Rock mass unloading simulation evaluation method for high and steep slope excavation construction

Abstract

The invention relates to the technical field of slope stability prediction and analysis, in particular to a rock mass unloading simulation evaluation method for high and steep slope excavation construction. The method comprises the following steps: firstly, performing finite element simulation on the high and steep slope and acquiring various data of a rock mass unit; further analyzing the change of main stress data and the time sequence change of generated horizontal and vertical displacement in the unloading process of the rock mass unit, and analyzing the synchronous change of the main stress data and the time sequence change to obtain the synchronous change intensity; further acquiring a displacement transient coefficient of the current simulation; further according to the response condition of the stress of the supporting anchor rod to the displacement when the rock mass unit is unloaded, in combination with the displacement transient coefficient, a disturbance influence coefficient of current simulation is obtained; finally, the unloading safety coefficient and the disturbance influence coefficient are fused to obtain the estimated unloading stability, accurate prediction of the rock mass unloading induced instability risk in the high and steep slope excavation process is achieved, and the slope construction safety and the supporting system reliability are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of slope stability prediction and analysis, and in particular to a rock mass unloading simulation and evaluation method for high and steep slope excavation construction. Background Art

[0002] In the construction of high and steep slopes, the finite element method (FEM) is mainly relied upon. By gradually removing units or applying blasting loads, the unloading disturbance and stress release path caused by actual excavation are simulated, and the risk of unloading-induced rock softening and damage is quantitatively evaluated. This enables accurate prediction of the slope unloading effect and zoning early warning, providing a reliable basis for construction optimization.

[0003] However, most existing finite element simulation methods are based on the assumption of step-by-step unloading, focusing only on the changes in the mechanical state before and after unloading to evaluate the stress evolution of rock masses on steep slopes. However, under severe disturbance conditions such as blasting and excavation, these methods ignore the perturbations that affect rock stability, such as stress wave propagation and peak tensile stress excitation. Consequently, they fail to fully simulate the transient dynamic characteristics of the rock mass response during unloading, resulting in an incomplete evolution mechanism and making it difficult to accurately predict the instability behavior of rock masses induced by excavation and unloading on steep slopes. Summary of the Invention

[0004] In order to solve the technical problem that existing finite element simulations are difficult to capture the transient dynamic characteristics of rock masses, resulting in unsatisfactory predictions of rock mass unloading instability, the present invention aims to provide a rock mass unloading simulation and assessment method for high and steep slope excavation construction. The technical solutions adopted are as follows: Perform finite element simulation on the steep slope to divide the unloaded rock mass units; obtain the principal stress data of the rock mass units during construction and simulation, the horizontal and vertical displacements during construction, and the stress data of the support anchors; Obtaining the dynamic response strength of the principal stress based on the changes in the principal stress data of the rock mass unit during the unloading process; obtaining the displacement fluctuation coefficient of each rock mass unit during unloading based on the time series changes in the horizontal and vertical displacements generated by each rock mass unit during unloading; analyzing the synchronous changes in the dynamic response strength and the displacement fluctuation coefficient of the rock mass unit during construction to obtain the synchronous change strength; Analyze the historical correlation changes between the dynamic response intensity and the displacement fluctuation coefficient, and obtain the displacement transient coefficient of the current simulation by combining the synchronous change intensity and the dynamic response intensity during simulation; obtain the disturbance influence coefficient of the current simulation based on the response of the support anchor stress to the displacement of the rock unit when unloading, and combining the displacement transient coefficient; Based on the unloading safety factor and the disturbance influence coefficient output by the finite element simulation, the estimated unloading stability of the rock mass unit is obtained.

[0005] Furthermore, the method for obtaining the dynamic response strength includes: During the unloading process of the rock mass unit, the dynamic response intensity of the corresponding principal stress is obtained according to the principal stress change rate between the starting time and the time when the principal stress reaches its maximum value, combined with the range of the principal stress.

[0006] Furthermore, the method for obtaining the displacement fluctuation coefficient includes: During the unloading process of the rock mass unit, the horizontal displacement at the first and last moments and the range difference of the horizontal displacement during the unloading process are integrated to obtain the horizontal displacement fluctuation factor; the vertical displacement at the first and last moments and the range difference of the vertical displacement during the unloading process are integrated to obtain the vertical displacement fluctuation factor; The horizontal displacement fluctuation factor and the vertical displacement fluctuation factor are integrated to obtain the displacement fluctuation coefficient of the rock mass unit when it is unloaded.

[0007] Furthermore, the method for obtaining the synchronous change intensity includes: A dynamic response strength sequence and a displacement fluctuation coefficient sequence are constructed in the same order of rock mass units, and synchronous variation strength is obtained based on the DTW matching distance between the dynamic response strength sequence and the displacement fluctuation coefficient sequence.

[0008] Furthermore, the method for obtaining the displacement transient coefficient includes: Screening out the historical dynamic response intensities within a preset neighborhood of the dynamic response intensity currently being simulated as reference dynamic response intensities, analyzing the correlation change between the reference dynamic response intensities and the corresponding displacement fluctuation coefficients, and obtaining a correlation factor; The synchronous change intensity, the dynamic response intensity during simulation and the correlation factor are integrated to obtain the displacement transient coefficient of the current simulation.

[0009] Furthermore, the method for obtaining the correlation factor includes: A linear fit is performed on the reference dynamic response intensity and the corresponding displacement fluctuation coefficient, where the horizontal axis corresponds to the reference dynamic response intensity and the vertical axis corresponds to the displacement fluctuation coefficient, and the slope of the fit is used as a correlation factor.

[0010] Furthermore, the method for obtaining the disturbance influence coefficient includes: According to the response of the stress of the support anchor to the displacement of the rock unit when it is unloaded, the stress change of the support anchor corresponding to the change of the unit displacement fluctuation coefficient is obtained as the impact strength coefficient; The displacement transient coefficient and the impact intensity coefficient are integrated to obtain the disturbance influence coefficient of the current simulation.

[0011] Furthermore, the method for obtaining the impact strength coefficient includes: The rock mass units of historical construction are sorted in time series. In the time series, the average value of the ratio of the change in stress of the support anchor rods of adjacent rock mass units to the change in the displacement fluctuation coefficient is used as the impact strength coefficient.

[0012] Furthermore, the method for obtaining the estimated unloading stability includes: After negative correlation mapping and normalization of the disturbance influence coefficient of the current rock mass unit, the mapped value is merged with the unloading safety factor to obtain the estimated unloading stability.

[0013] Furthermore, the rock mass units whose estimated unloading stability is lower than a preset stability threshold are marked as high-risk areas.

[0014] The present invention has the following beneficial effects: The present invention first performs finite element simulation on the steep slope and obtains various data of the rock mass unit to provide a basis for subsequent analysis; further, the dynamic response strength is obtained according to the change of the principal stress data to characterize the instantaneous disturbance amplitude of the principal stress during the unloading process; further, the displacement fluctuation coefficient of each rock mass unit during unloading is obtained according to the time series change of the horizontal and vertical displacements generated by unloading, and the displacement fluctuation generated by the rock mass unit during unloading is quantified; further, the synchronous change of the dynamic response strength and the displacement fluctuation coefficient is analyzed to obtain the synchronous change strength, characterize the consistency relationship of the change trends of the two, and provide a basis for subsequent simulation and evaluation of the current rock mass unloading feasibility. The invention provides a basis for the displacement transient that can be generated; further analyzes the correlation changes of the historical dynamic response intensity and the displacement fluctuation coefficient, extracts the change relationship between the principal stress and the displacement, combines the synchronous change intensity and the dynamic response intensity during simulation, predicts the displacement transient coefficient, and provides a basis for the subsequent prediction of the influence of the displacement change during unloading on the support anchor; further, according to the response of the stress of the support anchor to the displacement of the rock unit during unloading, combined with the displacement transient coefficient, obtains the current simulated disturbance influence coefficient, and evaluates the dynamic influence of unloading on the support structure; finally, the unloading safety factor and the disturbance influence coefficient are integrated to obtain the estimated unloading stability. The present invention integrates finite element simulation and unloading dynamic response characteristics, obtains the principal stress and displacement fluctuation changes of the rock mass, constructs the disturbance influence coefficient, corrects the unloading safety factor, accurately evaluates the unloading stability, and effectively solves the problem that the existing methods are difficult to capture the transient disturbance of the rock mass and the prediction of the instability risk is inaccurate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions and advantages of the embodiments of the present invention or the prior art, the following briefly introduces the drawings required for use in the embodiments or the prior art descriptions. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0016] Figure 1 A flow chart of a rock mass unloading simulation evaluation method for high and steep slope excavation construction provided by one embodiment of the present invention; Figure 2 A real-life picture of a high and steep slope provided by one embodiment of the present invention; Figure 3 A real-life picture of a high and steep slope construction support facility provided by one embodiment of the present invention; Figure 4 A schematic diagram of a rock mass unit of a high and steep slope provided by one embodiment of the present invention; Figure 5 A schematic diagram of the unloading displacement direction of a rock mass unit on a steep slope provided by one embodiment of the present invention; Figure 6 A schematic diagram of a support anchor provided in accordance with an embodiment of the present invention. DETAILED DESCRIPTION

[0017] To further illustrate the technical means and effectiveness of the present invention in achieving its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effectiveness of a rock unloading simulation and assessment method for high and steep slope excavation construction proposed by the present invention. In the following description, references to different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics of one or more embodiments may be combined in any suitable manner.

[0018] Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0019] The following describes in detail a specific scheme of a rock mass unloading simulation evaluation method for high and steep slope excavation construction provided by the present invention with reference to the accompanying drawings.

[0020] See also Figure 1 , which shows a flow chart of a rock mass unloading simulation evaluation method for high and steep slope excavation construction provided by one embodiment of the present invention, specifically comprising: Step S1: Perform finite element simulation on the steep slope to divide the unloaded rock mass units; obtain the principal stress data of the rock mass units during construction and simulation, the horizontal and vertical displacements during construction, and the stress data of the support anchors.

[0021] In one embodiment of the present invention, to conduct finite element simulations and assessments of rock unloading during steep slope excavation, the geometric morphology and structural characteristics of the slope must first be determined. Unmanned aerial vehicle (UAV) photogrammetry technology, equipped with high-precision sensors, captures high-resolution images and surface information of the steep slope, enabling precise measurement and three-dimensional terrain modeling of the slope area. Simultaneously, combining on-site geological surveys with 3D laser scanning technology, key information such as slope elevation, slope angle parameters, rock strata interfaces, and the spatial distribution of joints and faults is collected and recorded. This allows for data on the changes in horizontal and vertical displacement of each rock unit (the finite element software divides the steep slope into several rock units to be unloaded) after unloading.

[0022] The finite element data model was established using ANSYS software.

[0023] Collect principal stress data during on-site excavation: CSIR-type strain gauges are embedded in pre-drilled holes in each rock unit to measure the deformation response of the rock mass during relaxation, thereby inferring the original stress state and obtaining the principal stress values ​​through tensor inversion.

[0024] Collecting parameters related to rock unloading during laboratory simulation tests: Principal stresses during unloading are simulated and measured through true triaxial rock testing. Loading devices (hydraulic or rigid) are set up in three orthogonal directions. A standard-sized rock cylinder is drilled and installed in the true triaxial loading device. Forces are applied to the rock using an actual excavation design simulating rock unloading. The principal stresses are recorded using strain gauges or pressure sensors to obtain the principal stress data during the simulation.

[0025] Data collection for high-steep slope support facilities: Based on the design and installation of on-site support structures, the mechanical parameters of support materials, such as anchors, are collected in real time to monitor tensile stress. An anchor stress monitoring system (anchor sensors) is installed on high-steep slopes to record dynamic stress changes during the unloading phase and obtain stress data for support anchors.

[0026] See also Figure 2 , which shows a real picture of a high and steep slope provided by an embodiment of the present invention; please refer to Figure 3 , which shows a real-life view of a high and steep slope construction support facility provided by one embodiment of the present invention. Figure 4 , which shows a schematic diagram of a rock mass unit of a high and steep slope provided by the present invention, Figure 4 The arrow in the figure points to a rock unit.

[0027] Step S2: According to the changes in the principal stress data of the rock unit during the unloading process, the dynamic response strength of the principal stress is obtained; according to the time series changes in the horizontal and vertical displacements generated by each rock unit during unloading, the displacement fluctuation coefficient of each rock unit during unloading is obtained; and the synchronous changes in the dynamic response strength and displacement fluctuation coefficient of the rock unit during construction are analyzed to obtain the synchronous change strength.

[0028] When using the finite element method to simulate and evaluate the rock unloading effect during the excavation construction process of steep slopes, it uses a single-step convergence solution mechanism to divide the rock mass into units. When a unit is deleted to unload the rock mass, the equilibrium equation is used to solve the equilibrium point of the current state. It does not pay attention to the fluctuations and nonlinear mutations during the unloading process, and ignores the millisecond-level stress wave propagation and transient response involved in processes such as blasting, rapid unloading, and local instability, thereby underestimating the risk of rock disturbance.

[0029] Therefore, the unloading process of the same rock mass was simulated and tested in the laboratory. According to the changes in the principal stress data of the rock unit during the unloading process, the dynamic response intensity of the principal stress was obtained, the transient stress mutation was extracted, and the transient disturbance amplitude of the principal stress during the unloading process was characterized.

[0030] Considering that during actual high and steep slope excavation, the principal stresses of the rock mass can cause horizontal slippage and vertical settlement, support structures are installed to prevent slope collapse and stabilize the slope displacements caused by unloading. To analyze the impact of disturbances on support facilities, we first couple the principal stress fluctuations with the rock mass unit displacement response to identify sudden displacement changes caused by transient stress response fluctuations. Therefore, it is also necessary to obtain the dynamic response intensity during the actual mechanical excavation of the rock mass, and according to the time series changes of the horizontal and vertical displacements generated by the unloading of each rock mass unit, obtain the displacement fluctuation coefficient of each rock mass unit during unloading, and quantify the displacement fluctuations generated by the rock mass unit during unloading, in preparation for the subsequent coupling analysis of the principal stress fluctuations and the displacement response of the rock mass unit.

[0031] Preferably, in one embodiment of the present invention, during the unloading process of the rock mass unit, the greater the range of the principal stress, the greater the maximum difference between the instantaneous stress before and after the unloading disturbance, and the greater the instantaneous disturbance amplitude; the greater the change in the principal stress from the initial moment of rock mass unloading to the time when the principal stress reaches the maximum value, that is, the higher the rate of change, the more severe the instantaneous disturbance of the principal stress during unloading, which means that the dynamic response of the rock mass during the unloading process is stronger; Based on this, the dynamic response intensity of the corresponding principal stress is obtained according to the principal stress change rate between the starting moment and the maximum principal stress value, combined with the range of the principal stress.

[0032] As an example, the maximum principal stress is used as the numerator, and the time from the start to the maximum principal stress is used as the denominator. The ratio of the fractions represents the principal stress change rate, and the product of the principal stress change rate and the principal stress range is used as the dynamic response strength of the corresponding rock mass unit during the unloading process. The principal stress change rate and the principal stress range up to the maximum principal stress are used to represent the change in the principal stress data of the rock mass unit during the unloading process, and are integrated by multiplication.

[0033] It should be noted that the stress state in the rock mass is three-dimensional. Since the maximum principal stress has the most significant impact on slope stability, only the maximum principal stress data are analyzed here. The dynamic response strength analysis process of the shelter unit during actual construction and experimental simulation is consistent, so only one example is taken here for description.

[0034] Preferably, in one embodiment of the present invention, the displacement of the rock mass unit in one direction at the first and last moments during the unloading process represents the cumulative displacement caused by unloading, and to a certain extent reflects the permanent deformation of the rock mass during the entire unloading process; and the difference between the maximum displacement and the minimum displacement in one direction during the unloading process represents the displacement rebound or fluctuation amplitude, which can reflect the transient response intensity and nonlinear deformation capacity caused by disturbance during the unloading process; Based on this, the horizontal displacement at the first and last moments and the range of the horizontal displacement during the unloading process are integrated to obtain the horizontal displacement fluctuation factor; the vertical displacement at the first and last moments and the range of the vertical displacement during the unloading process are integrated to obtain the vertical displacement fluctuation factor.

[0035] The horizontal displacement fluctuation factor and the vertical displacement fluctuation factor are integrated to obtain the displacement fluctuation coefficient of the rock mass unit when unloading.

[0036] As an example, the absolute value of the difference in horizontal displacement between the first and last moments of the unloading process is used as the horizontal displacement, and the product of the horizontal displacement and the range of the horizontal displacement is used as the horizontal displacement fluctuation factor. Similarly, the absolute value of the difference in vertical displacement between the first and last moments of the unloading process is used as the vertical displacement, and the product of the vertical displacement and the range of the vertical displacement is used as the vertical displacement fluctuation factor. The average value of the horizontal displacement fluctuation factor and the vertical displacement fluctuation factor is taken as the displacement fluctuation coefficient of the corresponding rock mass unit when unloading.

[0037] Among them, the time series changes of horizontal and vertical displacements caused by unloading of rock units are respectively analyzed through the displacement at the first and last moments and the displacement extreme difference during the unloading process. Finally, the two directions are integrated to comprehensively characterize the rock movement characteristics caused by unloading, preparing for the subsequent coupling analysis of principal stress fluctuations and rock unit displacement responses.

[0038] It should be noted that when there are multiple horizontal and vertical displacement measurement points on the rock mass unit and multiple measurement data are obtained, the average value of the displacement at the same time point in each direction is taken as the displacement data of the rock mass unit in each direction.

[0039] See also Figure 5 , which shows a schematic diagram of the unloading displacement direction of a rock mass unit of a high and steep slope provided by the present invention, Figure 5 The two arrows in the figure are perpendicular to each other, showing the horizontal and vertical directions. The vertical downward direction is the positive vertical direction, and the horizontal left direction is the positive horizontal direction.

[0040] During the excavation and construction of high and steep slopes, the rock mass will experience two stages: stress redistribution and deformation response during the excavation and unloading process. The sudden stress drop is often accompanied by instantaneous displacement changes. By analyzing the relationship between the principal stress and displacement fluctuation of each rock mass unit, the stress release and deformation response mechanism of the rock mass during the unloading disturbance process can be revealed. Therefore, the synchronous changes of the dynamic response intensity and displacement fluctuation coefficient of the rock mass unit during construction are analyzed, the synchronous change intensity is obtained, and the consistency relationship between the change trends of the two is characterized, which provides a basis for subsequent simulation and evaluation of the displacement transients that may be caused by the current rock mass unloading.

[0041] Preferably, in one embodiment of the present invention, considering that the Dynamic Time Warping (DTW) algorithm can automatically find the optimal matching path between sequences, thereby revealing their overall similarity, and the smaller the DTW matching distance, the higher the change similarity and the greater the intensity of the synchronous change; Therefore, the dynamic response intensity sequence and displacement fluctuation coefficient sequence are constructed in the same order of rock mass units, and the synchronous variation intensity is obtained based on the DTW matching distance between the dynamic response intensity sequence and the displacement fluctuation coefficient sequence.

[0042] As an example, the rock mass units are sorted in chronological order according to the start time of data acquisition of the rock mass units, and the dynamic response intensity sequence and displacement fluctuation coefficient sequence are constructed. The DTW matching distance is used as the independent variable, and after negative correlation mapping through the exp (-x) function, the mapped value is used as the synchronous change intensity.

[0043] The DTW matching distance is used to show the synchronous changes in the dynamic response intensity and the displacement fluctuation coefficient. exp(-x) is an exponential function with the natural constant e as the base, and x is the independent variable. The DTW algorithm and the acquisition of the DTW matching distance are both existing technologies and will not be described in detail.

[0044] As another example, rock mass elements are sorted in ascending order (smallest to largest) based on their peak principal stress values ​​(maximum values).

[0045] Step S3: Analyze the correlation changes between the historical dynamic response intensity and the displacement fluctuation coefficient, and obtain the displacement transient coefficient of the current simulation by combining the synchronous change intensity and the dynamic response intensity during simulation; obtain the disturbance influence coefficient of the current simulation based on the response of the support anchor stress to the displacement of the rock unit when it is unloaded and the displacement transient coefficient.

[0046] Changes in principal stresses can lead to deformation and displacement of the rock mass. By analyzing the instantaneous fluctuations of principal stresses and combining the changing relationship between principal stresses and displacements, we can predict the displacement trend of the slope and the displacement transient coefficient of the next rock unit to be unloaded.

[0047] Therefore, the correlation changes between the historical dynamic response intensity and the displacement fluctuation coefficient are analyzed. Based on the dynamic response intensity of the principal stress of the rock unit unloading currently simulated and evaluated in the laboratory under the same excavation mechanical drilling and blasting settings, combined with the synchronous change intensity that characterizes the change trend relationship, the displacement transient coefficient that may be generated by the current simulated and evaluated rock unloading is obtained, which is convenient for subsequent prediction of the impact of displacement changes during unloading on the support anchor rods and the prediction of the stability of the rock unloading.

[0048] Preferably, in one embodiment of the present invention, considering that historical dynamic response intensities similar to the current simulated dynamic response intensity are more reference-oriented, historical dynamic response intensities within a preset neighborhood of the current simulated dynamic response intensity are first screened out as reference dynamic response intensities; As an example, the preset neighborhood is 70% to 130%, based on the dynamic response intensity of the current simulation. As the benchmark, its preset neighborhood is [ , ].

[0049] Furthermore, considering that the greater the dynamic response intensity of the principal stress during unloading, the greater the change amplitude and intensity of the principal stress, the more likely it is to cause displacement fluctuations, and the larger the displacement fluctuation coefficient, the two show a positive correlation feature. Therefore, the correlation change between the reference dynamic response intensity and the corresponding displacement fluctuation coefficient is analyzed to obtain the correlation factor; As an example, a linear fit is performed on the reference dynamic response intensity and the corresponding displacement fluctuation coefficient. The horizontal axis corresponds to the reference dynamic response intensity, and the vertical axis corresponds to the displacement fluctuation coefficient. Considering that the slope represents the change in the displacement fluctuation coefficient caused by the change in the unit principal stress dynamic response intensity, the fitting slope is used as a correlation factor to represent the correlation change relationship between the historical dynamic response intensity and the displacement fluctuation coefficient.

[0050] The least square method is used for linear fitting, which is a well-known technology and will not be described in detail.

[0051] Finally, the synchronous change intensity, the dynamic response intensity during simulation and the correlation factor are integrated to obtain the displacement transient coefficient of the current simulation.

[0052] As an example, since the dynamic response intensity during simulation is the direct cause of displacement fluctuations, the correlation factor characterizes the driving strength of the principal stress change in the historical data on the displacement fluctuation response. The product of the dynamic response intensity during simulation and the correlation factor is used as the displacement fluctuation degree of the current simulation assessment to obtain the displacement fluctuation potential of the rock mass unit under the current disturbance conditions. The synchronous variation intensity reflects the similarity between the principal stress fluctuation and the displacement fluctuation in the temporal evolution law. It is a correction term for the matching degree between history and simulation. After being multiplied by the synchronous variation intensity, the product is used as the displacement transient coefficient of the current simulation.

[0053] During excavation or unloading of steep slopes, the existing stress field within the rock mass is rapidly released, often triggering sudden and intense transient displacement changes. These sudden and intense changes can easily induce local shearing, cracking, or loosening, acting as precursors to slope instability, block fall, and landslides. Furthermore, these sudden displacement changes can directly transmit stress waves to installed support structures such as anchor bolts, generating an impact response far greater than that of conventional static loads.

[0054] Therefore, according to the response of the stress of the support anchor to the displacement of the rock unit when unloading, combined with the displacement transient coefficient, the current simulated disturbance influence coefficient is obtained, and its dynamic impact on the support structure is evaluated by tracking the response intensity of the instantaneous displacement mutation.

[0055] Preferably, in one embodiment of the present invention, first, based on the response of the stress of the support anchor rod to the displacement of the rock unit when unloading, the stress change of the support anchor rod corresponding to the change of the unit displacement fluctuation coefficient is obtained as the impact strength coefficient.

[0056] As an example, the rock units of historical construction are sorted in time series (according to the start time of data collection). In the time series, the average value of the ratio of the change in the stress of the support anchor rods of adjacent rock units to the change in the displacement fluctuation coefficient is used as the impact strength coefficient.

[0057] Among them, the stress of the support anchor is the average tensile stress peak of all support anchors in the area where the rock unit is located when unloading, that is, the average value of the maximum tensile stress of all support anchors; the absolute value of the difference in the stress of the support anchors of adjacent rock units is used as the numerator, the absolute value of the difference in the displacement fluctuation coefficient is used as the denominator, and the average value of the fractional ratio corresponding to all adjacent rock units is used as the impact strength coefficient.

[0058] As another example, historically constructed rock mass elements are sorted in ascending order by the peak (maximum) principal stress values.

[0059] The displacement transient coefficient and the impact intensity coefficient are further integrated to obtain the disturbance influence coefficient of the current simulation.

[0060] As an example, the product of the displacement transient coefficient and the impact strength coefficient is taken as the independent variable, and after normalization through the sigmoid function, it is used as the disturbance influence coefficient of the current simulation, which indicates the degree of impact on the support anchor rod under the displacement transient coefficient that may be caused when the rock unit of the current simulation evaluation is unloaded.

[0061] See also Figure 6 , which shows a schematic diagram of a support anchor provided by an embodiment of the present invention, Figure 6 The facilities perpendicular to the slope surface are support anchors.

[0062] Step S4: Based on the unloading safety factor and disturbance influence coefficient output by the finite element simulation, the estimated unloading stability of the rock mass unit is obtained.

[0063] Finite element technology is used to simulate and evaluate the rock unloading effect on steep slopes. Ideally, by removing the unloading of rock mass elements, the safety factor of the steep slope after unloading is derived, reflecting the overall stability of the slope system. However, during actual slope excavation, transient stress fluctuations caused by mechanical drilling and blasting can undermine slope stability and lead to complex failure modes such as joint cracking, shear slip, and rock collapse. Therefore, the impact of transient stress fluctuations during unloading needs to be incorporated into the finite element simulation and evaluation process.

[0064] Therefore, the estimated unloading stability of the rock mass unit is finally obtained based on the unloading safety factor and disturbance influence coefficient output by the finite element simulation.

[0065] Preferably, in one embodiment of the present invention, after the disturbance influence coefficient of the current rock mass unit is negatively correlated and normalized, the mapped value is fused with the unloading safety factor to obtain the estimated unloading stability.

[0066] As an example, the difference between the constant 1 and the disturbance influence coefficient is used as the mapping value of the disturbance influence coefficient for negative correlation mapping and normalization, and the product of the mapping value and the unloading safety factor is used as the estimated unloading stability.

[0067] In one embodiment of the present invention, rock mass units whose estimated unloading stability is lower than a preset stability threshold are also marked as high-risk areas. As an example, the preset stability threshold is 0.3.

[0068] For high-risk areas, high-strength support measures can be deployed in advance, such as increasing anchor bolt placement, increasing prestressing levels, or adding damping devices, to enhance the slope's ability to resist localized unloading disturbances. This invention, through a closed-loop simulation-identification-optimization mechanism, accurately predicts and effectively controls the risk of unloading-induced instability during the excavation of steep slopes, improving slope construction safety and support system reliability.

[0069] In summary, to address the technical problem that existing finite element simulations have difficulty capturing the transient dynamic characteristics of rock masses, resulting in unsatisfactory predictions of rock mass unloading instability, the present invention proposes a rock mass unloading simulation and assessment method for high-steep slope excavation construction. The present invention first performs finite element simulation on the high-steep slope and obtains various data of the rock mass unit. The method further analyzes the changes in the principal stress data of the rock mass unit during the unloading process and the time-series changes in the horizontal and vertical displacements generated, and analyzes the synchronous changes between the two to obtain the synchronous change intensity. The correlation between the historical dynamic response intensity and the displacement fluctuation coefficient is further analyzed, and the synchronous change intensity and the dynamic response intensity during the simulation are combined to obtain the displacement transient coefficient of the current simulation. The current simulation disturbance influence coefficient is further obtained based on the response of the support anchor stress to the displacement of the rock mass unit during unloading, combined with the displacement transient coefficient. Finally, the unloading safety factor and the disturbance influence coefficient are integrated to obtain the estimated unloading stability. Through a closed-loop mechanism of simulation-identification-optimization, the method achieves accurate prediction and effective control of the risk of rock mass unloading-induced instability during high-steep slope excavation, thereby improving slope construction safety and support system reliability.

[0070] It should be noted that the order in which the embodiments of the present invention are described above is for illustrative purposes only and does not necessarily represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require the specific order or sequential order shown to achieve the desired results. In certain embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0071] The various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on the differences from other embodiments.

Claims

1. A rock mass unloading simulation and evaluation method for high and steep slope excavation construction, characterized in that: The method comprises: Perform finite element simulation on the steep slope to divide the unloaded rock mass units; obtain the principal stress data of the rock mass units during construction and simulation, the horizontal and vertical displacements during construction, and the stress data of the support anchors; Obtaining the dynamic response strength of the principal stress based on the changes in the principal stress data of the rock mass unit during the unloading process; obtaining the displacement fluctuation coefficient of each rock mass unit during unloading based on the time series changes in the horizontal and vertical displacements generated by each rock mass unit during unloading; analyzing the synchronous changes in the dynamic response strength and the displacement fluctuation coefficient of the rock mass unit during construction to obtain the synchronous change strength; Analyze the historical correlation changes between the dynamic response intensity and the displacement fluctuation coefficient, and obtain the displacement transient coefficient of the current simulation by combining the synchronous change intensity and the dynamic response intensity during simulation; obtain the disturbance influence coefficient of the current simulation based on the response of the support anchor stress to the displacement of the rock unit when unloading, and combining the displacement transient coefficient; Based on the unloading safety factor and the disturbance influence coefficient output by the finite element simulation, the estimated unloading stability of the rock mass unit is obtained.

2. The rock unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The method for obtaining the dynamic response strength includes: During the unloading process of the rock mass unit, the dynamic response intensity of the corresponding principal stress is obtained according to the principal stress change rate between the starting time and the time when the principal stress reaches its maximum value, combined with the range of the principal stress.

3. The rock unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The method for obtaining the displacement fluctuation coefficient includes: During the unloading process of the rock mass unit, the horizontal displacement at the first and last moments and the range difference of the horizontal displacement during the unloading process are integrated to obtain the horizontal displacement fluctuation factor; the vertical displacement at the first and last moments and the range difference of the vertical displacement during the unloading process are integrated to obtain the vertical displacement fluctuation factor; The horizontal displacement fluctuation factor and the vertical displacement fluctuation factor are integrated to obtain the displacement fluctuation coefficient of the rock mass unit when it is unloaded.

4. The rock mass unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The method for obtaining the synchronous change intensity includes: A dynamic response strength sequence and a displacement fluctuation coefficient sequence are constructed in the same order of rock mass units, and synchronous variation strength is obtained based on the DTW matching distance between the dynamic response strength sequence and the displacement fluctuation coefficient sequence.

5. The rock mass unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The method for obtaining the displacement transient coefficient includes: Screening out the historical dynamic response intensities within a preset neighborhood of the dynamic response intensity currently being simulated as reference dynamic response intensities, analyzing the correlation change between the reference dynamic response intensities and the corresponding displacement fluctuation coefficients, and obtaining a correlation factor; The synchronous change intensity, the dynamic response intensity during simulation and the correlation factor are integrated to obtain the displacement transient coefficient of the current simulation.

6. The rock unloading simulation evaluation method for high and steep slope excavation construction according to claim 5 is characterized in that: The method for obtaining the correlation factor includes: A linear fit is performed on the reference dynamic response intensity and the corresponding displacement fluctuation coefficient, where the horizontal axis corresponds to the reference dynamic response intensity and the vertical axis corresponds to the displacement fluctuation coefficient, and the slope of the fit is used as a correlation factor.

7. The rock unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The method for obtaining the disturbance influence coefficient includes: According to the response of the stress of the support anchor to the displacement of the rock unit when it is unloaded, the stress change of the support anchor corresponding to the change of the unit displacement fluctuation coefficient is obtained as the impact strength coefficient; The displacement transient coefficient and the impact intensity coefficient are integrated to obtain the disturbance influence coefficient of the current simulation.

8. The rock unloading simulation evaluation method for high and steep slope excavation construction according to claim 7 is characterized in that: The method for obtaining the impact strength coefficient includes: The rock mass units of historical construction are sorted in time series. In the time series, the average value of the ratio of the change in stress of the support anchor rods of adjacent rock mass units to the change in the displacement fluctuation coefficient is used as the impact strength coefficient.

9. The rock mass unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The method for obtaining the estimated unloading stability includes: After negative correlation mapping and normalization of the disturbance influence coefficient of the current rock mass unit, the mapped value is merged with the unloading safety factor to obtain the estimated unloading stability.

10. The rock mass unloading simulation evaluation method for high and steep slope excavation construction according to claim 1 is characterized in that: The rock mass units whose estimated unloading stability is lower than a preset stability threshold are marked as high-risk areas.

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