Method and system for evaluating deterioration of mechanical properties of disturbed soft soil based on pore index difference

Abstract

This invention discloses a method and system for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index differences. Specifically, it relates to the field of soft soil foundation engineering investigation and repair reinforcement technology, and is used to solve the problem that existing methods are difficult to accurately assess the spatial differentiation of mechanical properties caused by internal damage differences in disturbed soft soil, resulting in a lack of targeted repair design. The method is achieved by acquiring and disturbing soil samples, dividing characteristic pore size intervals and determining the dominant damage pore size intervals based on nuclear magnetic resonance T2 spectra, conducting a series of macroscopic mechanical tests on soil samples with different degrees of disturbance to construct a set of macroscopic states and classify macroscopic state categories, and finally establishing a characterization relationship between the dominant damage pore size intervals and macroscopic state categories. Based on this relationship, the mechanical property deterioration level of the soil sample can be accurately determined, thereby providing a basis for differentiated repair design.

Description

Technical Field

[0001] This invention relates to the field of soft soil foundation engineering investigation, repair and reinforcement technology, and more specifically, to a method and system for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index. Background Technology

[0002] In the repair and reinforcement of soft soil foundations, accurate engineering geological investigation is the foundation for designing effective treatment schemes. Currently, for soft soil foundations that have been subjected to loads, vibrations, or environmental disturbances, engineering practice mainly relies on drilling and sampling combined with conventional indoor geotechnical tests, such as consolidation tests and shear tests, as well as in-situ tests, such as static cone penetration tests and standard penetration tests, to obtain the physical and mechanical parameters of the soil. These methods evaluate the overall engineering properties of the foundation by measuring macroscopic indicators such as soil strength, compression modulus, and permeability coefficient, and then carry out reinforcement design accordingly, such as determining the replacement depth, pile length, or grouting volume.

[0003] However, after being disturbed, the deterioration of the mechanical properties of soft soil exhibits significant spatial heterogeneity. Conventional investigation methods are insufficient to accurately reveal this spatial differentiation caused by differences in internal structural damage. Consequently, the disturbed area is often treated as a homogeneous body in the repair design, failing to differentiate the design based on the gradient changes in the actual degree of soil damage. This often results in insufficiently targeted repair schemes, potentially leading to over-reinforcement in mildly deteriorated areas and insufficient reinforcement in severely deteriorated areas, which fails to effectively control post-construction settlement and affects the overall reliability of the repair project. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the present invention provides a method and system for evaluating the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] The method for assessing the deterioration of mechanical properties of disturbed soft soil based on the difference in porosity index includes the following steps:

[0007] S1. Obtain disturbed soft soil and prepare soil samples;

[0008] S2. Perform dry-wet cycle simulation disturbance on the soil sample to obtain the disturbed soil sample;

[0009] S3. Based on the nuclear magnetic resonance T2 spectrum, the pores of the soil sample and the disturbed soil sample are divided into several characteristic pore size intervals, and the change rate of each characteristic pore size interval before and after the disturbance is calculated. The characteristic pore size interval with the largest change rate is determined as the dominant damage pore size interval.

[0010] S4. From several disturbed soil samples with different degrees of disturbance, conduct unconfined compressive strength test, compression test and permeability test respectively, and characterize the strength index, compression index and permeability index of each soil sample as a set of macroscopic states.

[0011] S5. Based on the distribution pattern of the macroscopic state set of all soil samples, divide them into several macroscopic state categories that characterize the deterioration stages of different mechanical properties.

[0012] S6. Establish the characterization relationship between the dominant damage pore size range and the macroscopic state category, and determine the mechanical property deterioration level of the soil sample to be judged based on the characterization relationship.

[0013] Further, the disturbed soft soil is acquired and soil samples are prepared, including:

[0014] Multiple sampling points were selected based on the inferred distribution of disturbance intensity gradient within the site to be evaluated.

[0015] Disturbed soft soil that retains its original structure was obtained from multiple sampling points;

[0016] The disturbed soft soil that retains its original structure was prepared into soil samples for nuclear magnetic resonance testing and macroscopic mechanical experiments.

[0017] Furthermore, multiple sampling points are selected based on the inferred disturbance intensity gradient distribution within the site to be evaluated, including arranging the sampling points in order from near to far in a direction perpendicular to the inferred disturbance source.

[0018] Furthermore, the soil samples were subjected to simulated wet-dry cycles to obtain disturbed soil samples, including:

[0019] Soil samples used for nuclear magnetic resonance testing and macroscopic mechanical experiments were placed in a controlled environment chamber;

[0020] The soil sample was dehydrated according to the preset drying temperature and time.

[0021] The soil sample was then saturated according to the preset immersion method and time.

[0022] The dehydration and saturation processes are repeated a preset number of times to obtain a disturbed soil sample with a preset degree of disturbance.

[0023] Furthermore, the dehydration treatment of the soil sample according to the preset drying temperature and time includes: drying the soil sample under constant temperature conditions until its quality changes tend to stabilize; the saturation treatment of the soil sample according to the preset soaking method and time includes: using the vacuum saturation method to make the soil sample fully saturated.

[0024] Furthermore, based on the nuclear magnetic resonance T2 spectrum, the pore size of the soil sample and the disturbed soil sample were divided into several characteristic pore size intervals, and the rate of change of each characteristic pore size interval before and after disturbance was calculated. The characteristic pore size interval with the largest rate of change was determined as the dominant damage pore size interval, including:

[0025] Obtain the nuclear magnetic resonance T2 spectra of soil samples and soil samples after disturbance with a preset degree of disturbance;

[0026] Based on the correspondence between nuclear magnetic resonance T2 values ​​and pore size, several characteristic pore size intervals corresponding to different pore size ranges are defined on the T2 spectrum.

[0027] Calculate the signal amplitude integrals of the soil sample and the disturbed soil sample in each characteristic aperture range;

[0028] For each characteristic aperture range, calculate the integral rate of change of the signal amplitude of the soil sample relative to the soil sample after disturbance;

[0029] By comparing the integral rate of change of signal amplitude across all characteristic aperture ranges, the characteristic aperture range with the largest integral rate of change of signal amplitude is determined as the dominant damage aperture range.

[0030] Furthermore, unconfined compressive strength tests, compression tests, and permeability tests were conducted on several disturbed soil samples with different degrees of disturbance. The strength, compression, and permeability indices corresponding to each soil sample were collectively characterized as a set of macroscopic states, including:

[0031] Soil samples with different preset disturbance levels were selected after disturbance;

[0032] For each selected disturbed soil sample, unconfined compressive strength test, compression test and permeability test were performed sequentially;

[0033] Unconfined compressive strength is obtained from unconfined compressive strength test as strength index, compression coefficient is obtained from compression test as compression index, and permeability coefficient is obtained from permeability test as permeability index.

[0034] The unconfined compressive strength, compression coefficient, and permeability coefficient of the same disturbed soil sample are stored together as a set of correlated data to form the macroscopic state set of the soil sample.

[0035] Furthermore, based on the distribution pattern of the macroscopic state set of all soil samples, several macroscopic state categories characterizing different stages of mechanical property deterioration were identified, including:

[0036] The unconfined compressive strength, compression coefficient, and permeability coefficient of all soil samples in the macroscopic state set are standardized to form a standardized index dataset.

[0037] Calculate the Euclidean distance between the standardized index datasets of any two soil samples to obtain the distance matrix characterizing the macroscopic similarity between soil samples;

[0038] Based on the distance matrix, cluster analysis was used to group all soil samples into several groups with similar macroscopic states.

[0039] Each aggregate group is defined as a macroscopic state category, and each macroscopic state category represents a stage of mechanical property deterioration.

[0040] Furthermore, a characterization relationship is established between the dominant damage pore size range and the macroscopic state category, and the mechanical property degradation level of the soil sample to be judged is determined based on the characterization relationship, including:

[0041] The dominant damage pore size range of all soil samples under each macroscopic condition category is statistically analyzed, and a mapping table is formed by establishing a correspondence between each macroscopic condition category and the dominant damage pore size range that occurs most frequently.

[0042] For the soil sample to be judged, obtain the dominant damage pore size range of the soil sample to be judged;

[0043] The dominant damage pore size range of the soil sample to be judged is compared with the mapping table. If the dominant damage pore size range of the soil sample to be judged is consistent with the dominant damage pore size range corresponding to a certain macroscopic state category in the mapping table, then the mechanical property deterioration level of the soil sample to be judged is determined to be the deterioration stage represented by that macroscopic state category.

[0044] On the other hand, the present invention provides a system for evaluating the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, comprising the following modules:

[0045] The soil sample preparation module is used to acquire disturbed soft soil and prepare soil samples;

[0046] The wet-dry disturbance module is used to simulate wet-dry cycles to disturb soil samples and obtain disturbed soil samples.

[0047] The pore size analysis module is used to divide the pores of soil samples and disturbed soil samples into several characteristic pore size intervals based on nuclear magnetic resonance T2 spectra, calculate the rate of change of each characteristic pore size interval before and after disturbance, and determine the characteristic pore size interval with the largest rate of change as the dominant damage pore size interval.

[0048] The macro-parameter testing module is used to conduct unconfined compressive strength tests, compression tests, and permeability tests on several disturbed soil samples with different degrees of disturbance, and to characterize the strength index, compression index, and permeability index of each soil sample into a set of macro-states.

[0049] The state classification module is used to classify several macroscopic state categories that characterize the deterioration stages of different mechanical properties based on the distribution pattern of the macroscopic state set of all soil samples.

[0050] The degradation characterization module is used to establish the characterization relationship between the dominant damage pore size range and the macroscopic state category, and to determine the degradation level of the mechanical properties of the soil sample to be judged based on the characterization relationship.

[0051] Compared with the prior art, the present invention has the following beneficial effects:

[0052] 1. By establishing a deterministic correlation between microscopic pore structure damage and macroscopic mechanical property deterioration, a refined identification and spatial zoning of the deterioration type and degree of disturbed soft soil foundation properties were achieved. A key microscopic damage identifier was proposed, using the dominant damage pore size range as the key microscopic damage marker, and quantitatively correlated with the macroscopic state categories defined through multi-index collaborative analysis. This solves the problem that conventional exploration methods can only obtain the average value of macroscopic indicators, failing to reveal the fundamental issue of spatial differentiation of mechanical properties caused by differences in internal structural damage. Its evaluation logic delves from phenomenon description to mechanism explanation, enabling the judgment of soil state to move beyond a general qualitative assessment of strength and weakness, and instead clearly identify the dominant pore size range where damage occurs and its corresponding specific mechanical response mode. This provides an unprecedentedly refined stratification basis for engineering geological evaluation.

[0053] 2. Based on the aforementioned refined identification and zoning capabilities, direct and quantitative decision support is provided for the repair and reinforcement design of soft soil foundations. This effectively overcomes the drawback of treating disturbed areas as homogeneous bodies in traditional designs, which leads to a one-size-fits-all approach. By substituting the microscopic test results of the soil samples to be judged into the established characterization relationship, the degradation level, i.e., the macroscopic state category, can be quickly and accurately determined. This allows designers to conduct differentiated reinforcement designs based on the actual damage gradient within the foundation. For example, economical and moderate measures can be adopted in mildly degraded areas, while key reinforcement can be carried out in severely degraded areas. This fundamentally improves the pertinence and scientific nature of the repair plan, optimizes resource allocation, and enhances the overall controllability of the repair project while ensuring the safety and reliability of the project. Attached Figure Description

[0054] Figure 1 This is a flowchart of the method for evaluating the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, as described in this invention.

[0055] Figure 2 This is a schematic diagram of the structure of the system for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, as proposed in this invention. Detailed Implementation

[0056] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0057] Example 1: Figure 1 The present invention provides a method for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, which includes the following steps:

[0058] S1. Obtain disturbed soft soil and prepare soil samples;

[0059] S2. Perform dry-wet cycle simulation disturbance on the soil sample to obtain the disturbed soil sample;

[0060] S3. Based on the nuclear magnetic resonance T2 spectrum, the pores of the soil sample and the disturbed soil sample are divided into several characteristic pore size intervals, and the change rate of each characteristic pore size interval before and after the disturbance is calculated. The characteristic pore size interval with the largest change rate is determined as the dominant damage pore size interval.

[0061] S4. From several disturbed soil samples with different degrees of disturbance, conduct unconfined compressive strength test, compression test and permeability test respectively, and characterize the strength index, compression index and permeability index of each soil sample as a set of macroscopic states.

[0062] S5. Based on the distribution pattern of the macroscopic state set of all soil samples, divide them into several macroscopic state categories that characterize the deterioration stages of different mechanical properties.

[0063] S6. Establish the characterization relationship between the dominant damage pore size range and the macroscopic state category, and determine the mechanical property deterioration level of the soil sample to be judged based on the characterization relationship.

[0064] The core of the porosity index difference in this embodiment is embodied in step S3. This step does not simply calculate the arithmetic difference of the total pore volume, but rather uses nuclear magnetic resonance T2 spectra to finely divide the pore system into several characteristic pore size intervals, and calculates the rate of change of the integral of the signal amplitude before and after the disturbance for each interval. By comparing these rates of change, the characteristic pore size interval with the largest absolute value of the rate of change is identified as the dominant damage pore size interval. This dominant damage pore size interval is essentially a refined and structured porosity index difference, precisely quantifying the specific pore size range in which the most significant damage to the soil pore structure caused by the disturbance occurs. Therefore, the dominant damage pore size interval achieves a directional and mechanistic characterization of the porosity index difference, thus laying a precise microscopic foundation for subsequent correlation with macroscopic mechanical properties.

[0065] To implement step S1 of the method for assessing the deterioration of the mechanical properties of disturbed soft soil based on porosity index difference—namely, acquiring disturbed soft soil and preparing soil samples—it is necessary to complete the selection of sampling points, acquisition of undisturbed soil samples, and preparation of test soil samples. Multiple sampling points are selected based on the inferred disturbance intensity gradient distribution within the site to be assessed. The disturbance intensity gradient distribution refers to the degree of influence of engineering construction activities on the surrounding foundation soil, which spatially decreases with increasing distance from the disturbance source. The method for inferring the disturbance intensity gradient distribution is to identify the location of the main disturbance source within the site based on site surveys and engineering drawings. A main disturbance source location is, for example, the edge of an excavated foundation pit. When selecting sampling points, they are arranged in order from near to far in the direction perpendicular to the inferred disturbance source. The direction perpendicular to the inferred disturbance source is a radial direction perpendicular to the edge of the foundation pit and pointing outwards from the site. The sampling order from nearest to furthest means that the first sampling point is placed approximately 1 meter from the edge of the excavation pit, the second approximately 5 meters from the edge, the third approximately 15 meters from the edge, and the fourth approximately 30 meters from the edge. The sampling point layout covers a spatial range from strong disturbance to weak disturbance to almost no disturbance. The location of each sampling point is determined on-site using measuring instruments, and the coordinates are recorded.

[0066] Disturbed soft soil samples with preserved original structure were obtained from multiple sampling points. The method for obtaining these samples was to use a thin-walled open-faced soil sampler at each sampling point. The thin-walled open-faced soil sampler was a metal cylinder with an inner diameter of at least 79 mm. During sampling, the thin-walled open-faced soil sampler was vertically pressed into the ground to a predetermined depth. The predetermined depth was the soft soil layer depth within 1 to 2 meters below the surface. The pressing process was kept smooth and continuous. Once the thin-walled open-faced soil sampler reached the predetermined depth, it was removed along with the soil column inside. After removal, both ends of the thin-walled open-faced soil sampler were sealed with plastic wrap and tape to prevent soil moisture evaporation and structural changes, ensuring that the obtained soft soil samples retained their original structure and water content after being disturbed in situ. At least two parallel undisturbed soil samples were obtained from each sampling point.

[0067] The disturbed soft soil, retaining its original structure, is prepared into soil samples for NMR and macroscopic mechanical tests. In the laboratory, the sealing material at both ends of a thin-walled open sampler is removed, and the cylindrical undisturbed soil sample is ejected from the sampler. For NMR testing, the soil sample is prepared by cutting a small piece from the middle of the undisturbed soil column using a wire saw. The piece is sized to fit completely into the NMR instrument's sample detection coil. Examples of small piece sizes include a cube with sides of 20 mm or a cylinder with a diameter of 10 mm and a height of 20 mm. The cutting tool is kept sharp and handled gently during the cutting process. The prepared NMR test soil sample is wrapped in plastic film and stored in a humidifier. For macroscopic mechanical tests, the soil sample is prepared by cutting from different parts of the undisturbed soil column using a ring cutter. The soil sample used for the unconfined compressive strength test is a cylinder with a diameter of 39.1 mm and a height of 80 mm, prepared using a ring cutter with an inner diameter of 39.1 mm and a height of 80 mm. The soil sample used for the compression test was a cylinder with a diameter of 61.8 mm and a height of 20 mm, prepared using a consolidated ring cutter with an area of ​​30 square centimeters. The soil sample used for the permeability test was sized according to the requirements of the testing instrument; for example, a cylinder with a diameter of 101 mm and a height of 40 mm was used. During the ring cutter cutting process, the ring cutter was pressed vertically downwards. After cutting, excess soil at both ends was trimmed to ensure close contact between the soil sample and the inner wall of the ring cutter, and that both ends were flat. At least three sets of soil samples for nuclear magnetic resonance (NMR) testing and three sets for macroscopic mechanical testing were prepared in parallel from the disturbed soft soil obtained from each sampling point, maintaining its original structure. All prepared soil samples for NMR and macroscopic mechanical testing were numbered, and the numbering information was recorded corresponding to the coordinates and depth information of the sampling point from which they originated. This completed step S1, obtaining a series of soil samples from different locations with estimated disturbance intensities, prepared to standard test dimensions.

[0068] To implement step S2 of the method for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index—namely, simulating wet-dry cycle disturbance of the soil sample and obtaining the disturbed soil sample—a controlled environmental disturbance simulation of the prepared soil sample needs to be completed. The soil samples used for nuclear magnetic resonance (NMR) testing and macroscopic mechanical experiments are placed in a controlled environment chamber. A controlled environment chamber is an experimental device capable of precisely controlling the internal air temperature and humidity. When placing the soil samples, remove them from the humidifier. For small soil samples used for NMR testing, place them along with their plastic wrapping film on the sample rack inside the controlled environment chamber. For ring sample soil samples used for macroscopic mechanical experiments, place the ring containing the soil sample on the sample rack inside the controlled environment chamber. Ensure sufficient gaps are left between the soil samples during placement. The door of the controlled environment chamber must be tightly closed after placement.

[0069] The soil sample is dehydrated according to a preset drying temperature and time. The preset drying temperature is a constant air temperature value set to simulate natural evaporation or drainage effects in engineering. For example, the preset drying temperature is set to 40 degrees Celsius. The preset drying time is the time elapsed until the soil sample mass stabilizes. The specific operation of the dehydration process involves activating the heating and dehumidification functions of the controlled environment chamber to maintain the air temperature inside the chamber at the preset drying temperature, for example, 40 degrees Celsius, and turning on the fan inside the chamber to promote air circulation. The soil sample is then placed under the condition of maintaining a constant preset drying temperature, for example, 40 degrees Celsius. During the dehydration process, the mass change of the soil sample needs to be monitored periodically. The monitoring method is as follows: every 6 hours, the controlled environment chamber is closed, the soil sample is quickly removed, and the total mass of the soil sample and its container is weighed using an electronic balance with an accuracy of 0.01 grams. The total mass value is recorded, and then the soil sample is immediately returned to the controlled environment chamber, and the constant temperature conditions are restarted. The weighing operation must be completed as quickly as possible. The criterion for judging whether the quality change tends to stabilize is that the maximum difference between the total mass values ​​obtained from three consecutive weighings does not exceed five-thousandths of the initial total mass value recorded before the start of the soil sample dehydration treatment. When the maximum difference between the total mass values ​​obtained from three consecutive weighings does not exceed five-thousandths of the initial total mass value recorded before the start of the soil sample dehydration treatment, the dehydration treatment is considered complete. The total time elapsed from the start to the completion of the dehydration treatment is recorded; this total time is the actual drying time. Dehydrating the soil sample according to the preset drying temperature and time includes drying the soil sample under constant temperature conditions until its quality change tends to stabilize.

[0070] The soil sample is saturated according to a preset immersion method and time. The preset immersion method is vacuum saturation. The preset saturation time is the time required for the soil sample to reach full saturation during the vacuum saturation process. The specific operation of the saturation treatment is to remove the dehydrated soil sample from the controlled environment chamber. Prepare the vacuum saturation device, which includes a vacuum cylinder, a vacuum pump connected to the vacuum cylinder, and a water inlet pipe. Place the soil sample on the support inside the vacuum cylinder. Seal the vacuum cylinder lid. Start the vacuum pump to evacuate the air inside the vacuum cylinder, reducing the air pressure inside the cylinder to a stable low value, for example, below 10 kPa, and maintain this low pressure state for a period of time, for example, 2 hours. After maintaining the low pressure state, while keeping the vacuum pump running, slowly open the valve of the water inlet pipe connected to the distilled water container, allowing distilled water to slowly inject into the vacuum cylinder under negative pressure until the distilled water completely submerges all the soil sample. Close the inlet valve and continue operating the vacuum pump to maintain the soil sample in a low-pressure environment while submerged, for example, for 4 hours. Then, turn off the vacuum pump and slowly open the vent valve on the vacuum cylinder to restore the pressure to atmospheric pressure. Under atmospheric pressure, continue immersing the soil sample in distilled water for, for example, 12 hours. The criteria for complete saturation are no air bubbles escaping from the soil sample surface and no significant change in soil volume. Saturation treatment of the soil sample is performed according to the preset immersion method and time, including using vacuum saturation to achieve complete saturation.

[0071] The dehydration and saturation processes are repeated for a preset number of cycles. The preset number of cycles is a pre-defined set of wet-dry alternations to obtain different degrees of disturbance. For example, the preset number of cycles can be set to 1, 3, 5, and 10. Repeating the operation means that for soil samples requiring multiple cycles, after one saturation treatment, the next dehydration process is immediately restarted. That is, the soil sample is placed again in a controlled environment chamber and dried at the same preset drying temperature until its mass change tends to stabilize, and then the same vacuum saturation treatment is performed. This cycle is repeated until the number of wet-dry alternations experienced by the soil sample reaches the value specified in the preset number of cycles. After each cycle, the soil sample needs to be marked, and the number of cycles completed needs to be recorded. A disturbed soil sample with a preset degree of disturbance is obtained. A disturbed soil sample with a preset degree of disturbance refers to a soil sample that has undergone a specific preset number of wet-dry cycle simulation disturbances. Different preset number of cycles corresponds to different preset degrees of disturbance. After completing the simulation for all preset number of cycles, the obtained disturbed soil sample is removed from the water, and excess surface moisture is gently absorbed with a damp towel. The disturbed soil samples used for subsequent nuclear magnetic resonance (NMR) testing should be immediately wrapped in a new plastic film to prevent moisture evaporation and tested as soon as possible. For subsequent macroscopic mechanical tests, the disturbed soil samples should be kept within the ring sampler. Permeable stones and filter paper should be placed at both ends of the ring sampler, and the sides of the ring sampler should be wrapped with plastic wrap to retain moisture. The samples should be left to stand in a constant temperature environment for a period of time, such as 24 hours, to allow for uniform moisture distribution within the soil sample before testing. This completes step S2, yielding a series of disturbed soil samples with different preset disturbance levels.

[0072] To implement step S3 in the method for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, it is necessary to divide the pores of the soil sample and the disturbed soil sample into characteristic pore size intervals based on the NMR T2 spectrum, calculate the rate of change of the characteristic pore size intervals before and after disturbance, and determine the characteristic pore size interval with the largest rate of change as the dominant damage pore size interval. Obtain the NMR T2 spectra of the soil sample and the disturbed soil sample with a preset disturbance level. The instrument used to obtain the NMR T2 spectra is a low-field NMR analyzer. Remove the soil sample and the disturbed soil sample with a preset disturbance level from the humidifier and place them in the sample tube at the center of the NMR analyzer's RF coil. Set the test parameters of the NMR analyzer, including the dominant frequency, echo time, and number of echoes. For example, the dominant frequency is set to 12 MHz. The echo time is set to 0.2 ms. The number of echoes is set to 2048. Start the NMR analyzer for data acquisition. The nuclear magnetic resonance (NMR) analyzer converts the acquired echo train data into NMR T2 spectra using an inversion algorithm. The inversion algorithm is the instrument's built-in standard inversion software. This yields the NMR T2 spectrum curves corresponding to the soil sample or the disturbed soil sample.

[0073] Based on the correspondence between NMR T2 values ​​and pore size, several characteristic pore size intervals corresponding to different pore size ranges are defined on the NMR T2 spectrum. This correspondence is described by an empirical formula indicating that, under saturation, pore size is directly proportional to the transverse relaxation time T2. Based on this correspondence, different pore size ranges can be correspondingly divided into intervals on the T2 value abscissa. The method for defining characteristic pore size intervals is to observe all NMR T2 spectrum curves and determine the overall distribution range of T2 values, for example, from 0.01 milliseconds to 1000 milliseconds. Following the classification conventions for common pores in soft soil, the entire T2 distribution range is divided into several continuous intervals. The classification is based on the pore size category represented by the T2 value. For example, the range of T2 values ​​from 0.01 ms to 1 ms is defined as characteristic pore size range one, corresponding to micropores; the range of T2 values ​​from 1 ms to 10 ms is defined as characteristic pore size range two, corresponding to small pores; the range of T2 values ​​from 10 ms to 100 ms is defined as characteristic pore size range three, corresponding to medium pores; and the range of T2 values ​​from 100 ms to 1000 ms is defined as characteristic pore size range four, corresponding to large pores. Ultimately, four characteristic pore size ranges corresponding to different pore size ranges are defined on the NMR T2 spectrum.

[0074] Calculate the signal amplitude integral for both the soil sample and the disturbed soil sample within each characteristic pore size interval. The signal amplitude integral refers to the area enclosed by the curve and the horizontal axis within the T2 value range corresponding to the characteristic pore size interval for the NMR T2 spectrum curve. This area represents the relative pore volume of the soil sample within this characteristic pore size interval. The method for calculating the signal amplitude integral is numerical integration. Discrete data points of the NMR T2 spectrum are exported from the NMR analyzer; each data point contains a T2 value and its corresponding signal amplitude. For the soil sample's NMR T2 spectrum, for each defined characteristic pore size interval, all data points whose T2 values ​​fall within that interval are selected from the discrete data points. The selected data points are then sorted in ascending order of their T2 values. The signal amplitude integral for this characteristic pore size interval is calculated by summing and averaging the signal amplitudes of two adjacent data points after sorting, multiplying this sum by the difference in T2 values ​​between the two data points, and finally summing all such multiplications. The signal amplitude integral is equal to the sum of all adjacent data point pairs within the characteristic aperture interval. The contribution of each data point pair is half the sum of the signal amplitudes of the preceding and following data points, multiplied by the difference between the T2 value of the following data point and the T2 value of the preceding data point. This method is used to calculate the signal amplitude integral in each characteristic aperture interval for both the soil sample and each disturbed soil sample with a preset disturbance level.

[0075] For each characteristic pore size interval, the rate of change of the integral signal amplitude of the soil sample relative to the soil sample after disturbance is calculated. The rate of change of the integral signal amplitude is an indicator used to quantify the relative change in pore volume within the characteristic pore size interval before and after disturbance. The method for calculating the rate of change of the integral signal amplitude is as follows: for the same characteristic pore size interval, the integral signal amplitude value of the soil sample in that interval is taken as the baseline value, denoted as A. The integral signal amplitude value of a soil sample with a specific preset disturbance level in the same characteristic pore size interval is taken, denoted as B. The rate of change of the integral signal amplitude of the soil sample relative to the soil sample in this characteristic pore size interval, C, is then calculated using the formula: C = ((BA) / A) × 100%. This formula yields a percentage value. For each characteristic pore size interval, the rate of change of the integral signal amplitude of the soil sample relative to the soil sample with a specific preset disturbance level is calculated using this formula.

[0076] The integral rate of change of signal amplitude is compared across all characteristic aperture intervals, and the characteristic aperture interval with the largest integral rate of change is determined as the dominant damage aperture interval. For each disturbed soil sample with a specific preset disturbance level, after calculating the integral rate of change of signal amplitude across all characteristic aperture intervals, a set of rate of change values ​​is obtained. Comparing the integral rate of change of signal amplitude across all characteristic aperture intervals means finding the value with the largest absolute value in this set of rate of change values. The characteristic aperture interval with the largest integral rate of change of signal amplitude is the characteristic aperture interval corresponding to the rate of change value with the largest absolute value. For example, for a soil sample disturbed to a preset disturbance level C, the calculated rate of change is 5% in characteristic aperture interval one, -10% in characteristic aperture interval two, 20% in characteristic aperture interval three, and -5% in characteristic aperture interval four. Comparing the absolute values ​​of these rates of change, the absolute value of 5% is 5, the absolute value of -10% is 10, the absolute value of 20% is 20, and the absolute value of -5% is 5. The largest absolute value is 20, corresponding to characteristic pore size interval three. Therefore, the dominant damage pore size interval of this disturbed soil sample is determined as characteristic pore size interval three. For each disturbed soil sample with a different preset disturbance degree, the above comparison and determination process is performed independently, thereby determining a dominant damage pore size interval for each disturbed soil sample.

[0077] To implement step S4 of the method for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, it is necessary to obtain macroscopic mechanical indices and construct a macroscopic state set from disturbed soil samples with different degrees of disturbance. Disturbed soil samples with different preset degrees of disturbance are selected. These samples are those obtained after undergoing simulated wet-dry cycles with different preset numbers of cycles in step S2. The selection method is as follows: from all soil samples prepared and disturbed in step S2, several soil samples that can represent a complete disturbance gradient range are selected based on their identified preset degrees of disturbance. For example, if four preset degrees of disturbance correspond to 1, 3, 5, and 10 wet-dry cycles respectively, at least one parallel sample is selected from each preset degree of disturbance, for a total of at least four disturbed soil samples with different preset degrees of disturbance for subsequent macroscopic mechanical tests.

[0078] For each selected disturbed soil sample, unconfined compressive strength test, compression test, and permeability test were performed sequentially. The specific procedure for the unconfined compressive strength test was as follows: the statically cured ring sample was pushed out of the ring sampler, and both ends of the sample were trimmed with a trimming knife to ensure a height-to-diameter ratio of 2:1. The trimmed cylindrical soil sample was placed on the lower pressure plate of the unconfined compressor. The displacement and force sensors of the unconfined compressor were adjusted to zero. Axial pressure was applied to the soil sample at a constant axial strain rate of 1% to 2% per minute. During loading, the unconfined compressor automatically recorded the axial pressure and axial strain data until a clear failure surface appeared or the axial stress peaked and then stabilized. Loading was then stopped.

[0079] The specific procedure for performing a compression test is as follows: A consolidation ring containing a disturbed soil sample is placed in the pressure chamber of the consolidation apparatus. Permeable stones and filter paper are placed sequentially at the top and bottom of the soil sample. A displacement measuring device is installed. A first-level vertical pressure, for example 12.5 kPa, is applied to the soil sample using a lever or pneumatic system. Under each level of vertical pressure, the change in soil sample height over time is recorded. When the change in compression per unit time is less than a specific threshold, the compression at that pressure level is considered to have reached stability. The specific threshold is set based on observations of the change in compression over time under each pressure level in previous tests. When the compression curve enters a clearly flattened phase, a small change much smaller than the typical compression rate of that stage is selected as the judgment criterion. This value must ensure that it can effectively identify a state where compression has tended to stabilize, while avoiding unnecessary excessive waiting time; for example, a compression rate of less than 0.005 mm per hour can be used as an empirical value. After stabilization is achieved, the final compression at that pressure level is recorded. Then apply the next level of vertical pressure, which is twice the pressure of the previous level, for example, applying 25 kPa, 50 kPa, 100 kPa, and 200 kPa in sequence. Repeat the above pressurization and stabilization observation process until the final predetermined vertical pressure is applied.

[0080] The specific procedure for conducting a permeability test depends on the type of permeability testing instrument. When using a variable head permeameter, a permeameter ring containing a disturbed soil sample is installed on the permeameter. Deaerated water is injected into the permeameter to fully saturate the soil sample. An initial head difference is set, for example, 50 cm. The valve is opened, and the process of the head difference decreasing over time is recorded. A stopwatch is used to record the time it takes for the head difference to decrease from the initial value to another predetermined value. This test is repeated several times. When using a constant head permeameter, the inlet water level is kept constant, and the amount of water flowing out at the outlet within a fixed time period is collected using a graduated cylinder and a stopwatch. This measurement is repeated multiple times.

[0081] Unconfined compressive strength is obtained from unconfined compressive strength tests as a strength index. The unconfined compressive strength value is the maximum pressure per unit area that a soil sample withstands when it fails under unconfined compressive conditions. It is obtained by finding the maximum axial stress value during the entire loading process from the axial pressure and axial strain data recorded by the unconfined compression tester. This maximum axial stress value is the unconfined compressive strength value, and the unit is usually kilopascal (kPa).

[0082] The compressibility coefficient is obtained from compression tests as a compression index. The compressibility coefficient is a parameter characterizing the compressibility of soil. The method for obtaining it involves selecting a pressure range within the actual stress variation range of the engineering project, based on the relationship curve between void ratio and vertical pressure obtained from compression tests. In this case, a pressure range is selected where the vertical pressure increases from 100 kPa to 200 kPa. The compressibility coefficient within this pressure range is calculated as follows: the compressibility coefficient equals the void ratio at the beginning of the pressure range minus the void ratio at the end of the pressure range, divided by the pressure value at the end of the pressure range minus the pressure value at the beginning of the pressure range. The calculated compressibility coefficient is expressed in kPa.

[0083] The permeability coefficient is obtained as a permeability index from permeability tests. The permeability coefficient is a parameter characterizing the water permeability of soil. It is obtained by calculating based on data recorded from the permeability tests. For variable head tests, the permeability coefficient is calculated using the formula: k = (a × H × ln(h1 / h2)) / (As × Δt); where k is the permeability coefficient, a is the cross-sectional area of ​​the permeameter tube, H is the soil sample height, h1 is the initial head difference, h2 is the final head difference, ln is the natural logarithm, As is the cross-sectional area of ​​the soil sample, and Δt is the time taken for the head difference to change from h1 to h2. Substituting the time and head difference data recorded for each test into the formula yields multiple calculated permeability coefficient values, and the arithmetic mean of these values ​​is taken as the permeability coefficient of the soil sample. For constant head tests, the permeability coefficient is equal to the volume of water flowing through the soil sample per unit time multiplied by the soil sample height, then divided by the cross-sectional area of ​​the soil sample multiplied by the head difference multiplied by the unit time. The average value of multiple measurements is taken. The unit of permeability coefficient is usually centimeters per second.

[0084] The unconfined compressive strength, compression coefficient, and permeability coefficient of the same disturbed soil sample are stored as a set of correlated data, forming the macroscopic state set of the soil sample. The specific implementation involves creating a data table. Each row in this table represents a disturbed soil sample. Each row contains multiple data fields, including a soil sample number field, an unconfined compressive strength value field, a compression coefficient field, and a permeability coefficient field. The soil sample number field records the unique identifier of the soil sample. The unconfined compressive strength, compression coefficient, and permeability coefficient obtained from the above tests and calculations for the disturbed soil sample are respectively filled into the corresponding data fields. These three values ​​collectively describe the macroscopic mechanical state of the soil sample in the three dimensions of strength, compressibility, and permeability; their set constitutes the macroscopic state set of the soil sample. For example, for a disturbed soil sample with sample number B-3, its unconfined compressive strength is 45.6 kPa, its compression coefficient is 0.35 kPa, and its permeability coefficient is 5.2 × 10⁻⁶. -6The values ​​in centimeters per second are then stored as a set of data in the row corresponding to soil sample number B-3 in the data table, thus forming the macroscopic state set of soil sample number B-3. For each selected soil sample with a different preset disturbance degree, the above-mentioned test, index acquisition, and data storage operations are performed to obtain multiple macroscopic state sets corresponding to all selected soil samples.

[0085] To implement step S5 of the method for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, it is necessary to classify the macroscopic state categories representing different stages of mechanical property deterioration based on the distribution pattern of the macroscopic state sets of all soil samples. The unconfined compressive strength, compression coefficient, and permeability coefficient values ​​in the macroscopic state sets of all soil samples are standardized to form a standardized index dataset. The standardization method eliminates the differences in dimensions and orders of magnitude among different macroscopic mechanical indices. Specifically, for each macroscopic mechanical index, the arithmetic mean and standard deviation of the original values ​​of all soil samples under that index are calculated. The arithmetic mean is equal to the sum of the original values ​​of all soil samples for that index divided by the total number of soil samples. The standard deviation is equal to the original value of each soil sample for that index minus the arithmetic mean, the square of the result, the sum of all squares, divided by the total number of soil samples minus one, and finally the square root of the result. For each macroscopic mechanical index of each soil sample, its standardized value is equal to the original value of that soil sample under that index minus the arithmetic mean of all soil samples under that index, and then divided by the standard deviation of all soil samples under that index. Through this calculation, the standardized values ​​of each macroscopic mechanical index will form a new data sequence with a mean of 0 and a standard deviation of 1. The three standardized values ​​of each soil sample—the standardized value of unconfined compressive strength, the standardized value of compressibility coefficient, and the standardized value of permeability coefficient—are then sequentially combined into a three-dimensional vector. The collection of these three-dimensional vectors from all soil samples constitutes the standardized index dataset.

[0086] Calculate the Euclidean distance between the standardized index datasets of any two soil samples to obtain a distance matrix characterizing the similarity of the macroscopic states between the soil samples. Euclidean distance quantifies the degree of difference between the macroscopic states of any two soil samples. For a standardized index dataset containing N soil samples, calculate the Euclidean distance between the i-th soil sample and the j-th soil sample. Specifically, extract the standardized index dataset vector of the i-th soil sample, which contains three values, denoted as Xi1, Xi2, and Xi3. Extract the standardized index dataset vector of the j-th soil sample, denoted as Xj1, Xj2, and Xj3. Calculate the Euclidean distance Dij between these two vectors. Euclidean distance is a current technology, and the calculation process will not be elaborated further. The smaller the value of Dij, the more similar the macroscopic states of the i-th and j-th soil samples are. Repeat the above calculation for each pair of soil samples in the standardized index dataset. Arrange these distance values ​​into an N x N square matrix, where the element in the i-th row and j-th column is Dij. This square matrix is ​​the distance matrix.

[0087] Based on the distance matrix, cluster analysis is used to aggregate all soil samples into several groups with similar macroscopic conditions. Cluster analysis is a multivariate statistical analysis method that groups data objects to achieve high similarity within groups and low similarity between groups. The dissimilarity between objects is quantitatively described by the Euclidean distance values ​​in the distance matrix. The average between-group connectivity method in hierarchical clustering is used for aggregation. The operation steps are as follows: During initialization, each soil sample is treated as an independent initial class. The minimum distance value between all current classes is found in the distance matrix. Assuming that the two classes with the minimum current distance are class A1 and class B1, the minimum distance between them is denoted as Dmin. It is then determined whether Dmin is less than or equal to a preset clustering stopping threshold. The preset clustering stopping threshold is a distance critical value pre-set based on practical engineering experience and the requirements for classification precision. The preset clustering stopping threshold can be set, for example, to 70% of the average of all initial Euclidean distances. If Dmin is less than or equal to the preset clustering stopping threshold, then class A1 and class B1 are merged into a new class C1. The distance between class C1 and other classes D1 needs to be recalculated using the inter-group average connection method. That is, the distance between class C1 and class D1 is equal to the average distance between all soil samples in class A1 and all soil samples in class D1, plus the average distance between all soil samples in class B1 and all soil samples in class D1, then divided by 2. The distance matrix is ​​updated according to this rule, deleting rows and columns representing classes A1 and B1, adding rows and columns representing class C1, and filling in the recalculated distance values. After updating the matrix, the search continues for the current minimum distance. If Dmin is greater than the preset clustering stopping threshold, the aggregation process stops. At this point, based on the number of classes remaining when aggregation stops, several groups with similar macroscopic states are obtained.

[0088] Each cluster is defined as a macroscopic state category, and each macroscopic state category represents a stage of mechanical property deterioration. The definition process involves assigning a unique category identifier to each cluster obtained after cluster analysis, such as Category I. The mechanical characteristics commonly exhibited by the set of macroscopic states of all soil samples within this cluster define the engineering connotation of that macroscopic state category. For example, if all soil samples in Category I generally have high normalized values ​​for unconfined compressive strength, low normalized values ​​for compression coefficient, and low normalized values ​​for permeability coefficient, then this category represents a stage of slight mechanical property deterioration. If all soil samples in Category II have very low normalized values ​​for unconfined compressive strength, high normalized values ​​for compression coefficient, and high normalized values ​​for permeability coefficient, then this represents a stage of severe deterioration. In this way, the original discrete set of macroscopic states of soil samples is summarized into a finite set of macroscopic state categories with clearly defined mechanical property connotations.

[0089] To implement step S6 of the method for assessing the mechanical property deterioration of disturbed soft soil based on porosity index difference, it is necessary to establish a characterization relationship between the dominant damage pore size interval and the macroscopic state category, and to determine the mechanical property deterioration level of the soil sample to be assessed based on this characterization relationship. The dominant damage pore size intervals for all soil samples under each macroscopic state category are statistically analyzed. The macroscopic state category classification results obtained in step S5 are integrated with the dominant damage pore size intervals determined for each soil sample in step S3. A list containing three columns of data is prepared. The first column is the soil sample number. The second column is the macroscopic state category to which the soil sample was finally assigned in step S5. The third column is the dominant damage pore size interval determined for the soil sample in step S3. Based on this list, for each macroscopic state category, all rows in the list whose macroscopic state category column equals the category name are selected. The dominant damage pore size interval columns corresponding to these rows are checked, and the frequency of each dominant damage pore size interval is counted. The method for counting frequency is to iterate through all soil samples belonging to a specific macroscopic state category, record the dominant damage pore size interval for each soil sample, and then calculate the frequency of the same dominant damage pore size interval. For example, if macroscopic state category I contains 5 soil samples, and the dominant damage pore size interval for 3 soil samples is characteristic pore size interval two, and the dominant damage pore size interval for 2 soil samples is characteristic pore size interval one, then characteristic pore size interval two appears 3 times, and characteristic pore size interval one appears 2 times.

[0090] A mapping table is created by establishing a correspondence between each macroscopic state category and the most frequently occurring dominant damage aperture interval. The method for establishing this correspondence is as follows: for each macroscopic state category, find the highest frequency from a statistically obtained set of occurrences. The dominant damage aperture interval corresponding to this highest frequency is determined as the dominant damage aperture interval corresponding to that macroscopic state category. For example, for macroscopic state category I, if the frequency of characteristic aperture interval two (3) is greater than the frequency of characteristic aperture interval one (2), then macroscopic state category I is associated with characteristic aperture interval two of the dominant damage aperture interval. All macroscopic state categories are processed using the same logic. The mapping table is created by creating a new table with two columns. The first column is the macroscopic state category, and the second column is the corresponding dominant damage aperture interval. Each established correspondence is entered as a row in this mapping table. For example, one row of the mapping table records macroscopic state category I and characteristic aperture interval two of the dominant damage aperture interval, and another row records macroscopic state category II and characteristic aperture interval three of the dominant damage aperture interval. This mapping table forms a lookup relationship from microscopic damage features to macroscopic state categories.

[0091] For the soil sample to be evaluated, the dominant damage pore size range is obtained. The soil sample to be evaluated refers to a new soil sample from the engineering site to be evaluated whose mechanical property degradation level is unknown. The method for obtaining the dominant damage pore size range of the soil sample to be evaluated is to repeat the operation procedure of step S3. The nuclear magnetic resonance T2 spectrum of the soil sample to be evaluated is obtained. The soil sample to be evaluated is tested using a low-field nuclear magnetic resonance analyzer under the same test conditions and parameter settings as in step S3. Test parameters, for example, are set to a dominant frequency of 12 MHz, an echo time of 0.2 ms, and a number of echoes of 2048. Based on the nuclear magnetic resonance T2 spectrum obtained from the test, the characteristic pore size range definition standard is used, which is exactly the same as that in step S3. The criteria for defining characteristic pore size intervals are predefined and fixed before establishing the mapping table. For example, characteristic pore size interval one corresponds to a T2 value of 0.01 ms to 1 ms, characteristic pore size interval two corresponds to 1 ms to 10 ms, characteristic pore size interval three corresponds to 10 ms to 100 ms, and characteristic pore size interval four corresponds to 100 ms to 1000 ms. Then, the signal amplitude integral of the soil sample to be judged is calculated in each characteristic pore size interval, and the rate of change of the signal amplitude integral of each interval relative to a reference state is further calculated. This reference state is selected as the original soil sample state at the same site without engineering disturbance. By comparing the rate of change of the signal amplitude integral of all characteristic pore size intervals, the characteristic pore size interval with the largest absolute value of the rate of change is determined as the dominant damage pore size interval of the soil sample to be judged.

[0092] The dominant damage pore size range of the soil sample to be judged is compared with the mapping table. This comparison is a query-matching process. The dominant damage pore size range of the soil sample to be judged is read. In the mapping table established in step S6, the column for dominant damage pore size range is scanned to find records that are exactly the same as the dominant damage pore size range of the soil sample to be judged. If the dominant damage pore size range of the soil sample to be judged matches the dominant damage pore size range corresponding to a certain macroscopic state category in the mapping table, the mechanical property degradation level of the soil sample to be judged is determined to be the degradation stage represented by that macroscopic state category. For example, scanning the mapping table reveals that the characteristic pore size range three of the dominant damage pore size range appears in the row associated with macroscopic state category II. Since the characteristic pore size range three of the dominant damage pore size range of the soil sample to be judged matches the dominant damage pore size range corresponding to macroscopic state category II in the mapping table, the mechanical property degradation level of the soil sample to be judged is determined to be macroscopic state category II. The degradation stage represented by macroscopic state category II has been defined in step S5, for example, representing a moderate mechanical property degradation stage. If the dominant damage pore size range of the soil sample to be judged does not have a completely consistent record in the mapping table, it is judged as an unknown category. Finally, the judgment result of the soil sample to be judged is output, that is, its macroscopic state category or the corresponding deterioration stage description.

[0093] Example 2: Figure 2 A schematic diagram of the structure of the permeability index difference-based mechanical property deterioration assessment system for disturbed soft soil is provided. The system includes the following modules:

[0094] The soil sample preparation module is used to acquire disturbed soft soil and prepare soil samples;

[0095] The dry-wet disturbance module is used to simulate dry-wet cycle disturbance of soil samples to obtain disturbed soil samples;

[0096] The pore size analysis module is used to divide the pores of soil samples and disturbed soil samples into several characteristic pore size intervals based on nuclear magnetic resonance T2 spectra, calculate the rate of change of each characteristic pore size interval before and after disturbance, and determine the characteristic pore size interval with the largest rate of change as the dominant damage pore size interval.

[0097] The macro-parameter testing module is used to conduct unconfined compressive strength tests, compression tests, and permeability tests on several disturbed soil samples with different degrees of disturbance, and to characterize the strength index, compression index, and permeability index of each soil sample into a set of macro-states.

[0098] The state classification module is used to classify several macroscopic state categories that characterize the deterioration stages of different mechanical properties based on the distribution pattern of the macroscopic state set of all soil samples.

[0099] The degradation characterization module is used to establish the characterization relationship between the dominant damage pore size range and the macroscopic state category, and to determine the degradation level of the mechanical properties of the soil sample to be judged based on the characterization relationship.

[0100] All calculations involved in the embodiments are dimensionless numerical calculations, and the preset parameters and thresholds in the calculations are set by those skilled in the art according to the actual situation.

[0101] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0102] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0103] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0104] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and in actual implementation, there may be other division methods. For example, several modules or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection between apparatuses or modules may be electrical, mechanical, or other forms.

[0105] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0106] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for assessing the deterioration of mechanical properties of disturbed soft soil based on the difference in porosity index, characterized in that, Includes the following steps: S1. Obtain disturbed soft soil and prepare soil samples; S2. Perform dry-wet cycle simulation disturbance on the soil sample to obtain the disturbed soil sample; S3. Based on the nuclear magnetic resonance T2 spectrum, the pores of the soil sample and the disturbed soil sample are divided into several characteristic pore size intervals, and the change rate of each characteristic pore size interval before and after the disturbance is calculated. The characteristic pore size interval with the largest change rate is determined as the dominant damage pore size interval. S4. From several disturbed soil samples with different degrees of disturbance, conduct unconfined compressive strength test, compression test and permeability test respectively, and characterize the strength index, compression index and permeability index of each soil sample as a set of macroscopic states. S5. Based on the distribution pattern of the macroscopic state set of all soil samples, divide them into several macroscopic state categories that characterize the deterioration stages of different mechanical properties. S6. Establish the characterization relationship between the dominant damage pore size range and the macroscopic state category, and determine the mechanical property deterioration level of the soil sample to be judged based on the characterization relationship.

2. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 1, characterized in that, Acquiring disturbed soft soil and preparing soil samples includes: Multiple sampling points were selected based on the inferred distribution of disturbance intensity gradient within the site to be evaluated. Disturbed soft soil that retains its original structure was obtained from multiple sampling points; The disturbed soft soil that retains its original structure was prepared into soil samples for nuclear magnetic resonance testing and macroscopic mechanical experiments.

3. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 2, characterized in that, Multiple sampling points are selected based on the inferred disturbance intensity gradient distribution within the site to be evaluated, including: sampling points are arranged in order from near to far in the direction perpendicular to the inferred disturbance source.

4. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 1, characterized in that, The soil samples were subjected to a wet-dry cycle to simulate disturbance, and the disturbed soil samples were obtained, including: Soil samples used for nuclear magnetic resonance testing and macroscopic mechanical experiments were placed in a controlled environment chamber; The soil sample was dehydrated according to the preset drying temperature and time. The soil sample was then saturated according to the preset immersion method and time. The dehydration and saturation processes are repeated a preset number of times to obtain a disturbed soil sample with a preset degree of disturbance.

5. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 4, characterized in that, The dehydration treatment of soil samples according to the preset drying temperature and time includes: drying the soil samples under constant temperature conditions until their quality changes tend to stabilize; the saturation treatment of soil samples according to the preset soaking method and time includes: using the vacuum saturation method to make the soil samples fully saturated.

6. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 1, characterized in that, Based on nuclear magnetic resonance T2 spectra, the pore size of the soil sample and the disturbed soil sample were divided into several characteristic pore size intervals. The rate of change of each characteristic pore size interval before and after disturbance was calculated, and the characteristic pore size interval with the largest rate of change was determined as the dominant damage pore size interval, including: Obtain the nuclear magnetic resonance T2 spectra of soil samples and soil samples after disturbance with a preset degree of disturbance; Based on the correspondence between nuclear magnetic resonance T2 values ​​and pore size, several characteristic pore size intervals corresponding to different pore size ranges are defined on the T2 spectrum. Calculate the signal amplitude integrals of the soil sample and the disturbed soil sample in each characteristic aperture range; For each characteristic aperture range, calculate the integral rate of change of the signal amplitude of the soil sample relative to the soil sample after disturbance; By comparing the integral rate of change of signal amplitude across all characteristic aperture ranges, the characteristic aperture range with the largest integral rate of change of signal amplitude is determined as the dominant damage aperture range.

7. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 1, characterized in that, Unconfined compressive strength tests, compression tests, and permeability tests were conducted on several disturbed soil samples with different degrees of disturbance. The strength, compression, and permeability indices of each soil sample were collectively characterized as a set of macroscopic states, including: Soil samples with different preset disturbance levels were selected after disturbance; For each selected disturbed soil sample, unconfined compressive strength test, compression test and permeability test were performed sequentially; Unconfined compressive strength is obtained from unconfined compressive strength test as strength index, compression coefficient is obtained from compression test as compression index, and permeability coefficient is obtained from permeability test as permeability index. The unconfined compressive strength, compression coefficient, and permeability coefficient of the same disturbed soil sample are stored together as a set of correlated data to form the macroscopic state set of the soil sample.

8. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 1, characterized in that, Based on the distribution pattern of the macroscopic state set of all soil samples, several macroscopic state categories characterizing different stages of mechanical property deterioration are identified, including: The unconfined compressive strength, compression coefficient, and permeability coefficient of all soil samples in the macroscopic state set are standardized to form a standardized index dataset. Calculate the Euclidean distance between the standardized index datasets of any two soil samples to obtain the distance matrix characterizing the macroscopic similarity between soil samples; Based on the distance matrix, cluster analysis was used to group all soil samples into several groups with similar macroscopic states. Each aggregate group is defined as a macroscopic state category, and each macroscopic state category represents a stage of mechanical property deterioration.

9. The method for assessing the deterioration of mechanical properties of disturbed soft soil based on porosity index difference according to claim 1, characterized in that, Establish a characterization relationship between the dominant damage pore size range and the macroscopic state category, and determine the mechanical property degradation level of the soil sample to be judged based on the characterization relationship, including: The dominant damage pore size range of all soil samples under each macroscopic condition category is statistically analyzed, and a mapping table is formed by establishing a correspondence between each macroscopic condition category and the dominant damage pore size range that occurs most frequently. For the soil sample to be judged, obtain the dominant damage pore size range of the soil sample to be judged; The dominant damage pore size range of the soil sample to be judged is compared with the mapping table. If the dominant damage pore size range of the soil sample to be judged is consistent with the dominant damage pore size range corresponding to a certain macroscopic state category in the mapping table, then the mechanical property deterioration level of the soil sample to be judged is determined to be the deterioration stage represented by that macroscopic state category.

10. A system for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index, used to implement the method for assessing the deterioration of the mechanical properties of disturbed soft soil based on the difference in porosity index as described in any one of claims 1-9, characterized in that, Includes the following modules: The soil sample preparation module is used to acquire disturbed soft soil and prepare soil samples; The wet-dry disturbance module is used to simulate wet-dry cycles to disturb soil samples and obtain disturbed soil samples. The pore size analysis module is used to divide the pores of soil samples and disturbed soil samples into several characteristic pore size intervals based on nuclear magnetic resonance T2 spectra, calculate the rate of change of each characteristic pore size interval before and after disturbance, and determine the characteristic pore size interval with the largest rate of change as the dominant damage pore size interval. The macro-parameter testing module is used to conduct unconfined compressive strength tests, compression tests, and permeability tests on several disturbed soil samples with different degrees of disturbance, and to characterize the strength index, compression index, and permeability index of each soil sample into a set of macro-states. The state classification module is used to classify several macroscopic state categories that characterize the deterioration stages of different mechanical properties based on the distribution pattern of the macroscopic state set of all soil samples. The degradation characterization module is used to establish the characterization relationship between the dominant damage pore size range and the macroscopic state category, and to determine the degradation level of the mechanical properties of the soil sample to be judged based on the characterization relationship.

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