A method for identifying drilling stress distribution parameters

Abstract

The present invention discloses a method for identifying borehole stress distribution parameters, and belongs to the technical field of coal mine safety mining engineering. First, the collected borehole stress is preprocessed to eliminate abnormal jump stress; then the peak stress and peak stress depth are identified; the original rock stress level of the borehole is estimated; finally, the elastic core boundary and elastic core resistance line of the borehole are calculated to obtain the peak stress and depth of the borehole, the original rock stress of the borehole, the elastic energy core boundary of the borehole and its resistance line. By analyzing the measured stress distribution of the borehole, the borehole stress parameters used in the impact hazard assessment model are automatically determined, which can provide a data basis for automatically assessing the impact hazard level of the coal body in the lane near the borehole after the intelligent pressure relief drilling rig drills.

Description

Technical Field

[0001] The invention relates to a method for identifying borehole stress distribution parameters and belongs to the technical field of coal mine safety mining engineering. Background Art

[0002] Rock burst is a serious mine dynamic disaster, and its occurrence is mainly related to high stress concentration in coal seams. Large-diameter drilling and pressure relief in coal seams is one of the main technical means to prevent rock burst. Its principle is: by constructing large-diameter boreholes in coal seams, the stress concentration in the coal body around the tunnel is reduced, the stress peak area is transferred to the deep coal body, the elastic energy accumulated in the coal body is released, and the rock burst danger level is reduced. When constructing large-diameter boreholes, by monitoring the working status of the drill rig and drill rod, the stress level at different depths of the borehole can be inverted, and then the stress distribution characteristics of the borehole can be used to evaluate the impact hazard of the coal body in the tunnel near the borehole.

[0003] In response to the problem of evaluating the impact hazard of coal seam tunnels, the present invention discloses a method for identifying borehole stress distribution parameters. Based on the measured stress distribution of the borehole, the method identifies parameters such as the borehole peak stress and its depth, the borehole original rock stress, the borehole elastic core boundary and its resistance line through computer programming. These parameters are required in the proposed high-stress impact model of tunnel surrounding rock under mining vibration load conditions. After obtaining these parameters, the intelligent pressure relief drilling rig can use the impact hazard assessment model to evaluate the impact hazard of the coal body on the side of the tunnel after drilling, and then guide and optimize the subsequent drilling pressure relief work. Summary of the invention

[0004] Purpose of the invention: To address the deficiencies of the prior art, a method for identifying borehole stress distribution parameters is provided, which can automatically identify parameters such as borehole peak stress and its depth, borehole original rock stress, borehole elastic core boundary and its resistance line using the measured borehole stress distribution.

[0005] Technical solution: To achieve the above purpose, a borehole stress distribution parameter identification method of the present invention uses a computer to identify the borehole stress distribution parameters based on the borehole stress distribution obtained after drilling by a drilling rig. The identified parameters include the borehole peak stress and its depth, the borehole original rock stress, the borehole elastic core boundary and its resistance line;

[0006] Specifically:

[0007] First, the stress values ​​at different depths of the borehole are obtained, and then the stress distribution of the borehole is preprocessed to eliminate the abnormal jump stress of jump increase or decrease;

[0008] For the pre-processed borehole stress, the stress levels of each measuring point in the borehole are compared from shallow to deep to find the peak stress of the borehole, and then the depth of the borehole at the peak stress is obtained according to the depth data of the measuring point corresponding to the peak stress of the borehole;

[0009] The potential borehole stress distribution characteristics are divided into five types. According to the discrimination conditions, the measured borehole stress distribution type is determined. Then, the borehole original rock stress level is estimated by using the borehole original rock stress estimation method corresponding to the borehole stress distribution type.

[0010] The elastic core boundary and elastic core resistance line of the borehole are calculated using the obtained original rock stress level, peak stress value and depth value.

[0011] Furthermore, the specific steps to eliminate abnormal stress data with jump increase or decrease are:

[0012] The preset definition of abnormal stress is the stress data point with an average change of greater than or equal to 10MPa per meter. That is, for two adjacent stress data points, when the following formula is satisfied, the stress data of the deeper point of the borehole is determined to be abnormal data and defined as invalid data;

[0013]

[0014] Where: i and σ i-1 are the stress values ​​of the i-th and i-1-th measuring points of the borehole, in MPa; L i and L i-1 are the drilling depths corresponding to the i-th and i-1-th data points of the drilling hole, respectively, in meters.

[0015] Furthermore, the calculation method for finding the maximum drilling stress and its corresponding drilling depth is:

[0016] σ max =max(σ i )

[0017]

[0018] Where: max is the peak drilling stress, in MPa; σ i is the stress value of the i-th measuring point in the borehole, in MPa; is the depth of the peak stress of the borehole, in m; L i is i The drilling depth corresponding to the stress, that is, the drilling depth corresponding to the i-th measuring point, in meters.

[0019] Furthermore, the five types of borehole stress distribution are as follows: 1) the borehole bottom completely enters the original rock stress area; 2) the borehole bottom is in the stress plateau state; 3) the borehole bottom is in the early stage of decline after the stress peak; 4) the borehole bottom is in the late stage of decline after the stress peak; 5) other types;

[0020] By comparing the measured borehole stress distribution with the conditional expressions of the above five types of borehole stress distribution, the distribution type of the measured borehole stress is determined, and then the final in-situ rock stress is estimated according to the in-situ rock stress estimation method of each type of borehole stress;

[0021] Furthermore, the specific judgment conditions for the five types of borehole stress distribution and the corresponding estimation methods of original rock stress are as follows:

[0022] 1) The type of borehole stress distribution when the bottom of the borehole completely enters the original rock stress area needs to meet the following three sets of judgment conditions:

[0023]

[0024]

[0025]

[0026] Where: max is the peak drilling stress, in MPa; is the average stress of the hole 1m below the bottom, in MPa; L n is the hole bottom depth, in m; is the peak stress depth of the borehole, in m; L P-E is the distance from the stress peak to the bottom of the hole: when the coal seam thickness (t m ) is less than or equal to 4m, the coal seam thickness is taken; when the coal seam thickness is greater than 4m, 4m is taken; t m is the thickness of the coal seam, in m; and They are the average stresses at the 1st, 2nd and 3rd meters from the bottom of the borehole, in MPa;

[0027] The method for determining the original rock stress of this distribution type is: if the average stress value of the last 1m of the borehole is If it is greater than the self-weight stress γH calculated according to the buried depth of the borehole, the average stress value of the last 1m of the borehole is taken as the original rock stress of the borehole, that is, Otherwise, the self-weight stress γH calculated according to the borehole burial depth is taken as the original rock stress of the borehole;

[0028] Where: γ is the average bulk density of the overlying rock, in MN / m3 ; H is the depth of the borehole, in m; σ ini is the estimated original borehole rock stress, in MPa;

[0029] 2) The borehole stress distribution type where the bottom of the borehole is in a stress plateau state, when the three sets of judgment conditions 1) the bottom of the borehole completely enters the original rock stress zone cannot be met at the same time, the following conditions need to be met:

[0030]

[0031] The method for determining the original rock stress of this distribution type is: taking the self-weight stress calculated according to the buried depth of the borehole as the original rock stress;

[0032] 3) The type of borehole stress distribution when the bottom of the borehole is in the early stage of decline after the stress peak. If the three sets of judgment conditions in 1) the bottom of the borehole completely enters the original rock stress area cannot be met at the same time, the following conditions need to be met:

[0033]

[0034] Where: and They are the average stresses at the 1st, 2nd, 3rd and 4th meters from the bottom of the hole, in MPa;

[0035] The original rock stress determination method for this distribution type is: firstly Estimate an original rock stress value; if the original rock stress of the borehole estimated by the above formula is greater than the self-weight stress calculated according to the burial depth, then take the estimated value as the original rock stress of the borehole; otherwise, take the self-weight stress calculated according to the burial depth of the borehole as the original rock stress of the borehole;

[0036] 4) The type of borehole stress distribution when the bottom of the borehole is in the late stage of decline after the stress peak. If the three sets of judgment conditions of 1) the bottom of the borehole completely enters the original rock stress area cannot be met at the same time, the following conditions need to be met:

[0037]

[0038] The original rock stress determination method for this distribution type is to estimate the original rock stress in the drilling area using the following formula:

[0039]

[0040]

[0041] In the formula: int() is the integer operator;

[0042] If the original rock stress of the borehole estimated by the above formula is greater than the self-weight stress calculated according to the burial depth, the estimated value is taken as the original rock stress of the borehole; otherwise, the self-weight stress calculated according to the burial depth of the borehole is taken as the original rock stress of the borehole;

[0043] 5) The judgment conditions of the drilling stress distribution types of other types are: the drilling stress distribution does not meet the judgment conditions of the previous four drilling stress distribution types;

[0044] The method for determining the original rock stress of this distribution type is: take the self-weight stress calculated according to the buried depth of the borehole as the original rock stress of the borehole.

[0045] Furthermore, the method for obtaining the borehole elastic core boundary and elastic core resistance line is:

[0046] Using the obtained original rock stress value, peak stress value and depth value of the borehole, the stress values ​​are compared in turn in the deep and shallow parts of the borehole with the peak stress of the borehole as the center; the stress in the shallow part of the borehole is reduced to k times the original rock stress, which is the lower boundary L of the elastic core. C-lower The value range of k is 1.2 to 1.5. The upper boundary L of the elastic core is where the stress in the deep part of the borehole is reduced to k times the original rock stress. C-upper ; The lower boundary of the elastic core of drilling stress L C-lower That is the elastic core resistance line.

[0047] Beneficial effect: The method for identifying borehole stress distribution parameters provided by the present invention can identify borehole stress parameters such as borehole peak stress, peak stress depth, original rock stress, elastic core boundary, elastic core resistance line, etc. based on the measured borehole stress distribution, thereby providing a parameter basis for realizing automatic assessment of the impact hazard of coal bodies in the laneways near the borehole by intelligent pressure relief drilling rigs. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 It is a high stress impact model of coal body on the side of the road under dynamic load conditions of the present invention;

[0049] Figure 2 is a flow chart of a method for identifying drilling stress distribution parameters of the present invention;

[0050] Figure 3 Schematic diagram of the bottom of a borehole completely entering the original rock stress zone of the type of the present invention;

[0051] Figure 4 Schematic diagram of the bottom of a borehole in a stress plateau state according to the present invention;

[0052] Figure 5 It is a schematic diagram of the bottom of a borehole of the present invention being in the early stage of a decline after a stress peak;

[0053] Figure 6 It is a schematic diagram of the bottom of a borehole of the type of the present invention being in the late stage of decline after the stress peak and the bottom of the borehole being in the late stage of decline after the stress peak;

[0054] Figure 7 This is a schematic diagram of the drilling stress distribution obtained when the drilling rig is drilling in the case;

[0055] Figure 8 This is a schematic diagram of the stress distribution parameter identification results based on drilling stress distribution in the case. DETAILED DESCRIPTION

[0056] The present invention will be further described below in conjunction with the accompanying drawings.

[0057] The borehole stress distribution parameters that need to be identified are the parameters used in the high stress impact model of the coal body on the side of the roadway under the condition of mine vibration load, that is, the pure static load condition is equivalent to the dynamic load of 0.

[0058] The shock model is described as follows:

[0059] The stress distribution state in the coal body of the roadway is as follows: Figure 1 As shown in the figure, from the surface of the coal body in the roadway to the deep part of the coal body, there are stress reduction zone, stress increase zone and original rock stress zone. Among them, the stress increase zone poses the greatest threat to the roadway, especially the area with obvious stress increase, which is called the elastic core zone here. Under the superposition of pure static load or surrounding dynamic load, when the stress in the elastic core zone of the coal body in the roadway reaches the coal body failure stress level, part of the elastic energy accumulated in the elastic core zone is consumed in the elastic core coal body failure process, and the remaining part is mainly released in the form of kinetic energy (shock wave). According to the results of the triaxial loading test of laboratory coal samples, the coal sample must reach a certain stress level before unloading before impact failure will occur. This stress level is the critical stress level for the coal sample to undergo impact failure. When the shock wave generated by the impact failure of the elastic core of the coal body in the roadway propagates to the coal body on the surface of the roadway, if the peak vibration velocity of the coal body particles on the surface of the roadway exceeds the critical vibration velocity of the particles, the coal body on the surface of the roadway will undergo impact failure, as shown in the figure. Figure 1 As shown. Therefore, the occurrence of roadway coal body impact needs to meet two conditions: roadway elastic core impact failure condition and roadway surface coal body impact critical velocity condition. When using the measured borehole stress distribution to evaluate the risk of roadway coal body impact near the borehole, it is necessary to identify stress distribution parameters such as peak stress, peak stress depth, original rock stress, elastic core boundary, elastic core resistance line, and the identification process is as follows: Figure 2 shown.

[0060] This method is divided into the following four steps: Step 1: pre-processing of borehole stress to eliminate abnormal jump stress; Step 2: identifying peak stress and peak stress depth; Step 3: estimating the stress level of the original rock of the borehole; Step 4: calculating the elastic core boundary and elastic core resistance line of the borehole.

[0061] Step 1: Pre-treatment of drilling stress to eliminate abnormal jump stress

[0062] Due to the influence of factors such as the working state of the drilling rig, differences in coal body structure, and the reliability of stress inversion technology, the measured borehole stress distribution may have local jumps or decreases, which is seriously inconsistent with the actual continuous and smooth stress distribution. At the same time, when identifying the stress distribution parameters, the borehole stress change gradient needs to be used to judge the characteristics of the borehole stress distribution. The jump change of the borehole stress will seriously affect the accuracy of the corresponding analysis. Therefore, before identifying the stress distribution parameters, it is necessary to preprocess the measured borehole stress distribution to eliminate abnormal stress data that jumps or decreases. Abnormal stress is defined as a stress data point with an average change of greater than or equal to 10MPa per meter. That is, for two adjacent stress data points, when the following formula is satisfied, the stress data at the deeper point of the borehole is determined to be abnormal data and defined as invalid data.

[0063]

[0064] Where: i and σ i-1 are the stress values ​​of the i-th and i-1-th measuring points of the borehole, in MPa; L i and L i-1 The drilling depths corresponding to the i-th and i-1-th data points of the drilling hole, in meters

[0065] Step 2: Identify peak stress and peak stress depth

[0066] Select the pre-processed drilling stress, compare the stress levels of each measuring point from shallow to deep, and find the maximum drilling stress and its corresponding drilling depth, as shown in the following formula:

[0067] σ max =max(σ i )

[0068]

[0069] Where: max is the peak drilling stress, in MPa; σ i is the stress value of the i-th measuring point in the borehole, in MPa; is the depth of the peak stress of the borehole, in m; L i is iThe drilling depth corresponding to the stress, that is, the drilling depth corresponding to the i-th measuring point, in meters.

[0070] Step 3: Estimate the stress level of the original rock in the borehole

[0071] The measured borehole stress distribution is complex and diverse. From the perspective of estimating the original rock stress level of the borehole, the borehole stress distribution can be divided into five types: 1) the bottom of the borehole completely enters the original rock stress area; 2) the bottom of the borehole is in a stress plateau state; 3) the bottom of the borehole is in the early stage of decline after the stress peak; 4) the bottom of the borehole is in the late stage of decline after the stress peak; 5) other situations. For each type of borehole stress distribution, the corresponding original rock stress estimation method is different, which is explained below in combination with the characteristics of borehole stress distribution.

[0072] 1) The bottom of the borehole completely enters the original rock stress area

[0073] There are three main aspects to judge whether the bottom of the borehole has completely entered the original rock stress zone: 1) The stress at the bottom of the hole must be sufficiently reduced relative to the peak stress of the borehole, set to at least 5MPa; 2) There must be a sufficient distance between the bottom of the hole and the peak stress position of the borehole, so that the borehole stress can be reduced from the peak to the original rock stress level. The distance depends on the thickness of the coal seam: 3) The bottom of the hole has entered the stress stability zone, and there is no obvious increase or decrease in the stress level. The stress difference of the last 3 meters is used as the evaluation condition. The above three conditions can be expressed by the following three sets of relationship formulas:

[0074]

[0075]

[0076]

[0077] Where: max is the peak drilling stress, in MPa; is the average stress of the hole 1m below the bottom, in MPa; L n is the hole bottom depth, in m; is the peak stress depth of the borehole, in m; L P-E is the distance from the stress peak to the bottom of the hole: when the coal seam thickness (t m ) is less than or equal to 4m, the coal seam thickness is taken; when the coal seam thickness is greater than 4m, 4m is taken; t m is the thickness of the coal seam, in m; and They are the average stresses at the 1st, 2nd and 3rd meters from the bottom of the borehole, in MPa.

[0078] If the borehole stress distribution satisfies the above three sets of relations, it is considered that the bottom of the borehole has completely entered the original rock stress zone (see Figure 3 ).

[0079] If the average stress value of the last 1m of the drilling is If it is greater than the self-weight stress γH calculated according to the buried depth of the borehole, the average stress value of the last 1m of the borehole is taken as the original rock stress of the borehole, that is, Otherwise, the self-weight stress γH calculated according to the borehole burial depth is taken as the original rock stress of the borehole.

[0080] Where: γ is the average bulk density of the overlying rock, in MN / m 3 ; H is the depth of the borehole, in m; σ ini is the estimated original borehole rock stress, in MPa;

[0081] 2) The bottom of the borehole is in a stress plateau state

[0082] If the borehole stress distribution cannot simultaneously satisfy the three sets of relations in 1), but the difference between the stress in the last 3 meters of the hole bottom and the peak stress is within 2 MPa, then the borehole bottom is considered to be in a stress plateau state (see Figure 4 ). The discriminant relationship for the plateau stress state at the bottom of the borehole is as follows:

[0083]

[0084] If the bottom of the borehole is in a stress plateau state, the original rock stress cannot be determined by the borehole stress distribution, and the deadweight stress calculated according to the borehole burial depth is taken as the original rock stress of the borehole.

[0085] 3) The bottom of the borehole is in the early stage of decline after the stress peak

[0086] If the borehole stress distribution cannot simultaneously satisfy the three sets of relationships in 1), but the average stress gradient in the last 4 meters of the hole bottom is in a continuous upward trend, it is considered that the borehole bottom is in the early stage of decline after the stress peak (see Figure 5 ). At this time, the drilling stress distribution satisfies the following relationship:

[0087]

[0088] Where: and They are the average stresses at the 1st, 2nd, 3rd and 4th meters from the bottom of the hole, respectively, in MPa.

[0089] If the bottom of the borehole is in the early stage of decline after the stress peak, the original rock stress in the borehole area can be estimated by the following formula:

[0090]

[0091] If the original rock stress of the borehole estimated by the above formula is greater than the self-weight stress calculated according to the borehole burial depth, the estimated value is taken as the original rock stress of the borehole; otherwise, the self-weight stress calculated according to the borehole burial depth is taken as the original rock stress of the borehole.

[0092] 4) The bottom of the borehole is in the late stage of decline after the stress peak

[0093] If the borehole stress distribution cannot satisfy the three sets of relations in 1) at the same time, but the average stress gradient in the last 4 meters of the hole bottom is in a continuous downward trend, it is considered that the borehole bottom is in the late stage of decline after the stress peak (see Figure 6 ). At this time, the drilling stress distribution satisfies the following relationship:

[0094]

[0095] If the bottom of the borehole is in the late stage of decline after the stress peak, the original rock stress in the borehole area can be estimated by the following formula:

[0096]

[0097]

[0098] In the formula: int() is the integer operator.

[0099] If the original rock stress of the borehole estimated by the above formula is greater than the self-weight stress calculated according to the borehole burial depth, the estimated value is taken as the original rock stress of the borehole; otherwise, the self-weight stress calculated according to the borehole burial depth is taken as the original rock stress of the borehole.

[0100] 5) Other situations

[0101] If the borehole stress distribution does not conform to the previous four conditions, the self-weight stress of the borehole area is calculated according to the borehole burial depth as the original rock stress of the borehole.

[0102] Step 4: Calculate the borehole elastic core boundary and elastic core resistance line

[0103] After obtaining the original rock stress, peak stress and depth of the borehole from the previous three steps, the stress values ​​are compared in the deep and shallow parts of the borehole with the peak stress as the center. The stress in the shallow part of the borehole is reduced to k times the original rock stress (σ core = kσ ini , k is usually between 1.2 and 1.5) is the lower boundary of the elastic core L C-lower The upper boundary L of the elastic core is where the stress in the deep part of the borehole decreases to k times the original rock stress. C-upper The lower boundary L of the elastic core of drilling stress C-lower That is the elastic core resistance line.

[0104] The following is an explanation based on specific cases:

[0105] Example background: An intelligent pressure relief drill was used to drill a coal seam tunnel (coal thickness is 2.5m, buried depth is 600m, and the average bulk density of the overlying rock is 2.5MN / m 3 ) to decompress large-diameter boreholes. During the decompression process, the stress distribution state of the borehole was obtained by inverting the drill pipe response parameters monitored by the drilling rig, such as Figure 7 The borehole depth is 25m, and the accuracy of the borehole stress obtained by inversion is one stress data point every 10cm.

[0106] Step 1: Use the relationship The drilling stress is pre-processed to remove the abnormal jump stress. After all the drilling stress is compared, it is determined that there is no abnormal jump stress, and the drilling stress can be directly used for subsequent analysis.

[0107] Step 2: Compare the stress magnitudes of each point in the borehole from shallow to deep, and finally determine the maximum value of the borehole stress and its corresponding borehole depth as σ max =35.4MPa and like Figure 8 shown.

[0108] Step 3: Compare and judge whether the stress distribution characteristics of the borehole meet the judgment conditions of the various types of borehole stress distribution given in the present invention. After comparison and confirmation, the borehole stress distribution does not meet the third set of judgment conditions in type 1) "the bottom of the borehole completely enters the original rock stress area" The judgment condition of type 2) "the bottom of the borehole is in a stress plateau state" is not met Does not meet the judgment condition of type 3) "the bottom of the borehole is in the early stage of decline after the stress peak" The judgment condition in type 4) "the bottom of the borehole is in the late stage of decline after the stress peak" is met Therefore, the original rock stress estimation formula in type 4) "the bottom of the borehole is in the late stage of decline after the stress peak" is used to calculate the original rock stress of the borehole, and the calculation result is σ ini =18.5MPa. The borehole self-weight stress calculated according to the borehole burial depth is γH = 15MPa, which is less than the estimated original rock stress σ ini =18.5MPa, so the estimated original rock stress of 18.5MPa is taken as the final original rock stress, such as Figure 8 shown.

[0109] Step 4: Take k = 1.2, that is, 1.2 times the original rock stress (18.5 × 1.2 = 22.2 MPa) as the borehole elastic core boundary stress (σ core), taking the peak stress of the borehole (35.4MPa and 15.5m) as the center, the stress of each measuring point in the shallow and deep parts of the borehole is compared to find the lower and upper boundaries of the elastic core, which are L C-lower =9.8m and L C-upper =23.7m. Therefore, the borehole elastic core resistance line is L C-lower =9.8m, such as Figure 8 shown.

[0110] In summary, the stress distribution parameters based on the stress distribution of the coal body in the roadway are finally obtained as follows: peak stress of the borehole and its depth (σ max =35.4MPa and ), borehole original rock stress (σ ini =18.5MPa), borehole elastic core boundary (L C-lower =9.8m and L C-upper =23.7m) and its resistance line (L C-lower =9.8m).

Claims

1. A method for identifying drilling stress distribution parameters, characterized in that: Based on the borehole stress distribution obtained after drilling by the drilling rig, the borehole stress distribution parameters are identified by computer. The identified parameters include the peak stress and depth of the borehole, the original rock stress of the borehole, the elastic core boundary of the borehole and its resistance line. Specifically: First, the stress values ​​at different depths of the borehole are obtained, and then the stress distribution of the borehole is preprocessed to eliminate the abnormal jump stress of jump increase or decrease; For the pre-processed borehole stress, the stress levels of each measuring point in the borehole are compared from shallow to deep to find the peak stress of the borehole, and then the depth of the borehole at the peak stress is obtained according to the depth data of the measuring point corresponding to the peak stress of the borehole; The potential borehole stress distribution characteristics are divided into five types. According to the discrimination conditions, the measured borehole stress distribution type is determined. Then, the borehole original rock stress level is estimated by using the borehole original rock stress estimation method corresponding to the borehole stress distribution type. The elastic core boundary and elastic core resistance line of the borehole are calculated by using the obtained original rock stress level, peak stress value and depth value of the borehole; According to the characteristics of borehole stress distribution, there are five types of borehole stress distribution, namely: 1) the type in which the bottom of the borehole completely enters the original rock stress area; 2) the type in which the bottom of the borehole is in a stress plateau state; 3) the type in which the bottom of the borehole is in the early stage of decline after the stress peak; 4) The bottom of the borehole is in the late stage of decline after the stress peak; 5) Other types; The method for determining the original rock stress of the type where the bottom of the borehole completely enters the original rock stress zone is: if the average stress value of the last 1m of the borehole is If it is greater than the self-weight stress γH calculated according to the buried depth of the borehole, the average stress value of the last 1m of the borehole is taken as the original rock stress of the borehole, that is, Otherwise, the self-weight stress γH calculated according to the borehole burial depth is taken as the original rock stress of the borehole; The method for determining the original rock stress of the type of stress plateau state at the bottom of the borehole is as follows: the self-weight stress calculated according to the buried depth of the borehole is taken as the original rock stress; The method for determining the original rock stress of the type in which the bottom of the borehole is in the early stage of decline after the stress peak is: first, Estimate an in situ rock stress value; If the original rock stress of the borehole estimated by the above formula is greater than the self-weight stress calculated according to the burial depth, the estimated value is taken as the original rock stress of the borehole; otherwise, the self-weight stress calculated according to the burial depth of the borehole is taken as the original rock stress of the borehole; and They are the average stresses at the 1st, 2nd and 3rd meters from the bottom of the borehole respectively; The method for determining the original rock stress of the borehole bottom in the late stage of decline after the stress peak is as follows: if the estimated original rock stress of the borehole is greater than the self-weight stress calculated according to the burial depth, the estimated value is taken as the original rock stress of the borehole; otherwise, the self-weight stress calculated according to the burial depth of the borehole is taken as the original rock stress of the borehole; The method for determining the original rock stress of other types of situations is: take the self-weight stress calculated according to the buried depth of the borehole as the original rock stress of the borehole.

2. The drilling stress distribution parameter identification method according to claim 1, characterized in that The specific steps to eliminate abnormal stress data that jumps or decreases are: The preset definition of abnormal stress is the stress data point with an average change of greater than or equal to 10MPa per meter. That is, for two adjacent stress data points, when the following formula is satisfied, the stress data of the deeper point of the borehole is determined to be abnormal data and defined as invalid data; Where: i and σ i-1 are the stress values ​​of the i-th and i-1-th measuring points of the borehole, in MPa; L i and L i-1 are the drilling depths corresponding to the i-th and i-1-th data points of the drilling hole, respectively, in meters.

3. The drilling stress distribution parameter identification method according to claim 1, characterized in that The calculation method to find the maximum drilling stress and its corresponding drilling depth is: s max =max(σ i ) Where: max is the peak drilling stress, in MPa; σ i is the stress value of the i-th measuring point in the borehole, in MPa; is the depth of the peak stress of the borehole, in m; L i is i The drilling depth corresponding to the stress, that is, the drilling depth corresponding to the i-th measuring point, in meters.

4. The drilling stress distribution parameter identification method according to claim 1, characterized in that: By comparing the measured borehole stress distribution with the conditional expressions of the above five types of borehole stress distribution, the distribution type of the measured borehole stress is determined, and then the final in-situ rock stress is estimated according to the in-situ rock stress estimation method of each type of borehole stress.

5. The drilling stress distribution parameter identification method according to claim 4, characterized in that: The specific judgment conditions for the five types of borehole stress distribution and the corresponding estimation methods of original rock stress are as follows: 1) The type of borehole stress distribution when the bottom of the borehole completely enters the original rock stress area needs to meet the following three sets of judgment conditions: Where: max is the peak drilling stress, in MPa; is the average stress of the hole 1m below the bottom, in MPa; L n is the hole bottom depth, in m; is the peak stress depth of the borehole, in m; L P-E is the distance from the stress peak to the bottom of the hole: when the coal seam thickness (t m ) is less than or equal to 4m, the coal seam thickness is taken; when the coal seam thickness is greater than 4m, 4m is taken; t m is the thickness of the coal seam, in m; and They are the average stresses at the 1st, 2nd and 3rd meters from the bottom of the borehole, in MPa; Where: γ is the average bulk density of the overlying rock, in MN / m 3 ; H is the depth of the borehole, in m; σ ini is the estimated original rock stress of the borehole, in MPa; 2) The borehole stress distribution type where the bottom of the borehole is in a stress plateau state, when the three sets of judgment conditions 1) the bottom of the borehole completely enters the original rock stress zone cannot be met at the same time, the following conditions need to be met: 3) The type of borehole stress distribution when the bottom of the borehole is in the early stage of decline after the stress peak. If the three sets of judgment conditions in 1) the bottom of the borehole completely enters the original rock stress area cannot be met at the same time, the following conditions need to be met: Where: and They are the average stresses at the 1st, 2nd, 3rd and 4th meters from the bottom of the hole, in MPa; 4) The type of borehole stress distribution when the bottom of the borehole is in the late stage of decline after the stress peak. If the three sets of judgment conditions of 1) the bottom of the borehole completely enters the original rock stress area cannot be met at the same time, the following conditions need to be met: The original rock stress determination method for this distribution type is to estimate the original rock stress in the drilling area using the following formula: In the formula: int() is the integer operator; 5) The judgment conditions for other types of drilling stress distribution types are: the drilling stress distribution does not meet the judgment conditions of the previous four types of drilling stress distribution types.

6. The drilling stress distribution parameter identification method according to claim 1, characterized in that: The method for obtaining the borehole elastic core boundary and elastic core resistance line is: Using the obtained original rock stress value, peak stress value and depth value of the borehole, the stress values ​​are compared in turn in the deep and shallow parts of the borehole with the peak stress of the borehole as the center; the stress in the shallow part of the borehole is reduced to k times the original rock stress, which is the lower boundary L of the elastic core. C-lower The value range of k is 1.2 to 1.

5. The upper boundary L of the elastic core is where the stress in the deep part of the borehole is reduced to k times the original rock stress. C-upper ; The lower boundary of the elastic core of drilling stress L C-lower That is the elastic core resistance line.

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