CN116754372A - Method for determining rock mass ground stress value based on Kaiser effect - Google Patents
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
- G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N29/00—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object
- G01N29/14—Investigating or analysing materials by the use of ultrasonic, sonic or infrasonic waves; Visualisation of the interior of objects by transmitting ultrasonic or sonic waves through the object using acoustic emission techniques
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
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- G—PHYSICS
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- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
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- G01N2203/0256—Triaxial, i.e. the forces being applied along three normal axes of the specimen
Abstract
The invention provides a method for determining a rock mass ground stress value based on a Kaiser effect, which comprises the following steps: performing an indoor rock compression test to obtain acoustic emission activity characteristics of each rock sample in the loading process; acquiring peak frequency characteristics of all acoustic emission impact signals of a rock sample, and defining a signal with the front 30% of the acoustic emission peak frequency value as a high-frequency acoustic emission signal by utilizing an acoustic emission impact signal peak frequency-time diagram drawn according to the peak frequency characteristics; calculating the fractal dimension of a high-frequency acoustic emission signal of a rock sample, and determining an axial stress value corresponding to the occurrence time of the Kaiser effect of the rock sample according to the calculated fractal dimension; and obtaining the rock mass ground stress value at the sampling depth according to the axial stress positive value corresponding to the occurrence time of the Kaiser effect of the rock sample. The invention realizes accurate measurement of the rock mass ground stress value on the basis of scientifically searching the rock Kaiser effect point.
Description
Technical Field
The invention belongs to the technical field of underground resource development and utilization, and particularly relates to a method for determining a rock mass ground stress value based on a Kaiser effect.
Background
In recent years, with the large-scale development and exhaustion of earth resources on the earth surface and shallow layers, people start to enter deep underground engineering, the average reservoir depth of the deepest developed oil and gas fields on the world and the land is over 7300 meters, and the exploitation of the earth resources on the deep and the construction and utilization of underground space are important directions of geotechnical engineering. The ground stress is an important influencing factor of deformation and instability of underground engineering, and determining the ground stress characteristics of the rock mass in an engineering site selection area is an important precondition for realizing engineering safety design.
Currently, the method for measuring the rock ground stress mainly comprises two main types of field test methods and indoor test methods. The field test method mainly comprises a hydraulic fracturing method, a full-stress relief method, a geophysical prospecting method and the like, but the methods have the defects of long time consumption, high cost, multiple interference influence factors and the like because of higher requirements on field test conditions, and have poor application effects in the ground stress measurement practice of ultra-deep underground engineering.
The indoor test method comprises an acoustic emission method, a non-elastic strain recovery method, a circumferential wave velocity anisotropy analysis method and the like, and the methods have the advantages of simplicity in operation, strong repeatability, convenience in test operation and the like, but also have the problems of difficult interpretation of test data, low accuracy of test results and the like. Taking an acoustic emission method as an example, when the material receives an external force load, strain energy stored in the material can emit elastic waves to generate an acoustic emission phenomenon; when the stress born by the material is released from the historical highest level, the material is reloaded, when the stress does not reach the previous maximum stress value, few acoustic emissions are generated, and when the stress reaches and exceeds the historical highest level, a large amount of acoustic emissions are generated, and the phenomenon is called as a Kaiser effect which is the basic theory of determining the rock ground stress by an acoustic emission method.
The acquisition of the Kaiser effect point directly affects the rock ground stress measurement result, and the scientific search of the Kaiser effect point of the rock is the key for realizing the accurate measurement of the ground stress. Therefore, for the technical difficulty in determining the rock crustal stress by the acoustic emission method, a simple and practical experimental method which can be operated and executed is needed to realize the scientific and accurate determination of the rock crustal stress value.
Disclosure of Invention
The invention aims to solve the technical problem of providing a method for determining a rock mass ground stress value based on a Kaiser effect aiming at the defects of the prior art.
In order to solve the technical problems, the invention comprises the following steps:
a method for determining a rock mass crustal stress value based on a kessel effect, comprising the steps of:
s1, performing an indoor rock compression test: for obtaining a deep rock sample on site, vertically placing the deep rock sample, taking the central axis direction of the rock sample as a Z axis, taking the normal plane of the Z axis as an XOY plane, and establishing a space rectangular coordinate system; then drilling cores on the rock mass sample along the directions of X, Y, Z and X45 DEG Y, X45 DEG Z, Y DEG Z to obtain six rocks Dan Shiyang in the six directions; respectively carrying out an indoor rock triaxial compression test on each rock sample to obtain acoustic emission activity characteristics of each rock sample in the loading process;
s2, acquiring peak frequency characteristics of all acoustic emission impact signals of each rock sample, and defining a signal with the front 30% of the acoustic emission peak frequency value as a high-frequency acoustic emission signal by utilizing an acoustic emission impact signal peak frequency-time diagram drawn according to the peak frequency characteristics;
s3, calculating the fractal dimension of the high-frequency acoustic emission signal of each rock sample, and determining an axial stress value corresponding to the occurrence time of the Kaiser effect of the rock sample according to the calculated fractal dimension;
and S4, obtaining the rock mass ground stress value at the sampling depth according to the axial stress positive value corresponding to the occurrence time of the six-rock Dan Shiyang Kaiser effect.
Further, in the step S1, the diameter of the rock mass sample is not less than 120mm; the rock sample is a standard cylinder sample, and the diameter of the rock sample is 50mm, and the height of the rock sample is 100mm.
Further, in the step S1, when the triaxial compression test is performed on the rock sample in the room, the confining pressure of the triaxial compression test is set to beWherein gamma is the rock weight, h is the burial depth of the sampled sample; acoustic emission sensors are distributed around the rock sample, and acoustic emission information in the rock sample cracking and damaging process is collected; and (3) counting test data to obtain axial stress-time curves of rock samples in six groups of test processes, an acoustic emission impact counting rate-time curve, acoustic emission signal waveform characteristics and occurrence time.
Further, in the step S2, the step of calculating the peak frequency characteristic of the acoustic emission impact signal of each rock sample is as follows:
s21, for each acoustic emission impact signal, acquiring a time data length value L of the acoustic emission impact signal waveform n N is the number of acoustic emission signals and the length value L i Scaling the maximum value of the width a as a comparison waveform;
s22, determining a comparison waveform, and scaling the comparison waveform for a plurality of times: the scaling width a of the comparison waveform starts from 1 and increases in units of length until the maximum value L is reached n ；
S23, for each scaled comparison waveform, firstly aligning the acoustic emission impact signal waveform with the starting point of the comparison waveform, and then sequentially moving the comparison waveform rightward along a time axis according to unit time tau until the length of the acoustic emission impact signal waveform is covered completely; in the process, the approximation degree value WT of the acoustic emission impact signal waveform at the moment t and the comparison waveform under different comparison orders is calculated according to the following formula a-1 ，…，
Wherein a=1, …, L n ；
S24, obtaining the approximation degree value rangeWherein j is the maximum value of n ＝1,…,L n Obtaining the contrast waveform characteristic under the condition of the zoom width according to the zoom width value a' corresponding to the maximum value, and then calculating to obtain the center frequency value of the contrast waveform according to the following formula>
F in the formula C To compare the original standard center frequency of the waveform, F S The acoustic emission sampling frequency;
s25, constructing a three-dimensional time-frequency diagram of each acoustic emission impact signal by taking time as an X axis, frequency as a Y axis and voltage as a Z axis, and obtaining a peak frequency F corresponding to the position with the maximum voltage n 。
Further, in the step S22, the comparison waveform is according to the formulaAnd determining to obtain the product.
Further, in the step S3, a fractal dimension D of the high-frequency acoustic emission signal of each rock sample i The calculation steps are as follows:
s3-1, for each high-frequency acoustic emission signal, sequentially selecting the grid width delta according to the descending order of unit length k ＝[L i ，L i -1，L i -2，…，1]，k＝1,…,L i ，L i The time data length value of the waveform of the acoustic emission impact signal is represented by i, which is the number of the high-frequency acoustic emission signals;
s3-2 for a selected grid width delta k Voltage of high-frequency acoustic emission signal-the time diagram is divided into width δ k Is equal to the square grid to obtain the number N of the intersection of the waveform curve of the acoustic emission signal and the square grid k ；
S3-3, in terms of grid width delta k The number N of intersections of the waveform curve of the acoustic emission signal and the square grid is taken as the X axis k Plotting log delta for Y-axis k -logN k Curve, fitting the approximate straight line segment in the curve by least square method to obtain slope K of the straight line segment, and recording the slope K as fractal dimension D of the high-frequency acoustic emission signal i 。
Further, in the step S3, a fractal dimension D of the high-frequency acoustic emission signal of each rock sample is calculated i Then, the method further comprises the following steps of determining an axial stress value sigma corresponding to each rock Dan Shiyang Kessel effect occurrence moment N ：
S3-4, fractal dimension D i Is the minimum value D of (2) min The corresponding time is recorded as the Kaiser effect occurrence time;
s3-5, obtaining an axial stress value sigma corresponding to each rock Dan Shiyang Kaiser effect occurrence moment according to an axial stress-time curve of the rock sample obtained by an indoor test N Where N is the number of pieces of the rock sample.
Further, the step S4 specifically includes the following steps:
s41, utilizing six axial positive stress values sigma corresponding to six rock Dan Shiyang Kaiser effect points N+ The six stress component values sigma are calculated according to the following formula x 、σ y 、σ z 、τ xy 、τ yz And τ zx ：
σ N+ ＝σ x l 2 +σ y m 2 +σ z n 2 +2τ xy lm+2τ yz lm+2τ zx nl
Wherein l, m and n are respectively the chord values of the angle between the external normal direction of the rock sample and the X, Y, Z shaft;
s42, respectively calculating three intermediate variables P, W and theta according to the following formulas by using the six calculated stress component values:
wherein:
s43, calculating the rock mass ground stress value sigma at the sampling depth according to the following formula by using the three calculated intermediate variables P, W and theta 1 、σ 2 Sum sigma 3 ：
Further, in the step S4, a rock mass ground stress value σ at the sampling depth is calculated 1 、σ 2 Sum sigma 3 And then, the method further comprises the following steps of calculating the inclination angle and the azimuth angle of the main stress:
s44, obtaining the rock mass ground stress value sigma at the sampling depth by calculation 1 、σ 2 Sum sigma 3 The cosine value m of the included angle between the principal stress direction and the coordinate axes X, Y and Z direction is calculated according to the following formula i 、n i And l i ：
In the method, in the process of the invention,
s45, calculating the inclination angle alpha of the main stress according to the following formula 1 、α 2 And alpha 3 Azimuth angle beta 1 、β 2 And beta 3 ：
Where i=1, 2,3.
The beneficial effects of the invention are as follows:
the method for determining the rock mass crustal stress value based on the Kaiser effect is simple and feasible and can be operated and executed, and the accurate determination of the rock mass crustal stress value is realized on the basis of scientifically searching the rock Kaiser effect point.
Drawings
FIG. 1 is a schematic view of a rock sampling of the present invention;
FIG. 2 is a schematic layout view of acoustic emission sensors for a triaxial compression test of a salt rock sample according to the present invention;
FIG. 3 is a schematic diagram of stress-acoustic emission impact count rate versus time for a salt rock sample of the present invention;
FIG. 4 is a schematic diagram of acoustic emission signal waveforms of the present invention;
FIG. 5 is a frequency-voltage-time schematic of an acoustic emission waveform of the present invention;
FIG. 6 is an acoustic emission peak frequency versus time schematic of the present invention;
FIG. 7 is a voltage versus time schematic of an acoustic emission signal of the present invention;
FIG. 8 is a graph of the grid width versus number of intersections of the present invention;
fig. 9 is a schematic view of the spatial distribution of the ground stress of the rock mass according to the present invention.
Detailed Description
The invention will be described in further detail below with reference to the drawings and the detailed description. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The invention provides a method for determining a rock mass ground stress value based on a Kaiser effect, which comprises the following steps:
s1, performing an indoor rock compression test to obtain acoustic emission activity characteristics of the rock in the loading process.
In the step, a deep rock sample is obtained by a drilling coring method, the depth of the sample position is about 3000m, and the diameter of a cylindrical rock sample drilled by a drill bit is 120mm; for obtaining a deep rock sample on site, vertically placing the deep rock sample, taking the central axis direction of the rock sample as a Z axis, taking the normal plane of the Z axis as an XOY plane, and establishing a space rectangular coordinate system as shown in figure 1, wherein OX is the X axis direction, OY is the Y axis direction, O points are the intersection points of OX, OY and OZ axes, and the OX, OY and OZ axes are perpendicular to each other; then drilling cores on the rock mass sample along the directions of X, Y, Z and X45 DEG Y, X DEG Z, Y DEG Z by using a drilling coring method to obtain six rocks Dan Shiyang in the six directions; the rock sample is a standard cylinder sample, and the diameter of the rock sample is 50mm, and the height of the rock sample is 100mm; and respectively carrying out triaxial compression test on the six standard cylindrical sample samples in six directions to obtain acoustic emission activity characteristics of each rock sample in the loading process.
In the step, when the triaxial compression test of the rock sample is carried out in the room, the confining pressure of the triaxial compression test is set as the pressureWherein gamma is rock weight, 2.3g/cm 3 The buried depth h of the sampling sample is 3000m; acoustic emission sensors are arranged around the rock salt sample, as shown in fig. 2, acoustic emission information in the rock sample cracking and damaging process is collected; and (3) counting test data to obtain axial stress-time curves, acoustic emission impact counting rate-time curves, acoustic emission signal waveform characteristics and occurrence time of rock samples in six groups of test processes, wherein the acoustic emission impact counting rate-time curves, the acoustic emission signal waveform characteristics and the occurrence time are shown in figure 3.
S2, acquiring peak frequency characteristics of all acoustic emission impact signals of each rock sample, and defining a signal with the front 30% of the acoustic emission peak frequency value as a high-frequency acoustic emission signal by utilizing an acoustic emission impact signal peak frequency-time diagram drawn according to the peak frequency characteristics as shown in FIG. 6;
s3, calculating the fractal dimension of the high-frequency acoustic emission signal of each rock sample, and determining an axial stress value corresponding to the occurrence time of the Kaiser effect of the rock sample according to the calculated fractal dimension;
and S4, obtaining the rock mass ground stress value at the sampling depth according to the axial stress positive value corresponding to the occurrence time of the six-rock Dan Shiyang Kaiser effect.
Example 2
In the step S2, the peak frequency characteristic calculation step of the acoustic emission striking signal of each rock sample is as follows:
s21, for each acoustic emission impact signal, acquiring a time data length value L of the acoustic emission impact signal waveform n N is the number of acoustic emission signals and the length value L n Scaling the maximum value of the width a as a comparison waveform;
s22, according to the formulaDetermining a comparison waveform, and scaling the comparison waveform a plurality of times: the scaling width a of the comparison waveform starts from 1 and increases in units of length until the maximum value L is reached n ；
S23, for each scaled comparison waveform, firstly aligning the acoustic emission impact signal waveform with the starting point of the comparison waveform, and then sequentially moving the comparison waveform rightward along a time axis according to unit time tau until the length of the acoustic emission impact signal waveform is covered completely; in the process, the approximation degree value WT of the acoustic emission impact signal waveform at the moment t and the comparison waveform under different comparison orders is calculated according to the following formula a-1 ，…，
Wherein a=1, …, L n ；
S24, obtaining the approximation degree value rangeWherein j is the maximum value of n ＝1,…,L n Obtaining the contrast waveform characteristic under the condition of the zoom width according to the zoom width value a' corresponding to the maximum value, and then calculating to obtain the center frequency value of the contrast waveform according to the following formula>
F in the formula C To compare the original standard center frequency of the waveform, F S The acoustic emission sampling frequency;
s25, constructing a three-dimensional time-frequency diagram of each acoustic emission impact signal by taking time as an X axis, frequency as a Y axis and voltage as a Z axis, and obtaining a peak frequency F corresponding to the position with the maximum voltage n 。
The present embodiment will be described below taking an original acoustic emission impact signal waveform as an example.
(1) Calculating to obtain the time data length value L of the original acoustic emission impact signal waveform 1 =5120 and takes this value as the maximum value of the waveform scaling width a; (2) Scaling the comparison waveform by a width a=1 as shown in fig. 4; (3) Aligning the original acoustic emission impact signal waveform with the starting point of the comparison waveform, and calculating to obtain the approximation degree value WT of the original acoustic emission impact signal waveform and the comparison waveform at the moment t 1-1 = 0.0000261; (4) The comparison waveform is moved rightwards along the time axis for a unit time tau, and the approximation degree value WT of the original acoustic emission impact signal waveform and the comparison waveform at the moment t is calculated 1-2 = 0.0000903; (5) Repeating the step (4) until the waveform length of the original acoustic emission impact signal is covered completely, and respectively calculating the approximation degree value WT obtained by 5118 times of scaling 1-3 ＝0.0000719，WT 1-4 ＝0.0000665，…，WT 1-5120 =0; (6) Increasing the scaling width a by unit length to obtain a=2, …,5120 respectively; (7) When a=2, scaling the comparison waveform according to the width 2, repeating the steps (3) - (5) to obtain the approximation degree value WT under different comparison orders 2-1 ＝0.000178，WT 2-2 ＝0.000103，…，WT 2-5120 =0; when a=3, scaling the comparison waveform according to the width 3, repeating the steps (3) - (5) to obtain the approximation degree value WT under different comparison orders 3-1 ＝0.000117，…，WT 3-5120 =0; …; when a=5120, scaling the comparison waveform according to the width 5120, repeating steps (3) - (5) to obtain the approximation degree value WT under different comparison orders 5120-1 ＝0.001，…，WT 5120-5120 ＝0.000355。
(8) When j is 1 When=1, select the approximation range [ WT ] 1-1 ＝0.0000261，WT 2-1 ＝0.000178，…，WT 5120-1 ＝0.001]Obtaining a scaling width value corresponding to the maximum value, further obtaining a comparison waveform characteristic under the scaling width condition, and calculating to obtain a center frequency value F of the comparison waveform 1 = 139.67kHz. Original standard center frequency F of medium contrast waveform C Acoustic emission sampling frequency f=0.667 S ＝1000kHz。
(9) When j is 1 When=2, the approximation range [ WT ] is selected 1-2 ＝0.0000903，WT 2-2 ＝0.000103，…，WT 5120-2 ＝0.00035]Repeating the step (8) to obtain the central frequency value F of the comparison waveform 2 =95.23 kHz; when j is 1 When=3, the approximation range [ WT ] is selected 1-3 ＝0.0000719，WT 2-3 ＝0.0000865，…，WT 5120-3 ＝0.00047]Repeating the step (8) to obtain the central frequency value F of the comparison waveform 3 = 119.14kHz; …; when j is 1 When=5120, the approximation range [ WT ] is selected 1-5120 ＝0，WT 2-5120 ＝0，…，WT 5120-5120 ＝0.000355]Repeating the step (8) to obtain the central frequency value F of the comparison waveform 5120 ＝333.34kHz。
(10) Taking time as X axis, frequency as Y axis and voltage as Z axis, making three-dimensional time-frequency diagram of the original acoustic emission impact signal, and determining frequency F corresponding to the maximum voltage 1 =81 kHz; (11) Obtaining peak frequencies F of all acoustic emission impact signals in the test process according to the steps (1) - (10) 2 ＝258kHz、F 3 ＝146kHz、…，F 313 ＝85kHz。
(11) The peak frequency versus time plot of all acoustic emission impact signals was plotted, with the signal 30% before the acoustic emission peak frequency value defined as the high frequency acoustic emission signal, as shown in fig. 6.
Example 3
In step S3, the fractal dimension D of the high frequency acoustic emission signal of each rock sample i The calculation steps are as follows:
s3-1, for each high-frequency acoustic emission signal, sequentially selecting the grid width delta according to the descending order of unit length k ＝[L i ，L i -1，L i -2，…，1]，k＝1,…,L i ，L i The time data length value of the waveform of the acoustic emission impact signal is represented by i, which is the number of the high-frequency acoustic emission signals;
s3-2 for a selected grid width delta k Dividing a voltage-time diagram of a high-frequency acoustic emission signal into a width delta k Is shown in fig. 7 (delta) k 100) to obtain the number N of intersection of waveform curve of acoustic emission signal and square k ；
S3-3, in terms of grid width delta k The number N of intersections of the waveform curve of the acoustic emission signal and the square grid is taken as the X axis k Plotting log delta for Y-axis k -logN k Curve, fitting the approximate straight line segment in the curve by least square method to obtain slope K of the straight line segment, and recording the slope K as fractal dimension D of the high-frequency acoustic emission signal i 。
The present embodiment will be described below taking an original acoustic emission impact signal waveform as an example.
(1) Selecting the grid width delta k ＝δ 1 ，δ 1 Time data length value L equal to original acoustic emission impact signal waveform 1 =5120; (2) Dividing a voltage-time diagram of a high-frequency acoustic emission signal into widths delta 1 Is equal to the square grid to obtain the number N of the intersection of the waveform curve of the acoustic emission signal and the square grid 1 =1; (3) Width delta of grid k Decreasing according to unit length to obtain delta respectively k =5119, 5118, …,1. When the grid width delta k When=5119, repeating the step (2) to obtain the corresponding N 2 =1; when delta k When=5118, repeating the step (2) to obtain the corresponding N 3 =1; …; when delta k When=1, repeating the step (2) to obtain the corresponding(4) Drawing log delta by taking the grid width as an X axis and the intersecting number of the acoustic emission signal waveform curve and the square grid as a Y axis k -logN k As shown in fig. 8, a least square method is adopted to fit an approximate straight line segment in the curve to obtain the slope K=1.382 of the straight line segment, and the K value is recorded as the fractal dimension D of the high-frequency acoustic emission signal 1 . (5) According to the steps (1) - (4), calculating to obtain fractal dimension D of all other high-frequency acoustic emission signals 2 ＝1.348、D 3 ＝1.366、…、D i =1.362, i is the number of high frequency acoustic emission signals, obtain [ D ] 1 、D 2 、D 3 、…、D i ]The minimum value of (1) is 1.320, denoted Dmin.
Example 4
In step S3, the fractal dimension D of the high-frequency acoustic emission signal of each rock sample is calculated i Then, the method further comprises the following steps of determining an axial stress value sigma corresponding to each rock Dan Shiyang Kessel effect occurrence moment N ：
S3-4, fractal dimension D i Is the minimum value D of (2) min The corresponding time is recorded as the Kaiser effect occurrence time;
s3-5, obtaining an axial stress value sigma corresponding to each rock Dan Shiyang Kaiser effect occurrence moment according to an axial stress-time curve of the rock sample obtained by an indoor test N Where N is the number of pieces of the rock sample.
Example 5
In step S4, the rock mass ground stress value calculation step at the sampling depth is:
s41, utilizing six axial positive stress values sigma corresponding to six rock Dan Shiyang Kaiser effect points N+ The six stress component values sigma are calculated according to the following formula x 、σ y 、σ z 、τ xy 、τ yz And τ zx ：
σ N+ ＝σ x l 2 +σ y m 2 +σ z n 2 +2τ xy lm+2τ yz lm+2τ zx nl
Wherein l, m and n are respectively the chord values of the angle between the external normal direction of the rock sample and the X, Y, Z shaft;
s42, respectively calculating three intermediate variables P, W and theta according to the following formulas by using the six calculated stress component values:
wherein: j (J) 1 ＝σ x +σ y +σ z ，
S43, calculating the rock mass ground stress value sigma at the sampling depth according to the following formula by using the three calculated intermediate variables P, W and theta 1 、σ 2 Sum sigma 3 ：
σ 1 、σ 2 Sum sigma 3 The maximum value, the minimum value and the intermediate value among the three are respectively the rock mass maximum principal stress value, the rock mass minimum principal stress value and the rock mass intermediate principal stress value.
The acquisition of the rock mass ground stress value will be described by means of measured data.
(1) The positive stress values corresponding to the Kaiser effect points of the six groups of rock samples are respectively as follows: sigma (sigma) Nx ＝59.41MPa、σ Ny ＝56.58MPa、σ Nz ＝67.97MPa、σ Nxy45 ＝59.68MPa、σ Nyz45 ＝63.59MPa、σ Nzx45 = 67.71MPa; (2) calculating six stress component values respectively as follows: sigma (sigma) x ＝59.41MPa，σ y ＝56.58MPa，σ z ＝67.97MPa，τ xy ＝1.685MPa，τ yz ＝1.315MPa，τ zx =4.02 MPa; (3) Calculating to obtain intermediate variable J 1 、J 2 And J 3 The method comprises the following steps of: j (J) 1 ＝183.96，J 2 ＝11225，J 3 = 227280; (4) calculating to obtain intermediate variables P, W and theta respectively as follows: p= -55.8979, w= 0.5269, θ= -139.0422; (5) Calculating the rock mass ground stress value sigma at the sampling depth 1 、σ 2 Sum sigma 3 The method comprises the following steps of: sigma (sigma) 1 ＝69.82MPa，σ 2 ＝58.37MPa，σ 3 = 55.76Mpa, where σ 1 For maximum principal stress, sigma 2 Is the intermediate principal stress, sigma 3 Is the minimum principal stress as shown in fig. 9.
Example 6
In step S4, a rock mass ground stress value sigma at the sampling depth is calculated 1 、σ 2 Sum sigma 3 And then, the method further comprises the following steps of calculating the inclination angle and the azimuth angle of the main stress:
s44, obtaining the rock mass ground stress value sigma at the sampling depth by calculation 1 、σ 2 Sum sigma 3 The cosine value m of the included angle between the principal stress direction and the coordinate axes X, Y and Z direction is calculated according to the following formula i 、n i And l i ：
In the method, in the process of the invention,
s45, calculating the inclination angle alpha of the main stress according to the following formula 1 、α 2 And alpha 3 Azimuth angle beta 1 、β 2 And beta 3 ：
Where i=1, 2,3.
The calculation of the inclination angle and azimuth angle of the principal stress will be described below by means of measured data.
(1) Calculating cosine value l of included angle between main stress direction and direction of coordinate axis X, Y, Z 1 ＝0.3762、l 2 ＝0.4736、l 3 ＝0.7963、m 1 ＝0.1389、m 2 ＝-0.8786、m 3 ＝0.2717、n 1 ＝0.9161、n 2 ＝-0.0613、n 3 -0.2357; (2) calculating inclination angles of principal stresses as follows: alpha 1 ＝66.36、α 2 ＝-3.52、α 3 -13.63, azimuth angles: beta 1 ＝11.42、β 2 ＝-61.67、β 3 ＝-64.57。
Although embodiments of the present invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made therein without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (9)
1. A method for determining a rock mass crustal stress value based on a kessel effect, the method comprising the steps of:
s1, performing an indoor rock compression test: for obtaining a deep rock sample on site, vertically placing the deep rock sample, taking the central axis direction of the rock sample as a Z axis, taking the normal plane of the Z axis as an XOY plane, and establishing a space rectangular coordinate system; then drilling cores on the rock mass sample along the directions of X, Y, Z and X45 DEG Y, X45 DEG Z, Y DEG Z to obtain six rocks Dan Shiyang in the six directions; respectively carrying out an indoor rock triaxial compression test on each rock sample to obtain acoustic emission activity characteristics of each rock sample in the loading process;
s2, acquiring peak frequency characteristics of all acoustic emission impact signals of each rock sample, and defining a signal with the front 30% of the acoustic emission peak frequency value as a high-frequency acoustic emission signal by utilizing an acoustic emission impact signal peak frequency-time diagram drawn according to the peak frequency characteristics;
s3, calculating the fractal dimension of the high-frequency acoustic emission signal of each rock sample, and determining an axial stress value corresponding to the occurrence time of the Kaiser effect of the rock sample according to the calculated fractal dimension;
and S4, obtaining the rock mass ground stress value at the sampling depth according to the axial stress positive value corresponding to the occurrence time of the six-rock Dan Shiyang Kaiser effect.
2. The method for determining a rock mass crustal stress value based on the kesse effect according to claim 1, wherein in said step S1, said rock mass sample diameter is not less than 120mm; the rock sample is a standard cylinder sample, and the diameter of the rock sample is 50mm, and the height of the rock sample is 100mm.
3. The method for determining a rock mass crustal stress value based on the kesai effect according to claim 1, wherein in said step S1, when a triaxial compression test is performed on a rock sample in a room, a triaxial compression test confining pressure is set to beWherein gamma is the rock weight, h is the burial depth of the sampled sample; acoustic emission sensors are distributed around the rock sample, and acoustic emission information in the rock sample cracking and damaging process is collected; and (3) counting test data to obtain axial stress-time curves of rock samples in six groups of test processes, an acoustic emission impact counting rate-time curve, acoustic emission signal waveform characteristics and occurrence time.
4. The method for determining a rock mass crustal stress value based on the kesaic effect according to claim 1, wherein in said step S2, the peak frequency characteristic calculation step of the acoustic emission impact signal of each rock sample is:
s21, for each acoustic emission impact signal, acquiring a time data length value L of the acoustic emission impact signal waveform n N is the number of acoustic emission signals and the length value L n Scaling as a comparison waveformA maximum value of the width a;
s22, determining a comparison waveform, and scaling the comparison waveform for a plurality of times: the scaling width a of the comparison waveform starts from 1 and increases in units of length until the maximum value L is reached n ；
S23, for each scaled comparison waveform, firstly aligning the acoustic emission impact signal waveform with the starting point of the comparison waveform, and then sequentially moving the comparison waveform rightward along a time axis according to unit time tau until the length of the acoustic emission impact signal waveform is covered completely; in the process, the approximation degree value of the acoustic emission impact signal waveform at the moment t and the comparison waveform under different comparison orders is calculated according to the following formula
Wherein a=1, …, L n ；
S24, obtaining the approximation degree value rangeWherein j is the maximum value of n ＝1,…,L n Obtaining the contrast waveform characteristic under the condition of the zoom width according to the zoom width value a' corresponding to the maximum value, and then calculating to obtain the center frequency value of the contrast waveform according to the following formula>
F in the formula C To compare the original standard center frequency of the waveform, F S The acoustic emission sampling frequency;
s25, constructing a three-dimensional time-frequency diagram of each acoustic emission impact signal by taking time as an X axis, frequency as a Y axis and voltage as a Z axis,and obtain the peak frequency F corresponding to the maximum voltage n 。
5. The method of determining a rock mass crustal stress value according to claim 4, wherein in step S22, said comparison waveform is according to the formulaAnd determining to obtain the product.
6. The method for determining rock mass crustal stress values based on the kesse effect according to claim 1, wherein in said step S3, the fractal dimension D of the high frequency acoustic emission signal of each rock sample i The calculation steps are as follows:
s3-1, for each high-frequency acoustic emission signal, sequentially selecting the grid width delta according to the descending order of unit length k ＝[L i ，L i -1，L i -2，…，1]，k＝1,…,L i ，L i The time data length value of the waveform of the acoustic emission impact signal is represented by i, which is the number of the high-frequency acoustic emission signals;
s3-2 for a selected grid width delta k Dividing a voltage-time diagram of a high-frequency acoustic emission signal into a width delta k Is equal to the square grid to obtain the number N of the intersection of the waveform curve of the acoustic emission signal and the square grid k ；
S3-3, in terms of grid width delta k The number N of intersections of the waveform curve of the acoustic emission signal and the square grid is taken as the X axis k Plotting log delta for Y-axis k -logN k Curve, fitting the approximate straight line segment in the curve by least square method to obtain slope K of the straight line segment, and recording the slope K as fractal dimension D of the high-frequency acoustic emission signal i 。
7. The method for determining a rock mass crustal stress value according to claim 6, wherein in step S3, a fractal dimension D of the high-frequency acoustic emission signal of each rock sample is calculated i Thereafter, the method further comprises the following steps to determineAxial stress value sigma corresponding to each rock Dan Shiyang Kaiser effect occurrence moment N ：
S3-4, fractal dimension D i Is the minimum value D of (2) min The corresponding time is recorded as the Kaiser effect occurrence time;
s3-5, obtaining an axial stress value sigma corresponding to each rock Dan Shiyang Kaiser effect occurrence moment according to an axial stress-time curve of the rock sample obtained by an indoor test N Where N is the number of pieces of the rock sample.
8. The method for determining a rock mass crustal stress value based on the kesse effect according to claim 1, wherein said step S4 comprises the steps of:
s41, utilizing six axial positive stress values sigma corresponding to six rock Dan Shiyang Kaiser effect points N+ The six stress component values sigma are calculated according to the following formula x 、σ y 、σ z 、τ xy 、τ yz And τ zx ：
σ N+ ＝σ x l 2 +σ y m 2 +σ z n 2 +2τ xy lm+2τ yz lm+2τ zx nl
Wherein l, m and n are respectively the chord values of the angle between the external normal direction of the rock sample and the X, Y, Z shaft;
s42, respectively calculating three intermediate variables P, W and theta according to the following formulas by using the six calculated stress component values:
wherein:
J 1 ＝σ x +σ y +σ z
s43, calculating the rock mass ground stress value sigma at the sampling depth according to the following formula by using the three calculated intermediate variables P, W and theta 1 、σ 2 Sum sigma 3 ：
9. The method for determining a rock mass crustal stress value based on the kesse effect according to claim 8, wherein in said step S4, a rock mass crustal stress value σ at a sampling depth is calculated 1 、σ 2 Sum sigma 3 And then, the method further comprises the following steps of calculating the inclination angle and the azimuth angle of the main stress:
s44, obtaining the rock mass ground stress value sigma at the sampling depth by calculation 1 、σ 2 Sum sigma 3 The cosine value m of the included angle between the principal stress direction and the coordinate axes X, Y and Z direction is calculated according to the following formula i 、n i And l i ：
In the method, in the process of the invention,
s45, calculating the inclination angle alpha of the main stress according to the following formula 1 、α 2 And alpha 3 Azimuth angle beta 1 、β 2 And beta 3 ：
Where i=1, 2,3.
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