the variation pattern of shear strength and dynamic viscosity of the test sample within a certain shear rate range. The concentration of the test sample is determined based on the physical properties of the sediment sample, as follows: (1) Determine the density, natural water content, liquid limit and plastic limit of sediment samples; (2) Preliminary judgment of the state of sediments in their natural state by comparing the natural water content with the liquid limit; (3) Based on the liquid limit, convert the mass ratio of the solid phase to the liquid phase in the sediment and estimate the mass concentration of the sediment-water mixture under this moisture content. This is used to determine the configuration concentration of the sediment plume, requiring that the maximum concentration does not exceed the sediment concentration when its moisture content is the liquid limit; Step D: Rheological model construction: Obtain viscosity data of low-shear-rate, low-density sediment plumes, fit the rheological test data according to different rheological models, determine the rheological parameters of sediment plumes with different physical properties, and establish a plume rheological model: (1) Based on the power law model, the variation of shear strength with shear rate is quantified by data fitting, thereby determining the rheological parameters of the plume under different density conditions; (2) Constructing the relationship between the rheological parameters of the plume and its density; ; ; Among them, K(ρ) is the consistency coefficient, n(ρ) is the flow index, is the fitting constant, which reflects the trend of sediment plume consistency coefficient and flow index changing with density, and quantifies the effect of plume density on rheological parameters. and the impact of n; 、 are the plume density and b k 、b n power; (3) Establish a plume rheological model that takes into account changes in physical properties: ;

[0016] in, is the shear strength, is the shear rate.

[0017] In order to more clearly understand the solution of the present invention, this embodiment is described by taking the polymetallic nodule mining area in the northwest Pacific as an example. Specifically:

[0018] Step A: Project requirements analysis:

[0019] Based on an analysis of engineering requirements, this invention uses the Guidelines for Environmental Protection and Preservation of Deep-Sea Mining Activities (T / CAOE 41-2021) as a reference standard and selects a hydraulic lift mining method. Specifically, this hydraulic lift mining method relies on a surface mothership, which is connected to a submarine ore collection vehicle via a pipeline. The mining vehicle then transports the collected deep-sea minerals back to the surface mothership via a pipeline. The plume generated by this deep-sea mining method comes from two sources: first, the plume formed by the submarine ore collection vehicle operating and advancing on the seabed. The plume is formed by three factors: sediment disturbance during nodule collection, sediment resuspension caused by the mining vehicle's movement, and the direct discharge of submarine sediments collected along with the nodules after initial screening by the submarine ore collection vehicle onto the seabed. Second, after surface mineral processing, the tailings are discharged into the mid-sea waters via pipelines, forming a tailings plume composed of water, ore debris, and submarine sediment.

[0020] Regarding mining vehicle plumes, in situ seafloor monitoring data indicates that the movement of mining vehicles under normal operating conditions can resuspend nearly 50% of the surface sediments within the disturbed area. While the plume density currently monitored is below 1010 kg / m³, variations in clay content can significantly alter its rheological parameters (such as yield strength and viscosity). Experiments have shown that when the volume fraction of sediment is ≥13% (density ≈ 1240 kg / m³) and the proportion of viscous sediment reaches 50%, the plume exhibits non-Newtonian fluid characteristics. If the volume fraction is ≥4% (density ≈ 1060 kg / m³), the viscous sediment flow begins to transition to a non-Newtonian flow. Therefore, during severe disturbances, high-concentration mining vehicle plumes may also exhibit non-Newtonian fluid behavior during the release phase. For tailings plumes, their propagation progresses from pipe ejection to mixing with the ambient water. In the initial stages, the rheological properties of the tailings plume are dependent on the rheological properties of the sediment flow within the pipe. As the tailings plume propagates through the ocean, its physical properties (such as water content and density) change significantly due to the incorporation of ambient water, leading to changes in its rheological properties (such as yield strength and viscosity). This indicates that the propagation of the tailings plume from the pipeline through the ambient water inevitably undergoes a transition from a non-Newtonian to a Newtonian fluid. Consequently, the rheological properties of both the mining vehicle plume and the tailings plume change significantly during propagation, exhibiting a distinct density dependence.

[0021] The proposed method for quantifying the rheological dynamics of deep-sea mining plumes will be applied to quantify the density dependence of rheological parameters in sediment plumes from deep-sea mining areas. The target study area is the Magellanic Seamount region in the northwest Pacific Ocean, a region rich in polymetallic nodules and situated within a rare earth mineralization belt.

[0022] Rheological tests were conducted using a TA Instrument HR10 flat-plate rotational rheometer. The core component of this rheometer is the flat-plate measurement system, which can accurately obtain viscosity data for extremely low-density sediment plumes, solving the problem of inaccurate rheological parameter measurements of low-density sediment plumes under low shear rate conditions.

[0023] The testing principle of the TA Instrument HR10 flat plate rotational rheometer used in the present invention is as follows: (1) (2) (3) Where, is the shear strength, is the torque, is the plate radius, is the shear rate, is the angular velocity, is the gap height between the two plates, is the apparent viscosity.

[0024] The physical definition of shear rate is as follows:

[0025] in is the fluid flow rate (m·s -1 ), is the shear layer thickness (m). The shear rate describes the change in fluid velocity over a certain distance. For viscous fluids, the shear layer thickness generally does not exceed 0.01 m. Deep-sea mining plumes ejected from a pipeline will have a large initial velocity. However, as they propagate and diffuse in the marine environment, their final velocity tends to be consistent with that of the ambient water. According to engineering geological surveys, the maximum velocity of deep-sea mining plumes ejected from a pipeline is 2.85 m·s -1 , the ambient water velocity is 0.1 ~ 0.3 m / s (related to depth).

[0026] In this paper, we focus on the rheological characteristics of low-concentration plumes under low flow velocity conditions. Therefore, we consider the plume velocity to be similar to that of ambient water and take 0.25 m·s -1 , the shear layer thickness is 0.01 m, and the shear rate is 25 s -1 .

[0027] Step B: Engineering geological survey: First, we investigated the environmental parameters of the study area, including current velocity, water temperature, salinity, and turbidity. We then began sampling the area. We used a box sampler to obtain deep-sea surface sediment samples and a CTD water sampler to obtain bottom-sea water samples. The sampling depth was 5459.8 meters, and the sampling location was 19.00°N, 149.99°E.

[0028] Step C: Sample indoor test:

[0029] The concentration of the test sample is determined based on the physical properties of the sediment sample. Specifically, the density, natural moisture content, liquid limit, and plastic limit of the sediment sample need to be measured. By comparing the natural moisture content with the liquid limit, a preliminary judgment can be made on the state of the sediment in its natural state. Then, based on the liquid limit, the mass ratio of the solid phase to the liquid phase in the sediment is converted, and the mass concentration of the sediment dry sample-water mixture under this moisture content is estimated to determine the configuration concentration of the sediment plume. The maximum concentration is required not to exceed the sediment concentration under the liquid limit condition. Based on the physical properties of the sediment, sediment plume samples are prepared using mining sediment samples and bottom seawater samples. The specific operations are as follows: Specifically, the drying method measured the water content of the West Pacific sediments to be high, at 131.96%; the ring knife method measured the density of the West Pacific sediments to be 1247.18 kg / m 3 The combined liquid limit and plastic limit determination method determined that the liquid limit of the West Pacific sediments was 132.1%, the plastic limit was 43.6%, and the liquid index was 1.11, which is a high liquid limit clay and is liquid in its natural state. According to the liquid limit, when the plume water content is at the liquid limit, the mass ratio of water to sediment is about 100:75, that is, 1000 g of water (density 1000 kg / m 3The weight of the dry sediment sample in the 2017 study was 750 g, and its concentration can be estimated to be 750 g / L. Therefore, when preparing sediment plume samples, the concentration should be kept below 750 g / L. In this patent, to ensure clear comparison of plume rheological properties within a certain range of plume concentrations and to test the rheological properties of low-concentration sediment plumes as much as possible, the sediment plume samples were prepared with a maximum concentration of 400 g / L and a minimum concentration of 25 g / L. The particle size of kaolin and West Pacific sediments, after sieving to remove large particles, was measured using a Beckman Laser Particle Size Analyzer (LS13 320). The particle size distribution ranged from 0.3 to 70.0 µm, with a D50 of approximately 6.0 µm, a D90 of approximately 40.0 µm, and a peak particle size of approximately 4 µm, demonstrating an overall multimodal distribution. X-ray diffraction analysis of the mineral composition and content of West Pacific sediments revealed that non-clay minerals predominate in the sediments, accounting for 74.9% of the total. These minerals include feldspar, mica, hornblende, and quartz. Smaller amounts of clay minerals, such as illite, chlorite, montmorillonite, and kaolinite, account for 25.1%. The shear strength of undisturbed samples of West Pacific surface sediments is relatively low, at 493.76 Pa. However, shear stress causes internal structural damage, significantly reducing the shear strength. The residual strength after shear failure is 4.26 Pa, a two-order-of-magnitude decrease in strength. These test results demonstrate that West Pacific sediments possess unique physical and mechanical properties—high water content, high liquid limit, low shear strength, and a high concentration of clay minerals.

[0030] The preparation of plume samples requires reference to the water content, liquid limit, and density data of Western Pacific sediments. The minimum water content of the specific plume sample should be higher than its natural water content, and the maximum concentration should be lower than its natural density. Western Pacific sediment plumes of varying concentrations were prepared accordingly. The density of the plume samples was then measured using a Mettler Toledo ME204E density tester. See Table 1 for details: Table 1 Physical properties of plume samples .

[0031] The test sample in this example comes from the polymetallic nodule mining area in the northwest Pacific Ocean and is a typical heterogeneous deep-sea clay. When using this sediment to prepare a low-density sediment plume, the following problems will arise: (1) It is difficult for a conventional cross-plate rheometer to obtain low-density (<1.2 g / cm 3 ) The rheological parameters of the plume; (2) sediment plumes generally have settling problems during the test process, resulting in inaccurate rheological test data. This solution uses the Discovery HR10 rheometer produced by TA Instruments, which can achieve the measurement of low density (<1.2 g / cm 3) Quantification of sediment plume rheological parameters.

[0032] During the test, the temperature was kept stable at 20°C. Based on the environmental flow rate survey, the strain control mode was used, and the shear rate increment was 0.5 s⁻¹ per second for 50 seconds. The test data of the three sediment plumes were obtained in the shear rate range of 0 to 25 s⁻¹. Compared with traditional paddle rheometers, this device can obtain extremely low density (<1.05 g / cm 3 ) rheological parameters of the sediment plume. In addition, the flat rotor of the device prevents the sediment ions in the plume sample from settling during the test process. The test results are as follows Figure 2 shown.

[0033] Step D: Rheological model construction: In this example, a method for quantifying low-density Western Pacific sediments is proposed, as follows: (1) The power law model (see Equation 4) is not suitable for describing plastic fluids with significant yield stress, that is, high-concentration deep-sea mining plumes. However, for the low-density deep-sea mining plumes described in the present invention, the power law model can well describe its shear thinning characteristics, and only two parameters are more suitable for the establishment of a mathematical model. In addition, the present invention applies three typical non-Newtonian fluid rheological models, namely the power law model, the Bingham model and the Herschel-Bulkley model, to fit the rheological test results. The results show that the power law model has the highest fitting goodness of fit and can accurately characterize the evolution characteristics of the plume rheological test data. Therefore, the change law of shear strength with shear rate was finally quantified by the data fitting method based on the power law model, thereby determining the rheological parameters of the Western Pacific sediment plume under low shear rate and low density conditions. The fitting results are shown in Table 2, and the fitting curve is shown in Table 2. Figure 3 shown.

[0034] (4) in, is the shear strength, Pa; is the consistency coefficient, Pa·s n , is a parameter that characterizes viscosity and increases with increasing viscosity; is the shear rate, s -1 ; n is the flow index, dimensionless, reflecting the change in fluid viscosity with increasing shear rate. When n<1, the fluid is a shear-thinning fluid, when n>1, it is a shear-thickening fluid, and when n=1, the fluid viscosity does not change with increasing shear rate.

[0035] The fitting results show that the power law model can accurately describe the rheological characteristics of the western Pacific sediment plume under certain density conditions.

[0036] Table 2 Fitting results of rheological test data of the Western Pacific sediment plume .

[0037] (2) Then, the fitting results of the rheological test data of the Western Pacific sediment plume were further analyzed. By coupling the physical parameters of the plume sample with the rheological parameters, the evolution of the rheological properties of the deep-sea mining sediment plume during its propagation on the seabed was quantified. Due to the dilution of the ambient water, the diffusion of the plume itself, and the flocculation and sedimentation of the sediments therein, the physical parameters of the deep-sea mining sediment plume will change during the propagation process. In order to quantitatively characterize the propagation process of the sediment plume, the present invention selects density as the key parameter and establishes a mathematical relationship between density and plume rheological parameters to achieve a quantitative description of the rheological dynamic characteristics during the plume propagation process.

[0038] In this paper, a data fitting method is used to construct the relationship between the rheological parameters (consistency coefficient and flow index) of the Western Pacific sediment plume and its density ( Figure 4 Based on a large amount of fitting work, the fitting effects of polynomial functions, power functions, and exponential functions were compared. The comparison results show that the power function is most suitable for describing the quantitative relationship between the two. Specifically, the rheological parameters (consistency coefficient and flow index) of the Western Pacific sediment plume have a power function relationship with density as follows: (5) (6) in, =0.01545, Pa·s n ·m 3 kg -1 ; =5.10211, dimensionless; =0.28035,m 3 kg -1 ; =3.94343, dimensionless.

[0039] and is the scale factor, which determines the overall magnitude of the rheological parameters k and n within the fitted density range and is related to b k and b n The position of the fitted curve in the coordinate space is jointly constrained.

[0040] and is the density sensitivity index, b>0, then the rheological parameter and Follow shows a power law growth (density increases and rheological behavior is enhanced); b<0, the rheological parameter and Follow It decays in a power law manner (increasing density weakens the rheological behavior).

[0041] This mathematical relationship shows that both the consistency coefficient and flow index of the Western Pacific sediment plume increase exponentially with increasing density, revealing the significant influence of density on the plume's rheological behavior. Specifically, the increase in the consistency coefficient reflects the significant increase in plume viscosity with increasing density, which is primarily attributed to the increased concentration of solid particles in the plume under high-density conditions and the enhanced interactions between sediment particles. The increase in the flow index indicates that, while the Western Pacific sediment plume still exhibits shear-thinning properties, this weakens as plume density increases.

[0042] (3) Based on the mathematical relationship between the rheological parameters and density of the Western Pacific sediment plume, a rheological model of the Western Pacific sediment plume that takes into account the changes in physical properties was established: (7) This model not only accurately describes the rheological properties of sediment plumes in the Western Pacific under varying density conditions, but also provides an important theoretical basis for predicting the diffusion and flow behavior of deep-sea mining plumes. By incorporating density as a key variable into the rheological model, the plume's dynamic behavior in the deep sea can be more accurately simulated, including its diffusion range, sedimentation rate, and impact on marine ecosystems. This has important guiding implications for optimizing deep-sea mining operations, reducing environmental impacts, and developing scientific ocean management strategies.

[0043] The above description is merely a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any person skilled in the art may utilize the technical contents disclosed above to change or modify them into equivalent embodiments with equivalent changes for application in other fields. However, any simple modification, equivalent change, and modification of the above embodiments made in accordance with the technical essence of the present invention without departing from the technical solution of the present invention shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for quantifying the rheological dynamics of plumes in deep-sea mining areas, characterized in that: The following steps are involved: Step A: Project requirements analysis: Determine the target deep-sea mining area and its geological conditions based on project requirements, investigate relevant environmental regulations for deep-sea mineral development, and the collection, transportation, and detection systems for deep-sea mineral development; Based on the above information, we further analyze the plume type, formation mechanism and plume distribution; Through the above analysis, the density dependence of sediment plume rheological parameters is further analyzed; Step B: Engineering geological survey: Investigate the environmental parameters of the target deep-sea mining area and obtain test samples from the target deep-sea mining area; Step C: Sample indoor test: Based on the rheometer, shearing is applied to the test sample to obtain the variation pattern of shear strength and dynamic viscosity of the test sample within a certain shear rate range. The concentration of the test sample is determined based on the physical properties of the sediment sample, as follows: (1) Determine the density, natural water content, liquid limit and plastic limit of sediment samples; (2) Preliminary judgment of the state of sediments in their natural state by comparing the natural water content with the liquid limit; (3) Based on the liquid limit, convert the mass ratio of the solid phase to the liquid phase in the sediment and estimate the mass concentration of the sediment-water mixture under this water content condition. In this way, the configuration concentration of the sediment plume is determined, and the maximum concentration is required not to exceed the sediment concentration under the liquid limit condition; Step D: Rheological model construction: Obtain viscosity data of low-shear-rate, low-density sediment plumes, fit the rheological test data according to different rheological models, determine the rheological parameters of sediment plumes with different physical properties, and establish a plume rheological model: (1) Based on the power law model, the variation of shear strength with shear rate is quantified by data fitting, thereby determining the rheological parameters of the plume under different density conditions; (2) Constructing the relationship between the rheological parameters of the plume and its density; ; ; Among them, K(ρ) is the consistency coefficient, n(ρ) is the flow index, is the fitting constant, reflecting the trend of sediment plume consistency coefficient and flow index with density, and quantifying the effect of plume density on rheological parameters K and n; 、 are the plume density and b k 、b n power; (3) Establish a plume rheological model that takes into account changes in physical properties: ; in, is the shear strength, is the shear rate.

2. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 1, characterized in that: The test samples in step B include surface sediments and bottom seawater.

3. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 2, characterized in that: The step B is specifically implemented in the following manner: (1) Dry and fully grind the surface sediments, and remove large particles of shells and gravel through a sieve; then add the obtained bottom seawater to prepare the test sample of the target concentration; (2) Use a density tester to measure the density of the plume sample.

4. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 3, characterized in that: The target concentration of the test samples was 25-400 g / l.

5. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 1, characterized in that: In the step C, the shear rate is between 0 and Within the range of Shear rate increment test data.

6. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 5, characterized in that: In the step C, during the test, the temperature is kept stable at 20° C., and the sediment plume test data is obtained using a strain control mode or a stress control mode.

7. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 1, characterized in that: In step D, when acquiring viscosity data, the rheological test loading conditions, i.e., the shear rate variation range, are set based on the geological survey results. The test principle is as follows: ; ; ; Where, is the shear strength, is the torque, is the plate radius, is the shear rate, is the angular velocity, is the gap height between the two plates, is the apparent viscosity; Shear rate describes the change in fluid velocity over a certain distance and its physical definition is as follows: ; in is the fluid flow rate, is the shear layer thickness.

8. The method for quantifying the rheological dynamics of deep-sea mining plumes according to claim 7, characterized in that: In step D, the low shear rate is 0 ~ 25 s -1 , low density is 1.035 ~ 1.2343 g / cm 3 .

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