Shield overlying strata collapse monitoring and early warning method based on distributed optical fibers

Abstract

The invention discloses a shield overlying strata collapse monitoring and early warning method based on distributed optical fibers, which comprises the following steps: S1, before tunneling of a tunnel, determining the distribution range of an overlying soft strata in a shield overlying strata above the tunnel to be excavated, and obtaining the predicted deformation of the overlying soft strata after excavation of the tunnel; s2, multiple layers of distributed optical fibers are arranged on the overlying soft stratum, and the distributed optical fibers penetrate through the overlying soft stratum in the tunneling direction of the tunnel; s3, after the tunnel is tunneled, the actual deformation amount of the overlying soft stratum is obtained through distributed optical fiber monitoring; and S4, comparing the actual deformation amount of each monitoring position with the predicted deformation amount to obtain the collapse deformation condition of the overlying soft stratum, and judging whether the overlying soft stratum is damaged or not. The shield overlying stratum collapse monitoring and early warning method based on the distributed optical fibers has the advantages that the actual deformation of the stratum can be accurately detected, and the stratum collapse condition can be accurately judged.

Description

Technical Field

[0001] The present invention relates to the technical field of formation monitoring and early warning, and specifically relates to a method for monitoring and early warning of the collapse of the overlying formation of a shield based on distributed optical fiber. Background Art

[0002] In recent years, during the construction of subway tunnels in coastal areas, progressive collapse events of the overlying formation have occurred many times. Their occurrence is difficult to predict. Some occur during the construction process, while some occur after the tunnel is excavated and supported. In severe cases, ground subsidence or even collapse occurs, seriously endangering the safety underground and on the ground. However, there is currently no effective measure to monitor the internal damage of the formation. Most only monitor the ground settlement and deformation, and it is impossible to accurately judge the internal situation of the formation.

[0003] The existing Chinese patent document with the application number 202410678982.3 discloses a safety monitoring system and method for an underground mining area based on optical fiber sensing technology, which specifically discloses the following: including armored optical cable safety monitoring wells distributed in a grid pattern on the ground of the mining area, three-component distributed acoustic sensing optical fibers fixed on the roof of the underground mining roadway, distributed strain or displacement sensing optical cables, distributed temperature sensing optical fibers, distributed chemical sensing optical fibers, and a multi-channel DAS / DSS / DTS / DCS composite modulation and demodulation instrument. Relying on the well-combined distributed optical fiber sensing network to conduct real-time monitoring of the local settlement area of the underground mining area. At the same time, according to the armored monitoring optical cables buried underground in the safety monitoring wells arranged in the underground mining area and fixed on the roof of the underground mining roadway, the temperature, strain or deformation, displacement, microseismic events, underground water level, and changes in underground water components in the underground mining area are monitored in real time. Timely reinforcement treatment and early warning information release are carried out for the sections where the roof of the mining roadway may fracture and subside, and geological disasters and underground water source pollution are avoided in time. This monitoring method uses the well-combined distributed optical fiber sensing network to conduct real-time monitoring of the local settlement area of the underground mining area. Specifically, armored multi-parameter monitoring optical cables are buried underground in the safety monitoring wells distributed in a grid pattern on the ground of the mining area, that is, multi-parameter monitoring optical cables are buried in a grid pattern on the ground of the mining area, and monitoring is carried out through the vertical multi-parameter monitoring optical cables. On the one hand, it is difficult to accurately detect the actual deformation of the formation; on the other hand, it is difficult to accurately judge the formation collapse situation only based on the monitoring data of the multi-parameter monitoring optical cables. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for monitoring and early warning of the collapse of the overlying formation of a shield based on distributed optical fiber that can accurately detect the actual deformation of the formation and accurately judge the formation collapse situation.

[0005] To solve the above technical problems, the present invention adopts the following technical solutions:

[0006] A monitoring and early warning method for the collapse of the overlying strata of a shield based on distributed optical fiber, comprising the following steps:

[0007] S1. Before tunnel excavation, determine the distribution range of the overlying soft strata in the overlying strata of the tunnel to be excavated, and obtain the predicted deformation amount of the overlying soft strata after tunnel excavation;

[0008] S2. Lay multiple layers of distributed optical fibers in the overlying soft strata, so that the distributed optical fibers penetrate the overlying soft strata along the tunnel excavation direction;

[0009] S3. After tunnel excavation, obtain the actual deformation amount of the overlying soft strata through monitoring by the distributed optical fiber;

[0010] S4. Compare the actual deformation amount and the predicted deformation amount at each monitoring position to obtain the collapse deformation situation of the overlying soft strata, and judge whether the overlying soft strata are damaged.

[0011] As a further improvement of the above technical solution:

[0012] In S1, generate a continuous predicted deformation curve based on each predicted deformation amount in the tunnel excavation direction; in S3, generate a continuous actual deformation curve based on each actual deformation amount in the tunnel excavation direction; in S4, compare the actual deformation curve and the predicted deformation curve to judge the collapse deformation situation of the overlying soft strata along the tunnel excavation direction, and judge the damage situation of the overlying soft strata.

[0013] The predicted deformation amount of the overlying soft strata after tunnel excavation is obtained by theoretical calculation.

[0014] The predicted deformation amount of the overlying soft strata after tunnel excavation is set as Uz, and it satisfies

[0015]

[0016] Where:

[0017]

[0018] d = βR

[0019] Among them, β takes 0 to 1;

[0020]

[0021] In the formula:

[0022] x is the horizontal distance of the predicted position from the excavation face in the tunnel excavation direction;

[0023] y is the vertical distance of the predicted position from the vertical plane passing through the tunnel axis;

[0024] z is the vertical distance from the predicted position to the ground;

[0025] h is the vertical distance from the tunnel axis to the ground;

[0026] R is the tunnel excavation radius;

[0027] d is the distance from the focus of soil movement to the tunnel axis;

[0028] η is the maximum soil loss rate;

[0029] V loss is the soil loss amount per unit length of the tunnel;

[0030] S max is the maximum ground settlement above the tunnel axis.

[0031] In the above-mentioned S1, the predicted deformation amount of the overlying soft stratum after the tunnel excavation is obtained by simulating with numerical simulation software.

[0032] In the above-mentioned S2, the thicker the overlying soft stratum is, the more layers of distributed optical fibers are set.

[0033] In the above-mentioned S2, the distributed optical fibers of each layer are horizontally spaced.

[0034] In the above-mentioned S2, first use a directional drilling rig for strata to enter from the first place on the ground and exit from the second place, and drill a monitoring hole in the overlying stratum of the shield along the tunnel driving direction. Then use the directional drilling rig for strata to pull back the distributed optical fiber from the second place on the ground to the first place to realize the layout of the distributed optical fiber.

[0035] The distributed optical fiber is sheathed with a protective sleeve.

[0036] In the above-mentioned S1, the distribution range of the overlying soft stratum in the overlying stratum of the shield above the tunnel to be excavated is determined by geological exploration of the overlying stratum of the shield.

[0037] It further includes step S5: performing anti-collapse treatment on the damaged overlying soft stratum.

[0038] Compared with the prior art, the advantages of the present invention are:

[0039] The method for monitoring and warning of the collapse of the overlying formation of a shield based on distributed optical fiber, on the one hand, monitors the actual deformation of the overlying soft formation through the distributed optical fiber penetrating the overlying soft formation along the tunnel excavation direction, that is, detects the actual collapse of the overlying soft formation. Compared with the multi-parameter monitoring optical cable for vertical monitoring, it can monitor the actual deformation of each continuous point of the distributed optical fiber in the tunnel excavation direction, and can more accurately detect the actual deformation of the overlying soft formation. Moreover, through the multi-layer arrangement of the distributed optical fiber (each layer of distributed optical fiber is arranged at intervals in the vertical direction), it can gradually monitor the actual deformation of each layer of the overlying soft formation, so as to more accurately judge the overall deformation of the overlying soft formation; on the other hand, by comparing and analyzing the actual deformation with the predicted deformation at each monitoring position, it can accurately judge the collapse of the overlying soft formation, and thus accurately judge whether the overlying soft formation is damaged. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 is a flow chart of the method for monitoring and warning of the collapse of the overlying formation of a shield based on distributed optical fiber of the present invention.

[0041] Figure 2 is a schematic structural diagram before tunnel excavation of the method for monitoring and warning of the collapse of the overlying formation of a shield based on distributed optical fiber of the present invention.

[0042] Figure 3 is a schematic structural diagram after tunnel excavation of the method for monitoring and warning of the collapse of the overlying formation of a shield based on distributed optical fiber of the present invention.

[0043] Figure 4 is a schematic structural diagram of the distributed optical fiber at the cavity position of the method for monitoring and warning of the collapse of the overlying formation of a shield based on distributed optical fiber of the present invention.

[0044] Figure 5 is a schematic structural diagram of the distributed optical fiber of the method for monitoring and warning of the collapse of the overlying formation of a shield based on distributed optical fiber of the present invention.

[0045] Each label in the figure represents:

[0046] 1, tunnel; 2, overlying formation of the shield; 3, overlying soft formation; 4, distributed optical fiber; 5, protective sleeve; 6, metal weight; 7, cavity; 8, inflection point. DETAILED DESCRIPTION OF THE INVENTION

[0047] The present invention will be further described in detail below with reference to the accompanying drawings of the specification and specific embodiments.

[0048] In the description of the present invention, it should be understood that the orientation or positional relationship indicated by the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings. It is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on the present invention.

[0049] In addition, the terms "first" and "second" are only used for descriptive purposes and should not be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, the features defined with "first" and "second" may explicitly or implicitly include one or more of such features. In the description of the present invention, the meaning of "a plurality" is two or more unless otherwise specifically defined.

[0050] In the present invention, unless otherwise clearly specified and defined, the terms "assembled", "connected", "joined", "fixed", etc. should be understood in a broad sense. For example, it may be a fixed connection, a detachable connection, or integrated; it may be a mechanical connection or an electrical connection; it may be directly connected or indirectly connected through an intermediate medium, and it may be the communication inside two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0051] Figures 1 to 5 An embodiment of the method for monitoring and warning of the collapse of the overlying strata of a shield based on distributed optical fiber according to the present invention is shown. The method for monitoring and warning of the collapse of the overlying strata of a shield based on distributed optical fiber in this embodiment includes the following steps:

[0052] S1. Before the tunneling of Tunnel 1, determine the distribution range of the overlying soft strata 3 in the overlying strata 2 of the shield above the tunnel 1 to be excavated, and obtain the predicted deformation amount (such as the predicted vertical displacement) of the overlying soft strata 3 after the excavation of Tunnel 1;

[0053] S2. As Figure 2 shown, lay multiple layers of distributed optical fibers 4 in the overlying soft strata 3 so that the distributed optical fibers 4 penetrate the overlying soft strata 3 along the tunneling direction of Tunnel 1;

[0054] S3. After the tunneling of Tunnel 1, monitor and obtain the actual deformation amount (such as the actual vertical displacement) of the overlying soft strata 3 through the distributed optical fibers 4;

[0055] S4. Compare the actual deformation amounts with the predicted deformation amounts at each monitoring position to obtain the caving deformation condition of the overlying soft stratum 3, and determine whether the overlying soft stratum 3 is damaged. It can be understood that the comparison is between the actual deformation amount and the predicted deformation amount at the same monitoring position.

[0056] This method for monitoring and warning of the caving of the overlying stratum of a shield tunneling based on distributed optical fiber. On the one hand, through the distributed optical fiber 4 running through the overlying soft stratum 3 along the tunneling direction of the tunnel 1 to monitor the actual deformation amount of the overlying soft stratum 3, that is, to detect the actual caving condition of the overlying soft stratum 3. Compared with the multi-parameter monitoring optical cable in the vertical direction, it can monitor the actual deformation amounts of consecutive points of the distributed optical fiber 4 in the tunneling direction of the tunnel 1, and can more accurately detect the actual deformation amount of the overlying soft stratum 3. Moreover, through the multi-layer arrangement of the distributed optical fiber 4 (each layer of the distributed optical fiber 4 is arranged at intervals in the vertical direction), it can gradually monitor the actual deformation conditions of each layer of the overlying soft stratum 3, so as to more accurately judge the overall deformation condition of the overlying soft stratum 3. On the other hand, through the comparison and analysis of the actual deformation amount and the predicted deformation amount at each monitoring position, it can accurately judge the caving condition of the overlying soft stratum 3, so as to accurately judge whether the overlying soft stratum 3 is damaged.

[0057] Further, in this embodiment, in S1, a continuous predicted deformation curve is generated according to the predicted deformation amounts in the tunneling direction of the tunnel 1; in S3, a continuous actual deformation curve is generated according to the actual deformation amounts in the tunneling direction of the tunnel 1; in S4, the actual deformation curve and the predicted deformation curve are compared to judge the caving deformation condition of the overlying soft stratum 3 along the tunneling direction of the tunnel 1, and the damage condition of the overlying soft stratum 3 is judged.

[0058] Judgment is made according to the shape of the continuous actual deformation curve (which can also be called the vertical displacement curve) of the actual deformation amounts of the overlying soft stratum 3 monitored by the distributed optical fiber 4 in the tunneling direction of the tunnel 1. When the deformation of the overlying soft stratum 3 is normal, the shape of the actual deformation curve along the direction of the distributed optical fiber 4 is gentle. Once the caving phenomenon of the overlying soft stratum 3 occurs, as Figure 3 and Figure 4 shown, a cavity 7 is formed at the caving position. The distributed optical fiber 4 at the cavity 7 at the caving position will monitor a larger vertical displacement, which will be significantly greater than the result monitored by the distributed optical fiber 4 in the intact overlying soft stratum 3. Therefore, an obvious inflection point 8 will appear between the normal displacement and the abnormal displacement on the actual deformation curve. At this time, it can be considered that the overlying soft stratum 3 has undergone caving damage, and there is an inflection point 8 at each end of the caving part. The horizontal distance between the two inflection points 8 can be used as an estimated value of the caving span at this position, as a reference for later engineering treatment.

[0059] By comparing the actual deformation curve and the predicted deformation curve, if the predicted deformation amount at the predicted point of the predicted deformation curve is taken as the monitoring control value, and if the actual deformation amount at the corresponding point on the actual deformation curve exceeds 2 to 3 times the monitoring control value, it can be preliminarily determined that there is a high probability that the overlying soft stratum 3 has been damaged.

[0060] By comparing the actual deformation curve and the predicted deformation curve, the caving situation of the overlying soft stratum 3 can be judged more accurately, so as to more accurately judge whether the overlying soft stratum 3 has been damaged.

[0061] Furthermore, in this embodiment, the predicted deformation amount of the strata 2 overlying the shield after the excavation of the tunnel 1 is obtained by theoretical calculation. For example, in this embodiment, the predicted deformation amount of the strata 2 overlying the shield after the excavation of the tunnel 1 is set as Uz, and it satisfies

[0062]

[0063] Among them:

[0064]

[0065] d = βR

[0066] Among them, β takes values from 0 to 1; generally, for extremely poor soft clay, β can take values from 0 to 0.2; for relatively poor soft clay, β can take values from 0.2 to 0.3; for medium cohesive soil, β can take values from 0.3 to 0.4; for hard cohesive soil and sandy soil, β can take values from 0.4 to 1.0.

[0067]

[0068] In the formula:

[0069] x is the horizontal distance of the predicted position from the excavation face in the tunneling direction of the tunnel 1;

[0070] y is the vertical distance of the predicted position from the vertical plane passing through the axis of the tunnel 1;

[0071] z is the vertical distance of the predicted position from the ground;

[0072] h is the vertical distance of the axis of the tunnel 1 from the ground;

[0073] R is the excavation radius of the tunnel 1;

[0074] d is the distance from the focus of soil movement to the axis of the tunnel 1;

[0075] η is the maximum soil loss rate;

[0076] V loss is the soil loss amount per unit length of the tunnel 1;

[0077] S maxIt is the maximum ground settlement amount above the axis of Tunnel 1.

[0078] Furthermore, in this embodiment, in S1, the predicted deformation amount of the overlying soft stratum 3 after the excavation of Tunnel 1 is obtained by simulating with numerical simulation software. For example, by using numerical simulation software such as Midas to simulate the excavation process of Tunnel 1, the predicted deformation amount of the overlying soft stratum 3 caused by the tunneling construction of Tunnel 1 can be obtained.

[0079] Furthermore, in this embodiment, in S2, the thicker the overlying soft stratum 3 is, the more layers of distributed optical fiber 4 are set. According to the distribution of the overlying soft stratum 3, especially according to the vertical distribution depth of the overlying soft stratum 3, the setting quantity and position of the corresponding distributed optical fiber 4 are designed.

[0080] Furthermore, in this embodiment, in S2, the distributed optical fibers 4 of each layer are horizontally spaced. To achieve the overall monitoring effect on the overlying soft stratum 3 and reduce the monitoring dead angle.

[0081] Furthermore, in this embodiment, in S2, first use a stratum directional drilling rig to enter from the first place on the ground and exit from the second place, and drill a monitoring hole in the overlying stratum 2 of the shield along the tunneling direction of Tunnel 1, and then use the stratum directional drilling rig to pull back the distributed optical fiber 4 from the second place on the ground to the first place to realize the laying of the distributed optical fiber 4.

[0082] Furthermore, in this embodiment, a protective sleeve 5 is sleeved outside the distributed optical fiber 4. A protective sleeve 5 is wrapped outside the distributed optical fiber 4. This protective sleeve 5 can prevent water, pressure and prevent the optical fiber from being pulled off, and can make the optical fiber closely attached to the overlying stratum 2 of the shield, increasing the sensitivity of the optical fiber to the state change of the overlying stratum 2 of the shield. Metal weights 6 are distributed under the protective sleeve 5.

[0083] Furthermore, in this embodiment, in S1, the distribution range of the overlying soft stratum 3 in the overlying stratum 2 of the shield above the tunnel 1 to be excavated is determined by geological exploration of the overlying stratum 2 of the shield.

[0084] Furthermore, in this embodiment, it further includes step S5: performing anti-collapse treatment on the damaged overlying soft stratum 3. According to the monitoring results and judgment results of the overlying soft stratum 3, timely treat the damaged overlying soft stratum 3 to protect the safety of the personnel and equipment in the excavated Tunnel 1 and avoid further developing into a ground-through landslide.

[0085] It should be noted that the so-called "direction along the tunneling direction of Tunnel 1" does not specifically refer to a direction that must coincide or be parallel to the axial direction of Tunnel 1. That is to say, as long as the overall direction is the same, a direction at an angle to the tunneling direction of Tunnel 1 is also "along the tunneling direction of Tunnel 1". In fact, after the distributed optical fiber 4 is arranged, generally, the plane where the distributed optical fiber 4 is located coincides or is parallel to the vertical plane passing through the axis of Tunnel 1, or is close to coincidence or parallel. Each point on the distributed optical fiber 4 is not necessarily strictly coplanar, but tends to be on a plane, and this plane is called the plane where the distributed optical fiber 4 is located.

[0086] This method for monitoring and warning the collapse of the overlying stratum of a shield based on distributed optical fiber uses multi-layer distributed optical fiber 4 monitoring means and the comparison means of the actual deformation amount and the predicted deformation amount at each monitoring position to realize the monitoring and warning of the progressive failure phenomenon of the overlying soft stratum 3, and is the monitoring of the internal change situation of the overlying stratum 2 of the shield, which well meets the monitoring requirements of the existing urban subway tunnel 1 project.

[0087] Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the above-disclosed technical content without departing from the scope of the technical solution of the present invention, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the scope of the protection of the technical solution of the present invention.

Claims

1. A shield tunneling overlying stratum collapse monitoring and early warning method based on distributed optical fiber, characterized in that: The steps include: S1. Before the tunnel (1) is excavated, the distribution range of the overlying weak stratum (3) in the shield overlying stratum (2) above the tunnel (1) to be excavated is determined, and the predicted deformation of the overlying weak stratum (3) after the tunnel (1) is excavated is obtained; S2, laying multiple layers of distributed optical fibers (4) in the overlying soft stratum (3), so that the distributed optical fibers (4) penetrate the overlying soft stratum (3) along the excavation direction of the tunnel (1); S3, after the tunnel (1) is excavated, the actual deformation of the overlying soft stratum (3) is obtained through distributed optical fiber (4) monitoring; S4. Compare the actual deformation amount and the predicted deformation amount at each monitoring position to obtain the collapse deformation situation of the overlying soft stratum (3), and determine whether the overlying soft stratum (3) is damaged.

2. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 1 is characterized by: In S1, a continuous predicted deformation curve is generated based on each predicted deformation in the tunnel (1) driving direction; in S3, a continuous actual deformation curve is generated based on each actual deformation in the tunnel (1) driving direction; in S4, the actual deformation curve and the predicted deformation curve are compared to determine the collapse deformation of the overlying soft stratum (3) along the tunnel (1) driving direction, and to determine the damage of the overlying soft stratum (3).

3. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 1 is characterized by: The predicted deformation of the stratum (2) overlying the shield after excavation of the tunnel (1) is obtained by theoretical calculation.

4. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 3 is characterized by: The predicted deformation of the overlying soft stratum (3) after the tunnel (1) is excavated is set as U z ,satisfy in: d = βR Among them, β ranges from 0 to 1; Where: x is the horizontal distance from the predicted position to the excavation face in the tunnel (1) excavation direction; y is the vertical distance of the predicted position from the vertical plane passing through the axis of the tunnel (1); z is the vertical distance of the predicted position from the ground; h is the vertical distance between the axis of the tunnel (1) and the ground; R is the excavation radius of the tunnel (1); d is the distance from the soil moving focus to the axis of the tunnel (1); η is the maximum soil loss rate; V loss is the soil loss per unit length of tunnel (1); S max is the maximum ground settlement above the axis of tunnel (1).

5. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 1 is characterized by: In S1, the predicted deformation of the overlying soft stratum (3) after the tunnel (1) is excavated is obtained by simulation using numerical simulation software.

6. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 1 is characterized by: In the S2, the thicker the overlying soft stratum (3), the more layers of the distributed optical fiber (4) are provided, and the distributed optical fibers (4) of each layer are horizontally spaced.

7. The shield tunneling overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 1 is characterized by: In S2, a stratum directional drill is first used to enter from a first location on the ground and exit from a second location, and a monitoring hole is directionally drilled in the stratum (2) overlying the shield along the excavation direction of the tunnel (1). Then, the stratum directional drill is used to pull the distributed optical fiber (4) back from the second location on the ground to the first location, thereby realizing the deployment of the distributed optical fiber (4).

8. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to claim 1 is characterized by: The outer jacket of the distributed optical fiber (4) is provided with a protective sleeve (5).

9. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to any one of claims 1 to 8, characterized in that: In the above S1, the distribution range of the overlying weak stratum (3) in the shield overlying stratum (2) above the tunnel (1) to be excavated is determined by conducting a geological survey on the shield overlying stratum (2).

10. The shield overlying stratum collapse monitoring and early warning method based on distributed optical fiber according to any one of claims 1 to 8, characterized in that: The method further comprises step S5, performing anti-collapse treatment on the damaged overlying soft stratum (3).

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