Shield segment arrangement and type selection method

Abstract

A shield segment arrangement and type selection method, relating to the technical field of shield construction. The method comprises: on the basis of segment design parameters, determining the number of segments, a fitted minimum curve radius, a turning angle, the ratio of tapered rings to standard rings, and the taper of each point on each tapered ring; and on the basis of the taper of each point on each tapered ring, calculating, with the ratio of the tapered rings to the standard rings as a reference, the number of circles corresponding to a cycle and optimal segment arrangement selection positions of each circle of segments in the cycle. The method reduces misalignment of formed tunnels or even segment cracking caused by inaccurate segment type selection, thereby improving the quality of formed tunnels.

Description

Shield segment layout and selection method

[0001] This disclosure claims priority to the Chinese patent application filed with the China Patent Office on November 29, 2023, with application number 202311613135.0, and the entire contents of the above application are incorporated by reference into this disclosure. Technical Field

[0002] The present disclosure relates to the technical field of shield construction, for example, to a shield segment layout and selection method. Background Art

[0003] The curve of the shield tunnel is fitted by controlling the wedge shape of the segments. From the perspective of the entire shield excavation process, the shield machine moves forward in a serpentine manner. Taking the tunnel centerline as the benchmark and considering factors such as the influence of the shield tail gap, the shield machine posture is continuously adjusted using the wedge shape of the segments to ensure that the deviation of the formed tunnel is within the allowable deviation range.

[0004] Currently, the mainstream shield tunnel segment designs in China are divided into two main types: the "universal ring" and the "standard ring + wedge ring" approach. However, the theoretical basis for fitting the wedge shape in curved tunnels remains the same, differing only in the flexibility of the capping block location.

[0005] The "standard ring + wedge ring" type can meet the requirements for segment layout and segment selection for curved tunnels by properly selecting left and right wedge ring types, supplemented by standard rings, and selecting all capping blocks at points in the upper semicircle. This will facilitate segment assembly to a certain extent. However, the segment factory must have at least three types of segment production molds: left and right wedge rings, and standard rings.

[0006] The "Universal Ring" type has only one segment type, and the segment factory only needs to set up a single segment production mold. However, during on-site shield tunneling construction, segment layout and segment selection require the use of nearly every point on the circle to fit the curvilinear elements of the designed tunnel. If the capping block at the selected point is located in the lower semicircle, assembly becomes more difficult, resulting in a decrease in segment assembly quality.

[0007] Therefore, accurate segment layout and selection are key to controlling tunnel quality during shield construction and reducing misalignment, cracking, and water leakage. Currently, segment layout and selection still rely on a relatively crude calculation and management approach. In actual construction, three factors are considered: 1. The relationship between the shield machine's attitude and the tunnel centerline; 2. The cylinder stroke difference (thrust cylinder + articulation cylinder); and 3. The shield tail clearance. A rough estimate is used to determine the segment assembly points, but no rigorous calculations are performed. In straight sections, this kind of experience-based, rough selection may not result in serious tunnel quality defects. However, in curved sections, especially those with small radius flat curves less than 500m, rough selection often results in axis deviations exceeding design limits, increased segment misalignment, and even segment cracking.

[0008] Summary of the Invention

[0009] The present disclosure provides a shield segment layout and selection method, which can reduce the misalignment of formed tunnels and even cracking of segments caused by inaccurate segment selection, and improve the quality of formed tunnels.

[0010] The technical solution adopted in the present disclosure is to provide a shield segment layout and selection method, including:

[0011] Determine the number of segments, the minimum fitting curve radius, the turning angle, the ratio of the wedge ring to the standard ring, and the wedge amount at each point on the wedge ring based on the segment design parameters;

[0012] Taking the ratio of the wedge ring to the standard ring as a reference and combining the wedge amount of each point on the wedge ring, the number of rings corresponding to a cycle and the optimal segment layout selection point of each ring in the cycle are calculated. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] FIG1 is a flow chart of a shield segment layout and selection method according to an embodiment of the present disclosure;

[0014] FIG2 is a schematic diagram of calculating the wedge amount of each point on a wedge ring in an embodiment of the present disclosure;

[0015] FIG3 is a schematic diagram of the optimal segment layout in an embodiment of the present disclosure. DETAILED DESCRIPTION

[0016] The embodiment of the present disclosure relates to a shield segment layout and selection method, as shown in FIG1 , comprising the following steps:

[0017] Step 1: Based on the segment design parameters, determine the number of segments, the minimum curve radius, the turning angle, the ratio of the wedge ring to the standard ring, and the wedge amount at each point on the wedge ring. This step includes:

[0018] (1) Determine the segment design parameters involved in the ring selection. In this embodiment, the ring type is determined to be a standard ring + a wedge ring, and the outer diameter, width and maximum wedge amount of the ring are used as the segment design parameters.

[0019] (2) calculating the minimum number of segments required to fit a circular tunnel based on the maximum wedge amount, the outer diameter of the ring, and the width of the ring;

[0020] (3) calculating the turning angle according to the maximum wedge amount and the outer diameter of the pipe ring;

[0021] (4) Calculate the ratio of the wedge ring to the standard ring based on the maximum wedge amount, the outer diameter of the pipe ring, the width of the pipe ring and the radius of the line turning curve;

[0022] (5) Calculate the wedge amount of each point on the wedge ring based on the maximum wedge amount.

[0023] Taking Suzhou Metro Line 1 as an example, its pipe ring type adopts "standard ring + wedge ring", the outer diameter of the pipe segment D = 6200mm, the pipe ring width w = 1200mm, the maximum wedge amount is L = 37.2mm, and the wedge amount is divided into two parts, which are symmetrically arranged on the two side ring surfaces of the wedge ring, that is, an isosceles wedge ring.

[0024] First, the minimum number of segments N required to fit a circular tunnel is calculated based on the maximum wedge amount L and the outer diameter D of the ring. The calculation method is: The result is 1047.2 rings. D is the outer diameter of the tube ring, and L is the maximum wedge amount.

[0025] Then, the minimum curve radius r is calculated based on the number of segments and the curve radius of the line. The calculation method is: The result is 200m.

[0026] The turning angle is then calculated based on the maximum wedge amount and the outer diameter of the pipe ring. The calculation method is: θ = L / D * (180 / π). According to the calculation, the turning angle of a wedge ring is 0.344°. θ is the turning angle, D is the outer diameter of the pipe ring, and L is the maximum wedge amount.

[0027] The ratio μ of the wedge ring to the standard ring is calculated based on the maximum wedge amount, the outer diameter of the pipe ring and the width of the pipe ring. The calculation method is: r1 is the designed curve radius of the route. In this implementation, r1 = 600m, and the calculated result is 0.5, meaning a wedge ring is required every 3.6m. Where μ is the ratio of the wedge ring to the standard ring, r1 is the curve radius of the route, L is the maximum wedge amount, D is the outer diameter of the pipe ring, and w is the width of the pipe ring.

[0028] Finally, the wedge amount of each point on the wedge ring is calculated based on the outer diameter of the pipe ring and the maximum wedge amount. As shown in Figure 2, point b is the narrowest point of the wedge segment, point a is any point on the circumference of the wedge surface, and the circular surface P is the circular surface where the narrowest point b of the wedge segment is located. The center of the wedge ring can be projected onto the center o of the circular surface P, and any point a on the circumference of the wedge surface can be projected onto point a' on the circular surface P. Then the angle between the line connecting point a' and the center o and the line connecting point b and the center o is B. Therefore, the wedge amount of each point on the wedge ring can be calculated by Calculations show that, assuming angle B is 90°, the wedge depth at point a on the wedge ring is 18.6 mm. X is the wedge depth at a point on the wedge ring, L is the maximum wedge depth, and the angle B is the line connecting the point on the wedge ring projected onto the circular surface P where the narrowest point of the wedge segment is located and the center of the circular surface P.

[0029] Step 2: Based on the ratio of the standard ring to the wedge ring, and the wedge volume at each point on the wedge ring, calculate the number of rings corresponding to one cycle and the optimal segment layout selection points for each ring within the cycle. This includes:

[0030] Determine the number of standard rings and wedge rings according to their ratio, and select the assembly points;

[0031] The cumulative advance amount under different layouts is calculated, and the layout with the smallest cumulative advance amount error is taken as the optimal segment layout for the corresponding number of cycles. The advance amount is calculated based on the wedge amount of the splicing points on the wedge ring.

[0032] Taking Xi'an Metro Line 4 as an example, the segment design parameters for Xi'an Metro Line 4 are as follows: segment outer diameter: 6000mm, segment width: 1500mm, maximum wedge amount: 38mm, using isosceles wedge rings. Design type: standard ring + left and right wedge rings.

[0033] Point arrangement: 12 points, meaning each ring has 10 longitudinal bolts + 12 circumferential bolts = 22 bolts. At this point, the segment selection points are 12, with the angle between any two points being 30°. When selecting segments on-site, points 0 and 6 are generally not selected. Points 1-5 and 7-11 are selected according to the principle of staggered assembly. The upper semicircle, points 1-3, and points 9-11 are preferably selected. The optimal configuration for this embodiment is to alternate between points 1 and 11. Based on this information, the left and right wedge values ​​and the upper and lower wedge values ​​for each point on the left and right turn rings can be calculated using the aforementioned formulas.

[0034] When the curve radius is 450 meters and the turn is right, the optimal state is to alternate between 1 and 11 o'clock. It can be calculated that when assembled at 1 o'clock, the left wedge amount is 37.1mm, the right wedge amount is 0.9mm, and the left lead amount is 36.2mm. Similarly, the upper lead amount can be calculated as 11.8mm. When assembled at 11 o'clock, the left lead amount is 36.2mm and the upper lead amount is -11.8mm.

[0035] The minimum curve radius for fitting is calculated based on the line radius and horizontal lead, resulting in a 20mm left lead for every 1.5m. For a curve with a radius of 450m, 24 rings are used as a loop for segment selection. The cumulative lead under various layouts is calculated, and the one with the smallest cumulative lead error is selected as the final choice. This implementation ultimately selects 13 rings as right wedge rings and 11 rings as standard rings. All wedge rings are assembled at either 1 or 11 o'clock, and the layout is shown in Figure 3. The actual cumulative lead is 36.2*13=470.6mm. Compared to the theoretical cumulative lead of 24 rings (24*20=480mm), the lead error is 9.4mm, within 15mm, meeting the selection requirements.

[0036] The present invention analyzes the segment design parameters and obtains a function calculation formula for the segment advance amount at each point, which is used to accurately calculate the left and right advance correction wedge amounts and the upper and lower advance correction wedge amounts of the corresponding points of the selected segment model, and obtains the number of segments, the ratio of the standard ring and the wedge ring, and the wedge amount of each point on the wedge ring. By designing the segment using the "standard ring + wedge ring" type, an analysis is performed on a certain small-radius flat curve shield tunnel, and a segment best-fit segment layout calculation method is given. The optimal segment layout diagram of the shield tunnel is accurately given, thereby greatly reducing the misalignment of the formed tunnel and even the cracking of the segment due to inaccurate segment selection, and improving the quality of the formed tunnel.

Claims

1. A shield segment layout and selection method, comprising: According to the segment design parameters, determine the number of segments, the minimum fitting curve radius, the turning angle, the ratio of the wedge ring to the standard ring, and the wedge amount at each point on the wedge ring; Taking the ratio of the wedge ring to the standard ring as a reference and combining the wedge amount of each point on the wedge ring, the number of rings corresponding to a cycle and the optimal segment layout selection point of each segment in the cycle are calculated.

2. The shield segment layout and selection method according to claim 1, wherein: The method of determining the number of segments, the minimum fitting curve radius, the turning angle, the ratio of the wedge ring to the standard ring, and the wedge amount of each point on the wedge ring according to the segment design parameters includes: The outer diameter of the pipe ring, the width of the pipe ring and the maximum wedge amount are used as the design parameters of the pipe segment; Calculating the minimum number of segments required to fit a circular tunnel according to the maximum wedge amount, the outer diameter of the ring and the width of the ring; Calculating the turning angle according to the maximum wedge amount and the outer diameter of the pipe ring; Calculate the ratio of the wedge ring to the standard ring based on the maximum wedge amount, the outer diameter of the pipe ring, the width of the pipe ring and the line turning curve radius; The wedge amount at each point on the wedge ring is calculated based on the maximum wedge amount.

3. The shield segment layout and selection method according to claim 2, wherein: The minimum number of segments required to fit a circular tunnel It is obtained by calculation, where N is the minimum number of segments required to fit a circular tunnel, D is the outer diameter of the ring, and L is the maximum wedge amount.

4. The shield segment layout and selection method according to claim 2, wherein: The turning angle θ=L / D*(180 / π) is obtained by calculation, wherein θ is the turning angle, D is the outer diameter of the pipe ring, and L is the maximum wedge amount.

5. The shield segment layout and selection method according to claim 2, wherein: The ratio of the wedge ring to the standard ring is given by It is calculated as follows: μ is the ratio of the wedge ring to the standard ring, r1 is the line turning curve radius, L is the maximum wedge amount, D is the outer diameter of the pipe ring, and w is the width of the pipe ring.

6. The shield segment layout and selection method according to claim 2, wherein: The wedge amount at each point on the wedge ring is It is calculated, where X is the wedge amount of a point on the wedge ring, L is the maximum wedge amount, and the angle between the line connecting the point on the circular surface P where a point on the wedge ring is projected to the narrowest point of the wedge segment and the center of the circular surface P and the line connecting the point on the narrowest point of the wedge segment and the center of the circular surface P is B.

7. The shield segment layout and selection method according to claim 1, wherein: The ratio of the wedge ring to the standard ring is used as a reference, and the wedge amount of each point on the wedge ring is combined to calculate the number of rings corresponding to a cycle and the optimal segment layout selection point of each segment in the cycle, including: Determine the number of standard rings and wedge rings according to the ratio of the wedge ring to the standard ring, and select the assembly point; The cumulative advance amount under different layouts is calculated, and the layout with the smallest cumulative advance amount error is taken as the optimal segment layout for the corresponding number of cycles, where the advance amount is calculated based on the wedge amount of the splicing points on the wedge ring.

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