Ground balancing fixture for distributed fiber optic seismic monitoring

Abstract

The utility model discloses a ground balance fixing device for distributed optical fiber earthquake monitoring, including nail body and the pressure block of being located nail body upper portion and with nail body integrated molding, the pressure block is equipped with the groove along the direction of being perpendicular to nail body axis and extending horizontally, for along the axial length direction of sensing optical cable continuously containing, limiting and pressing and pasting sensing optical cable, the length L of groove is greater than the diameter D of nail body. The utility model will traditional discrete point shape fixing mode, change for along the continuous linear fixing of optical fiber axial, through the groove of length L greater than nail body diameter D, the optical fiber length range is continuously limited and pressed and pasted to the ground, has guaranteed that optical fiber and ground surface medium form stable, uniform and continuous acoustic coupling interface.

Description

Technical Field

[0001] This utility model relates to the field of earthquake monitoring technology, and in particular to a ground-balanced fixed device for distributed fiber optic earthquake monitoring. Background Technology

[0002] Distributed fiber optic acoustic sensing (DAS) technology is an advanced technology that uses communication optical cables as continuous distributed sensors for real-time vibration and acoustic monitoring. By detecting changes in the phase or intensity of backscattered light along the optical fiber, it can sense and locate environmental vibrations at any location within a range of several kilometers. It is now widely used in earthquake monitoring, geological exploration, oil and gas field development, pipeline safety, and perimeter security. In a DAS monitoring system, the acoustic coupling quality between the sensing optical cable and the measured medium (such as the earth's surface) is a key factor determining the validity and accuracy of the monitoring data. Ideally, the sensing optical cable should achieve continuous, tight, and stable physical contact with the medium surface to ensure that surface vibration energy can be efficiently and without distortion transmitted to the optical cable. Poor coupling will lead to severe signal attenuation, increased noise levels, and may introduce false signals, ultimately affecting the accurate identification and analysis of earthquake events, underground structures, or security threats.

[0003] Currently, when deploying DAS (Digital Optical Array) sensing optical cables in the field or at engineering sites, the commonly used ground fixing methods mainly include nailing, which uses metal U-shaped nails, saddle nails, or similar ground stakes to drive the optical cable into the ground. However, existing nailing methods, especially commonly used U-shaped nails, are essentially a "point-like" or "hoop-like" fixing method. The mechanism of these nails is mainly to apply downward pressure to the optical cable at discrete points or to form local clamping. The fixing method is discontinuous and easily forms suspended sections. For example, point fixing at a fixed point causes the compressive force to concentrate in a very small area of ​​the optical cable. Under long-term stress or impact, it may crush or wear down the optical cable sheath. Between two fixed points, the optical cable lacks effective restraint and is easily detached from the ground due to its own stress release, thermal expansion and contraction, or micro-undulations of the ground surface, forming a suspended section. The suspended optical cable will, like a string, generate parasitic oscillations under wind or environmental vibrations, introducing strong noise unrelated to the monitoring target. Furthermore, the nails used in the transmission nailing method result in uneven coupling quality between the optical cable and the ground surface and poor signal consistency. For example, the optical cable only makes close contact with the ground at discrete nailing points, and the coupling state between the contact points is unstable and inconsistent. This leads to uneven signal fidelity and phase response acquired by the DAS system along the length of the optical cable, which seriously interferes with the analysis of wave field continuity and affects the accuracy of velocity structure inversion and event localization. Utility Model Content

[0004] The purpose of this invention is to provide a ground-balanced fixing device for distributed fiber optic seismic monitoring, so as to solve one or more technical problems existing in the prior art, and at least provide a beneficial option or create conditions.

[0005] To solve the above-mentioned technical problems, the technical solution adopted by this utility model is as follows: This utility model provides a ground balancing and fixing device for distributed fiber optic seismic monitoring, including a nail body and a pressure block located on the upper part of the nail body and integrally formed with the nail body. The pressure block has a groove extending horizontally in a direction perpendicular to the axis of the nail body, which is used to continuously accommodate, limit and press the sensing optical cable along the axial length direction of the sensing optical cable. The length L of the groove is greater than the diameter D of the nail body.

[0006] This invention transforms the traditional discrete point-fixing method into a continuous linear fixation along the optical fiber axis. Through a groove with a length L greater than the diameter D of the nail, the optical fiber is continuously limited and pressed against the ground within a length range of several centimeters or even tens of centimeters, ensuring the formation of a stable, uniform and continuous acoustic coupling interface between the optical fiber and the ground surface medium.

[0007] As a further improvement of this utility model: the length L of the trench is greater than the width W of the trench opening. L>W means that the trench forms a long strip or narrow elongated groove, which ensures that the optical fiber is guided and constrained on a clear linear path with the same direction as the laying direction. The longer contact length relative to the smaller opening width makes the compressive force borne by the unit length of optical cable more uniform and dispersed, thereby improving the stability of the coupling interface.

[0008] As a further improvement of this utility model: the ratio of the groove length L to the nail diameter D, L / D, is 2:1 to 5:1; the ratio of the groove length L to the groove opening width W, L / W, is 3:1 to 6:1. This improved solution optimizes and limits the groove size through a specific ratio range, achieving the best engineering balance between structural strength, ease of installation, material cost, and fixing effect.

[0009] As a further improvement of this utility model: in the projected outline of the trench on the horizontal plane, the projected length of the trench is greater than the projected width of the trench. The projection length being greater than the width ensures, from the top view perspective (looking down at the ground surface plane), that the extension dimension of the trench in the direction of optical cable laying is greater than its dimension in the width direction, thus defining the trench as a long strip shape and providing a continuous constraint function along the length direction.

[0010] As a further improvement of this utility model, the cross-sectional shape of the trench is one of the following: semi-circular, fan-shaped (smaller than semi-circular), trapezoidal, or irregular shape where the maximum width of the cross-sectional profile is smaller than the width W of the groove opening in the trench width direction. This improved solution provides flexibility to adapt to different optical cable types, different ground conditions, and different clamping force requirements.

[0011] As a further improvement of this utility model, the length L of the trench is 8 cm to 15 cm. The applicant's practical experience in laying out land seismic survey lines has verified that 8-15 cm is the optimal length range that simultaneously satisfies excellent fixing effect and good engineering applicability. At the same time, for manual handheld installation, a length of 8-15 cm is neither too short (resulting in poor effect) nor too long (e.g., exceeding 20 cm) (causing the device to be bulky, inconvenient to carry, or difficult to implant in hard soil).

[0012] As a further improvement of this utility model, the ground balancing fixing device also includes a nail head coaxially arranged with the nail body. The nail head has a flat structure and is integrally formed with the nail body and the pressure block. The flat nail head provides a flat hammering force surface, so that the hammering force can be transmitted vertically downward along the nail body axis, reducing the deviation during the implantation process, ensuring that the device is implanted vertically, and thus allowing the bottom plane of the trench to evenly press the optical fiber.

[0013] As a further improvement of this utility model: the end of the nail body is provided with a nail tip, which is conical or pyramidal. The conical or pyramidal nail tip at the end of the nail body reduces the initial resistance when the device is inserted into the soil, enabling smooth and labor-saving implantation, and guiding the nail body to maintain vertical penetration.

[0014] As a further improvement of this utility model: the nail body has cross-shaped reinforcing ribs. The cross-shaped reinforcing ribs are rib-like protrusions formed inside or on the outer surface of the nail body and distributed in a cross shape, used to increase structural rigidity.

[0015] As a further improvement of this utility model, the inner wall of the trench is covered or embedded with a flexible buffer layer. The flexible buffer layer, while ensuring the fixation firmness, physically protects the outer sheath of the sensing optical cable from mechanical damage, thus extending the service life of the expensive sensing optical cable. Attached Figure Description

[0016] The present invention will be further described below with reference to the accompanying drawings and embodiments; Figure 1 This is a schematic diagram of the ground balancing and fixing device in the embodiment; Figure 2 This is a structural diagram of a traditional nail tool in the existing technology; Figure 3 This is a schematic diagram of another traditional nail tool in the existing technology.

[0017] In the attached diagram: 100: nail body, 110: nail tip, 120: cross-shaped reinforcing rib, 200: pressure block, 210: groove, 300: nail head, 10: steel nail, 20: semi-open hoop, 30: insert body, 40: hook body, L: groove length, W: groove width, D: nail body diameter. Detailed Implementation

[0018] This section will describe in detail the specific embodiments of the present utility model. The preferred embodiments of the present utility model are shown in the accompanying drawings. The purpose of the drawings is to supplement the textual description with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the present utility model, but they should not be construed as limiting the scope of protection of the present utility model.

[0019] In the description of this utility model, it should be understood that the directional descriptions, such as up, down, front, back, left, right, etc., indicate the directional or positional relationship based on the directional or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0020] In the description of this utility model, if there are words such as "several", they mean one or more, "multiple" means two or more, "greater than", "less than", "exceeding" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself.

[0021] In the description of this utility model, unless otherwise explicitly defined, terms such as "setting," "installation," and "connection" should be interpreted broadly, and those skilled in the art can reasonably determine the specific meaning of the above terms in this utility model in conjunction with the specific content of the technical solution.

[0022] Reference Figures 1 to 3 The following are several embodiments of a ground balancing and fixing device for distributed fiber optic seismic monitoring according to this utility model.

[0023] An embodiment of this utility model provides a ground balancing and fixing device for distributed fiber optic seismic monitoring, such as... Figure 1 As shown, it includes a nail body 100 and a pressure block 200 located on the upper part of the nail body 100 and integrally formed with the nail body 100. The pressure block 200 has a groove 210 extending horizontally in a direction perpendicular to the axis of the nail body 100, which is used to continuously accommodate, limit and press the sensing optical cable along the axial length direction of the sensing optical cable. The length L of the groove 210 is greater than the diameter D of the nail body 100.

[0024] In this embodiment, the groove is a horizontally extending elongated groove, and the pressure block is a block-shaped structure connected to the nail body, used to support and form the groove. Continuous containment, limiting, and pressing refer to the functions that the elongated groove performs for the sensing optical cable. Therefore, those skilled in the art can clearly understand that the pressure block is a component with a horizontally extending groove. The length L of the groove is greater than the diameter D of the nail body to structurally ensure that the pressing action must be a linear segment rather than a point-like pressing, continuously and linearly pressing the optical cable into and adhering it to the surface soil, overcoming local suspension caused by microscopic unevenness of the surface, and achieving continuous coupling.

[0025] During construction, the sensing optical cable is first laid along the ground surface. Then, the trench of this device is aligned with the optical cable, so that the cable is directly below the trench. A hammer head is provided on the top of the vertical hammering device or the upper part of the pressure block, and in the optional embodiments described below, a hammering nail is also provided to insert the nail into the ground soil. During this process, the bottom of the trench (i.e., the bottom plane of the trench) continuously and linearly presses the optical cable into and adheres it to the surface soil. After installation, the optical cable, wrapped and guided by the trench, makes seamless contact with the ground along the length of the trench. When seismic waves cause vibrations in the surface particles, the vibrational energy is efficiently transmitted to the optical fiber through this continuous and tight contact surface, and the optical fiber generates a corresponding strain signal.

[0026] In the transmission scheme, such as Figure 2 The traditional mounting hardware shown consists of a single steel nail 10 and a detachable metal or plastic semi-open clamp 20. During installation, the optical cable is first placed on the ground, secured with the semi-open clamp, and then the steel nail is driven into the ground through a hole in the clamp to fix the entire assembly. Due to its modular structure, large-scale field deployments require carrying and managing both parts simultaneously, along with complex alignment operations, severely impacting deployment speed and increasing labor and time costs. Furthermore, under long-term environmental vibration, temperature cycling, or soil stress, the connection between the steel nail and the semi-open clamp is prone to loosening, causing the clamp to float, rotate, or even detach from the nail. Semi-open clamps are typically thin, with a very limited contact area with the optical cable, essentially remaining a discrete point-like or extremely short clamp fixation. For example... Figure 3 Another conventional nail tool shown has a hook 40 extending laterally from the top of the insert body 30. The hook for fixing the optical cable is integrated with the insert body inserted into the ground, avoiding the problem of separate parts. Although it is integrally formed, its hook structure is usually just a short arm extending laterally from the body, with the end bent into a hook shape. The optical cable is placed inside the hook or hung on the hook. The contact surface is extremely small. The contact between the optical cable and the device is limited to the tiny arc surface inside the hook, which is a typical point contact or extremely short line segment contact.

[0027] Compared to traditional methods, this embodiment transforms the traditional discrete point-fixation method into a continuous linear fixation along the fiber optic axis. Through grooves with a length L greater than the nail diameter D, the fiber is continuously confined and pressed against the ground over a length range of several centimeters to tens of centimeters, ensuring a stable, uniform, and continuous acoustic coupling interface between the fiber and the surface medium. This solves the problem of fiber optic suspension caused by gravity relaxation, stress release, or environmental disturbances (such as wind or minor vibrations), significantly improving the spatial consistency and phase fidelity of the seismic wave signals acquired by the DAS system. It effectively suppresses noise and signal distortion introduced by uneven coupling, laying the physical foundation for subsequent high-precision seismic imaging and source location.

[0028] In an optional embodiment, such as Figure 1 As shown, the length L of the trench 210 is greater than the width W of the trench opening. In this embodiment, L > W means that the trench forms a long strip or narrow elongated groove, ensuring that the optical fiber is guided and constrained on a clear linear path with the same direction as the laying direction. The longer contact length relative to the smaller opening width makes the compressive force per unit length of optical cable more uniform and dispersed, improving the stability of the coupling interface.

[0029] In an optional embodiment, such as Figure 1 As shown, the ratio of the length L of the groove 210 to the diameter D of the nail body 100, L / D, is 2:1 to 5:1; the ratio of the length L of the groove 210 to the groove width W, L / W, is 3:1 to 6:1.

[0030] This embodiment optimizes and limits the trench size by using a specific ratio range of L / D from 2:1 to 5:1 and L / W from 3:1 to 6:1, achieving the best engineering balance between structural strength, ease of installation, material cost, and fixing effect. The lower limit of L / D (2:1) ensures that the trench has a basic linear constraint length, which clearly distinguishes it from point fixing; the upper limit (5:1) prevents problems such as excessively long clamping blocks leading to loosening at both ends due to only a single nail fixing, easy deformation of the overall structure, or excessive requirements for surface flatness during installation. Similarly, the L / W ratio range ensures that the trench has a suitable elongation-to-narrowness ratio: sufficient length provides good guidance and pressing, while a reasonable width facilitates the rapid insertion of optical fibers and avoids installation difficulties caused by excessive narrowness or excessive lateral pressure on the optical cable.

[0031] In an optional embodiment, such as Figure 1As shown, in the projected outline of the trench 210 on the horizontal plane, the trench projection length is greater than the trench projection width. In engineering drawings and structural understanding, the horizontal projection outline of a component directly reflects its coverage and shape characteristics on the main working plane (i.e., the ground surface). In this embodiment, the projection length is greater than the width, ensuring from a top-down view (looking down at the ground surface) that the extension scale of the trench in the optical cable laying direction is greater than its width scale, limiting the trench to a long strip shape. Regardless of the specific cross-sectional shape of the trench (semicircle, fan shape, trapezoid, dovetail shape, etc.) and its depth in the vertical direction, as long as its projection on the horizontal plane shows a shape where the length is greater than the width, the structure can provide continuous constraint function along the length direction, belonging to a trench variant that can realize the linear pressing concept of this utility model.

[0032] In an optional embodiment, such as Figure 1 As shown, the cross-sectional shape of the trench 210 is one of the following: semi-circular, fan-shaped (smaller than semi-circular), trapezoidal, or irregular shape where the maximum width of the cross-sectional profile is smaller than the width W of the trench opening in the trench width direction. The irregular shape may include, but is not limited to, a bell-shaped cross-section, a cross-section with an inwardly concave arc at the bottom, or a cross-section with inwardly extending flanges (lips) on both sides of the trench opening. The common feature of these shapes is that after the optical cable is inserted into the trench opening, its widest point is confined inside the trench opening, thus providing a certain degree of anti-detachment function. In this embodiment, the semi-circular cross-section has the best matching degree with standard circular optical cables, providing uniform lateral wrapping; the fan-shaped cross-section (smaller than semi-circular) has a larger opening, facilitating rapid insertion of the optical cable and is suitable for temporary rapid deployment. Trapezoidal cross sections (especially inverted trapezoidal ones) can prevent optical cables from coming off upwards, while the wider bottom of the groove provides a larger pressing area. Irregular cross sections with a maximum width smaller than the groove opening (such as arc grooves with inward-curving bottoms or structures with lips) can create a snap-fit ​​effect on the optical cable, preventing it from popping out of the groove. This embodiment provides flexibility to adapt to different optical cable types, different ground conditions, and different clamping force requirements.

[0033] In an optional embodiment, the length L of the trench 210 is 8 cm to 15 cm. When it is less than 8 cm, the linear fixing effect begins to weaken, and for slightly undulating surfaces, it may not be able to cover a complete crest-trough cycle, still posing a risk of localized suspension. When it is greater than 15 cm, the excessive length of the clamping block may exceed the fixing capacity of a single nail, and twisting may occur during hammering. Furthermore, it increases the requirements for mold manufacturing and material costs, resulting in decreased marginal benefits. The 8-15 cm length has been proven by the applicant in practical application during the deployment of land seismic survey lines to be the optimal length range that simultaneously satisfies excellent fixing effect and good engineering applicability. At the same time, a length of 8-15 cm is neither too short and ineffective for manual handheld installation, nor too long (e.g., exceeding 20 cm) that results in a bulky and inconvenient device, or difficulty in implantation in hard soil.

[0034] In an optional embodiment, the ground balancing fixing device further includes a nail head 300 coaxially arranged with the nail body 100. The nail head 300 has a flat structure and is integrally formed with the nail body 100 and the pressure block 200. The flat nail head provides a flat hammering force surface, allowing the hammering force to be transmitted vertically downward along the nail body axis, reducing deviation during implantation, ensuring vertical implantation of the device, and thus enabling the bottom plane of the trench to uniformly press the optical fiber. The integrally formed design enhances the structural strength of the connection between the nail head, pressure block, and nail body, avoiding loosening or breakage that may occur under repeated hammering of the separate structure.

[0035] In an optional embodiment, such as Figure 1 As shown, the end of the nail body 100 is provided with a nail tip 110, which is conical or pyramidal. The conical or pyramidal nail tip at the end of the nail body reduces the initial resistance when the device is inserted into the soil, enabling smooth and labor-saving implantation, and guiding the nail body to maintain vertical penetration.

[0036] In an optional embodiment, such as Figure 1 As shown, the nail body 100 has cross-shaped reinforcing ribs 120. These cross-shaped reinforcing ribs are rib-like protrusions formed in a cross pattern on the inside or outer surface of the nail body, used to increase structural rigidity. When hammered into the soil, especially on sloping ground or when encountering underground rocks, the nail body will withstand a huge lateral bending moment. The cross-shaped cross section provides an extremely high moment of inertia, making the nail body less prone to bending, thereby ensuring that the pressure block and groove maintain a horizontal posture and continuously provide uniform pressing force.

[0037] In an optional embodiment, the inner wall of the trench is covered or embedded with a flexible buffer layer. The flexible buffer layer provides physical protection for the outer sheath of the sensing optical cable from mechanical damage while ensuring secure fixation. The flexible buffer layer can be made of materials such as rubber, silicone, polyurethane coatings, or inserts, which can absorb and disperse the impact force and frictional stress between the optical cable and the rigid inner wall of the trench during hammering and long-term vibration, effectively preventing the optical cable sheath from being crushed, cut, or excessively worn, thus extending the service life of the expensive sensing optical cable.

[0038] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. Those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present invention, and these equivalent modifications or substitutions are all included within the scope defined by the claims of this application.

Claims

1. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring, characterized in that, It includes a nail body (100) and a pressure block (200) located on the upper part of the nail body (100) and integrally formed with the nail body (100). The pressure block (200) has a groove (210) extending horizontally in a direction perpendicular to the axis of the nail body, which is used to continuously accommodate, limit and press the sensing optical cable along the axial length direction of the sensing optical cable. The length L of the groove (210) is greater than the diameter D of the nail body (100).

2. The ground balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: The length L of the groove (210) is greater than the width W of the groove (210).

3. A ground balancing and fixing device for distributed fiber optic seismic monitoring according to claim 2, characterized in that: The ratio of the length L of the groove (210) to the diameter D of the nail body (100) is 2:1 to 5:1; the ratio of the length L of the groove (210) to the width W of the groove (210) is 3:1 to 6:

1.

4. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: In the projection profile of the groove (210) on the horizontal plane, the projection length of the groove is greater than the projection width of the groove.

5. A ground balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: The cross-sectional shape of the groove (210) is one of the following: semi-circular, fan-shaped (smaller than semi-circular), trapezoidal, or irregular shape in which the maximum width of the cross-sectional profile is smaller than the groove width W in the groove width direction.

6. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: The length L of the groove (210) is 8 cm to 15 cm.

7. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: It also includes a nail head (300) coaxially arranged with the nail body (100), the nail head (300) having a flat structure and being integrally formed with the nail body (100) and the pressure block (200).

8. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: The end of the nail body (100) is provided with a nail tip (110), which is conical or pyramidal.

9. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: The nail body (100) has a cross-shaped reinforcing rib (120).

10. A ground-based balancing and fixing device for distributed fiber optic seismic monitoring according to claim 1, characterized in that: The inner wall of the trench (210) is covered or embedded with a flexible buffer layer.

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