A method for analyzing the cracking range of surrounding rock in large deformation tunnels

Abstract

This invention provides a method for analyzing the cracking range of surrounding rock in large deformation tunnels. The method includes the following steps: setting up boreholes in the surrounding rock and extracting information on the rock mass structural surfaces; grouping the structural surfaces according to their attitude and depth from the borehole opening to determine displacement observation points; obtaining the initial distance measurements of the displacement observation points in the surrounding rock boreholes; repeatedly reading the distance measurement information of the observation points during the deformation of the surrounding rock and calculating the displacement of the structural surfaces; statistically analyzing the relationship between the displacement of the structural surfaces and their attitude and borehole depth to determine the dominant structural surface attitude and the distribution of the degree of cracking in the surrounding rock. This invention uses a laser-type multi-point displacement meter to monitor the displacement of rock blocks on both sides of the structural surfaces in real time during the deformation of the surrounding rock, and calculates the normal and tangential displacements of the structural surfaces using formulas. This can effectively obtain the cracking range of the surrounding rock and the normal and tangential displacements of the structural surfaces at different parts of the surrounding rock during the excavation of underground engineering projects.

Description

Technical Field

[0001] This invention relates to the field of deep-buried tunnel construction technology, specifically a method for analyzing the cracking range of surrounding rock in tunnels with large deformation. Background Technology

[0002] Large deformation of surrounding rock is a common phenomenon in underground engineering, manifested as significant intrusion of the surrounding rock into the tunnel interior. It is characterized by complex controlling factors, dramatic development over time, and severe damage to the engineering structure. Currently, research on the deformation mechanism, support theory, and stability control of surrounding rock in large deformation tunnels primarily treats the surrounding rock as a continuous body, with relatively little attention paid to discontinuous structures such as structural planes.

[0003] Existing methods for observing the interior of surrounding rock in underground engineering projects such as tunnels and roadways include borehole television and laser ranging. However, the results obtained by these devices are mostly applied to rock mass deformation, and their analysis and research on the deformation characteristics of structural planes and the extent of cracking in the surrounding rock are very limited.

[0004] Structural planes are an important component of rock masses, widely distributed within them and closely related to rock cracking. Due to the highly random distribution of structural planes within the rock mass and their elongated, irregular scale, obtaining information and historical monitoring of structural planes within the surrounding rock of tunnel engineering presents significant challenges. Therefore, a complete analytical method for determining the extent of cracking in tunnel surrounding rock has not yet been established.

[0005] Therefore, it is necessary to design a method that can accurately analyze the cracking range of the surrounding rock in tunnels with large deformation. Summary of the Invention

[0006] To address the aforementioned problems in existing research, this invention proposes a method for analyzing the cracking range of surrounding rock in large deformation tunnels, comprising the following steps:

[0007] Drill holes in the surrounding rock and extract information on the rock mass structure.

[0008] The structural surfaces are grouped according to their orientation and depth from the borehole opening to determine displacement observation points;

[0009] Initial distance measurement of displacement observation points in the surrounding rock borehole;

[0010] During the deformation of the surrounding rock, the distance measurement information of the observation points was read multiple times to calculate the displacement of the structural surface.

[0011] The relationship between structural plane displacement, structural plane attitude, and borehole depth was statistically analyzed to determine the attitude of the dominant structural plane and to determine the degree of cracking in the surrounding rock by measuring the normal displacement of the structural plane within the surrounding rock.

[0012] Furthermore, the process of repeatedly reading the distance measurement information from the observation points during the deformation of the surrounding rock and calculating the displacement of the structural surface is as follows:

[0013] D n1 =(L b -L a sinα (2)

[0014]

[0015] D s1 =(L b -L a cosα (4)

[0016]

[0017] ΔD n =D n1 -D′ n1 (6)

[0018] ΔD s =D s1 -D′ s1 (7)

[0019] In the formula: D n1 This represents the initial normal width of the structural surface;

[0020] L a Let be the initial depth of point a at the edge of the structural surface;

[0021] L b Let b be the initial depth at the edge point of the structural surface;

[0022] α is the angle between the structural plane where the observation point is located and the borehole;

[0023] D' n1 The normal width of the structural surface after deformation;

[0024] L' a Let be the deformed depth of point a at the edge of the structural surface;

[0025] L' b Let be the deformed depth of point b at the edge of the structural surface;

[0026] a' is the deformed depth of point a at the edge of the structural surface;

[0027] b' is the deformed depth of point b at the edge of the structural surface;

[0028] D s1 This represents the initial tangential width of the structural surface;

[0029] D' s1 The tangential width of the structural surface after deformation;

[0030] ΔD n This represents the normal displacement of the structural surface;

[0031] ΔD s This represents the tangential displacement of the structural plane.

[0032] Furthermore, the rock mass structure information is obtained through borehole television equipment, and the rock mass structure information includes: (1) the depth of the structure surface from the borehole opening; and (2) the rotation angle of the borehole probe television.

[0033] Furthermore, the orientation of the structural surface is the angle between the structural surface and the borehole.

[0034] Furthermore, the observation point is the intersection of the structural plane and the two sides of the rock block boundary.

[0035] Furthermore, the structural surface displacement includes: (1) structural surface normal displacement; (2) structural surface tangential displacement.

[0036] Furthermore, the initial distance measurement of the observation point is obtained by drilling and installing a laser rangefinder multi-point displacement meter.

[0037] Furthermore, the relationship between the displacement of the structural plane and the orientation of the structural plane and the borehole depth is statistically analyzed to determine the dominant orientation of the structural plane. The process is as follows: The displacements of N groups of included-angle structural planes are statistically compared, and the group of included-angle structural planes with the largest sum of squares of normal and tangential displacements is determined. This orientation is the dominant orientation of the surrounding rock cracking during large deformation.

[0038] Furthermore, the process of determining the dominant structural plane's attitude and the degree of surrounding rock cracking by analyzing the relationship between the statistical structural plane displacement, the structural plane's attitude, and the borehole depth is as follows:

[0039] After calculating the normal and tangential displacements of each group of structural surfaces, the normal displacements of structural surfaces with the same included angle in boreholes at different locations in the tunnel were statistically analyzed, and a gradient diagram of the normal displacement of the structural surfaces was drawn. The range of severe cracking of the surrounding rock was selected when the normal displacement exceeded 10 mm.

[0040] Furthermore, the structural surfaces are grouped according to their orientation and depth from the borehole opening to determine displacement observation points:

[0041] Based on the depth of the structural planes within the borehole, they were grouped. Each borehole was divided into multiple equally spaced observation segments. Within each segment, one structural plane with an included angle α ranging from 0 to 30°, 30 to 60°, and 60 to 90° was selected as the observation target. The specific observation location for each structural plane was the two edges of the structural plane within the borehole. Compared with existing methods for obtaining deformation information of surrounding rock in large deformation tunnels, selecting the intersection points of the structural plane and the surrounding rock on both sides within the borehole for displacement monitoring can effectively eliminate the monitoring error caused by the overall deformation of the surrounding rock in subsequent calculations, obtaining accurate values ​​of structural plane deformation and ensuring the accuracy of the obtained results.

[0042] 1. This invention leaves a laser rangefinder-type multi-point displacement meter inside the surrounding rock borehole, which can obtain structural surface displacement information at multiple time points during the deformation process, and thus obtain the variation law of structural surface displacement and surrounding rock crack range over time.

[0043] 2. This invention divides the structural surfaces within each borehole into several groups based on their distance from the borehole opening. Within each group, one structural surface with an angle to the borehole ranging from 0° to 30°, 30° to 60°, and 60° to 90° is selected as the observation object. The structural surface displacement results obtained by this method can effectively reflect the depth distribution law of surrounding rock cracking range and the relationship between surrounding rock cracking and the attitude of structural surfaces. Attached Figure Description

[0044] Figure 1 This is a schematic diagram of the drilling arrangement according to an embodiment of this application;

[0045] Figure 2 This is a two-dimensional unfolded view of the structural surface of an embodiment of this application;

[0046] Figure 3 This is a schematic diagram of the structural plane space of an embodiment of this application;

[0047] Figure 4 This is a schematic diagram of the internal structure of the borehole according to an embodiment of this application;

[0048] Figure 5 This is a schematic diagram of the borehole structural surface ranging before the surrounding rock deformation in an embodiment of this application;

[0049] Figure 6 This is a schematic diagram of borehole structural surface ranging after surrounding rock deformation according to an embodiment of this application;

[0050] Figure 7 This is a schematic diagram of the crack range within the surrounding rock according to an embodiment of this application;

[0051] Figure 8 This is a schematic diagram of the structural surface displacement distribution according to an embodiment of this application;

[0052] Figure 9 This is a schematic diagram of historical displacement monitoring of a single structural surface according to an embodiment of this application. Detailed Implementation

[0053] To better explain and facilitate understanding of the present invention, the present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

[0054] This embodiment discloses a method for analyzing the cracking range of surrounding rock in large deformation tunnels, including the following steps:

[0055] S1: Deploy surrounding rock boreholes and extract information on rock mass structure surfaces;

[0056] S2: Group the structural surfaces according to their orientation and depth from the borehole opening, and determine the displacement observation points;

[0057] S3: Obtain the initial distance measurement of the displacement observation point of the surrounding rock borehole; the observation point is the intersection of the structural surface and the two sides of the rock block boundary;

[0058] S4: During the deformation of the surrounding rock, the distance measurement information of the observation point is read multiple times to calculate the displacement of the structural surface; the displacement of the structural surface includes: (1) the normal displacement of the structural surface; (2) the tangential displacement of the structural surface.

[0059] S5: Analyze the relationship between structural plane displacement, structural plane attitude, and borehole depth to determine the dominant structural plane attitude and the distribution of surrounding rock cracking. The structural plane attitude is the angle between the structural plane and the borehole.

[0060] The rock mass structure information is obtained through borehole television equipment, and the rock mass structure information includes: (1) the depth of the structure surface from the borehole opening; (2) the rotation angle of the borehole probe television.

[0061] Equally spaced boreholes are drilled around the tunnel chamber, such as... Figure 1 As shown. After drilling is completed, the broken rock inside the hole is cleared, and a borehole television device is set up. Multiple target points are selected on each structural surface inside the borehole, and the coordinate information of the target points is read: the depth l of the coordinate point from the borehole opening and the rotation angle θ of the borehole probe television. The horizontal and vertical coordinates of the structural surface are obtained by fitting the coordinates of multiple target points into a two-dimensional unfolded diagram, as shown. Figure 2 As shown. The target point coordinates are fitted using a function of the following form:

[0062] l(θ)=a*sin(θ+b)+c (1)

[0063] In the formula, l(θ) represents the current borehole depth, and a, b, and c are fitting constants. Based on the fitted function, at least three second target points are constructed, and the plane normal vector is calculated based on the second target points. Based on the plane normal vector and the second target points, the plane equation is solved to calculate the angle α between the structural surface and the borehole, as shown below. Figure 3 As shown.

[0064] The initial distance measurement of the observation point was obtained by drilling and installing a laser rangefinder multi-point displacement meter.

[0065] Remove the television equipment from the borehole, set up a laser rangefinder multi-point displacement meter, spray reflective paint on selected observation points, and measure the initial depth L from the borehole opening at each observation point using the scale on the displacement meter rod. a ,L b ,L c ,L d ...

[0066] Read the distances from each observation point to the centerline of the displacement gauge: a, b, c, d...

[0067] During the deformation of the surrounding rock, information from observation points was read multiple times to calculate the displacement of the structural surfaces.

[0068] After the surrounding rock deformation begins, the structural planes undergo tangential and normal displacements, such as... Figure 6 As shown, the depth of each observation point from the borehole opening was read again at different times: L' a ,L' b ,L' c ,L' d ...

[0069] Read the distances of each observation point from the displacement centerline at this time: a', b', c', d'...

[0070] The process of grouping structural surfaces based on their orientation and depth from the borehole opening to determine displacement observation points is as follows:

[0071] The borehole passes through multiple structural planes, such as... Figure 4 As shown. In this application, structural surfaces are grouped according to their depth within the borehole. Each borehole is divided into multiple equally spaced observation segments. Within each segment, one structural surface with an included angle α in the ranges of 0–30°, 30–60°, and 60–90° is selected as the observation object. The specific observation location for each structural surface is the two edges (A, B, C, D...) of the structural surface within the borehole. Figure 5 As shown.

[0072] During the large deformation of the surrounding rock, although the borehole position will shift significantly with the surrounding rock, the normal and tangential displacements of the structural plane can be calculated by the change in distance between observation points on both sides of the structural plane. That is, the process of calculating the displacement of the structural plane by repeatedly reading the distance measurement information of the observation points during the deformation of the surrounding rock is as follows:

[0073] D n1 =(L b -L a sinα (2)

[0074]

[0075] D s1 =(L b -L a cosα (4)

[0076] .

Claims

1. A method for analyzing the cracking range of surrounding rock in large deformation tunnels, characterized in that: Includes the following steps: Drill holes in the surrounding rock and extract information on the rock mass structure. The structural surfaces are grouped according to their orientation and depth from the borehole opening to determine displacement observation points; Initial distance measurement of displacement observation points in the surrounding rock borehole; During the deformation of the surrounding rock, the distance measurement information of the observation points was read multiple times to calculate the displacement of the structural surface. The relationship between structural plane displacement, structural plane attitude, and borehole depth was statistically analyzed to determine the attitude of the dominant structural plane and to determine the degree of cracking in the surrounding rock by measuring the normal displacement of the structural plane within the surrounding rock. The process of repeatedly reading distance measurement information from observation points during surrounding rock deformation and calculating structural surface displacement is as follows: (2) (3) (4) (5) (6) (7) In the formula: D n1 This represents the initial normal width of the structural surface; L a Let be the initial depth of point a at the edge of the structural surface; L b Let b be the initial depth at the edge point of the structural surface; a’ The distance from point a on the edge of the structural surface to the central axis of the hole after deformation; b’ The distance from point b at the edge of the structural surface to the central axis of the hole after deformation; D’ n1 The normal width of the structural surface after deformation; L’ a Let be the deformed depth of point a at the edge of the structural surface; L’ b Let be the deformed depth of point b at the edge of the structural surface; D s1 This represents the initial tangential width of the structural surface; D’ s1 The tangential width of the structural surface after deformation; Δ D n This represents the normal displacement of the structural surface; Δ D s This represents the tangential displacement of the structural surface; α The angle between the structural plane where the observation point is located and the borehole; The process of determining the dominant structural plane's attitude and the degree of surrounding rock cracking by analyzing the relationship between the statistical structural plane displacement, its attitude, and borehole depth, and by determining the normal displacement of the structural plane within the surrounding rock, is as follows: After calculating the normal and tangential displacements of each group of structural surfaces, the normal displacements of structural surfaces with the same included angle in boreholes at different locations in the tunnel are statistically analyzed, a gradient diagram of the normal displacements of structural surfaces is drawn, and the range of severe cracking of the surrounding rock is selected as the range of normal displacement exceeding 10 mm. The process of determining the dominant structural plane attitude by statistically analyzing the relationship between structural plane displacement, structural plane attitude, and borehole depth is as follows: Statistically compare the displacements of N groups of included-angle structural planes, and determine the group of included-angle structural planes with the largest sum of squares of normal and tangential displacements. This attitude is the dominant attitude of surrounding rock cracking during large deformation.

2. The method for analyzing the cracking range of surrounding rock in a large deformation tunnel according to claim 1, characterized in that: The rock mass structure information is obtained through borehole television equipment, and the rock mass structure information includes: (1) the depth of the structure surface from the borehole opening; (2) the rotation angle of the borehole probe television.

3. The method for analyzing the cracking range of surrounding rock in a large deformation tunnel according to claim 1, characterized in that: The orientation of the structural plane is the angle between the structural plane and the borehole.

4. The method for analyzing the cracking range of surrounding rock in a large deformation tunnel according to claim 1, characterized in that: The observation points are the intersections of the structural plane and the two sides of the rock block boundary.

5. The method for analyzing the cracking range of surrounding rock in a large deformation tunnel according to claim 1, characterized in that: The structural surface displacement includes: (1) structural surface normal displacement; (2) structural surface tangential displacement.

6. The method for analyzing the cracking range of surrounding rock in a large deformation tunnel according to claim 1, characterized in that: The initial distance measurement of the observation point was obtained by drilling and installing a laser rangefinder multi-point displacement meter.

7. The method for analyzing the cracking range of surrounding rock in a large deformation tunnel according to claim 1, characterized in that: The process of grouping structural surfaces based on their orientation and depth from the borehole opening to determine displacement observation points includes: Based on the depth of the structural plane within the borehole, the borehole is grouped into multiple equally spaced observation segments. The angle between the structural plane where the observation point is located and the borehole is taken for each segment. α One structural plane in each of the ranges of 0~30°, 30~60°, and 60~90° was selected as the observation object; the specific observation position for each structural plane was the two sides of the structural plane inside the borehole.

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