CN-121999155-A - Fault stability evaluation method based on two-dimensional earth surface deformation non-uniformity

CN121999155ACN 121999155 ACN121999155 ACN 121999155ACN-121999155-A

Abstract

The invention discloses a fault stability assessment method based on two-dimensional earth surface deformation non-uniformity, which comprises the steps of obtaining an area two-dimensional earth surface deformation field, calculating spatial difference degree of the two-dimensional earth surface deformation field, carrying out normalization processing on the two-dimensional earth surface deformation field to form a two-dimensional non-uniformity field, superposing the two-dimensional non-uniformity field and a fault structure, calculating a weakening sensitivity factor of a fault position, carrying out time-step reduction on a fault mechanical parameter according to the weakening sensitivity factor, constructing a dynamic update model of the fault mechanical parameter evolving along with disturbance accumulation, inputting the updated fault mechanical parameter, simulating a fault local instability process and forming a simulation event sequence, carrying out trend comparison on the simulation event sequence and a monitoring event sequence, and determining a fault mechanical parameter dynamic update model for assessing fault stability. According to the invention, the three-dimensional strain concentration effect is equivalently represented by utilizing the difference degree of the two-dimensional deformation field, and fault weakening trend can be identified by utilizing monitoring deformation data or engineering disturbance simulation data without constructing a full three-dimensional coupling model.

Inventors

SHEN HAIMENG
LI XIAYING
XU NUWEN
LI QI

Assignees

中国科学院武汉岩土力学研究所

Dates

Publication Date: 20260508
Application Date: 20260114

Claims (10)

1. A fault stability assessment method based on two-dimensional surface deformation non-uniformity is characterized by comprising the following steps: S1, acquiring a two-dimensional earth surface deformation field of an area, wherein the deformation field is from earth surface deformation monitoring data or numerical simulation data based on engineering disturbance conditions; s2, calculating the spatial difference degree of the two-dimensional earth surface deformation field, and carrying out normalization processing to form a two-dimensional non-uniformity field representing deformation non-uniformity; s3, superposing the two-dimensional non-uniformity field and the fault structure, and calculating a weakening sensitivity factor corresponding to the fault position in a fault projection area; S4, carrying out time-step reduction on the fault mechanical parameters according to the weakening sensitivity factors, setting a residual strength lower limit, and constructing a dynamic update model of the fault mechanical parameters evolving along with disturbance accumulation; S5, inputting updated fault mechanical parameters into the geomechanical numerical model, simulating a fault local instability process and forming a simulation event sequence; S6, comparing the trend of the simulation event sequence with that of the monitoring event sequence, and determining the value of the fault strength reduction parameter in the step S4 according to the comparison result, so as to determine a fault mechanical parameter dynamic update model, wherein the model is used for evaluating the actual activity characteristics of faults.
2. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 1, wherein in S1, the surface deformation monitoring data comprises InSAR, GNSS, level detection data.
3. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 1, wherein in S1, the engineering disturbance condition-based numerical simulation data includes geomechanical numerical simulation results based on injection, extraction, reservoir operating pressure changes, subsurface engineering disturbances or structural stress evolution, and regional deformation fields generated based on empirical models, near-field-far-field deformation coupling models or engineering simplification models.
4. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 1, wherein in S2, spatial variance is calculated for the two-dimensional surface deformation field by adopting an eight-neighborhood laplace differential mode, and normalization processing is performed based on the 95 th percentile of the variance field.
5. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 4, wherein the spatial diversity field is calculated as follows: in the formula, The spatial difference degree field is represented by a spatial difference degree field, Plane coordinates of the two-dimensional earth surface deformation field; Representing the position of a two-dimensional earth deformation field in plane coordinates The amount of surface deformation at the location; Representing the position Surface deformation at the kth adjacent position around N 8 Expressed in terms of coordinate position A set of eight neighborhood positions for the center; 95 th percentile pair based on difference field Normalization processing: in the formula, Representing normalized two-dimensional surface deformation non-uniformity values; expressed in a two-dimensional surface deformation field, a spatial difference degree field For use as a normalized reference value.
6. The method for evaluating the fault stability based on the two-dimensional surface deformation non-uniformity according to claim 1, wherein in S3, the calculation of the attenuation sensitivity factor adopts a weighted manner of attenuation along with the distance in the fault projection area, and the attenuation range is limited in a local area around the fault.
7. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 6, wherein to reflect the influence of surface non-uniformity on different positions of faults decays with distance, an exponential decay kernel function is used: in the formula, D is the position s on fault and the coordinate position in two-dimensional surface deformation field L is the characteristic attenuation length scale; attenuation sensitivity factor for position s on fault Calculated as follows: Wherein A S represents a two-dimensional surface deformation field integral region selected by taking the position s on the fault as the center, and is used for representing the space influence range of deformation non-uniformity around the fault point s.
8. The method for evaluating the stability of a fault based on the two-dimensional surface deformation non-uniformity according to claim 1, wherein in S4, the mechanical parameters of the fault comprise cohesive force and friction angle, and the initial mechanical parameters of any point S on the fault comprise initial cohesive force by adopting a linear reduction model Initial friction angle Thereby obtaining the initial shear strength : In the formula, Representing normal stress at position s on the fault; in order to prevent the fault strength from approaching zero in the process of reducing, the residual cohesive force is set Angle of friction with residual ; The cohesive force and friction angle of the position s on the fault at the time step t+1 are updated as follows: in the formula, And Respectively representing cohesive force of the position s on the fault at time steps t and t+1; And The friction angles of the position s on the fault at time steps t and t+1 are respectively represented; , Is a reduction coefficient, and , ∈(0,1]; Is a weakening sensitivity factor, and ∈[0,1]; The updated shear strength is: in the formula, The shear strength of the position s at the fault at time step t+1 is indicated.
9. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 1, wherein in S5, an event identification mode based on slip increment and contact failure is adopted, namely, when the fault contact position point meets any one of the following conditions, the tangential slip increment exceeds a set threshold value, the contact is converted from a cohesive state to a fracture or slip state, and the shear strength is completely exhausted and instability occurs.
10. The fault stability assessment method based on two-dimensional surface deformation non-uniformity according to claim 1, wherein in S6, the simulated event sequence and the monitored event sequence are compared by adopting time normalization and cumulative event number normalization, the event starting period and cumulative growth trend consistency of the simulated event sequence and the monitored event sequence are compared, and the value of the breaking layer strength breaking parameter in step S4 is determined according to the event starting period and cumulative growth trend consistency, so that a fault mechanical parameter dynamic update model is determined.

Description

Fault stability evaluation method based on two-dimensional earth surface deformation non-uniformity Technical Field The invention relates to the technical field of underground engineering deformation analysis, fault mechanical behavior and microseismic activity evaluation, in particular to a fault stability evaluation method based on two-dimensional surface deformation non-uniformity. Background During injection, production, or other subsurface engineering activities, the earth's surface often develops a deformation profile with significant spatial differences. A large number of researches show that the spatial non-uniformity of deformation can reflect the strain concentration and local instability trend of the underground, and is an important factor influencing fault sliding and microseismic activities. However, to accurately describe how spatial differences in surface deformation affect fault weakness and mobility, it is often necessary to construct a fully three-dimensional coupled geomechanical model that comprehensively models the subsurface three-dimensional stress structure, fault geometry, and mechanical evolution. The three-dimensional model has high data requirement and large calculation amount, is difficult to realize in multi-fault system and regional scale application, and cannot meet the requirements of engineering sites on quick evaluation and scheme comparison. Therefore, the prior art lacks a method capable of directly utilizing the spatial non-uniformity of the two-dimensional surface deformation to represent the equivalent effect of underground strain concentration under the condition of no three-dimensional complex calculation, and accordingly realizing fault weakening trend evaluation and microseismic activity analysis. Disclosure of Invention Aiming at the problems that in the prior art, a three-dimensional coupling geomechanical model is large in calculated amount, a multi-fault system is difficult to analyze efficiently, fault weakening trend cannot be estimated by directly utilizing two-dimensional earth surface deformation obtained through monitoring, and the like, the invention provides a fault stability estimation method based on the two-dimensional earth surface deformation non-uniformity. The technical scheme adopted by the invention is as follows: A fault stability assessment method based on two-dimensional surface deformation non-uniformity comprises the following steps: S1, acquiring a two-dimensional earth surface deformation field of an area, wherein the deformation field is from earth surface deformation monitoring data or numerical simulation data based on engineering disturbance conditions; s2, calculating the spatial difference degree of the two-dimensional earth surface deformation field, and carrying out normalization processing to form a two-dimensional non-uniformity field representing deformation non-uniformity; s3, superposing the two-dimensional non-uniformity field and the fault structure, and calculating a weakening sensitivity factor corresponding to the fault position in a fault projection area; S4, carrying out time-step reduction on the fault mechanical parameters according to the weakening sensitivity factors, setting a residual strength lower limit, and constructing a dynamic update model of the fault mechanical parameters evolving along with disturbance accumulation; S5, inputting updated fault mechanical parameters into the geomechanical numerical model, simulating a fault local instability process and forming a simulation event sequence; S6, comparing the trend of the simulation event sequence with that of the monitoring event sequence, and determining the value of the fault strength reduction parameter in the step S4 according to the comparison result, so as to determine a fault mechanical parameter dynamic update model, wherein the model is used for evaluating the actual activity characteristics of faults. In the above scheme, in S1, the surface deformation monitoring data includes InSAR, GNSS, and level detection data. In the above scheme, in S1, the numerical simulation data based on the engineering disturbance condition includes a geomechanical numerical simulation result based on injection, extraction, reservoir operating pressure change, underground engineering disturbance or structural stress evolution, and a regional deformation field generated based on an empirical model, a near-field-far-field deformation coupling model or an engineering simplification model. In the above scheme, in S2, the spatial difference is calculated for the two-dimensional surface deformation field by adopting an eight-neighborhood laplace difference mode, and normalization processing is performed based on the 95 th percentile of the difference field. In the above scheme, the spatial difference field is calculated as follows: in the formula, The spatial difference degree field is represented by a spatial difference degree field,Plane coordinates of the two-dimensiona