Method for evaluating geological disaster risk of city in loess area based on underground water level

Abstract

The present application relates to a loess area city geological disaster risk assessment method based on underground water level, including collecting the time series monitoring data of the target area underground water level, extracting the water level fluctuation amplitude, water level change rate and water level cumulative drop as the underground water evaluation index from the time series monitoring data; using undisturbed loess infiltration mechanics test under different underground water fluctuation conditions, calculating the corresponding underground water evaluation index according to various underground water fluctuation conditions, and correspondingly obtaining the loess mechanics parameter degradation from the undisturbed loess infiltration mechanics test, and constructing the loess mechanics parameter degradation evaluation equation and the like steps. The present application has the advantages that: the information loss caused by only using a single underground water level value is avoided; by constructing the influence relationship between the underground water level evaluation index and the loess mechanics parameter degradation, the continuous evaluation of the loess structure degradation process under the disturbance of underground water is realized, and the pertinence and reliability of the early warning result are improved.

Description

Technical Field

[0001] This invention belongs to the field of urban geological hazard assessment technology in loess areas, specifically involving a method for assessing urban geological hazard risk in loess areas based on groundwater level. Background Technology

[0002] The mechanical properties and structural stability of loess are highly sensitive to changes in groundwater level. Changes in groundwater depth and dynamic fluctuations directly cause loess strength reduction, structural damage, and subsidence deformation, which are the core causes of geological disasters such as landslides, ground subsidence, foundation settlement, and ground fissures in loess areas.

[0003] Urban human activities significantly disrupt the natural groundwater environment, causing frequent fluctuations and dynamic changes in groundwater levels, which can trigger geological disasters such as landslides, collapses, and ground fissures. Existing loess geological hazard assessment systems are mostly based on a single groundwater level indicator, and generally rely on direct groundwater level monitoring and on-site evaluation. This approach fails to reflect the cumulative damage effects of long-term groundwater changes on loess soil and cannot meet the application needs for refined prevention and control of urban geological disasters. Summary of the Invention

[0004] This invention provides a method for assessing urban geological disaster risks in loess areas based on groundwater levels, which can solve the problems in existing technologies where the evaluation indicators are singular and fail to reflect the cumulative damage effect of long-term groundwater changes on loess soil.

[0005] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: a method for assessing urban geological disaster risks in loess areas based on groundwater levels, comprising the following steps: Collect time-series monitoring data of groundwater level in the target area, and extract water level fluctuation amplitude, water level change rate and cumulative water level drop as groundwater evaluation indicators from the time-series monitoring data; Using undisturbed loess infiltration mechanical tests under different groundwater fluctuation conditions, the corresponding groundwater evaluation index is calculated based on various groundwater fluctuation conditions. The degree of deterioration of loess mechanical parameters is obtained from the undisturbed loess infiltration mechanical tests. The correspondence between groundwater evaluation index and the degree of deterioration of loess mechanical parameters is established, and the loess mechanical parameter deterioration evaluation equation is constructed. Collect real-time monitoring data of groundwater level in the target area, calculate the groundwater evaluation index for the day, input the groundwater evaluation index for the day into the loess mechanical parameter deterioration evaluation equation, and obtain the degree of deterioration of loess mechanical parameters for the day. The daily soil damage increment is calculated based on the degree of deterioration of the loess mechanical parameters on that day, and the total soil deterioration degree is updated daily by accumulating the historical damage status. A threshold calibration method is used to establish a mapping relationship between the total soil degradation degree and the disaster risk level. The real-time updated total soil degradation degree is compared with the threshold intervals corresponding to different disaster risk levels, and the disaster risk level of the target area is output.

[0006] Preferably, the water level fluctuation amplitude is the monthly groundwater level change amplitude of the target area; the water level change rate is the daily water level change rate of the target area; and the cumulative water level decrease is the quarterly cumulative groundwater level decrease of the target area.

[0007] Preferably, the formula for evaluating the deterioration of loess mechanical parameters is as follows: In the formula: denoted as the degree of deterioration of loess mechanical parameters at the current moment; x1 is the standardized value of water level fluctuation amplitude; x2 is the standardized value of water level change rate; x3 is the standardized value of cumulative water level drop; A and m1 are the fitting correction coefficients corresponding to water level fluctuation amplitude; B and m2 are the fitting correction coefficients corresponding to water level change rate; C and m3 are the fitting correction coefficients corresponding to cumulative water level drop; all the fitting correction coefficients are solved by fitting regression of the undisturbed loess infiltration mechanical test dataset; e is the natural constant.

[0008] Preferably, the undisturbed loess infiltration mechanical test dataset is a dataset corresponding to water level disturbance conditions and loess mechanical parameters, established through undisturbed loess infiltration mechanical tests; the loess mechanical parameters include cohesion, internal friction angle, compression modulus, and collapsibility deformation coefficient.

[0009] Preferably, the formula for calculating the total degree of soil deterioration is as follows: In the formula: D n D represents the total soil degradation degree on day n. n-1 The total soil degradation degree of the previous day; ΔD i This represents the daily increase in soil damage. The formula for calculating the daily soil damage increment is as follows: In the formula: ΔD i This represents the daily increase in soil damage. This represents the degree of deterioration of the loess's mechanical parameters on that day.

[0010] Preferably, establishing the mapping relationship between the total soil degradation degree and the disaster risk level includes the following steps: Collect long-term historical disaster data of the target area and classify four types of urban disasters in loess areas: landslides, ground subsidence, foundation collapse and settlement, and ground fissures. Based on the strength criteria of soil mechanics and the instability calculation formula, the initial critical threshold range corresponding to the instability of various types of urban disasters in loess areas was calculated. The initial critical threshold range was then corrected by combining the historical disaster data to obtain the graded threshold benchmark. By combining field water level monitoring stations and deformation monitoring equipment at potential hazard points, on-site verification was completed, and four threshold ranges were defined for safety, early warning, critical instability, and disaster outbreak.

[0011] Preferably, the standardized total soil degradation degree is a value within the range of 0 to 1; the mapping relationship between the total soil degradation degree and the disaster risk level is as follows: a total soil degradation degree of 0 to 0.30 corresponds to a safe level; a total soil degradation degree of 0.30 to 0.60 corresponds to a warning level; a total soil degradation degree of 0.60 to 0.85 corresponds to a critical instability level; and a total soil degradation degree of 0.85 to 1.00 corresponds to a disaster outbreak level.

[0012] Compared with existing technologies, this invention avoids the information gaps caused by using only a single groundwater level value by quantifying evaluation indicators such as the fluctuation amplitude, rate of change, and duration of groundwater level changes. By constructing the influence relationship between groundwater level evaluation indicators and the deterioration of loess mechanical parameters, it achieves continuous assessment of the loess structure deterioration process under the influence of groundwater disturbance.

[0013] The daily soil damage increment is calculated based on the deterioration results of loess mechanical parameters, and the total soil deterioration degree is updated daily. This can reflect the cumulative damage effect caused by long-term groundwater changes. Threshold calibration is performed for different urban environments and disaster types, so that risk assessment can be adapted to different groundwater conditions and disaster evolution characteristics in different urban areas, thereby improving the pertinence and reliability of early warning results. Attached Figure Description

[0014] Figure 1 This is a flowchart illustrating the evaluation method of the present invention; Figure 2 This is a schematic diagram illustrating the execution steps of the evaluation method of the present invention. Detailed Implementation

[0015] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "axial," "radial," and "circumferential" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the technical solution of this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0016] like Figure 1 As shown, this invention provides a method for assessing urban geological hazard risk in loess areas based on groundwater level, including the following steps: Collect time-series monitoring data of groundwater level in the target area, and extract the water level fluctuation amplitude, water level change rate and cumulative water level drop as groundwater evaluation indicators from the time-series monitoring data; Using undisturbed loess infiltration mechanical tests under different groundwater fluctuation conditions, the corresponding groundwater evaluation indexes were calculated based on various groundwater fluctuation conditions. The degree of deterioration of loess mechanical parameters was obtained from the undisturbed loess infiltration mechanical tests. The correspondence between groundwater evaluation indexes and the degree of deterioration of loess mechanical parameters was established, and the loess mechanical parameter deterioration evaluation equation was constructed. Real-time monitoring data of groundwater level in the target area is collected, the groundwater evaluation index for the day is calculated, and the groundwater evaluation index for the day is input into the loess mechanical parameter deterioration evaluation equation to obtain the degree of deterioration of loess mechanical parameters for the day. The daily soil damage increment is calculated based on the degree of deterioration of the loess mechanical parameters on that day, and the total soil deterioration degree is updated daily by combining the historical damage status. A threshold calibration method is used to establish a mapping relationship between the total soil degradation degree and the disaster risk level. The real-time updated total soil degradation degree is compared with the threshold intervals corresponding to different disaster risk levels, and the disaster risk level of the target area is output.

[0017] Specifically, addressing the shortcomings of existing technologies that rely solely on a single water level indicator, cannot comprehensively characterize urban artificial hydrological disturbances, and cannot establish a quantitative correlation between water level changes and loess mechanical deterioration, this invention first collects long-term groundwater level monitoring data across the entire region. It then extracts three multi-dimensional water level characteristic indicators: water level fluctuation amplitude, water level change rate, and cumulative water level decline, covering three typical forms of urban artificial disturbance: short-term water level mutations, monthly periodic fluctuations, and long-term continuous water level declines. Next, through multiple sets of controlled water level conditions and undisturbed loess saturation mechanical tests, the invention simultaneously records each set of water level indicators and the corresponding loess mechanical attenuation state, establishing a quantitative correspondence between the two. Finally, it constructs a deterioration evaluation equation, realizing the quantitative transformation of dynamic changes in groundwater level into the degree of loess soil deterioration, thus overcoming the shortcomings of existing evaluations that lack quantitative models and rely solely on qualitative assessments based on static water levels.

[0018] Building upon the previously established degradation evaluation equation, this method enables real-time quantitative calculation of daily urban groundwater dynamic disturbances. It addresses the limitations of existing static, one-time evaluation technologies that cannot dynamically track the real-time degradation status of soil, providing daily quantitative input values ​​for cumulative damage. Daily real-time groundwater level monitoring data for the target area is collected, and the original indicators of daily water level fluctuation amplitude, water level change rate, and cumulative water level decline are calculated. These three indicators undergo uniform extreme value standardization to eliminate dimensional differences. The standardized indicators are then substituted into the constructed loess mechanical parameter degradation evaluation equation to solve for the daily degree of loess mechanical parameter degradation. It is important to note that the standardized calculation must use the global maximum and minimum values ​​of the time-series indicators across the entire study area as a unified benchmark, and cannot be segmented by single day to ensure consistency in the daily standardized benchmark.

[0019] To address the shortcomings of existing technologies that neglect the irreversibility of loess immersion damage and fail to reflect the long-term cumulative damage effects of groundwater, this method quantifies daily soil damage based on the deterioration results of loess mechanical parameters. By accumulating these parameters daily, it achieves long-term dynamic tracking of soil damage, reconstructing the evolution of continuous loess deterioration under years of urban hydrological disturbance, and quantifying the long-term cumulative damage level of the soil. The degree of deterioration of loess mechanical parameters on a given day is directly used as the daily soil damage increment. The total soil deterioration degree accumulated from the previous day is read, and a recursive accumulation method is used to add the daily damage increment to the historical total deterioration degree, thus updating the daily total soil deterioration degree. When there is no significant water level disturbance or new soil damage on a given day, the daily damage increment is set to 0, and the total deterioration degree remains unchanged from the previous day.

[0020] Finally, a threshold calibration method is used to establish a differentiated classification standard. Using dynamically updated total soil deterioration as the unified quantitative basis, the standard automatically matches the corresponding risk level and outputs quantitative classification evaluation results, providing an objective basis for the refined and differentiated prevention and control of urban geological disasters. This addresses the shortcomings of existing technologies that use a unified judgment standard, cannot adapt to the instability mechanisms of different urban disasters, and have insufficient accuracy in evaluation results.

[0021] Preferably, the water level fluctuation amplitude is the monthly groundwater level change amplitude of the target area; the water level change rate is the daily water level change rate of the target area; and the cumulative water level drop is the quarterly cumulative groundwater level drop of the target area.

[0022] Specifically, this embodiment defines three types of indicators with dedicated statistical periods: the rate of water level change is measured on a daily scale, the fluctuation amplitude is measured on a monthly scale, and the cumulative decline is measured on a quarterly scale. It simultaneously covers three types of typical urban groundwater change characteristics: short-term sudden disturbances, medium-term periodic fluctuations, and long-term continuous water level declines. It captures the deteriorating effect of water level disturbances on loess at different time scales and makes up for the lack of time dimension representation in existing technologies.

[0023] Based on daily water level monitoring data of the target area, the daily water level change rate is calculated; the monthly fluctuation amplitude is obtained by calculating the difference between the highest and lowest water levels; and the quarterly cumulative decrease is obtained by calculating the difference between the beginning and end of the cycle. In the daily calculation model, the same indicator value is reused daily within the corresponding cycle for different cycle indicators. It should be noted that the statistical cycles for the three types of indicators are fixed and distinct, and the time scales should not be mixed to avoid confusing the damage contribution of short-term and medium-to-long-term groundwater disturbances. The sampling frequency of the monitoring data must match the requirements of daily-scale acquisition to ensure the completeness and continuity of monthly and quarterly indicator statistics.

[0024] The preferred formula for evaluating the deterioration of loess mechanical parameters is as follows: In the formula: denoted as the degree of deterioration of loess mechanical parameters at the current moment; x1 is the standardized value of water level fluctuation amplitude; x2 is the standardized value of water level change rate; x3 is the standardized value of cumulative water level drop; A and m1 are the fitting correction coefficients corresponding to water level fluctuation amplitude; B and m2 are the fitting correction coefficients corresponding to water level change rate; C and m3 are the fitting correction coefficients corresponding to cumulative water level drop; each fitting correction coefficient is solved by fitting regression of the undisturbed loess infiltration mechanical test dataset; e is the natural constant.

[0025] Specifically, this embodiment provides a deterioration equation with nonlinear superposition of factors, which matches the nonlinear response laws of three types of water level indicators and soil damage respectively. By adapting the fitting coefficients to the inherent geological characteristics of loess in the study area, it realizes the quantitative conversion from water level standardized indicators to the degree of soil deterioration on a single day, establishes a quantitative calculation equation, and improves the degree of evaluation quantification and calculation accuracy.

[0026] The equation uses a power function to characterize the damage growth law of water level fluctuation amplitude and water level change rate, and a negative exponential function to characterize the damage decay law of cumulative water level drop; A, B C To ensure the dataset is entirely based on undisturbed loess infiltration test data, a regression fitting solution can be obtained using the nonlinear least squares method and the Levenberg-Marquardt method. It should be noted that outlier data from the experiments must be removed and a significance test performed before regression fitting to prevent coefficient distortion from affecting computational accuracy; the input term x... 1、 x 2、 x3 must be a standardized indicator uniformly mapped to the [0,1] interval to ensure that the contribution weights of each indicator item are balanced.

[0027] Preferably, the undisturbed loess infiltration mechanical test dataset is a dataset corresponding to the water level disturbance condition and the loess mechanical parameters, which is established through undisturbed loess infiltration mechanical tests; the loess mechanical parameters include cohesion, internal friction angle, compression modulus, and collapsibility deformation coefficient.

[0028] Specifically, this embodiment clarifies that the dataset used for equation fitting is constructed from undisturbed loess infiltration mechanics tests. Four core loess mechanical indicators, namely cohesion, internal friction angle, compression modulus, and collapsibility deformation coefficient, are selected to characterize the degree of soil deterioration. This covers the mechanical characteristics corresponding to three types of loess disasters: shear instability, compression settlement, and collapsibility failure. This provides an experimental basis that fits the local strata for solving the deterioration equation coefficients, thereby improving the regional adaptability and reliability of the entire evaluation method.

[0029] Uncirculated loess samples from the study area were collected, and immersion tests were conducted under multiple water level disturbance conditions. The attenuation values ​​of four mechanical parameters were simultaneously measured under each condition, and the three water level indices were matched one-to-one to form an index-mechanical deterioration paired dataset. It should be noted that remolded loess samples must not be used in the tests; the natural structure of the loess must be preserved to ensure that the deterioration patterns in the tests closely reflect the actual field conditions. When setting up the test conditions, the gradient of the test conditions must cover the entire water level fluctuation range of the study area to avoid missing intervals in the fitted sample.

[0030] The preferred formula for calculating the total soil deterioration degree is as follows: In the formula: D n D represents the total soil degradation degree on day n. n-1 The total soil degradation degree of the previous day; ΔD i This represents the daily increase in soil damage. The formula for calculating the daily soil damage increment is as follows: In the formula: ΔD i This represents the daily increase in soil damage. This represents the degree of deterioration of the loess's mechanical parameters on that day.

[0031] Specifically, by formulating standardized cumulative calculation formulas and setting calculation boundary rules in conjunction with the inherent irreversible nature of loess damage, the calculation logic of the entire process can be unified, enabling dynamic and continuous tracking of the long-term damage state of the soil, truly restoring the attenuation law of loess mechanical properties under the long-term action of groundwater, and ensuring that the calculated total deterioration degree can objectively reflect the actual damage level of the soil.

[0032] The mechanical damage to loess caused by soaking and infiltration with groundwater is irreversible. Once the soil's shear strength, compressive strength, and resistance to collapse are weakened, the damaged properties cannot recover on their own, even if the groundwater level recedes and the soaking conditions disappear. The calculation boundary rule corresponding to this step is as follows: when the groundwater level does not fluctuate significantly on a single day and does not cause new disturbance to the soil, the daily deterioration increment is taken as 0, and the total soil deterioration degree remains unchanged from the previous moment; when the water level is disturbed and generates an effective deterioration increment, the total deterioration degree continues to accumulate and only increases, which fully conforms to the inherent soil and rock characteristics of loess.

[0033] Preferably, establishing the mapping relationship between the total soil degradation degree and the disaster risk level includes the following steps: Collect long-term historical disaster data of the target area and classify four types of urban disasters in loess areas: landslides, ground subsidence, foundation collapse and settlement, and ground fissures. Based on the strength criteria and instability calculation formula of soil mechanics, the initial critical threshold range corresponding to the instability of various types of urban disasters in loess areas was calculated. The initial critical threshold range was corrected by combining historical disaster data to obtain the graded threshold benchmark. By combining field water level monitoring stations and deformation monitoring equipment at potential hazard points, on-site verification was completed, and four threshold ranges were defined for safety, early warning, critical instability, and disaster outbreak.

[0034] Specifically, this embodiment clarifies the classification dimensions of threshold calibration, calibrating thresholds separately for different instability mechanisms of disasters to avoid accuracy deviations caused by a uniform standard across the entire region. The four types of disasters correspond to four different instability mechanisms: shear instability, roof collapse, compression deformation, and tensile cracking. Scene division needs to be determined in conjunction with the urban planning and land use types of the study area, and the boundaries need to match the spatial distribution of water level monitoring points to ensure that each scene has sufficient monitoring and disaster data support.

[0035] An initial critical threshold is obtained through theoretical calculations, and then corrected by combining actual historical disaster data, taking into account both the physical and mechanical basis of the threshold and its adaptability to the actual region. Among these: The "Geotechnical Strength Criterion" defaults to the Mohr-Coulomb strength criterion, which is commonly used in this field. , In the formula: It represents the shear strength of the soil. It is the soil cohesion; The effective stress is the normal stress of the shear plane; The friction angle within the soil.

[0036] "Instability Calculation Formulas" use different classic formulas for different types of disasters: The formula for calculating the stability coefficient of a landslide using the limit equilibrium method: , In the formula: K is the slope stability coefficient; L is the segment length of the sliding surface; N is the normal component of the sliding surface force; T is the tangential component of the sliding surface force. Formula for the critical stability thickness of the top slab of the soil cave corresponding to ground subsidence: , In the formula: γ represents the critical thickness of the roof slab of the earthen cave; γ represents the natural unit weight of loess. Formula for calculating the amount of subsidence corresponding to foundation subsidence settlement: , In the formula: This represents the total subsidence. This is the collapsibility coefficient of a single soil layer; The thickness of each soil layer; Formulas for soil tensile strength and ultimate tensile deformation corresponding to ground fissures: , In the formula: This represents the ultimate tensile strength of the soil.

[0037] First, the degree of mechanical parameter attenuation when the soil reaches the critical state of instability is calculated using the above formula. Then, it is mapped back to the total deterioration value of the soil to obtain the initial critical threshold range. Next, the water level data and deterioration calculation results corresponding to the occurrence of historical disasters are matched, and the initial threshold is corrected by statistical regression to obtain the graded threshold benchmark.

[0038] The revised thresholds were verified using on-site monitoring data, ultimately defining the numerical ranges corresponding to the four risk levels to ensure their applicability in the field. Based on long-term monitoring data from field water level monitoring stations and deformation monitoring data from potential hazard points, the actual soil deformation under different degrees of deterioration was compared, and the threshold benchmarks were adjusted. Finally, four risk levels were defined: safe, warning, critical instability, and disaster outbreak, corresponding to four states: no significant soil deterioration, deterioration beginning to appear, approaching critical instability, and reaching instability conditions, respectively.

[0039] Preferably, the standardized total soil degradation degree is a value within the range of 0 to 1; the mapping relationship between the total soil degradation degree and the disaster risk level is as follows: a total soil degradation degree of 0 to 0.30 corresponds to a safe level; a total soil degradation degree of 0.30 to 0.60 corresponds to a warning level; a total soil degradation degree of 0.60 to 0.85 corresponds to a critical instability level; and a total soil degradation degree of 0.85 to 1.00 corresponds to a disaster outbreak level.

[0040] Specifically, this embodiment provides a fixed four-level numerical range for the total soil deterioration degree from 0 to 1, forming an objective and unified quantitative judgment standard. This standard can be directly matched with the threshold benchmarks defined for each disaster type, eliminating the need for subjective human classification. This standardizes and reproducibles risk assessment results, facilitating unified early warning and control of urban geological disasters. The boundary values ​​for various disasters can be slightly adjusted based on this general range and their own instability characteristics.

[0041] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements 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 urban geological hazard risk in loess areas based on groundwater level, characterized in that, Includes the following steps: Collect time-series monitoring data of groundwater level in the target area, and extract water level fluctuation amplitude, water level change rate and cumulative water level drop as groundwater evaluation indicators from the time-series monitoring data; Using undisturbed loess infiltration mechanical tests under different groundwater fluctuation conditions, the corresponding groundwater evaluation index is calculated based on various groundwater fluctuation conditions. The degree of deterioration of loess mechanical parameters is obtained from the undisturbed loess infiltration mechanical tests. The correspondence between groundwater evaluation index and the degree of deterioration of loess mechanical parameters is established, and the loess mechanical parameter deterioration evaluation equation is constructed. Real-time monitoring data of groundwater level in the target area is collected, the groundwater evaluation index for the day is calculated, and the groundwater evaluation index for the day is input into the loess mechanical parameter deterioration evaluation equation to obtain the degree of deterioration of loess mechanical parameters for the day. The daily soil damage increment is calculated based on the degree of deterioration of the loess mechanical parameters on that day, and the total soil deterioration degree is updated daily by accumulating the historical damage status. A threshold calibration method is used to establish a mapping relationship between the total soil degradation degree and the disaster risk level. The real-time updated total soil degradation degree is compared with the threshold intervals corresponding to different disaster risk levels, and the disaster risk level of the target area is output.

2. The method for assessing urban geological hazard risk in loess areas based on groundwater level as described in claim 1, characterized in that: The water level fluctuation amplitude is the monthly groundwater level change amplitude of the target area; the water level change rate is the daily water level change rate of the target area; and the cumulative water level drop is the quarterly cumulative groundwater level drop of the target area.

3. The method for assessing urban geological hazard risk in loess areas based on groundwater level as described in claim 1, characterized in that, The formula for evaluating the deterioration of loess mechanical parameters is as follows: In the formula: denoted as the degree of deterioration of loess mechanical parameters at the current moment; x1 is the standardized value of water level fluctuation amplitude; x2 is the standardized value of water level change rate; x3 is the standardized value of cumulative water level drop; A and m1 are the fitting correction coefficients corresponding to water level fluctuation amplitude; B and m2 are the fitting correction coefficients corresponding to water level change rate; C and m3 are the fitting correction coefficients corresponding to cumulative water level drop; all the fitting correction coefficients are solved by fitting regression of the undisturbed loess infiltration mechanical test dataset; e is the natural constant.

4. The method for assessing urban geological hazard risk in loess areas based on groundwater level as described in claim 3, characterized in that: The dataset of undisturbed loess infiltration mechanical test is a dataset corresponding to water level disturbance conditions and loess mechanical parameters, established through undisturbed loess infiltration mechanical tests; the loess mechanical parameters include cohesion, internal friction angle, compression modulus, and collapsibility deformation coefficient.

5. The method for assessing urban geological hazard risk in loess areas based on groundwater level as described in claim 3, characterized in that, The formula for calculating the total degree of soil deterioration is as follows: In the formula: D n D represents the total soil degradation degree on day n. n-1 The total soil degradation degree of the previous day; ΔD i This represents the daily increase in soil damage. The formula for calculating the daily soil damage increment is as follows: In the formula: ΔD i This represents the daily increase in soil damage. This represents the degree of deterioration of the loess's mechanical parameters on that day.

6. The method for assessing urban geological hazard risk in loess areas based on groundwater level as described in claim 1, characterized in that: Establishing the mapping relationship between total soil degradation and disaster risk level includes the following steps: Collect long-term historical disaster data of the target area and classify four types of urban disasters in loess areas: landslides, ground subsidence, foundation collapse and settlement, and ground fissures. Based on the strength criteria of soil mechanics and the instability calculation formula, the initial critical threshold range corresponding to the instability of various types of urban disasters in loess areas was calculated. The initial critical threshold range was then corrected by combining the historical disaster data to obtain the graded threshold benchmark. By combining field water level monitoring stations and deformation monitoring equipment at potential hazard points, on-site verification was completed, and four threshold ranges were defined for safety, early warning, critical instability, and disaster outbreak.

7. The method for assessing urban geological hazard risk in loess areas based on groundwater level as described in claim 6, characterized in that, The standardized total soil degradation degree is a value ranging from 0 to 1; the mapping relationship between the total soil degradation degree and the disaster risk level is as follows: a total soil degradation degree of 0 to 0.30 corresponds to a safe level; a total soil degradation degree of 0.30 to 0.60 corresponds to a warning level; a total soil degradation degree of 0.60 to 0.85 corresponds to a critical instability level; and a total soil degradation degree of 0.85 to 1.00 corresponds to a disaster outbreak level.

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