CN-121994571-A - Deep sea rare earth sediment foundation preparation method based on supergravity centrifugal physical simulation

Abstract

The invention provides a deep sea rare earth sediment foundation preparation method based on hypergravity centrifugal physical simulation, which comprises the steps of similarity ratio design, solid phase formula design, initial layered filling in a model box, pore solution configuration, hypergravity centrifugal acceleration consolidation, and model sample and deep sea original shape similarity evaluation. According to the technical scheme, deep sea stress and temperature boundaries are reproduced at the same time in a laboratory scale, consolidation steady-state time is greatly shortened, a solid phase formula is aligned to an original mineral composition and a rare earth element REE spectrum, main ion intensity and pH/Eh value of seawater are actually measured in a pore water chemical alignment mode, the seawater can be stably prepared in batches without open sea sampling, the cost and risk of 'sea-out-salvage-transportation' are remarkably reduced, a large amount of 'deep sea rare earth sediment seawater samples' are prepared indoors at low cost, large-scale indoor mechanics, seepage and technology evaluation tests are supported, four quantization thresholds of physical property, chemistry, microcosmic property and mechanics are provided, consistency acceptance and engineering application are facilitated, and batch consistency and controllability are high.

Inventors

• LAI YING
• LI KUNYU
• KONG DEQIONG
• GUO XINGSEN
• YIN JIFU

Assignees

• 浙江大学

Dates

Publication Date

20260508

Application Date

20260323

Claims (6)

1. 1. A deep sea rare earth sediment foundation preparation method based on supergravity centrifugal physical simulation is characterized by comprising the following steps: step S1, similarity ratio design: Establishing geometrical similarity according to the actual water depth H of the target sea area and the designed water depth H in the model box, wherein the reduced scale ratio is 1/n=h/H, so as to determine the centrifugal acceleration ng; Step S2, designing a solid phase formula: The method comprises the steps of taking the mineral composition, the particle size distribution and the REE analysis spectrum of an acquired deep sea rare earth sediment as a benchmark, determining the approximate proportion of fine clay and powdery framework minerals of a target formula, so that the clay mineral-powdery framework-rare earth element content of a preparation raw material is the same as that of the deep sea rare earth sediment as the original form; s3, initial layered filling in the model box: Layering and filling the prepared parent metal by adopting the thickness of about 20-100 mm of each layer to form a solid phase filling layer, controlling the thickness error of each layer to be +/-2 mm, and obtaining an initial pore ratio e 0 ≈1.15e * in a tapping mode with the standard compaction energy of 20%, wherein e * is a target pore ratio; In the filling process, the temperature sensor is respectively embedded in the upper layer, the middle layer and the lower layer, the embedded depth is about 0.15h 1 、0.50h 1 and 0.85h 1 of the sample height h 1 , the pore pressure sensor and the soil pressure sensor are arranged at 0.3h 1 and 0.5h 1 , and for temperature boundary control, the initial precooling and the constant temperature of the model box are set within the range of the seabed temperature T 0 -2 ℃; Step S4, pore solution configuration: The preparation of the pore solution is based on the field actual measurement data of the deep sea water of the target sea area, and the ionic strength and the ionic ratio are duplicated by matching the concentrations of Na+, mg2+, ca2+, K+, cl-, SO 4 -and HCO 3 -ions, wherein the salinity tolerance error is not more than +/-2 per mill; Preparing pore solution in batches, pre-cooling to a target temperature T 0 , and injecting into a model box; step S5, hypergravity centrifugal acceleration consolidation Placing the model box in a large geotechnical centrifuge to construct an n.g supergravity environment, and finally, after the target centrifugal acceleration is reached, setting the saturation judgment basis as S r to be more than or equal to 0.95, setting the consolidation judgment basis as that U is more than or equal to 90% and pore water pressure is dissipated under the conditions of ng and T 0 ; s6, evaluating the original similarity of the model sample and the deep sea The relative error of porosity and compactness of the physical layer is required to be less than 10%, wherein the porosity ratio can be obtained by a mass-volume method, the compactness is converted by a maximum-minimum dry density method, the relative error of liquid phase conductivity and sea water original state contrast at 24 h steady state is not more than 15% as a chemical steady state criterion, the conductivity fluctuation during steady state is controlled within +/-2%, the relative difference of main peak positions of the pore distribution obtained by MIP of the microscopic layer is required to be less than 20%, the similarity coefficient of the distribution is not less than 0.85, at least five representative visual fields are collected by SEM, the semi-quantitative comparison is carried out on the pore neck/pore cavity ratio, the flocculation size and the flaky/flocculation orientation, and the relative error between the mechanical layer and original state is controlled within 20% by a T-bar detector by taking the rebound strength or equivalent characteristic value thereof as a reference.
2. 2. The preparation method of the deep sea rare earth sediment foundation based on the hypergravity centrifugal physical simulation is characterized in that the model box is of a hypergravity static model box adopting an aluminum alloy box body and steel base plate combined structure, 1.2 m multiplied by 0.95 multiplied by m multiplied by 1.0 m, the inner wall of the box body is treated by sand blasting and fluorocarbon transparent coating, a laser displacement meter is arranged below a cover plate of the model box, and a reflector corresponding to the laser displacement meter is required to be placed on the filled solid surface.
3. 3. The method for preparing the deep sea rare earth sediment foundation based on the physical simulation of the hypergravity centrifugation according to claim 1, wherein the fine-grained clay in the step S2 comprises kaolinite, illite, sodiumconite and chlorite, and the silty framework comprises quartz and feldspar.
4. 4. The method for preparing the deep sea rare earth sediment foundation based on the super-gravity centrifugal physical simulation, which is disclosed in claim 1, is characterized in that six to seven layers are paved in the step S3, the thickness of a single layer is 20-100 mm, and after paving, standing and precooling are carried out until the temperature reaches T 0 +/-2 ℃, and centrifugal loading is carried out.
5. 5. The method for preparing a deep sea rare earth sediment foundation based on the physical simulation of the hypergravity centrifugation according to claim 1, wherein the model pore solution configured in the step S4 is filtered by 0.22-0.45 μm and circulated in an inert material pipeline, and the pH deviation is less than or equal to +/-0.2.
6. 6. The deep sea rare earth sediment foundation preparation method based on the hypergravity centrifugal physical simulation is characterized in that a model box is placed in a large-scale geotechnical centrifuge in the step S5, an n.g hypergravity environment is built, a sectional g-up strategy is adopted, g values are gradually increased and pore pressure stability is maintained, namely 0- & gt 20 g steady state 1 min- & gt 40 g steady state 10 min- & gt 60 g steady state 10 min- & gt 80 g steady state 10 min- & gt 100 g, formal hypergravity acceleration consolidation is carried out under 100 g, then the equivalent consolidation degree U is maintained to be more than or equal to 90% at 100 g, and pore water pressure change tends to zero and the volume variable rate is less than 10- 7 S & lt-1 & gt as a termination criterion.

Description

Deep sea rare earth sediment foundation preparation method based on supergravity centrifugal physical simulation Technical Field The invention relates to the technical field of marine geotechnical engineering and supergravity physical simulation, in particular to a deep sea rare earth sediment foundation preparation method based on supergravity centrifugal physical simulation. Background The rare earth resource level of the Pacific deep sea sediment can be about 800-1000 times of the land rare earth reserves. Deep sea rare earth-rich sediment (REY-RICH SEDIMENTS) is characterized by fine grain composition, high porosity and significant enrichment of medium-heavy rare earth, and has been regarded as an important potential strategic resource carrier by various investigation and development works. Deep sea rare earth-rich sediment (REY-RICH SEDIMENTS) is endowed in a submarine environment with low temperature (about 0-4 ℃) and high hydrostatic pressure (linearly increasing along with water depth to thousands of meters of water depth which can reach tens of MPa), and has the advantages of fine particles, high porosity and remarkable REE enrichment. The method is characterized in that the method is used for acquiring an in-situ sample, the in-situ sample usually depends on ocean voyage, deep sea drill/coring, ROV/AUV and other 'out-sea exploitation-salvage-pressure maintaining/low-temperature transportation' links, and has the problems of difficult voyage organization, limited weather window, extremely high cost of acquisition equipment and an out-sea ship, limited pressure maintaining and sampling success rate and integrity and the like, and the sample is easy to undergo irreversible changes such as unloading-desorption-oxidation-ion exchange and the like in the processes of salvage up-going and long-distance transportation, so that the pore water chemistry and microstructure deviate from the in-situ. The existing standard substance and test material supply is difficult to cover the composite working condition of 'rare earth-rich-low temperature high pressure-high saturation', and the indoor mechanism and engineering evaluation of the system and batch are restricted. Although the traditional heavy indoor method can be used for sample forming and loading at normal temperature and normal pressure, the stress and temperature boundary of deep sea are difficult to reproduce at the same time, and the equivalent long-term consolidation-seepage-chemical balance is difficult to achieve in a controllable period, which causes the problems of insufficient stress level, consolidation history mismatch, pore structure and pore water state distortion and the like of a model soil body, and further causes systematic deviation of strength, seepage, microscopic characterization and in-situ. Thus, the sample-forming and test which simply relies on a very important environment is difficult to support the comparability, the repeatability and the large-scale research requirements of deep-sea rare earth sediments. The supergravity centrifugal physical simulation provides an equivalent reproduction path of an extreme environment for the pain point, namely, n.g supergravity is applied to a 1/n reduced scale model, so that a static water and effective force field (reduced scale effect) with the same magnitude as a prototype can be realized in a small scale, meanwhile, the time scale of the duration processes such as multiphase migration/convection diffusion is shortened approximately according to n2, the prototype can be equivalently prototype for about 27.4 years (reduced scale effect) in 1 day under the condition of 100g, and the physical simulation range of the problems of large scale and long duration is remarkably expanded. Therefore, by accelerating the saturation/consolidation effect under the combined control of the ng supergravity environment and the constant temperature field, the sample with higher consistency with the in-situ mechanical-physical-microstructure can be reproducibly obtained in a laboratory. The invention is based on a supergravity scale reduction/time reduction technical path, reproduces the high-pressure low-temperature occurrence environment of deep sea rare earth sediment, realizes the aim of stable batch preparation without depending on sea sampling, remarkably reduces the sample acquisition cost, shortens the sample acquisition period, improves the repeatability, and provides a unified and traceable sample foundation for developing large-scale indoor mechanics, seepage test and green ore collection technical process evaluation processes. Disclosure of Invention In order to make up the defects of the prior art, the invention provides a deep sea rare earth sediment foundation preparation method based on hypergravity centrifugal physical simulation. The invention is directed to the equivalent reproduction and batch preparation of samples of deep sea rare earth-rich sediment in low temperature (0-4 ℃) and high