CN-122020784-A - Anchoring side slope risk assessment method considering combined action of time-varying degradation and dynamic load of anchor rod

Abstract

The invention belongs to the technical field of geotechnical engineering and geological disaster prevention and control, and discloses an anchoring slope risk assessment method considering the combined action of time-varying degradation of an anchor rod and dynamic load, which comprises the steps of constructing an anchoring slope stability coefficient formula by combining time-varying attenuation rules of free section rod yield resistance, anchor rod-mortar interface and mortar-rock mass interface bonding caused by the time-varying degradation of the anchor rod based on a segmented sliding surface method and considering the dynamic load action; based on a Monte Carlo probability framework, a reliability index and failure probability are introduced to construct a coupling reliability assessment model, rock-soil mass, an anchoring system, environment and dynamic load parameters are defined as random variable sampling calculation, a coupling effect and failure mode control conversion mechanism are quantified, risk dynamic early warning is carried out based on a sensitivity analysis result, and maintenance advice is provided.

Inventors

• YANG LONGWEI
• WANG BO
• WEN YONGBO
• MENG XIANG
• ZHANG LIHUA
• PENG ZONGYI
• SU ZHEN
• QI ZHIYONG
• XU BO
• JIA JINQING
• TANG ZHENGYANG
• DU XUHUANG
• Mou You
• XIANG XIN
• WANG HAITAO

Assignees

• 中国长江电力股份有限公司

Dates

Publication Date

20260512

Application Date

20260114

Claims (10)

1. 1. The anchoring side slope risk assessment method considering the combined action of the time-varying degradation and the dynamic load of the anchor rod is characterized by comprising the following steps of: S1, data acquisition and processing, namely carrying out engineering geology and environment investigation to obtain slope rock-soil body parameters, anchoring system design parameters and environment aggressiveness data, and cleaning, standardizing and probability distribution fitting the multi-source data; s2, establishing a time-varying degradation model of an anchoring system, namely establishing an anchor rod degradation rate prediction model based on environmental parameters, and further respectively establishing mortar-rock interface bonding resistance Time-varying function and resistance time-varying function of anchor rod-mortar interface Time-varying function of yield resistance of free-section steel bar of anchor rod The overall time-varying resistance of the system takes the minimum of the three: The essence of the anchor system degraded along with the service time is characterized by the method, and the possible failure mode control mechanism conversion is performed; S3, constructing a limit state equation of the combined action of the time-varying degradation of the anchor rod and the dynamic load, namely, constructing the time-varying resistance Combining with a load effect caused by dynamic load, and establishing a limit state equation considering the coupling effect; S4, calculating and analyzing time-varying reliability, namely solving the limit state equation by adopting a reliability method, calculating failure probabilities P f (t) of the side slope in different service ages, drawing a time-varying curve of the failure probability, and analyzing an evolution rule of the time-varying curve; S5, sensitivity analysis and parameter optimization, namely analyzing which parameters have the greatest influence on the slope failure probability P f (t), and taking the 'reduction of the slope full life cycle failure probability' as a target, combining key parameters, and pertinently adjusting design parameters, so that the safety is ensured and meanwhile the economical efficiency is considered.
2. 2. The method for risk assessment of an anchored side slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod according to claim 1, wherein the step S1 comprises the following steps: S1.1, surveying rock-soil mass parameters, namely adopting a combination means of drilling, geophysical prospecting and in-situ testing to find out formation lithology, geological structure, development characteristics of rock mass structural plane and potential slip plane positions of a side slope, acquiring critical physical and mechanical parameters of volume weight, cohesive force, internal friction angle and elastic modulus of the rock-soil mass through an in-situ test and an indoor geotechnical test, and evaluating the space variability of the rock-soil mass; S1.2, investigation of the current situation of an anchoring system, namely checking the design parameters of the arrangement space, length, inclination angle, free section and anchoring section of the prestressed anchor rod, rod body material and specification and grouting body strength grade by referring to an original design drawing; The method comprises the following steps of S1.3, environmental aggressivity investigation, namely arranging a miniature weather station and underground water monitoring points in a side slope area, carrying out continuous monitoring for at least 1 complete year, sampling at anchor rod openings and different depths, testing chemical indexes of pH value, cl - ion concentration, SO 4 ² - ion concentration and resistivity of underground water, testing pH value of the underground water by adopting a pH meter, determining environmental corrosion level, collecting a grouting body core sample, measuring compactness, permeability and chloride ion diffusion coefficient of the grouting body core sample in a laboratory, and evaluating the protection capability of the grouting body core sample on steel bars; s1.4, data cleaning and standardization, namely cleaning all collected data, and removing abnormal values and invalid records; s1.5, unifying the dimensions, namely converting data of different sources and dimensions into a unified format and standard, and eliminating the influence of the dimensions by adopting a 'standard deviation standardization method'; s1.6, probability distribution fitting, namely carrying out probability distribution fitting on random variables such as rock and soil parameters and the like, and determining statistical characteristics of the random variables; s1.7, three-dimensional geological modeling, namely integrating geological investigation data by utilizing GIS or professional geological modeling software to construct a three-dimensional geological model capable of accurately reflecting the formation distribution, structural surface and potential slip surface of the side slope, and providing a geometric foundation for subsequent numerical analysis.
3. 3. The method for risk assessment of an anchored side slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod according to claim 1, wherein the step S2 comprises the following specific steps: S2.1, constructing an anchor rod uniform corrosion rate prediction model, namely calculating the annual corrosion rate i cor of an anchor rod body by adopting an empirical or theoretical model based on indoor accelerated corrosion test data and environment investigation data, and assuming that an anchor rope is uniformly corroded, wherein the corrosion rate calculation expression is as follows: ; kcr is the anchor cable body position correction coefficient, 1.0 is taken, kce is taken as the environmental condition correction coefficient, 4.0 is taken, T is taken as the environmental temperature, RH is the environmental relative humidity, dc is the anchor cable bond coat thickness, and sigma c is the grouting body compressive strength; S2.2, further, carrying out integral prediction on the corrosion rate i cor to obtain the corrosion amount of the anchor rod and steel bar service after t years of service: ; In the formula, Representative is the instantaneous nominal corrosion rate at a particular moment in time τ; S2.3, constructing a time-varying function of the bonding resistance of the mortar-rock mass interface: ; In the formula, The method is characterized by comprising the steps of (1) taking an average value of initial shear strength of grouting mortar and surrounding soil layers, wherein D is the diameter of a drilling hole of an anchor rod, and L m is the effective anchoring section length of a mortar-rock interface; s2.4, constructing a resistance time-varying function of the anchor rod-mortar interface: ; In the formula, The method is characterized by comprising the steps of (1) setting an initial shear strength value between a grouting body and an anchor rod, d b is the diameter of a drilling hole of the anchor rod, L n is the effective anchoring length of an anchor rod-mortar interface, and R (t) is the time-varying attenuation coefficient of the adhesive strength of the anchor rod-mortar interface under the corrosion action; The time-varying attenuation coefficient function expression R (t) is: ; wherein X p (t) is the mass corrosion ratio of the anchor rod in service at the t-th year, and is defined as the percentage ratio of the corrosion lost mass to the original mass; s2.5, constructing a yield resistance time-varying function of the free section steel bar of the anchor rod: ; Wherein d is the diameter of the anchor rod, f k0 is the initial yield strength before corrosion of the anchor rod and eta s (t) is the section corrosion rate of the anchor rod at the moment t, and alpha st (t) is the time-varying reduction coefficient of the yield strength of the anchor rod under the corrosion action at the moment t.
4. 4. The method for risk assessment of an anchored side slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod according to claim 1, wherein said step S3 comprises the steps of: S3.1, establishing an ultimate state equation of the anchoring slope under the action of time-varying degradation of the anchor rod based on the time-varying resistance-dynamic load effect: ; S3.2, establishing an anchor slope limit state equation under the action of dynamic load: the shear strength of the sliding surface of the horizontal stripe unit i can be expressed as follows according to the Mohr-Coulomb failure criterion: ; In the formula, In order for the cohesive force to be high, Is the internal friction angle of the steel plate, For normal stress, a certain safety reserve is needed for realizing long-term stability of the side slope body, namely the shear strength on the sliding surface of the side slope Only partially acting and tangential to the slip plane Forming a balance; assuming that the dynamic safety coefficient of the side slope body is The following steps are: ; In the formula, The length of the sliding arc at the bottom surface of the ith strip block; Is the normal force; According to the stress balance condition of the horizontal bar, the expression of the normal force is as follows: ; Wherein alpha i is the slip plane inclination angle, T' mi is the anchor rod tensile resistance component, and E i and X i are the normal force and the shearing force between strips respectively; Is the dead weight of the ith bar block; Is the difference in normal inter-bar force between adjacent bars; according to the force balance principle, the shearing forces interacted among the strips are counteracted with each other as a whole, the total resultant force is zero, and the expression is as follows: ; Wherein Q hi is the horizontal inertial force of the earthquake; for the axis of the anchor rod and the bar block an included angle between the tangent lines of the bottom surface; obtaining an anchor slope safety coefficient calculation formula under the action of earthquake: ; For the horizontal inertial force of the earthquake, the large effect of Gao Chengfang is considered, and the pseudo-static method is adopted for calculation: ; Acceleration amplification factor According to the sectional definition of the 'hydraulic building anti-seismic design specification'; when H is less than or equal to 40m, the dynamic amplification factors are distributed in a trapezoid, the dynamic amplification factor of the slope top is maximum, the amplification factor of the slope bottom is 1, and the amplification factor of the slope top is 2-3: ; when H is more than or equal to 40 m: ; Wherein H is the total height of the side slope, H i is the height from the center of the bar to the bottom of the slope, and S a is the seismic horizontal action peak acceleration; s3.3, establishing an anchoring slope limit state equation under the combined action of the time-varying degradation of the anchor rod and the dynamic load: ; the ultimate state equation of the anchoring slope under the combined action of the time-varying degradation of the anchor rod and the dynamic load is a function of the service time, the dynamic load horizontal acceleration and the soil parameters.
5. 5. The method for risk assessment of an anchored side slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod according to claim 1, wherein said step 4 comprises the steps of: S4.1, calculating a slope reliability index beta and failure probability P f by adopting a checking algorithm, writing a genetic algorithm code, and determining random variables of each parameter in a limit state equation Z; S4.2, acquiring failure probability of the anchored slope at different service time points by executing the time-varying reliability calculation flow, and deeply analyzing evolution rules of the anchored slope to reveal a slope long-term performance degradation mechanism under a time-varying degradation-dynamic load coupling effect.
6. 6. The method for risk assessment of an anchoring slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod as set forth in claim 5, wherein the step S4.1 is specifically implemented as follows: (1) The random uncertainty of the rock-soil body parameters, the earthquake motion parameters, the anchor rod corrosion environment parameters and the material resistance parameters is determined, the scientificity and the accuracy of probability evaluation results are ensured, and the distribution type and the statistical parameters of all variables are determined; (2) Converting the limit state function Z (t) into a standard normal space; (3) Solving for the verification point x, so that Z (x) =0 and is the closest point to the origin; (4) Calculating a reliability index beta, and calculating failure probability P f =phi (-beta) according to the beta; (5) Setting service age calculation nodes, namely 1) substituting the anchor rod corrosion delta d (T) at the moment into each node, calculating time-varying anchor force T (T), 2) generating a random sample of earthquake peak acceleration S a , 3) calculating beta and P f corresponding to each group of S a by adopting a checking point method, and taking the average value as the failure probability of the service age.
7. 7. The method for risk assessment of an anchored side slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod as set forth in claim 5, wherein the step S4.2 is specifically as follows: (1) And (2) determining a failure mode control mechanism conversion analysis method.
8. 8. The anchoring side slope risk assessment method considering the combined action of time-varying degradation and dynamic load of an anchor rod according to claim 7 is characterized in that nonlinear acceleration growth characteristics comprise 1) service age calculation nodes are set, for each node, side slope failure probability P f (t) of each node is obtained by combining the time-varying degradation parameters and the dynamic load parameters of the anchor rod through a reliability calculation method, 2) a curve of the service age-failure probability is drawn by taking the service age as a transverse axis and the failure probability as a longitudinal axis based on the data of each node P f (t), 3) slope change characteristics of the curve are observed, namely the curve form of mechanical property attenuation caused by the early stage and the middle and later stages of service are distinguished, the transition characteristics of the curve from gradual growth to abrupt growth are identified, and the stage division basis of nonlinear acceleration growth of the failure probability is defined.
9. 9. The method for evaluating the risk of the anchored slope taking the joint action of time-varying degradation and dynamic load of the anchor rod into consideration according to claim 7, wherein the failure mode control mechanism conversion analysis method comprises the following steps: 1) The dominant failure mode identification comprises the steps of defining potential dominant failure modes of an anchoring system, including bonding failure of a grouting body-rock mass interface, bonding failure of a rod body-grouting body interface and tensile strength failure of a free section rod body, calculating anchoring resistance corresponding to different failure modes under each service age node, determining the dominant failure mode of controlling the overall resistance of the anchoring system under each node, 2) analyzing the relevance of failure mode conversion and a P f (t) curve, drawing the P f (t) curve, identifying a curve acceleration turning point, and recording the dominant failure mode of the anchoring system from a grouting body-rock mass interface Failure of rod-grouting interface bond Conversion to free segment rod tensile strength failure The method comprises the steps of 'critical time points', comparing the acceleration turning points of the P f (t) curve with critical time points of the transformation of the dominant failure mode, analyzing the time correlation of the acceleration turning points and the critical time points, verifying the influence of the transformation of the failure mode on the increasing trend of the P f (t) curve, and 3) comparing the magnitude of the anchoring resistance corresponding to each failure mode to determine the dominant failure mode for controlling the integral resistance of the anchoring system under each age node.
10. 10. The method for evaluating the risk of an anchored side slope taking into account the combined action of time-varying degradation and dynamic load of an anchor rod according to claim 1, wherein the step S5 specifically comprises the following steps: S5.1, sensitivity analysis, namely calculating sensitivity coefficients of random variables by adopting a one-time second-order moment method or Monte Carlo simulation, and identifying key parameters with the greatest influence on failure probability; And S5.2, optimizing the parameters, namely, optimizing the key design parameters based on a sensitivity analysis result with the aim of reducing the failure probability of the whole life cycle.

Description

Anchoring side slope risk assessment method considering combined action of time-varying degradation and dynamic load of anchor rod Technical Field The invention relates to the technical field of geotechnical engineering and geological disaster prevention and control, in particular to an anchoring side slope risk assessment method considering the combined action of time-varying degradation and dynamic load of an anchor rod. Background In the field of geotechnical engineering at present, the stability evaluation of an anchoring slope mostly adopts a fixed value safety coefficient method or static reliability analysis, and mainly comprises the following steps: (1) Deterministic analysis method this is the most common analysis method in current engineering. The key idea is to evaluate the stability of the slope by calculating the safety coefficient of the slope through a safety coefficient method or a limit balance method. This approach is typically based on a static load assumption and considers material parameters, loads, etc. as fixed values, without taking into account their inherent randomness and time-varying nature. (2) In order to consider the uncertainty of rock and soil parameters, a reliability theory is introduced in part of research, and a one-time second moment method, monte Carlo simulation and other methods are adopted to calculate the failure probability or reliability index of the slope. However, such methods are still based on the assumption of "time-invariant", i.e. the probability distribution of the resistance and load of the structure is not considered to change throughout the life cycle of the structure, and only static snapshot evaluations of the reliability of the slope at a particular moment can be made. (3) Single factor analysis, when the influence of the environment on the performance of the anchor rod is analyzed, the existing research often carries out the research on the time-varying degradation of the anchor rod, dynamic load and other factors in isolation. On the other hand, a great deal of research is focused on dynamic response of the side slope under the action of dynamic load, the influence of dynamic load transmission on the side slope stress distribution is analyzed through numerical simulation, but the mechanical parameters of a default anchor rod are unchanged, and the reduction of the shock resistance of the anchor rod caused by corrosion is ignored. Both types of researches do not consider the synergistic effect of time-varying degradation-dynamic load, and the true failure mechanism of the anchoring slope under the complex working condition cannot be revealed. These methods have limitations in dealing with bolt time-varying degradation and dynamic load randomness, with the following drawbacks and deficiencies: (1) The prior art does not fully consider the time-varying degradation effect of the anchor rod, the evaluation result deviates from the reality that the traditional method does not incorporate the time-varying degradation of the anchor rod caused by the reduction of the sectional area and the reduction of the tensile strength due to corrosion, and the long-term stability of the slope cannot be accurately predicted, and (2) the expansion effect of the corrosion product can damage the interface bonding of the anchor rod and the grouting body, so that the anchoring force is further weakened. The prior art considers corrosion and dynamic load as independent actions, and does not analyze the synergistic effect, so that the slope instability mechanism cannot be revealed, namely the corrosion damage can reduce the ductility and fatigue life of an anchor rod, the anchor rod is more fragile under the dynamic load, and the environment and load randomness cannot be integrated, even if a reliability method is adopted, only one randomness is considered independently, and a comprehensive probability analysis model for integrating the two simultaneously is lacked. (4) In the prior art, the long-term benefit of the anchor rod design parameter is difficult to quantitatively evaluate, and the best opportunity for maintaining and reinforcing cannot be scientifically determined. In engineering practice, decisions often rely on empirical judgment or "passive response". Disclosure of Invention The invention aims to overcome the defects, provide an anchoring slope risk assessment method considering the combined action of time-varying degradation and dynamic load of an anchor rod, solve the problem that the combined action of time-varying degradation and dynamic load of the anchor rod cannot be comprehensively considered in the anchoring slope risk assessment in the prior art, improve the assessment precision by adopting a reliability assessment method, and provide a quantitative basis for design optimization and maintenance decision through sensitivity analysis. In order to solve the technical problems, the technical scheme adopted by the invention is that an anchoring side slope r