CN-122016475-A - Low-temperature freeze thawing environment rock mechanical property testing method based on microstructure evolution

CN122016475ACN 122016475 ACN122016475 ACN 122016475ACN-122016475-A

Abstract

The invention discloses a low-temperature freeze-thawing environment rock mechanical property testing method based on microstructure evolution, which relates to the technical field of rock mechanics and freeze-thawing tests and comprises the steps of obtaining a rock internal structure image sequence through controllable freeze-thawing cycle and reconstructing a vertical digital model through three dimensions. Sequentially extracting pore structure and mineral component information, and respectively carrying out evolution track tracking and migration quantification treatment to generate a pore structure evolution spectrum and a component migration evolution spectrum. And fusing the two types of atlas into a structural evolution feature vector for driving dynamics loading and synchronously collecting mechanical response signals, and finally constructing a correlation mapping table of mechanical properties and microscopic evolution. The method realizes dynamic and quantitative synchronous tracking of two microscopic evolution behaviors of rock pore expansion and mineral migration in the freeze thawing process, and establishes a real-time corresponding relation between the dynamic and quantitative synchronous tracking and macroscopic mechanical property change.

Inventors

PAN ZHENXING
Hou Zhixuan
YANG GENGSHE
TIAN JUNFENG
YANG QIAN
LIU HUI
LIU FANGLU
LIANG BO

Assignees

西安科技大学

Dates

Publication Date: 20260512
Application Date: 20260304

Claims (10)

1. The method for testing the rock mechanical properties in the low-temperature freeze-thawing environment based on microstructure evolution is characterized by comprising the following steps of: preparing a rock sample, placing the rock sample in a controllable low-temperature freeze-thawing simulation environment, starting periodic freeze-thawing cycle simulation, and obtaining an internal structure image sequence of the rock sample after treatment; Performing three-dimensional reconstruction processing on the internal structure image sequence of the rock sample to generate a digital three-dimensional structure model of the rock sample; extracting a pore structure geometric parameter set and a mineral component distribution map in the rock sample based on the digital three-dimensional structure model; performing evolution track tracking processing on the pore structure geometric parameter set to generate a pore structure evolution map; performing component migration quantification processing on the mineral component distribution map to generate a component migration evolution map; Inputting the pore structure evolution spectrum and the component migration evolution spectrum into a mechanical association model to generate a structure evolution feature vector; Based on the structural evolution feature vector, a driving force mechanical loading device applies a load of a preset mode to the rock sample, and synchronously acquires a mechanical response signal sequence of the rock sample; and constructing a rock mechanical property evolution association mapping table according to the mechanical response signal sequence of the rock sample and the corresponding structure evolution feature vector.
2. The method for testing the rock mechanical properties of a low-temperature freeze-thawing environment based on microstructure evolution according to claim 1, wherein the preparing the rock sample, placing the rock sample in a controllable low-temperature freeze-thawing simulation environment, starting periodic freeze-thawing cycle simulation, and obtaining an internal structure image sequence of the rock sample through processing comprises: Preparing a rock sample meeting preset geometric specification and initial state; placing the rock sample in a controllable low-temperature freeze-thawing simulation environment, and starting periodic freeze-thawing cycle simulation; at each preset freeze-thawing cycle node, interrupting the freeze-thawing simulation process, performing lossless scanning imaging processing on the rock sample, and acquiring an internal structure image sequence of the rock sample, wherein the method specifically comprises the following steps: controlling the temperature of the low-temperature freeze-thawing simulation environment to return to a preset reference temperature; taking out a rock sample from a low-temperature freeze thawing simulation environment, and placing the rock sample on a sample table of a nondestructive scanning device; Starting a ray source and a detector array of the nondestructive scanning device, and rotating and scanning around a rock sample; Collecting penetrating ray projection images of a rock sample at different rotation angles; performing tomographic reconstruction operation on all penetrating ray projection images to generate an internal structure tomographic image set of the rock sample at different preset freeze-thawing cycle nodes; and arranging the internal structure fault slice image sets along the axial direction to form an internal structure image sequence of the rock sample.
3. The method for testing the rock mechanical properties of a low-temperature freeze-thawing environment based on microstructure evolution according to claim 1, wherein the step of performing three-dimensional reconstruction processing on the internal structure image sequence of the rock sample to generate a digital three-dimensional structure model of the rock sample comprises the steps of: carrying out gray scale normalization and noise filtering treatment on each tomographic image in the internal structure image sequence of the rock sample; Performing pixel alignment and interpolation calculation on the processed tomographic image to construct initial three-dimensional voxel space data; in the three-dimensional voxel space data, a preset threshold segmentation algorithm is applied to distinguish the rock matrix, the pore space and the space areas of different mineral phases; And constructing the digital three-dimensional structural model for representing the distribution of substances in the rock sample based on the distinguished rock matrix, pore space and space regions of different mineral phases.
4. The method for testing the rock mechanical properties of the low-temperature freeze-thawing environment based on microstructure evolution according to claim 1, wherein extracting a pore structure geometric parameter set and a mineral component distribution map inside a rock sample based on the digital three-dimensional structure model comprises: Identifying all connected pore networks in the pore space characterized by the digital three-dimensional structure model; calculating the volume, the surface area, the equivalent diameter, the shape factor, the tortuosity and the connectivity parameters of each communicated pore network, and combining to form a pore structure geometric parameter set; In the different mineral phase space regions characterized by the digital three-dimensional structure model, according to the three-dimensional space coordinates of each mineral phase, the space distribution density and the adjacent relation are counted; And coding the spatial distribution density and the adjacent relation of each mineral phase in a map form to generate a mineral component distribution map.
5. The method for testing the rock mechanical properties of the low-temperature freeze-thawing environment based on microstructure evolution according to claim 1, wherein the step of performing evolution track tracking processing on the pore structure geometric parameter set to generate a pore structure evolution map comprises the steps of: extracting geometrical parameter changes of pores with the same spatial position in the freeze thawing cycle process from pore structure geometrical parameter sets corresponding to different freeze thawing cycle nodes; For each pore, calculating the volume change rate, the shape evolution vector and the communication state transition path between adjacent freeze-thawing cycle nodes; integrating the geometric parameter change, volume change rate, shape evolution vector and communication state transfer path of all pores, and drawing a dynamic relation diagram of the evolution of the pore structure along with the increase of freeze thawing cycle times, namely a pore structure evolution map.
6. The method for testing the mechanical properties of low-temperature freeze-thawing environment rock based on microstructure evolution according to claim 1, wherein the step of performing component migration quantization processing on the mineral component distribution spectrum to generate a component migration evolution spectrum comprises the steps of: comparing the mineral component distribution maps corresponding to different freeze-thawing cycle nodes, and identifying the spatial displacement of specific mineral particles; calculating a displacement vector of the spatial displacement of the specific mineral particles, and counting the statistical distribution characteristics of the displacement vectors of the mineral particles of the same type; marking mineral particles with remarkable displacement and displacement tracks thereof on the mineral component distribution map; And superposing and integrating the displacement and evolution tracks of the mineral particles observed in all the freeze-thawing cycle nodes to generate a map reflecting the migration rule and the evolution trend of the mineral components under the freeze-thawing action, namely a component migration evolution map.
7. The method for testing the mechanical properties of the rock in the low-temperature freeze-thawing environment based on the microstructure evolution according to claim 1, wherein the method for inputting the pore structure evolution spectrum and the component migration evolution spectrum into a mechanical association model to generate a structural evolution feature vector comprises the following steps: extracting a pore volume change rate sequence, a pore morphology evolution rate sequence and a pore network connectivity change sequence from the pore structure evolution map; extracting mineral displacement statistical characteristics, mineral boundary change sequences and microcrack expansion track descriptions from the component migration evolution spectrum; normalizing and vectorizing the pore volume change rate sequence, the pore morphology evolution rate sequence, the pore network connectivity change sequence, the mineral displacement statistical characteristics, the mineral boundary change sequence and the microcrack expansion track description to splice to form an original characteristic set; Inputting the original feature set into a feature dimension reduction and fusion layer of a pre-trained mechanical association model, wherein the mechanical association model compresses and fuses the high-dimensional original feature set into the low-dimensional structural evolution feature vector which is highly relevant to mechanical response.
8. The method for testing the mechanical properties of the rock in the low-temperature freeze-thawing environment based on the microstructure evolution according to claim 1, wherein the driving force mechanical loading device applies a load of a preset mode to the rock sample based on the feature vector of the microstructure evolution, and synchronously acquires a mechanical response signal sequence of the rock sample, comprising: Analyzing a structural evolution feature vector generated by a current freeze-thawing cycle node, wherein the structural evolution feature vector comprises pore structure stability evaluation and mineral component bonding strength evaluation information; Selecting a load application mode matched with the pore structure stability evaluation from a preset load mode library according to the pore structure stability evaluation and mineral component bonding strength evaluation information; converting the selected load application mode into a control instruction of a mechanical loading device, and applying axial stress, confining pressure and shearing force combination corresponding to the current structural state to the rock sample by the mechanical loading device; In the process of applying load, a mechanical response signal sequence of the rock sample is formed by synchronously acquiring stress, strain, acoustic emission signals and ultrasonic speed signals through a sensor array arranged on the rock sample.
9. The method for testing the mechanical properties of the rock in the low-temperature freeze-thawing environment based on the microstructure evolution according to claim 1, wherein the construction of the rock mechanical property evolution association mapping table according to the mechanical response signal sequence of the rock sample and the corresponding structural evolution feature vector comprises the following steps: processing a mechanical response signal sequence of the rock sample obtained under each freeze-thawing cycle node, and extracting mechanical parameters, wherein the mechanical parameters comprise peak strength, elastic modulus, poisson ratio and stress-strain curve characteristic parameters; Pairing the mechanical parameters extracted by each freeze-thawing cycle node with the structural evolution feature vectors corresponding to the freeze-thawing cycle nodes to form a 'mechanical parameter-structural evolution feature vector' data pair; Arranging the data pairs of the mechanical parameter-structure evolution characteristic vector of all the freeze-thawing cycle nodes according to the ascending order of the freeze-thawing cycle times; On the basis of the arranged data pairs, an association mapping structure is constructed, the association mapping structure takes freeze thawing cycle times as an index, the corresponding relation between mechanical parameters and structural evolution feature vectors is recorded, and a rock mechanical property evolution association mapping table is formed.
10. The method for testing the mechanical properties of the rock in the low-temperature freeze-thawing environment based on microstructure evolution according to claim 9, wherein a correlation mapping structure is constructed, the correlation mapping structure takes the number of freeze-thawing cycles as an index, records the correspondence between mechanical parameters and structural evolution feature vectors, and comprises the following steps: Establishing a multi-dimensional data table, and taking the freeze-thawing cycle times as a main index column of the multi-dimensional data table; in the multidimensional data table, a mechanical parameter array group and a structural evolution characteristic vector array group are established for each freeze-thawing cycle index row; Respectively filling the extracted peak strength, elastic modulus, poisson ratio and stress-strain curve characteristic parameters into corresponding sub-columns of the mechanical parameter column group of the corresponding row; Filling each dimension component of the structural evolution feature vector into a corresponding subcolumn of the structural evolution feature vector column group of the corresponding row respectively; and directly inquiring and acquiring the mapping relation between the corresponding mechanical parameter set and the structural evolution feature vector according to the freeze-thawing cycle times through the main index column of the multidimensional data table.

Description

Low-temperature freeze thawing environment rock mechanical property testing method based on microstructure evolution Technical Field The invention belongs to the technical field of rock mechanics and freeze thawing test, and particularly relates to a low-temperature freeze thawing environment rock mechanical property test method based on microstructure evolution. Background In cold region engineering and underground space development, mechanical property decay of rock after undergoing freeze thawing cycle is a key problem. The existing test method mainly depends on a macroscopic mechanical test, namely, after a set freezing and thawing period, macroscopic parameters such as uniaxial compressive strength, elastic modulus and the like of the rock are measured to evaluate damage. The method can only acquire the final mechanical state after the freeze thawing action, and the testing process is completely disjointed with the real-time change of the microstructure in the rock. The shortcomings of the prior art solutions focus on the lack of dynamic monitoring and quantitative description of the microscopic evolution process. Although microscopic observation or CT scanning technology has been applied, the method is generally only used for comparing static structural images before and after freeze thawing cycle, and cannot completely track dynamic evolution tracks of pores and microcracks in the cycle process, such as whole processes of initiation, expansion and convergence, and the conventional means are difficult to quantify migration behaviors of mineral components in the rock under the drive of freeze thawing. Moisture freezing expansion, thawing and seepage can cause cement dissolution, grain boundary slip and secondary mineral precipitation, but the spatial redistribution process of these microcomponents and their rates lack an effective dynamic quantitative characterization method. A testing method is needed, dynamic evolution tracking of pore structures in the rock and quantitative analysis of mineral component migration in the freeze thawing process can be synchronously realized, and the two kinds of microscopic dynamic evolution information are directly related to real-time macroscopic mechanical response so as to reveal the essential relation between microscopic mechanism and macroscopic expression of freeze thawing damage. Disclosure of Invention The present invention aims to solve at least one of the technical problems existing in the prior art; therefore, the invention provides a low-temperature freeze-thawing environment rock mechanical property test method based on microstructure evolution, which comprises the following steps: preparing a rock sample, placing the rock sample in a controllable low-temperature freeze-thawing simulation environment, starting periodic freeze-thawing cycle simulation, and obtaining an internal structure image sequence of the rock sample after treatment; Performing three-dimensional reconstruction processing on the internal structure image sequence of the rock sample to generate a digital three-dimensional structure model of the rock sample; extracting a pore structure geometric parameter set and a mineral component distribution map in the rock sample based on the digital three-dimensional structure model; performing evolution track tracking processing on the pore structure geometric parameter set to generate a pore structure evolution map; performing component migration quantification processing on the mineral component distribution map to generate a component migration evolution map; Inputting the pore structure evolution spectrum and the component migration evolution spectrum into a mechanical association model to generate a structure evolution feature vector; Based on the structural evolution feature vector, a driving force mechanical loading device applies a load of a preset mode to the rock sample, and synchronously acquires a mechanical response signal sequence of the rock sample; and constructing a rock mechanical property evolution association mapping table according to the mechanical response signal sequence of the rock sample and the corresponding structure evolution feature vector. Further, the preparing of the rock sample, placing the rock sample in a controllable low-temperature freeze-thawing simulation environment, starting a periodic freeze-thawing cycle simulation, and obtaining an internal structure image sequence of the rock sample through processing, wherein the method comprises the following steps: Preparing a rock sample meeting preset geometric specification and initial state; placing the rock sample in a controllable low-temperature freeze-thawing simulation environment, and starting periodic freeze-thawing cycle simulation; at each preset freeze-thawing cycle node, interrupting the freeze-thawing simulation process, performing lossless scanning imaging processing on the rock sample, and acquiring an internal structure image sequence of the rock s