Optical stress measurement system and method using borehole morphology

Abstract

The application discloses a borehole shape method optical ground stress measurement system and method. The method comprises the following steps: creating an ellipse shape general equation; creating a NW coordinate system with the center of a measurement device as the origin, the geomagnetic north (N) direction as the x axis and the geomagnetic west (W) direction as the y axis, and projecting the three-dimensional geometric shape of at least one borehole cross section in a range of any depth of a borehole into the NW coordinate system; fitting the ellipse shape general equation according to the three-dimensional geometric shape of the projected borehole cross section in the NW coordinate system; calculating ellipse shape parameters according to the fitted ellipse shape general equation; and measuring the ground stress according to the ellipse shape parameters.

Description

Technical Field

[0001] This invention relates to the field of geological surveying technology, and more specifically, to an optical geostress measurement system and method based on borehole morphology. Background Technology

[0002] With the development of economic and national defense construction, large-scale infrastructure projects have been launched one after another, especially those involving hydropower development, transportation, energy storage, resource extraction, nuclear waste storage and important national defense works. The vast majority of these major projects are based on rock mass, and technical personnel in this field inevitably have to pay attention to issues such as rock mass structure and geostress.

[0003] Rock mass structure consists of two basic units: structural planes and structural volumes. The shape, scale, properties, combination, and connection characteristics of structural planes and structural volumes determine the intrinsic characteristics of the rock mass. Rock masses are typically classified into monolithic, layered, fractured, and granular structures based on their geological category, integrity, and the type, level, combination, and development degree of structural planes. Detecting the type of rock mass structure is crucial for determining its stability under engineering loads, and research on structural planes has always been an important focus in the fields of rock mechanics and engineering geology both domestically and internationally.

[0004] In-situ stress is the force per unit area within a medium caused by rock deformation. It is one of the basic environments in which rock masses exist and is mainly composed of self-weight stress and tectonic stress. The existence of in-situ stress affects the bearing capacity, deformation, and failure mechanism of rock masses. Measuring in-situ stress in rock masses has theoretical and practical significance for geological structure research, earthquake prediction, and solving related problems in mining, water conservancy, and national defense engineering. It is an important part of geomechanics research. Summary of the Invention

[0005] Based on this, one embodiment of the present invention is an optical geostress measurement method based on borehole morphology.

[0006] The method includes:

[0007] General equation for creating an elliptical shape:

[0008] Equation (1), A·x 2 +2B·xy+C·y 2 +2D·x+2F·y+1=0;

[0009] In equation (1): A, B, C, D, and F are the coefficients in the general equation for the elliptical shape;

[0010] The relationship between creating an elliptical borehole cross-section and in-situ stress:

[0011] Equation (2),

[0012] In Equation 2: σ1 and σ2 are the maximum and minimum in-plane principal stresses, respectively;

[0013] The morphological parameters of the borehole cross-section before deformation are the initial borehole radius a;

[0014] The elliptical shape parameters of the cross-section of the drilled hole after deformation are the major semi-axis R and the minor semi-axis r;

[0015] E.μ represents the rock physical property parameters, namely elastic modulus and Poisson's ratio;

[0016] Create an NW coordinate system with the center of a measuring device as the origin, the geomagnetic north (N) direction as the x-axis and the geomagnetic west (W) direction as the y-axis, and project the three-dimensional geometry of at least one borehole cross-section at any depth range onto the NW coordinate system.

[0017] Based on the three-dimensional geometry of the borehole cross-section projected in the NW coordinate system, the general equation of the elliptical shape in equation (1) is fitted.

[0018] Calculate the ellipse shape parameters based on the fitted general equation of the ellipse shape;

[0019] The ground stress is measured based on the elliptical morphology parameters.

[0020] Preferred,

[0021] The general equation for fitting the elliptical shape is configured as follows:

[0022] Randomly select several random coordinate points projected onto the borehole cross section in the NW coordinate system, calculate the vertical distance from the random coordinate points to the general equation of the elliptical shape, and when the vertical distance reaches the expected value, default to fitting the general equation of the elliptical shape.

[0023] Preferred,

[0024] The ellipse shape parameters are configured as follows:

[0025] According to equation (1), the ellipse morphological parameters are expressed as follows:

[0026] Equation (3),

[0027] In equation (3): the angle between the major semi-axis and the geomagnetic north (N) direction is λ, with clockwise being positive;

[0028] The geostress was measured in the following configuration:

[0029] Calculate the maximum in-plane principal stress σ1, the minimum in-plane principal stress σ2, the azimuth angle λ of the minimum in-plane principal stress, and the azimuth angle λ+90° of the maximum in-plane principal stress according to equations (3) and (2).

[0030] Preferred,

[0031] The three-dimensional geometric configuration is obtained as follows:

[0032] Obtain at least two borehole wall projection points at the current horizontal height;

[0033] Create a first polar coordinate system for the measuring device, and calculate the first spatial position of the hole wall imaging point in the first polar coordinate system based on the parameters of the measuring device and at least two hole wall projection points.

[0034] A second polar coordinate system is created for the borehole wall. A coordinate transformation relationship between the first polar coordinate system and the second polar coordinate system is established based on the positional relationship between the measuring device and the borehole space. Based on the first spatial position and the coordinate transformation relationship, the second spatial position of the borehole wall imaging point in the second polar coordinate system is obtained. The borehole wall coordinate system is obtained based on the second spatial positions of the borehole wall imaging points at at least two consecutive horizontal heights.

[0035] Preferred,

[0036] The measuring device comprises a housing assembly and a laser assembly and a camera device deployed on the housing assembly;

[0037] The lifting device is configured to modulate the horizontal height of the housing assembly along the borehole axis;

[0038] The laser assembly is configured to illuminate at least the borehole wall at the current horizontal height;

[0039] The camera device is configured to acquire the projection point of the aperture wall of the illuminated aperture wall imaging point.

[0040] Preferred,

[0041] The measuring device is configured with a conical mirror deployed on the housing assembly;

[0042] The lens of the camera device is parallel to the axis of the conical mirror and at least covers a portion of the conical mirror;

[0043] The covered portion of the conical mirror is constructed with an upper conical mirror and a lower conical mirror;

[0044] The upper conical mirror and the lower conical mirror have different cone angles;

[0045] The camera device obtains the projection point of the first hole wall through the upper conical mirror;

[0046] The camera device obtains the projection point of the second hole wall through the lower conical mirror;

[0047] The host computer is configured to obtain the first spatial position of the hole wall imaging point in the first polar coordinate system based on the parameters of the measuring device and the first hole wall projection point and the second hole wall projection point.

[0048] Another aspect of the present invention is an optical geostress measurement system based on borehole morphology.

[0049] The system includes an ellipse establishment module, a relationship establishment module, a coordinate transformation module, and an ellipse measurement module;

[0050] The ellipse creation module is used to create the general equation for the shape of an ellipse:

[0051] Equation (1), A·x 2 +2B·xy+C·y 2 +2D·x+2F·y+1=0;

[0052] In equation (1): A, B, C, D, and F are the coefficients in the general equation for the elliptical shape;

[0053] The relationship establishment module is used to create the relationship between the elliptical shape of the borehole cross-section and the in-situ stress:

[0054] Equation (2),

[0055] In Equation 2: σ1 and σ2 are the maximum and minimum in-plane principal stresses, respectively;

[0056] The morphological parameters of the borehole cross-section before deformation are the initial borehole radius a;

[0057] The elliptical shape parameters of the cross-section of the drilled hole after deformation are the major semi-axis R and the minor semi-axis r;

[0058] E.μ represents the rock physical property parameters, namely elastic modulus and Poisson's ratio;

[0059] The coordinate transformation module is used to create an NW coordinate system with the center of a measuring device as the origin, the geomagnetic north (N) direction as the x-axis and the geomagnetic west (W) direction as the y-axis, and to project the three-dimensional geometry of at least one borehole cross-section at any depth range into the NW coordinate system.

[0060] The ellipse measurement module is used to fit the general equation of the ellipse shape of Equation (1) in the NW coordinate system based on the three-dimensional geometric shape of the borehole cross section projected; to calculate the ellipse shape parameters based on the fitted general equation of the ellipse shape; and to measure the ground stress based on the ellipse shape parameters.

[0061] In view of the above-mentioned solutions, the present invention will describe in detail the disclosed exemplary embodiments with reference to the accompanying drawings, which will also make other features and advantages of the embodiments of the present invention clear. Attached Figure Description

[0062] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0063] Figure 1 This is a topology diagram of the system in the embodiment;

[0064] Figure 2 This is a structural diagram of the system in the embodiment;

[0065] Figure 3 This is a structural diagram of the housing assembly in the embodiment;

[0066] Figure 4 This is a structural diagram of the conical mirror assembly in the embodiment;

[0067] Figure 5(a) is a structural diagram of the upper conical truncated mirror in the embodiment;

[0068] Figure 5(b) is a cross-sectional view of the upper conical truncated mirror in the embodiment;

[0069] Figure 6 This is a structural diagram of the lower conical truncated mirror in the embodiment;

[0070] Figure 7 This is a structural diagram of the laser assembly in the embodiment;

[0071] Figures 8(a) and 8(b) are structural diagrams of the laser conical mirror in the embodiment;

[0072] Figure 9 This is a structural diagram of the data acquisition component in the embodiment;

[0073] Figure 10 This is the main working view of the system image acquisition mode in the embodiment;

[0074] Figure 11(a) is a working front view of the system's laser acquisition mode in the embodiment;

[0075] Figure 11(b) is a top view of the system's laser acquisition mode in the embodiment;

[0076] Figure 12 This is a structural view of the system in the embodiment;

[0077] Figure 13 This is a flowchart of the borehole wall projection imaging method in the embodiment;

[0078] Figures 14(a) and 14(b) are schematic diagrams of the optical geostress measurement method of the borehole morphology method in the embodiment. Detailed Implementation

[0079] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0080] The present invention discloses an optical geostress measurement system based on the borehole morphology method of optical reflection principle, which is at least applied to borehole wall projection imaging of geological boreholes.

[0081] Figure 1 The system shown in this embodiment includes at least a measuring device 100, a lifting device 300, and a host computer 400.

[0082] The measuring device 100 is used to acquire borehole wall projection images of the borehole wall 530 at the current horizontal height and / or at a certain depth range based on the horizontal height. The lifting device 300 is used to drive the measuring device 100 to move vertically along the borehole. The host computer 400 is used to receive the borehole wall projection images acquired by the measuring device 100 at different horizontal heights, and to form a borehole wall projection image of the geological borehole by stitching together several consecutive borehole wall projection images.

[0083] refer to Figure 2 As shown, in this embodiment, the measuring device 100 includes a housing assembly 110, a conical mirror assembly 120, a laser assembly, and a data acquisition assembly 140.

[0084] Figure 3 As shown, the shell assembly 110 is cylindrical in shape and, from the far end into the borehole to the near end near the formation surface, sequentially includes a bottom cover 111, an upper glass tube connector 113, a transparent glass tube 112, a lower glass tube connector 116, a rear cover 114, and an inner support 115. The bottom cover 111, upper glass tube connector 113, transparent glass tube 112, lower glass tube connector 116, and rear cover 114 are all cylindrical structures with approximately the same cross-sectional radius. The bottom cover 111, upper glass tube connector 113, transparent glass tube 112, lower glass tube connector 116, and rear cover 114 are connected sequentially along the axial direction. The bottom cover 111 is connected to the upper glass tube connector 113, and the lower glass tube connector 116 is threadedly connected to the rear cover 114.

[0085] Specifically, the end of the lower connector 116 of the glass tube facing the upper connector 113 of the glass tube has an inwardly recessed lower annular step surface on its side wall. The end of the upper connector 113 of the glass tube facing the lower connector 116 of the glass tube has an inwardly recessed upper annular step surface on its side wall. The two ends of the transparent glass tube 112 are respectively fitted with the lower annular step surface and the upper annular step surface. After the transparent glass tube 112 is fitted with the upper annular step surface and the lower annular step surface, liquid colloids for bonding and sealing are injected between the transparent glass tube 112 and the upper annular step surface and the lower annular step surface, respectively. After the liquid colloids solidify, the transparent glass tube 112 forms a stable connection with the upper annular step surface and the lower annular step surface. The rear cover 114 of the outer shell is connected to an inner support 115 inside the housing assembly 110. The inner support 115 is used for the acquisition component 140, and the rear cover 114 of the outer shell has a cable port for wired communication between the acquisition component 140 and the outside.

[0086] Figure 4 As shown, the conical mirror assembly 120 is installed within the housing assembly 110. The conical mirror assembly 120 comprises a truncated mirror bracket 130, an upper conical truncated mirror 121, and a lower conical truncated mirror 122. The upper and lower conical truncated mirrors 121 and 122 are coaxially arranged along their length to form a conical body. The truncated mirror bracket 130 is threaded to the inside of the lower connector 116 of the glass tube, and the lower conical truncated mirror 122 is threaded to the end face of the truncated mirror bracket 130 facing the rear cover 114 of the housing. The upper conical truncated mirror 121 is threaded to the end face of the lower conical truncated mirror 122 facing the rear cover 114 of the housing. The upper and lower conical truncated mirrors 121 and 122 have different cone angles, and their axes coincide with the axis of the housing assembly 110.

[0087] As shown in Figures 5(a) and 5(b), in this embodiment, the upper conical truncated mirror 121 and the lower conical truncated mirror are provided with upper and lower conical surfaces with different cone angles.

[0088] The upper conical truncated mirror 121 has a cone angle of a° and four rotating grooves of c° are uniformly cut around the lower wall of the upper conical surface along the axis. Each groove is required to penetrate the wall, and the rotation angle between adjacent grooves is b°, where c° and b° < 90° and b° + c° = 90°. The laser beam 560 passing through the grooves projects a fan-shaped beam onto the borehole wall 530. Therefore, when the borehole wall 530 is far from the center of the measuring device 100, the borehole wall 530 in the plane of the beam is partially or completely irradiated.

[0089] Preferably, c° can be greater than or much greater than b°. In embodiments where the borehole wall 530 is close to the measuring device 100, the fan-shaped area of ​​the light beam emitted from the slot is large, thereby increasing the irradiation range of the borehole wall 530.

[0090] In some embodiments, b° may be greater than or much greater than c°, and a diffuser is installed in the slot to increase the fan-shaped area of ​​the beam emitted from the slot, thereby increasing the irradiation range of the borehole wall 530.

[0091] Figure 6 As shown, in this embodiment, the lower conical truncated mirror 122 is provided with a lower conical surface combined with the upper conical surface, and the cone angle of the lower conical surface is designed to be d°, where d° ≠ a°.

[0092] In this embodiment, after the upper conical truncated mirror 121 and the lower conical truncated mirror 122 are threadedly connected, the groove is located between the upper and lower conical surfaces and is perpendicular to the axis of the housing assembly 110 and faces the borehole wall 530 of the geological borehole.

[0093] Figure 3 The laser assembly is shown to be installed inside the housing assembly 110, specifically forming a fixed connection with the truncated mirror bracket 130. Figure 7 The laser assembly shown consists of a laser conical mirror 131, a laser transparent glass tube 132, a focusing lens 133, a laser diode 134, and a laser housing 135.

[0094] The central structure of the truncated mirror bracket 130 has a through bracket opening, and the laser housing 135 is threadedly connected to the bracket opening.

[0095] The laser housing 135 has an annular groove at its end facing the support opening. The laser transparent glass tube 132 is located inside the lower conical truncated mirror 122, with its end inserted into the annular groove. Liquid adhesive is applied to the portion of the laser transparent glass tube 132 inserted into the annular groove, and after the liquid adhesive cures, the laser transparent glass tube 132 and the laser housing 135 are firmly connected. The laser diode 134 is deployed inside the laser housing 135 and is firmly bonded to the laser housing 135. A focusing lens 133 is deployed between the laser housing 135 and the laser transparent glass tube 132. The laser housing 135 has a mounting platform formed inwards at its end facing the laser transparent glass tube 132. The focusing lens 133 is sealed and bonded to the mounting platform, achieving a firm connection with the laser housing 135 and a sealed separation between the laser housing 135 and the laser transparent glass tube 132.

[0096] The laser conical mirror 131 is deployed inside the laser transparent glass tube 132 and is bonded to the laser transparent glass tube 132 to achieve a stable connection.

[0097] As shown in Figures 8(a) and 8(b), in this embodiment, the axis of the laser conical mirror 131 is the same as the axis of the housing assembly 110, and the tip points vertically downwards toward the center of the laser diode 134, with a cone angle of e°. ​​The laser beam 560 emitted by the laser diode 134, after passing through the focusing lens 133, is incident on the tip of the laser conical mirror 131 and the conical surface centered at the tip. The conical surface of the laser conical mirror 131 reflects the laser beam 560 horizontally at a right angle, making the incident and reflected light perpendicular to each other; that is, the incident light is parallel to the axis of the housing assembly 110, and the emitted light is perpendicular to the axis of the housing assembly 110. Simultaneously, the emitted light reflected by the laser conical mirror 131 passes precisely through the groove created by the upper conical truncated mirror 121 and is projected onto the borehole wall 530.

[0098] When the laser beam 560 is projected onto the borehole wall 530, a portion of the borehole wall 530 is illuminated. The illuminated portion of the borehole wall 530 takes a portion of the laser beam 560 as incident light and reflects it onto the upper and lower conical surfaces, respectively. After reflecting the incident light, the upper and lower conical surfaces project the reflected light onto the direction of the rear cover 114 of the housing, specifically onto the lens axis of the camera device. Since the upper and lower conical truncated mirrors, the laser cone, and the laser are all located on the axis of the housing assembly 110, the multiple outgoing light beams reflected by the upper conical surface will converge at a focal point on the axis of the housing assembly 110, and the multiple outgoing light beams reflected by the lower conical surface will converge at a focal point on the axis of the housing assembly 110.

[0099] Preferably, the laser housing 135 has an outwardly protruding limiting peripheral plate on its periphery. The diameter of the limiting peripheral plate is larger than the diameter of the bracket opening. This allows the laser conical mirror 131 to pass through the groove when the limiting peripheral plate is in contact with the bracket opening, thus achieving the installation and limiting of the laser assembly on the conical mirror assembly 120.

[0100] Figure 9 The image shows the installation of the acquisition component 140 within the inner bracket 115 in this embodiment. The acquisition component 140 includes an acquisition housing, a processing circuit 141, a camera 142, and an LED light group 144.

[0101] In this embodiment, the processing circuit 141, camera 142 and LED light group 144 are mounted on the acquisition housing, and the acquisition housing is threadedly connected to the inner bracket 115.

[0102] Specifically, camera 142 is mounted on a data acquisition housing, and the lens of the acquisition housing is coaxial with the housing assembly 110. The vertically downward projected area of ​​the camera 142 lens at least covers the entire upper and lower conical surfaces. LED light groups 144 are mounted around the camera lens 143 on a ring-shaped light panel, which is fixedly connected to the data acquisition housing. The processing circuit 141 is a power supply and compass data acquisition circuit, an integrated electronic component made from finished electronic components such as an electronic compass, transformer module, noise reduction and filtering module, and digital-to-analog converter module, i.e., integrated on a PCB circuit board. The PCB circuit board performs functions such as geomagnetic direction measurement, voltage conversion, interference reduction, and analog-to-digital signal conversion. The PCB circuit board is threadedly connected to the data acquisition housing. Camera 142 and LED beads are connected to corresponding circuits on the PCB circuit board via signal lines.

[0103] Based on this, the measuring device 100 in this embodiment provides at least two different acquisition modes, namely image acquisition mode and laser acquisition mode.

[0104] Figure 10 The optical structure of the image acquisition mode in this embodiment is shown.

[0105] In this embodiment, when the measuring device 100 is implemented in image acquisition mode, firstly, the LED light group 144 emits a white light beam vertically downwards for illumination within the housing assembly 110. The white light beam is changed to a horizontal beam angle after passing through the upper conical truncated mirror 121 and the lower conical truncated mirror 122. The changed white light beam passes through the transparent glass tube 112 and illuminates the borehole wall 530 of the geological borehole, clearly illuminating the borehole wall 530. Subsequently, the illuminated portion of the borehole wall 530 emits upper and lower conical projection light rays 550. The upper conical projection light 540 is reflected by the upper conical truncated mirror 121 and enters the lens of the camera 142, while the lower conical projection light 550 is reflected by the lower conical truncated mirror 122 and enters the optical center of the camera 142 lens.

[0106] Therefore, in this embodiment, when the measuring device 100 is at a horizontal height, it can clearly acquire the white light projection image of the borehole wall 530. Meanwhile, because the upper and lower conical truncated mirrors 121 and 122 have different cone angles, depending on the configured cone angles, the first borehole wall region corresponding to the first projection image acquired by the camera 142 through the upper conical truncated mirror 121, and the second borehole wall region corresponding to the second projection image acquired through the lower conical truncated mirror 122, may exhibit three situations: tangent, intersecting, or far apart.

[0107] When tangent, the first hole wall region and the second hole wall region are adjacent and do not overlap. The camera 142 acquires the projected images of the first hole wall region and the second hole wall region at the current horizontal height, respectively.

[0108] When the distance is far, the first hole wall region and the second hole wall region are not adjacent, and the camera 142 acquires the projected images of the first hole wall region and the second hole wall region at the current horizontal height respectively.

[0109] When they intersect, the first hole wall region and the second hole wall region are adjacent and partially overlap. The camera 142 acquires the projected images of the first hole wall region and the second hole wall region at the current horizontal height, respectively. The first hole wall region and the second hole wall region acquired by the camera 142 partially overlap, that is, the camera 142 can acquire the projected images of the same hole wall region from different perspectives.

[0110] Figures 11(a) and 11(b) show the optical structure of the laser acquisition mode in this embodiment.

[0111] In this embodiment, when the measuring device 100 is implemented in laser acquisition mode, firstly, the laser emits a vertically upward laser beam 560 for calibration within the laser housing 135. After being reflected by the laser cone, the laser beam 560 becomes horizontal and scattered in all directions. The altered laser beam 560 passes precisely through the groove and enters the space between the laser assembly and the housing assembly 110, and is then projected onto the borehole wall 530 through the transparent glass tube 112. The laser beam 560 forms a monochromatic light band on the borehole wall 530. Subsequently, the portion of the borehole wall 530 illuminated by the monochromatic light band emits upper and lower cone projection light rays 550. The upper cone projection light 540 is reflected by the upper cone truncated mirror 121 and enters the lens of the camera 142, while the lower cone projection light 550 is reflected by the lower cone truncated mirror 122 and enters the optical center of the camera 142 lens.

[0112] Therefore, in this embodiment, when the measuring device 100 is at a horizontal height, it can clearly acquire the projected image of the borehole wall 530 laser. Meanwhile, because the upper and lower conical truncated mirrors 121 and 122 have different cone angles, depending on the configured cone angle, the first borehole wall region corresponding to the first projected image acquired by the camera 142 through the upper conical truncated mirror 121, and the second borehole wall region corresponding to the second projected image acquired through the lower conical truncated mirror 122, may exhibit three situations similar to the image acquisition mode: tangent, intersecting, and far apart. These will not be elaborated further here.

[0113] Figure 12As shown, in this embodiment, the lifting device 300 includes a cable pulling mechanism, an integrated upper cable 220 and lower cable 210, and a roller. An angle encoder is synchronously mounted on the roller. The distal end of the lower cable 210 has a threaded connecting rod, which is threaded downwards to the rear cover 114 of the outer casing. Cables are wrapped within the upper cable 220 and lower cable 210. The cables pass through a clearance hole in the rear cover 114 and connect to a PCB circuit board, where they are connected to corresponding circuits for transmitting the acquired media stream and other signals to the host computer 400. Simultaneously, as a medium for lifting the measuring device 100, the proximal end of the upper cable 220 bypasses the roller and faces horizontally towards the host computer 400, with the cable extending from the upper cable 220 and connecting to the host computer 400. Therefore, when the cable pulling mechanism displaces the cable, the measuring device 100 can also change its current horizontal height within the borehole. Of course, the cable pulling mechanism can be any mechanism capable of pulling the cable.

[0114] When camera 142 acquires image data, it transmits the collected image data to the PCB circuit for processing. After modulation, conversion, and marking of the corresponding geomagnetic data, the image data is transmitted to the host computer 400 via a transmission cable. The host computer 400 then acquires the hole wall projection image based on the processed image data. Simultaneously, the host computer 400 obtains the current moving direction and distance of the measuring device 100 using the angle encoder, and calculates the current horizontal height based on the initial horizontal height of the measuring device 100. At this point, the host computer 400 can associate each horizontal height with the corresponding acquired hole wall projection image and geomagnetic data.

[0115] In this embodiment, during image acquisition mode, the host computer 400 acquires multiple horizontal white light hole wall projection images, transforms and stitches these horizontal hole wall projection images to form a continuous projection image, thereby enabling hole wall projection imaging for geological boreholes of any depth range across the entire borehole section.

[0116] In this embodiment, during laser acquisition mode, the host computer 400 performs coordinate calculations based on polar coordinates to measure the three-dimensional geometric shape of the borehole wall 530.

[0117] Considering the wide depth range of geological boreholes, the area of ​​the borehole wall 530 acquired by the system of this invention at each horizontal height is small. Therefore, in order to achieve borehole wall projection imaging of the entire borehole section and any depth range, it is necessary to stitch together the borehole wall projection images acquired by the host computer 400.

[0118] This embodiment discloses a measurement method applied to geological boreholes. The method uses the optical geostress measurement system based on the borehole morphology method disclosed in this invention, which is based on an image acquisition mode.

[0119] S101, the transmission cable and measuring device 100 are driven to move vertically by the rope pulling device. The displacement of the transmission cable causes the roller to rotate. The rotation angle and rotation direction of the roller are collected by the angle encoder and the angle signal and direction signal are transmitted to the host computer 400. The host computer 400 obtains the real-time horizontal height of the measuring device 100 based on the rotation angle, direction and initial horizontal height of the roller.

[0120] S102, the LED light group 144 emits a white light beam vertically downwards. After being reflected by the laser mirror assembly, the white light beam passes through the housing assembly 110 and illuminates the borehole wall 530, thereby illuminating the borehole wall 530 within the current horizontal height range.

[0121] S103, the illuminated portion of the borehole wall 530 emits upper conical projection light rays and lower conical projection light rays 550, which are projected onto the upper conical truncated mirror 121 and the lower conical truncated mirror 122.

[0122] S104, the upper conical truncated mirror 121 and the lower conical truncated mirror 122 respectively reflect the upper conical projection light ray and the lower conical projection light ray 550 to the optical center 510 of the camera lens.

[0123] S105, the lens of camera 142 acquires the image signal after obtaining the reflected upper conical projection light and lower conical projection fiber, and sends the image signal to the processing unit. After signal modulation and conversion, and marking the geomagnetic direction data of the image, the image signal is sent to the host computer 400 to obtain the hole wall projection image.

[0124] S106, as the measuring device 100 moves along the axial direction of the geological borehole, the host computer 400 acquires the borehole wall projection images at each horizontal height, as well as the rotation angle and direction of the angle encoder, and aligns the borehole wall projection images with the conversion angle and rotation direction.

[0125] S107, the host computer 400 calculates the moving distance and moving direction of the measuring device 100 according to the rotation angle, rotation direction and roller diameter, and makes several consecutive borehole wall projection images correspond to the moving distance, moving direction and geomagnetic direction. The host computer 400 transforms and splices multiple borehole wall projection images to form a borehole wall projection image of the entire borehole section and any depth range of the geological borehole.

[0126] Considering that geological boreholes are located within rock masses, and that the stress conditions and rock mass structure within these masses cause varying degrees of deformation in the boreholes—for example, stress can deform the cross-section of a borehole in a complete rock mass from a circle to an ellipse—and can also cause displacement and shifting of incomplete rock masses, forming a sliding surface between two displaced rock masses. When a geological borehole passes through this sliding surface, the movement of the rock mass will cause discontinuities in the borehole wall 530, forming steep slopes or step surfaces. Therefore, the morphology of the borehole wall 530 within a rock mass is related to the properties and structure of the rock mass, and the three-dimensional geometric morphology analysis of the borehole wall 530 has significant practical implications and research value.

[0127] This embodiment discloses a measurement method applied to borehole walls. To analyze the three-dimensional geometry of the borehole wall 530 and achieve complete three-dimensional measurement, the method uses the optical geostress measurement system based on the borehole morphology method disclosed in this invention, which is based on a laser acquisition mode.

[0128] Previously, when the borehole wall 530 of the geological borehole entered the overlapping area 520 formed by the upper cone projection light ray and the lower cone projection light ray 550, the laser vertically irradiated the borehole wall 530, and a monochromatic light band was formed on the borehole wall 530. Here, an imaging point P and a symmetrical point P' of the borehole wall 530 were illuminated by the monochromatic light band.

[0129] The illuminated borehole wall 530 in the overlapping region 520 is projected onto the upper conical truncated mirror 121 and the lower conical truncated mirror 122, forming two monochromatic projection light bands respectively. The imaging point P of the borehole wall 530 is projected onto the upper conical surface of the upper conical truncated mirror 121 as point A, and onto the lower conical surface of the lower conical truncated mirror 122 as point C. The symmetrical point P' is projected onto the upper conical surface of the upper conical truncated mirror 121 as point B, and onto the lower conical surface of the lower conical truncated mirror 122 as point D.

[0130] The projections of the upper conical truncated mirror 121 and the lower conical truncated mirror 122 are incident on the lens optical center of the camera 142. The projected image information is captured by the photosensitive element of the camera 142, and the camera 142 acquires the projected image of the aperture wall. Here, points A and B of the upper conical truncated mirror 121 are established, and their corresponding points in the aperture wall projection image of the camera 142 are points A' and B', respectively. Points C and D of the lower conical truncated mirror 122 are corresponding points C' and D', respectively, in the aperture wall projection image of the camera 142.

[0131] When the borehole wall 530 and the measuring device 100 are relatively displaced, the positions of the upper conical truncated mirror 121 and the lower conical truncated mirror 122 relative to the borehole wall 530 change. The positions of the projection points (points A, B, C, and D) of points P and P' on the conical surfaces of the upper and lower conical truncated mirrors 121 and 122 change synchronously, thereby changing the positions of the projection points (points A', B', C', and D') of the borehole wall projection image projected by the camera 142.

[0132] Furthermore, this embodiment provides steps for calculating the spatial position of the symmetrical point P' of the borehole wall 530 in polar coordinates and for measuring its three-dimensional geometric shape.

[0133] S201, the spatial position of the lens optical center of the camera 142 is point F, O1 is the bottom midpoint of the lower conical truncated mirror 122, and the center point of the photosensitive element of the camera 142 is point O.

[0134] S202, Create a polar coordinate system for measuring device 100, i.e., the direction where O1 F is located is the polar axis, O1 is the origin, the north direction of the geomagnetic direction is the zero position, and the clockwise direction is the positive direction of the polar coordinate system.

[0135] S203, the symmetrical point P' of the borehole wall 530 is projected onto the lower conical truncated mirror 122 as point D, and simultaneously projected onto the upper conical truncated mirror 121 as point B. Passing through the optical center 510 of the camera lens, it is projected onto the photosensitive element to form a projected image. The projection point of point D on the photosensitive element is point D', and the projection point of point B on the photosensitive element is point B'.

[0136] S204. Based on the fixed connection between the photosensitive element, the optical center of the camera lens 142, the lower conical truncated mirror 122, and the upper conical truncated mirror 121, the distance O1F from the bottom midpoint (point O1) of the lower conical truncated mirror 122 to the optical center 510 (point F) of the camera lens, and the distance OF from the optical center 510 (point F) of the camera lens to the midpoint (point O) of the photosensitive element, can be determined. Based on the positional relationship between the projection points (points D' and B') of the photosensitive element and the center point (point O) of the photosensitive element, the mechanical dimensions of the upper and lower conical truncated mirrors 121 and 122, and the relative spatial positional relationship of the mechanical components, the spatial position of point P' in the polar coordinate system can be determined.

[0137] Therefore, when the laser beam 560 illuminates the borehole wall 530 and a monochromatic light band is formed on the borehole wall 530, if the symmetrical point P' is located within the monochromatic light band, then the spatial position of the borehole wall illuminated by the monochromatic light band in the polar coordinate system can be calculated based on the relative position of the monochromatic light band to the center point (point O) of the photosensitive element in the borehole wall projection image of the camera 142.

[0138] S205, the measuring device 100 moves along the axial direction of the borehole, illuminating the borehole wall 530 at different horizontal heights with a monochromatic light strip, thereby enabling the camera 142 to continuously acquire projection images of the borehole wall at different horizontal heights. Simultaneously, the rotation angle and direction of the rotary encoder are acquired in real time, so that the spatial position of the borehole wall in the polar coordinate system corresponds to the rotation angle and direction of the rotary encoder.

[0139] S206, based on the rotation angle, direction, and roller diameter of the rotary encoder, calculate the moving distance and moving direction of the measuring device 100, and establish the correspondence between the spatial position of the continuous hole wall in the polar coordinate system and the moving distance, moving direction, and geomagnetic direction data.

[0140] S207. Since the cross-sectional reference shape of a geological borehole is a general ellipse, the reference shape of the borehole wall 530 is a general elliptical cylinder. Therefore, a polar coordinate system is created for the borehole wall 530, with the borehole axis as the polar axis, the borehole opening center point as the origin, the north direction of the geomagnetic direction as the zero point, and clockwise as the positive direction. When the polar axis of the polar coordinate system is collinear with the polar axis of the measuring device 100, and the origin of the polar coordinate system is the relative distance between the bottom midpoint of the lower conical truncated mirror 122 and the borehole opening center point, the spatial position of the borehole wall calculated in the device polar coordinate system of the measuring device 100 can be transformed into the three-dimensional spatial position of the borehole wall 530, thus obtaining the three-dimensional geometric shape of the borehole wall within the entire borehole section and any depth range.

[0141] Furthermore, considering that geostress is a natural stress inherent in the Earth's crust, mainly composed of the self-weight stress of the rock mass and tectonic stress caused by geological structures, it is a major cause of deformation and instability in underground or slope engineering projects such as mining, water conservancy and hydropower, subways, and tunnels. High geostress during engineering construction is a direct factor controlling the successful completion of the entire project. Therefore, conducting geostress measurement has become an effective means of controlling and predicting geological hazards in underground engineering, providing important basic design data for the safe construction of engineering projects, and has significant research value in geotechnical engineering construction, disaster early warning, and other fields.

[0142] In response, this embodiment discloses an optical geostress measurement method based on borehole morphology for geological drilling. The method utilizes the optical geostress measurement system based on borehole morphology disclosed in this invention, which is based on a laser acquisition mode.

[0143] Prior to implementation of the method in this embodiment, the cross-section of the borehole wall 530 is configured to be elliptical. Then, the three-dimensional geometric shape data of the borehole wall 530 measured by the measuring device 100 is used to establish the relationship between the borehole shape and the ground stress. By measuring the borehole shape at different locations in the borehole, the ground stress state at different locations in the rock mass is calculated.

[0144] When continuous measurements are taken at different heights using the measuring device 100, it is necessary to continuously and quickly complete the measurement and calculation of the borehole cross-sectional shape and the in-situ stress. This embodiment presents a rapid calculation method for the complete borehole wall 530.

[0145] S501. Create the general equation for the elliptical shape, expressed as:

[0146] A·x 2 +2B·xy+C·y 2 +2D·x+2F·y+1=0

[0147] In Equation 1: A, B, C, D, and F are coefficients in the general equation for the elliptical shape.

[0148] The relationship between creating the elliptical shape of the borehole cross-section and the in-situ stress is expressed as:

[0149]

[0150] In Equation 2: σ1 and σ2 are the geostress components within the borehole cross section, which are the maximum in-plane principal stress and the minimum in-plane principal stress, respectively;

[0151] The morphological parameters of the borehole cross-section before deformation are: initial borehole radius a;

[0152] The elliptical shape parameters of the borehole cross-section after deformation are: major semi-axis R, minor semi-axis r;

[0153] E and μ represent the rock physical properties, namely the elastic modulus and Poisson's ratio.

[0154] According to elasticity mechanics and under the action of two-dimensional geostress, a borehole with a circular cross-section undergoes elastic deformation, and the deformation shape of the borehole cross-section is elliptical.

[0155] S502, Figures 14(a) and 14(b) show that an NW coordinate system is created with the center of the measuring device 100 as the origin, the magnetic north (N) direction measured by the electronic compass as the x-axis, and the magnetic west (W) direction as the y-axis. The three-dimensional geometric shape measurement data of a borehole cross section at any depth range is projected onto an NW coordinate system.

[0156] S503, in the NW coordinate system, according to the least squares method, Equation 1 is used to fit the three-dimensional geometric shape measurement data of the borehole cross-section to obtain the general equation for the fitted ellipse shape. Five points Q1 to Q5 are randomly selected from the three-dimensional geometric shape measurement data of the borehole cross-section, and the perpendicular distances between these five points and the general equation for the fitted ellipse shape are calculated. When the calculated results of the perpendicular distances meet the expectations, the general equation for the fitted ellipse shape is confirmed to meet the expectations, and the fitting effect meets the calculation requirements.

[0157] S504, Fit the general equation of the ellipse shape and calculate the ellipse shape parameters. According to Equation 1, the ellipse shape parameters are expressed as follows:

[0158] Formula 3;

[0159] In Equation 3: the angle between the major semi-axis and the geomagnetic north (N) direction is λ, with clockwise being positive.

[0160] S505, when the physical properties of the rock can be obtained through rock mechanics tests, E and μ are known quantities; the initial borehole radius a can be calculated from the outer diameter of the drilling tools, so the initial borehole radius a is a known quantity. Substituting the calculation results of Equation 3 into Equation 2, the maximum in-plane principal stress σ1 and the minimum in-plane principal stress σ2 can be solved. The azimuth angle of the minimum in-plane principal stress is λ, and the azimuth angle of the maximum in-plane principal stress is λ+90°.

[0161] This is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for measuring optical geostress using borehole morphology, characterized in that, The method includes: General equation for creating an elliptical shape: Equation (1), ; In equation (1): A, B, C, D, and F are the coefficients in the general equation for the elliptical shape; The relationship between creating an elliptical borehole cross-section and in-situ stress: Equation (2), ; In Equation 2: σ1 and σ2 are the maximum and minimum in-plane principal stresses, respectively; The morphological parameters of the borehole cross-section before deformation are the initial borehole radius a; The elliptical shape parameters of the cross-section of the drilled hole after deformation are the major semi-axis R and the minor semi-axis r; E.μ represents the rock physical property parameters, namely elastic modulus and Poisson's ratio; Create an NW coordinate system with the center of a measuring device as the origin, the magnetic north (N) direction as the x-axis and the magnetic west (W) direction as the y-axis, and project the three-dimensional geometry of at least one borehole cross-section at any depth range onto the NW coordinate system. Based on the three-dimensional geometric shape of the borehole cross section projected in the NW coordinate system, the general equation of the elliptical shape in equation (1) is fitted. Calculate the ellipse shape parameters based on the fitted general equation of the ellipse shape; The ground stress is measured based on the elliptical morphology parameters; The calculation of the ellipse shape parameters is configured as follows: According to equation (1), the ellipse morphological parameters are expressed as follows: Equation (3), ; In equation (3): the angle between the major semi-axis and the geomagnetic north (N) direction is λ, with clockwise being positive; The geostress was measured in the following configuration: Calculate the maximum in-plane principal stress σ1, the minimum in-plane principal stress σ2, the azimuth angle λ of the minimum in-plane principal stress, and the azimuth angle λ+90° of the maximum in-plane principal stress according to equations (3) and (2).

2. The optical geostress measurement method based on borehole morphology according to claim 1, characterized in that, The general equation for fitting the elliptical shape is configured as follows: Randomly select several random coordinate points projected onto the borehole cross section in the NW coordinate system, calculate the vertical distance from the random coordinate points to the general equation of the elliptical shape, and when the vertical distance reaches the expected value, default to fitting the general equation of the elliptical shape.

3. The optical geostress measurement method based on borehole morphology according to claim 1, characterized in that, The three-dimensional geometric configuration is obtained as follows: Obtain at least two borehole wall projection points at the current horizontal height; Create a first polar coordinate system for the measuring device, and calculate the first spatial position of the hole wall imaging point in the first polar coordinate system based on the parameters of the measuring device and at least two hole wall projection points. A second polar coordinate system is created for the borehole wall. A coordinate transformation relationship between the first polar coordinate system and the second polar coordinate system is established based on the positional relationship between the measuring device and the borehole space. Based on the first spatial position and the coordinate transformation relationship, the second spatial position of the borehole wall imaging point in the second polar coordinate system is obtained. The borehole wall coordinate system is obtained based on the second spatial positions of the borehole wall imaging points at at least two consecutive horizontal heights.

4. The optical geostress measurement method based on borehole morphology according to claim 3, characterized in that, The measuring device comprises a housing assembly and a laser assembly and a camera device deployed on the housing assembly; The lifting device is configured to modulate the horizontal height of the housing assembly along the borehole axis; The laser assembly is configured to illuminate at least the borehole wall at the current horizontal height; The camera device is configured to acquire the projection point of the aperture wall of the illuminated aperture wall imaging point.

5. The optical geostress measurement method based on borehole morphology according to claim 4, characterized in that, The measuring device is configured with a conical mirror deployed on the housing assembly; The lens of the camera device is parallel to the axis of the conical mirror and at least covers a portion of the conical mirror; The covered portion of the conical mirror is constructed with an upper conical mirror and a lower conical mirror; The upper conical mirror and the lower conical mirror have different cone angles; The camera device obtains the projection point of the first hole wall through the upper conical mirror; The camera device obtains the projection point of the second hole wall through the lower conical mirror; The host computer is configured to obtain the first spatial position of the hole wall imaging point in the first polar coordinate system based on the parameters of the measuring device and the first hole wall projection point and the second hole wall projection point.

6. An optical geostress measurement system based on borehole morphology, characterized in that, The system includes an ellipse establishment module, a relationship establishment module, a coordinate transformation module, and an ellipse measurement module; The ellipse creation module is used to create the general equation for the shape of an ellipse: Equation (1), ; In equation (1): A, B, C, D, and F are the coefficients in the general equation for the elliptical shape; The relationship establishment module is used to create the relationship between the elliptical shape of the borehole cross-section and the in-situ stress: Equation (2), ; In Equation 2: σ1 and σ2 are the maximum and minimum in-plane principal stresses, respectively; The morphological parameters of the borehole cross-section before deformation are the initial borehole radius a; The elliptical shape parameters of the cross-section of the drilled hole after deformation are the major semi-axis R and the minor semi-axis r; E.μ represents the rock physical property parameters, namely elastic modulus and Poisson's ratio; The coordinate transformation module is used to create an NW coordinate system with the center of a measuring device as the origin, the geomagnetic north (N) direction as the x-axis and the geomagnetic west (W) direction as the y-axis, and to project the three-dimensional geometry of at least one borehole cross-section at any depth range into the NW coordinate system. The ellipse measurement module is used to fit the general equation of the ellipse shape of Equation (1) in the NW coordinate system according to the three-dimensional geometric shape of the borehole cross section projected. Calculate the elliptical shape parameters based on the fitted general equation of the elliptical shape; measure the ground stress based on the elliptical shape parameters; The calculation of the ellipse shape parameters is configured as follows: According to equation (1), the ellipse morphological parameters are expressed as follows: Equation (3), ; In equation (3): the angle between the major semi-axis and the geomagnetic north (N) direction is λ, with clockwise being positive; The geostress was measured as follows: Calculate the maximum in-plane principal stress σ1, the minimum in-plane principal stress σ2, the azimuth angle λ of the minimum in-plane principal stress, and the azimuth angle λ+90° of the maximum in-plane principal stress according to equations (3) and (2).

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