Unsaturated soil foundation strength deterioration evaluation method and system considering water immersion effect

Abstract

The invention discloses an unsaturated soil foundation strength deterioration evaluation method and system considering a water immersion effect, and relates to the technical field of geotechnical engineering and electric power infrastructure safety, and the method comprises the following steps: obtaining water content state monitoring data of a foundation under a water immersion condition, determining a wetting front position based on the monitoring data, and extracting a propagation characteristic quantity of the wetting front position; based on the propagation characteristic quantity and the change rate of the water-containing state, matrix suction is corrected, and evolution suction is obtained; comparing the water content state with a preset structure starting criterion, determining an over-threshold water content increment, and accumulating to obtain a structure damage state quantity; based on the structural damage state quantity, an attenuation function is constructed to carry out attenuation modulation on the evolution suction, and equivalent shear strength is obtained; and outputting a foundation strength deterioration evaluation result based on the equivalent shear strength. According to the invention, a closed loop from data monitoring to safety early warning is realized, and a dynamic and accurate evaluation means is provided for foundation safety in an operation period.

Description

A method and system for assessing the strength degradation of unsaturated soil foundations considering water immersion Technical Field

[0001] This invention relates to the fields of geotechnical engineering and power infrastructure safety technology, and more specifically, to a method and system for assessing the strength degradation of unsaturated soil foundations that takes into account the effects of water immersion. Background Technology

[0002] As the scale of power grid construction expands, facilities such as substations and transmission towers rely on the foundation for long-term service. During operation, rainfall infiltration or groundwater fluctuations can cause the matric suction of unsaturated foundations to dissipate, leading to reduced bearing capacity and decreased stability, thus threatening power grid safety.

[0003] For example, the invention patent announcement CN119043951B discloses a method and system for predicting the shear strength of unsaturated soil, which includes the following steps: obtaining multiple hydraulic paths for any point on the soil water-holding curve; obtaining multiple sets of moisture absorption path curve integrals and desiccation path curve integrals for that point in different hydraulic histories based on the multiple hydraulic paths, wherein the hydraulic path includes moisture absorption path and desiccation path, and the hydraulic history is the repeated change process of moisture absorption and desiccation at that point from the initial state to the study state; inputting the multiple sets of moisture absorption path curve integrals and desiccation path curve integrals for any point on the soil water-holding curve in different hydraulic histories, as well as the saturated shear strength parameters of the test soil, into the modified shear strength formula to obtain the corresponding shear strength, thus completing the prediction of the shear strength of unsaturated soil. This invention can significantly improve the accuracy of unsaturated soil shear strength calculation and is conducive to the promotion and application of unsaturated soil strength calculation in practical engineering.

[0004] The aforementioned disclosed technical solutions have at least the following technical problems: lack of real-time response to dynamic immersion processes. Existing technologies focus on static prediction based on water-holding curves and hydraulic history integrals measured in laboratories, making it difficult to directly integrate real-time water content monitoring data from substations or transmission towers, and failing to characterize the instantaneous impact of the dynamic movement of the wetting front on foundation strength under sudden immersion conditions such as rainstorm infiltration.

[0005] The deviation in hydraulic response under non-equilibrium conditions is ignored. Existing methods are mostly based on hydraulic hysteresis models under equilibrium conditions, without considering the time lag effect of pore water pressure response relative to changes in aquifer state when the infiltration rate is fast in actual engineering. This leads to deviations in the strength assessment results during the rapid immersion stage.

[0006] The cumulative damage and degradation under immersion is not quantified. Although existing technologies consider the dependence of hydraulic paths (hygroscopic absorption and dehydration), they mainly focus on the correction of stress state variables and fail to effectively identify the irreversible physical damage to the cemented structure of foundation soil caused by long-term immersion or repeated wet-dry cycles. It is difficult to characterize the path-dependent deterioration law of foundation strength as it progresses with the immersion process.

[0007] To address the above problems, this invention proposes a solution. Summary of the Invention

[0008] To overcome the aforementioned deficiencies of the prior art, embodiments of the present invention provide a method and system for assessing the strength deterioration of unsaturated soil foundations that takes into account the effects of water immersion. This enables real-time and accurate assessment of foundation strength deterioration under water immersion conditions, while also adapting to the safety assessment requirements of power grid facilities, thus providing technical support for the safety control of power grid infrastructure foundations.

[0009] To achieve the above objectives, the present invention provides the following technical solution: a method for assessing the strength deterioration of unsaturated soil foundations considering the effects of immersion, comprising the following steps: acquiring monitoring data of the water content state of the foundation under immersion conditions; determining the location of the wetting front and extracting its propagation characteristic quantity based on the monitoring data; correcting the matrix suction based on the propagation characteristic quantity and the rate of change of the water content state to obtain the evolving suction; comparing the water content state with a preset structural initiation criterion to determine the excess water content increment and accumulating it to obtain the structural damage state quantity; constructing an attenuation function based on the structural damage state quantity to attenuate and modulate the evolving suction to obtain the equivalent shear strength; and outputting the foundation strength deterioration assessment result based on the equivalent shear strength.

[0010] In a preferred embodiment, determining the location of the wetting front based on the monitoring data specifically includes: acquiring time-series data of the water-bearing state from multiple monitoring points that are gradient-distributed along the foundation depth direction; establishing a spatiotemporal correlation matrix of the evolution of the water-bearing state with depth and time based on the spatial mapping of the time-series data; performing differential operations on the spatiotemporal correlation matrix to extract the partial derivative field of the water-bearing state with respect to time; and determining the location of the wetting front by identifying the set of abrupt peaks in the partial derivative field.

[0011] In a preferred embodiment, the extraction of its propagation characteristics includes: calculating the infiltration rate of the wetting front in the vertical depth direction based on the time variation sequence of the wetting front position; extracting the value corresponding to the position of the wetting front in the partial derivative field as the extreme value of the rate of change of the water-bearing state; calculating the water-bearing state gradient value of the wetting front according to the numerical gradient before and after the real-time position of the wetting front; and determining the infiltration rate, the extreme value of the rate of change, and the water-bearing state gradient value as the propagation characteristics.

[0012] In a preferred embodiment, the modified matrix suction includes: determining a matrix suction reference value corresponding to the current real-time water content based on a pre-determined soil-water characteristic curve; estimating the lag time of the pore water pressure response relative to the change in water content based on the infiltration rate; and using the lag time to perform time delay correction on the matrix suction reference value to obtain time-delay compensated matrix suction.

[0013] In a preferred embodiment, the modified matrix suction further includes: determining the influence weight of the wetting front shape on the matrix suction distribution based on the water content gradient value; using the influence weight to correct the amplitude of the matrix suction after time delay compensation; and combining the extreme value of the rate of change to smooth the modified matrix suction and output the evolutionary suction.

[0014] In a preferred embodiment, obtaining the structural damage state quantity includes: comparing the water content state with a preset structural initiation criterion to identify the damage evolution interval where the water content state exceeds a critical threshold; extracting the difference between the real-time water content state and the initial state within the damage evolution interval, and determining it as the excess water content increment; and integrating and accumulating the excess water content increment over time to obtain the structural damage state quantity.

[0015] In a preferred embodiment, constructing the attenuation function based on the structural damage state quantity includes: determining the degree of reduction in the contribution of matrix suction to the foundation soil due to the failure of the skeleton cementation based on the structural damage state quantity; establishing a strength reduction function between the structural damage state quantity and a strength reduction coefficient based on the degree of reduction; and calculating the strength reduction coefficient corresponding to the current cumulative damage using the strength reduction function.

[0016] In a preferred embodiment, the attenuation modulation of the evolving suction to obtain the equivalent shear strength includes: multiplying the strength reduction factor by the evolving suction to obtain an effective suction equivalent value after structural damage correction; combining the effective suction equivalent value with the internal friction angle parameter of the foundation soil to obtain the shear strength component contributed by the suction; and superimposing the shear strength component with the saturated shear strength of the foundation soil to output the equivalent shear strength.

[0017] In a preferred embodiment, the step of outputting the foundation strength deterioration assessment result based on the equivalent shear strength specifically involves: calculating the current safety factor or remaining bearing capacity of the foundation based on the equivalent shear strength, and comparing it with a preset stability threshold; and outputting an assessment conclusion containing a stability level or warning instruction based on the comparison result.

[0018] A system for assessing the strength deterioration of unsaturated soil foundations considering the effects of immersion includes: a frontal sensing module for acquiring monitoring data on the water content of the foundation under immersion conditions, determining the location of the wetting front based on the monitoring data, and extracting its propagation characteristics; a suction evolution module for correcting the matrix suction based on the propagation characteristics and the rate of change of the water content to obtain the evolved suction; a damage coupling module for comparing the water content with a preset structural initiation criterion to determine the excess water content increment and accumulating the structural damage state quantity; constructing an attenuation function based on the structural damage state quantity to attenuate and modulate the evolved suction to obtain the equivalent shear strength; and an assessment output module for outputting the foundation strength deterioration assessment result based on the equivalent shear strength.

[0019] Traditional methods directly substitute the measured water content into the equilibrium soil-water characteristic curve (SWCC) to obtain suction, ignoring the fact that unsaturated infiltration of water in the soil is a dynamic and non-equilibrium physical process, leading to a significant deviation of the assessed suction value from the transient reality. This invention dynamically extracts the wetting front propagation characteristic quantity based on water content monitoring data and uses this characteristic quantity to correct the matrix suction. This captures the non-equilibrium transient effects of water migration during immersion, thus calculating an evolutionary suction value that more accurately reflects reality. This solves the problem of inaccurate suction value assessment caused by directly using the equilibrium soil-water characteristic curve in traditional methods. Simultaneously, this invention constructs an attenuation function based on structural damage state quantities to modulate the attenuation of the evolutionary suction, separating and coupling the reversible and irreversible parts of strength degradation. The output equivalent shear strength simultaneously captures the instantaneous strength fluctuations caused by changes in water content and the long-term strength decay caused by the destruction of the cemented structure. Attached Figure Description

[0020] Figure 1 is a flowchart illustrating the strength degradation assessment method for unsaturated soil foundations considering water immersion according to the present invention; Figure 2 is a system structure diagram illustrating the strength degradation assessment method for unsaturated soil foundations considering water immersion according to the present invention; Figure 3 is a schematic diagram illustrating the soil-water characteristic curve fitting according to the present invention; Figure 4 is a schematic diagram illustrating the structural damage accumulation and strength reduction according to the present invention. Detailed Implementation

[0021] 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.

[0022] Example 1, Figure 1 shows the method for assessing the strength deterioration of unsaturated soil foundation considering water immersion according to the present invention, including the following steps: It should be noted that before starting this example, it is necessary to obtain the initial saturated shear strength parameters, initial saturation, and soil-water characteristic curve of the target unsaturated soil foundation. The specific steps are as follows: T1, Obtain undisturbed soil samples of the foundation and conduct shear tests to determine its initial saturated shear strength parameters. Specifically, undisturbed soil samples are vertically drilled using a thin-walled soil sampler next to the target substation foundation or transmission tower foundation. The sampling depth should cover the main load-bearing layer of the foundation, usually 1.5 times the foundation width below the base. The obtained soil samples are immediately sealed with plastic wrap and paraffin wax, placed in a constant temperature and humidity chamber, and transported to the laboratory to prevent changes in moisture content.

[0023] The initial saturated shear strength parameters were determined using the consolidated undrained triaxial shear test as specified in the "Standard for Geotechnical Testing Methods" (GB / T50123-2019). Undisturbed soil samples were prepared into standard triaxial specimens (typically 39.1 mm in diameter and 80 mm in height) and subjected to saturation treatment in a pressure chamber (usually using the reverse pressure saturation method to ensure the pore pressure coefficient B is greater than 0.95). Consolidation is then performed, and the confining pressure is preferably set at least three levels (e.g., 50 kPa, 100 kPa, and 150 kPa) based on the actual stress state of the foundation soil. After consolidation, undrained shearing is performed at a rate of 0.08 mm / min until the specimen fails. The deviatoric stress at failure is recorded. ,in For axial stress, according to the Mohr-Coulomb strength theory, the limit stress circles under different confining pressures are drawn; the intercept and slope of the envelope line represent the saturated effective cohesion of the soil. and saturated effective internal friction angle .

[0024] T2. Physical property tests are performed on the undisturbed soil sample to obtain its natural moisture content and dry density, and the initial saturation of the foundation soil is determined accordingly. Specifically, a portion is cut from the sealed soil sample, and its natural moisture content is determined using the drying method specified in the "Standard for Geotechnical Testing Methods" (GB / T50123-2019). The natural density of undisturbed soil samples was determined using the ring cutter method. Dry density of soil sample The specific calculation formula is as follows:

[0025] Based on the three-phase proportional conversion relationship, the initial saturation The calculation formula is as follows:

[0026]

[0027] Where e is the void ratio of the soil sample. This is the specific gravity of the soil particles (measured using the hydrometer bottle method). This is the density of water.

[0028] T3. Perform a pressure plate test on the undisturbed soil sample using a hygroscopic path to obtain the moisture content at equilibrium under different matrix suction levels, and convert it to volume saturation. Specifically: Take another undisturbed soil sample, place it in a vacuum saturation cylinder, evacuate it, and inject degassed water to fully saturate it. Place the saturated soil sample on the clay plate of the pressure plate apparatus, ensuring the air inlet value of the clay plate is higher than the maximum suction level. Apply a small initial suction level (e.g., 5 kPa) to allow the soil sample to reach drainage equilibrium on the clay plate (typically defined as a change in water mass of less than 0.01 g within 24 hours). After achieving the previous level of equilibrium, gradually reduce the applied air pressure to reduce the soil sample suction (i.e., the humidification path). The suction level sequence can be set as follows: 100 kPa, 50 kPa, 30 kPa, 10 kPa, 5 kPa. At each suction level, allow the soil sample to fully equilibrium and record the amount of water discharged from the soil sample (in the hygroscopic path, the soil sample will absorb water, recorded as a negative drainage volume). After equilibrium is reached, the total mass of the soil sample under this suction force is determined by weighing and then converted to the corresponding moisture content. .

[0029] Moisture content at each suction level Convert to volume saturation Specifically:

[0030] in, This refers to the volumetric water content. Porosity.

[0031] Table 1 shows the matrix suction-volume saturation relationship data obtained from a pressure plate test on a typical loess undisturbed soil sample.

[0032] Table 1

[0033] T4. Fit the volume saturation and matrix suction data to obtain the soil-water characteristic curve. Specifically, plot the obtained matrix suction and volume saturation data on a coordinate system and construct a continuous soil-water characteristic curve using a nonlinear fitting method. In this embodiment, the van Genuchten model is preferably used for fitting, and its expression is:

[0034] in, For effective saturation, For matrix suction, For fitting parameters, For maximum saturation, This represents the residual saturation.

[0035] Using nonlinear fitting tools in software such as Origin or MATLAB, the data in Table 1 are substituted into the VG model for fitting, thus obtaining the specific parameters describing the soil-water characteristic curve of the soil sample. Substituting the fitted parameters into the VG model formula yields a continuous soil-water characteristic curve that can be used to query the matrix suction corresponding to any saturation, or the saturation corresponding to any suction, as shown in Figure 3.

[0036] S1, acquire monitoring data of the water content of the foundation under immersion conditions, and based on the monitoring data, determine the location of the wetting front and extract its propagation characteristics; In this embodiment, acquiring monitoring data of the water content of the foundation under immersion conditions, and based on the monitoring data, determining the location of the wetting front and extracting its propagation characteristics specifically involves: S1.1, acquiring time-series data of the water content and establishing a spatiotemporal correlation matrix. m sensors are arranged along the foundation depth direction, with positions at depths of respectively... From the start time up to the current time With a fixed sampling interval Data was collected at n+1 time points, and the acquired water-bearing state time-series data was organized into a spatiotemporal correlation matrix M:

[0037] Here, the row index i of the matrix corresponds to the depth. The time corresponding to column index j Matrix elements Indicates depth ,time The monitored water content. In this embodiment, the water content is specifically measured using volume saturation. .

[0038] S1.2, perform differentiation on the spatiotemporal correlation matrix M to extract the partial derivative field of the water-bearing state with respect to time. This embodiment uses the central difference method for calculation. For points j=1 to n-1 inside the matrix:

[0039] For boundary points (j=0 and j=n), forward or backward difference can be used.

[0040] S1.3, the step of determining the location of the wetting front by identifying the set of abrupt peaks in the partial derivative field specifically involves: for each time step... ,exist In the j-th column of the matrix, find the element with the largest absolute value as the mutation peak. The row index of this peak is... corresponding depth That is, at that moment moist front position By processing all time points, a temporal sequence of the wet front's location is obtained. .

[0041] The time variation sequence based on the location of the moist front described in S1.4 Calculate the infiltration rate of the wetting front in the vertical depth direction. The specific calculation formula is as follows:

[0042] Extracting the partial derivative field The value corresponding to the location of the wetting front is used as the extreme value of the rate of change of the water content. .

[0043] According to the real-time location of the moist front (corresponding depth) Calculate the spatial gradient of water state along the depth direction at the wetting front using the water state values ​​of adjacent monitoring points. :

[0044] S1.5, the infiltration rate, the extreme value of the rate of change, and the water state gradient value are determined as the propagation characteristic quantities, forming a three-dimensional feature vector. .

[0045] S2, based on the propagation characteristic quantity and the rate of change of the water content state, the matrix suction is corrected to obtain the evolving suction; in this embodiment, the step of correcting the matrix suction based on the propagation characteristic quantity and the rate of change of the water content state to obtain the evolving suction specifically involves: S2.1, determining the matrix suction reference value corresponding to the current real-time water content state according to the pre-measured soil-water characteristic curve, specifically: for time... ,depth (Especially for the frontal position) The monitored water content (volume saturation) By querying the SWCC function, the corresponding matrix suction value under equilibrium state is obtained, which is called the matrix suction reference value, denoted as . :

[0046] in, This represents the obtained soil-water characteristic curve function, such as the inverse function of the van Genuchten model.

[0047] S2.2, due to the inertia of the unsaturated seepage process of water in the soil, the change in pore water pressure lags behind the change in water content (volume saturation). This lag time is related to the water transport velocity, i.e., the infiltration rate. Related. The method estimates the lag time of pore water pressure response relative to changes in aquifer state based on the infiltration rate. Specifically:

[0048] in, The time-delay characteristic parameter (unit: m) can be calibrated by fitting the phase difference between the measured pore water pressure response curve and the saturation change curve through an indoor one-dimensional transient infiltration test. It is a very small positive number.

[0049] S2.3, the matrix suction reference value is corrected by time delay using the hysteresis time. Specifically, for the current moment... Use historical moments The equilibrium suction corresponding to the water content state serves as a better estimate of the actual suction at the current moment. The matrix suction after time-delay compensation. The calculation is as follows:

[0050] like If the sampling time point is not specified, numerical methods such as linear interpolation can be used to obtain the water content from the time series data. .

[0051] S2.4, Determine the influence weight of the wetting front shape on the matrix suction distribution based on the water content gradient value. This embodiment presents an exemplary functional relationship:

[0052] in, The gradient influence coefficient is a correction parameter related to soil properties. It controls the sensitivity of the gradient to the suction amplitude and can be calibrated by comparing the deviation between the soil strength test results and the equilibrium theory prediction under different gradient conditions.

[0053] S2.5, the amplitude of the time-delay compensated matrix suction is corrected using the aforementioned influence weights. The corrected matrix suction is then obtained. :

[0054] By combining the extreme values ​​of the rate of change, the corrected matrix suction is smoothed. This embodiment employs an adaptive weighted moving average filtering method. For the current time... suction sequence Its smoothed value, i.e., the final output evolutionary attraction, is... The specific calculation formula is as follows:

[0055]

[0056] Among them, the dynamic smoothing window radius It is a non-negative integer. The radius of the baseline smoothing window (a dimensionless positive integer). This is the rate of change adjustment coefficient, which controls the sensitivity of the smoothing intensity to the rate of change of water content. It can be set according to the signal-to-noise ratio of the data and the desired smoothing effect. This is the floor function.

[0057] It should be noted that, due to the heterogeneity of the pore structure and the dynamic infiltration effect in natural foundations, the wetting front exhibits a non-ideal transition zone with a water-bearing state gradient. The spatial geometry (steepness) of its leading edge reflects the intensity of the local seepage field. This invention, by extracting the water-bearing state gradient value, quantifies the modulation effect of the leading edge shape on the distribution of the matrix suction field, correcting the prediction bias of the traditional equilibrium model in dynamic infiltration assessment.

[0058] S3, compare the water content state with a preset structural initiation criterion to determine the excess water content increment, and accumulate the structural damage state quantity; in this embodiment, comparing the water content state with the preset structural initiation criterion to determine the excess water content increment and accumulate the structural damage state quantity specifically means that the preset structural initiation criterion is a critical volume saturation threshold. The critical volumetric saturation threshold of the soil can be determined through experimental calibration. Specifically, unconfined compressive strength tests can be conducted on undisturbed soil samples at different constant saturation levels. A normalized strength versus saturation curve can be plotted, and the saturation level corresponding to the point where the strength shows a clear inflection point (i.e., the onset of irreversible decline) can be determined as the critical volumetric saturation threshold of the soil. .

[0059] S3.1, for any monitoring point (depth) At time t, the monitored water content (volume saturation) will be recorded. and If a comparison is made, If the soil cementation structure is in a stable or undamaged state, then the soil cementation structure is in a stable state or in an unactivated damage state; if If this occurs, the soil enters a state of damage evolution. By traversing the time series, it can be identified that the water content at this monitoring point exceeds the critical volume saturation threshold. All time periods, the set of these time periods is called the damage evolution interval.

[0060] S3.2, Extract the difference between the real-time water content state and the initial state within the damage evolution interval, and determine it as the excess water content increment.

[0061] The initial state is the initial saturation. For any time t within the damage evolution interval, the excess water content (dimensionless) at that time is defined as the portion of the real-time water content exceeding the larger of the initial state and the critical volume saturation threshold:

[0062] S3.3, the excess water content increment is integrated and accumulated over time to obtain the structural damage state quantity. For any monitoring point (depth...) As of the current time t, its structural damage state quantity Calculated using the following formula:

[0063] Among them, the integral variable It represents starting from immersion in water ( The time from the current time t, It is the Heaviside step function (unit step function), when When H=1, otherwise H=0, the integrand is... It is the increase in water content beyond the threshold that changes over time.

[0064] S4. Based on the structural damage state variables, an attenuation function is constructed to attenuate and modulate the evolving suction force, thereby obtaining the equivalent shear strength; as shown in Figure 4, Figure 4 is a schematic diagram of structural damage accumulation and strength reduction, displaying the structural damage state variables with time as the axis. Monotonically increasing from 0, intensity reduction coefficient From the monotonically decreasing coupling evolution characteristic of 1, when the damage state quantity reaches the characteristic damage dose At this point, the reduction factor approaches the inherent minimum reduction factor of the soil. Based on this correlation, according to the structural damage state quantity Determine the degree of reduction in the contribution of matrix suction to the foundation soil due to the failure of the skeleton cementation, and construct a system accordingly. An intensity reduction function that increases and monotonically decreases.

[0065] In this embodiment, the step of constructing an attenuation function based on the structural damage state quantity to attenuate and modulate the evolving suction force to obtain the equivalent shear strength is specifically as follows: S4.1, in this embodiment, the degree of attenuation is quantified into a strength reduction coefficient. (Dimensionless), with a range of (0,1). Based on the degree of reduction, a strength reduction function is constructed that monotonically decreases as the structural damage state quantity increases. Specifically, it means: utilizing Structural damage state quantity Normalization yields a dimensionless damage index. Its range is [0,∞). In this embodiment, an exponential decay model is used to establish the damage index. With strength reduction factor The intensity reduction function between them is as follows:

[0066] in, The minimum reduction factor (dimensionless, ), It is a damage-sensitive factor.

[0067] It should be noted that, This parameter represents the typical cumulative immersion water volume required for a specific soil mass to undergo significant strength degradation of its cementation structure under immersion conditions. It is an inherent property of soil's resistance to wetting damage and is calibrated through indoor cyclic wetting shear tests: different amplitudes and durations of water are applied to undisturbed soil samples, and their strength decay curves are measured. The cumulative damage volume corresponding to a decrease in strength to a certain percentage of the initial value (e.g., 37% or 50%) is determined. .

[0068] S4.2, the step of using the intensity reduction function to calculate the intensity reduction coefficient corresponding to the current cumulative damage specifically involves using the damage index at the current moment. Substituting the above intensity reduction function, the intensity reduction coefficient at the current moment can be calculated. .

[0069] S4.3, the strength reduction factor With the evolutionary attraction Multiplying these values ​​yields the effective suction equivalent value after structural damage correction. .

[0070] Furthermore, by combining the effective suction equivalent value with the internal friction angle parameter of the foundation soil, the shear strength component contributed by suction is obtained. According to the widely accepted extended Mohr-Coulomb strength criterion in unsaturated soil mechanics, the shear strength component contributed by suction... :

[0071] in, This is the friction angle related to matrix suction. For most soils, its value is approximately equal to the saturated effective internal friction angle. For special cases such as highly plastic clay, it should be determined independently through triaxial tests of unsaturated soil with controlled matrix suction.

[0072] S4.4, the shear strength component is superimposed with the saturated shear strength of the foundation soil to output the equivalent shear strength. :

[0073] in, Calculate the effective normal stress on the surface.

[0074] S5, output the foundation strength deterioration assessment results based on the equivalent shear strength.

[0075] In this embodiment, the step of outputting the foundation strength deterioration assessment result based on the equivalent shear strength specifically involves: S5.1, calculating the current safety factor or remaining bearing capacity of the foundation based on the equivalent shear strength. This embodiment uses the safety factor as an example. Based on the type of the target power grid facility (such as tower foundations or substation raft foundations), a recognized stability analysis model is selected. This embodiment uses the overturning stability of a transmission tower extended foundation under lateral loads as an example. An overturning safety factor calculation model based on limit equilibrium theory is adopted. The overturning stability of the foundation is characterized by the ratio of the overturning moment to the overturning torque. Its real-time overturning safety factor... :

[0076] in, To resist overturning moment, For overturning moment, Let H be the base area, H be the horizontal load acting on the top surface of the foundation (such as wind load), h be the vertical distance (m) from the line of action of the horizontal load to the foundation base, i.e., the overturning arm, and W be the total self-weight of the foundation and the overlying soil. It is the lever arm of the point of application of the resultant force of its own weight from the point of overturning.

[0077] S5.2, the calculated real-time overturning safety factor Compared with the preset stability threshold A comparison is made. The preset stability threshold is... According to industry standards, the minimum safety factor for overturning stability of tower foundations subjected to short-term wind loads is typically specified as 1.5. Therefore, in this embodiment, the preset stability threshold... .

[0078] Based on the comparison results, the system automatically generates and outputs an evaluation conclusion that includes a stability level or warning instructions. If the foundation is stable; if If the foundation is unstable and the safety factor is lower than the standard limit, the strength deterioration caused by water immersion has seriously affected the stability of the foundation, and a red warning is issued. It is recommended to immediately carry out on-site drainage and check the equipment status.

[0079] Example 2, Figure 2 shows a system for assessing the strength deterioration of unsaturated soil foundations considering immersion, comprising: a frontal sensing module for acquiring monitoring data of the water content of the foundation under immersion conditions, determining the location of the wetting front and extracting its propagation characteristics based on the monitoring data; a suction evolution module for correcting the matrix suction based on the propagation characteristics and the rate of change of the water content to obtain the evolved suction; a damage coupling module for comparing the water content with a preset structural initiation criterion to determine the excess water content increment and accumulating the structural damage state quantity; constructing an attenuation function based on the structural damage state quantity to attenuate and modulate the evolved suction to obtain the equivalent shear strength; and an assessment output module for outputting the foundation strength deterioration assessment result based on the equivalent shear strength.

[0080] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0081] 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.

[0082] 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 design 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.

[0083] 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.

[0084] 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.

[0085] 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 strength deterioration of unsaturated soil foundations considering water immersion, characterized in that, Includes the following steps: Acquire water content monitoring data of the foundation under immersion conditions, determine the location of the wetting front based on the monitoring data, and extract its propagation characteristics. Based on the propagation characteristic quantity and the rate of change of the water content state, the matrix suction is corrected to obtain the evolutionary suction; the water content state is compared with the preset structure initiation criterion to determine the excess water content increment, and the structural damage state quantity is accumulated. Based on the structural damage state quantity, an attenuation function is constructed to attenuate and modulate the evolving suction force to obtain the equivalent shear strength; based on the equivalent shear strength, the foundation strength deterioration assessment result is output.

2. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 1, characterized in that, The determination of the location of the wetting front based on the monitoring data specifically includes: acquiring time-series data of the water-bearing state of multiple monitoring points distributed in a gradient along the foundation depth direction; establishing a spatiotemporal correlation matrix of the evolution of the water-bearing state with depth and time based on the spatial mapping of the time-series data; performing differential operations on the spatiotemporal correlation matrix to extract the partial derivative field of the water-bearing state with respect to time; and determining the location of the wetting front by identifying the set of abrupt peaks in the partial derivative field.

3. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 2, characterized in that, The extraction of its propagation characteristics includes: calculating the infiltration rate of the wetting front in the vertical depth direction based on the time variation sequence of the wetting front position; extracting the value corresponding to the position of the wetting front in the partial derivative field as the extreme value of the rate of change of the water-bearing state; calculating the water-bearing state gradient value of the wetting front according to the numerical gradient before and after the real-time position of the wetting front; and determining the infiltration rate, the extreme value of the rate of change, and the water-bearing state gradient value as the propagation characteristics.

4. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 3, characterized in that, The modified matrix suction includes: determining a matrix suction reference value corresponding to the current real-time water content based on a pre-determined soil-water characteristic curve; estimating the lag time of the pore water pressure response relative to the change in water content based on the infiltration rate; and using the lag time to perform time delay correction on the matrix suction reference value to obtain time-delay compensated matrix suction.

5. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 4, characterized in that, The modified matrix suction further includes: determining the influence weight of the wetting front shape on the matrix suction distribution based on the water content gradient value; using the influence weight to correct the amplitude of the matrix suction after time delay compensation; and combining the extreme value of the rate of change to smooth the modified matrix suction and output the evolutionary suction.

6. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 5, characterized in that, The process of obtaining the structural damage state quantity includes: comparing the water content state with a preset structural initiation criterion to identify the damage evolution interval where the water content state exceeds a critical threshold; extracting the difference between the real-time water content state and the initial state within the damage evolution interval and determining it as the excess water content increment; and integrating and accumulating the excess water content increment over time to obtain the structural damage state quantity.

7. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 6, characterized in that, The step of constructing an attenuation function based on structural damage state quantities includes: determining the degree of reduction in the contribution of matrix suction to the foundation soil due to the failure of the skeleton cementation based on the structural damage state quantities; establishing a strength reduction function between the structural damage state quantities and a strength reduction coefficient based on the degree of reduction; and calculating the strength reduction coefficient corresponding to the current cumulative damage using the strength reduction function.

8. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 7, characterized in that, The step of attenuating and modulating the evolving suction to obtain the equivalent shear strength includes: multiplying the strength reduction factor by the evolving suction to obtain the effective suction equivalent value after structural damage correction; combining the effective suction equivalent value with the internal friction angle parameter of the foundation soil to obtain the shear strength component contributed by the suction; and superimposing the shear strength component with the saturated shear strength of the foundation soil to output the equivalent shear strength.

9. The method for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in claim 8, characterized in that, The process of outputting the foundation strength deterioration assessment result based on the equivalent shear strength specifically involves: calculating the current safety factor or remaining bearing capacity of the foundation based on the equivalent shear strength, and comparing it with a preset stability threshold; based on the comparison result, outputting an assessment conclusion that includes a stability level or warning instruction.

10. A system for assessing the strength deterioration of unsaturated soil foundations considering water immersion as described in any one of claims 1-9, characterized in that, include: The frontal sensing module is used to acquire monitoring data on the water content of the foundation under immersion conditions, determine the location of the moist front based on the monitoring data, and extract its propagation characteristics. The suction evolution module is used to correct the matrix suction based on the propagation characteristic quantity and the rate of change of the water content state, so as to obtain the evolved suction. The damage coupling module is used to compare the water content state with the preset structure activation criterion, determine the water content increment exceeding the threshold, and accumulate the structural damage state quantity. Based on the structural damage state quantity, an attenuation function is constructed to attenuate and modulate the evolving suction force to obtain the equivalent shear strength. The evaluation output module is used to output the foundation strength deterioration evaluation result based on the equivalent shear strength.

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