Dynamic pushing rectification construction method for large-curvature bridge

Abstract

The application discloses a dynamic pushing rectification construction method for a large-curvature bridge, which comprises the following steps: step one, arranging a pushing system; step two, extracting a design centerline track of the curved bridge, dividing the design centerline of the bridge into a plurality of arc segments, and performing linear regression fitting on each arc segment by using a straight line; step three, arranging a positioning target point on a beam segment to be pushed; step four, optimizing a pushing direction; step five, calculating a whole pushing component set {Delta x i , Delta y i} of the whole curved bridge; step six, sequentially performing short-stroke pushing; step seven, re-calibrating the positioning target point and the design centerline track; step eight, performing dynamic rectification calculation; step nine, executing dynamic rectification; and step ten, repeating steps six to nine until the linear regression fitting of all the segments is completed. The application solves the technical problem that the rectification method in the traditional pushing process is usually based on the experience of a field team and is temporarily adjusted, the method lacks accuracy, and the installation stress risk is increased.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of construction engineering, and particularly relates to a dynamic pushing and deviation rectifying construction method for a large-curvature bridge. BACKGROUND

[0002] The project is an entry ramp project of a bridge, the bridge is 16.7 m wide, the beam is 2.2 m high, and the beam bottom transverse slope is 2%. During the construction period, the traffic of the entry A ramp needs to be kept smooth, and the steel box beam of the C14-C18 ramp bridge cannot be installed by using the conventional hoisting process. After repeated research and demonstration by the project team, it is proposed to install the steel box beam of the part of the overpass entry ramp bridge by using the walking pushing process, and the second link and the third link of the steel box beam are pushed by being temporarily connected into a whole. As known to all, the beam segment will deviate during the pushing process. In the past, the deviation rectifying method for the pushed beam segment was usually based on the experience of the site team for temporary adjustment. This method lacks accuracy and has the risk of increasing the installation stress. SUMMARY

[0003] The purpose of the present application is to provide a dynamic pushing and deviation rectifying construction method for a large-curvature bridge, and to solve the technical problem that the traditional deviation rectifying method during the pushing process is usually based on the experience of the site team for temporary adjustment, which lacks accuracy and has the risk of increasing the installation stress.

[0004] In order to achieve the above-mentioned purpose, the present application adopts the following technical solutions.

[0005] A dynamic pushing and deviation rectifying construction method for a large-curvature bridge, comprising the following steps.

[0006] Step one, laying out the pushing system: the walking pushing equipment in the pushing system is symmetrically laid out along the design center line of the curved bridge, so as to ensure that the longitudinal pushing oil cylinder of each walking pushing equipment is along the tangent of the bridge stroke, and the transverse pushing oil cylinder is along the radial direction of the bridge stroke.

[0007] Step two, extracting the design center line track of the curved bridge, and dividing the design center line of the bridge into a plurality of arc segments; the end point coordinates of the stroke arc segment on the design center line are (x1, y1), (x2, y2),..., (x i , y i ), …, (x n , y n ); a straight line is used to linearly regress and fit each arc segment, and the radian and radius of each arc segment are θ i and r i respectively; wherein i and n are positive integers, and i

[0008] Step three, setting the positioning target points on the beam segment to be pushed: at least two end point coordinates A(x j , yj ) and B(x k , y k ), and project the end point coordinates A and B on the beam segment to be jacked to form positioning target points A'(x j ', y j ') and B'(x k ', y k '); wherein j and k are positive integers less than or equal to n, and j≠k.

[0009] Step four, optimize the jacking direction to the direction of the linear regression fitted straight line, and the transverse jacking cylinder and the longitudinal jacking cylinder of the walking jacking equipment each time jacking component is Δx i and Δy i .

[0010] θ i = 2 x arcsin(500 / 2r i ).

[0011] Δx i = r i (1 - cosθ i ).

[0012] Δy i = r i x sinθ i .

[0013] Step five, calculate the jacking component set {Δx i , Δy i} at all end point coordinates in the entire curved bridge.

[0014] Step six, according to the entire jacking component set {Δx i , Δy i} calculated in step five, set the jacking distance Δx i and Δy i of the transverse jacking cylinder and the longitudinal jacking cylinder of the walking jacking equipment corresponding to the beam segment to be jacked below, and perform short stroke jacking one by one.

[0015] Step seven, after every 2-3 times of short stroke jacking, combine the jacking component Δx i and Δy i of the transverse jacking cylinder and the longitudinal jacking cylinder, calculate the theoretical corresponding end point coordinates of the current positioning target point on the design centerline of the bridge as C(x j+m , y j+m ) and D(x k+m , y k+m ); and re-mark the current position coordinates A'(x j+m ', y j+mB'(x k+m , y k+m ); when jacking 2 times, m = 2; when jacking 3 times, m = 3.

[0016] Step eight, dynamic deviation correction calculation is carried out, and a dynamic deviation correction coordinate calculation method is as follows: calculating a positioning target point deviation correction stroke S j and S k :

[0017]

[0018]

[0019] Step nine, dynamic deviation correction is carried out: according to the positioning target point deviation correction stroke S j and S k calculated in step eight, the displacement of the transverse jacking cylinder of the step jacking equipment at the corresponding position is used to jacking S j and S k , so as to approach the target coordinate.

[0020] Step ten, when S j ' < L / 2000 and S k ' < L / 2000, the next stroke jacking is carried out, and steps six to nine are repeated until the whole linear regression fitting line segment jacking is completed.

[0021] Preferably, the step jacking equipment is provided at the bottom of each beam segment to be jacked, and at least two groups of step jacking equipment are arranged along the bridge center line, and each group of step jacking equipment is symmetrically arranged along the bridge center line; the spacing between the radially adjacent step jacking equipment is adapted to the width of the beam segment to be jacked.

[0022] Preferably, the curvature of the curved bridge is greater than or equal to 1 / 60.

[0023] Preferably, in step one, the jacking system comprises temporary piers, step jacking equipment, guide beams and assembly supports; the temporary piers are arranged along the center axis of the designed bridge; the assembly supports are arranged between adjacent temporary piers, and an assembly platform is arranged at the top of the assembly support; the step jacking equipment is installed at the top of the temporary pier; the beam segment to be jacked is placed on the top of the step jacking equipment; and the guide beam is installed at the front end of the beam segment to be jacked.

[0024] Preferably, in step two, the length of the straight line segment for linear regression fitting with each arc segment is not greater than 500 mm.

[0025] Preferably, in step nine, the specific method for approaching the target coordinate is as follows.

[0026] Step 1, for j position, set the lateral pushing oil cylinder of the outer side walking pushing device to move S to the target direction j , set the lateral pushing oil cylinder of the inner side walking pushing device to move S to the target direction j .

[0027] Step 2, for k position, set the lateral pushing oil cylinder of the outer side walking pushing device to move S to the target direction k , set the lateral pushing oil cylinder of the inner side walking pushing device to move S to the target direction k .

[0028] Step 3, start to push radially at the same time for the j position and k position of the to-be-pushed beam segment part.

[0029] Step 4, recheck and reacquire the position coordinates of the positioning target point of the to-be-pushed beam segment after correction as A'(x j+m ”, y j+m ”) and B'(x k+m ”, y k+m ”),

[0030] and calculate the positioning target point correction calculation stroke S j ' and S k ' in combination with the correction calculation stroke formula of each walking pushing device:

[0031]

[0032]

[0033] Step 5, judge whether S j ' > L / 2000 and S k ' > L / 2000 are true, if true, repeat step 9 for correction again until the requirements are met, and then proceed to the next pushing; wherein L is the length of the pushing section between oil cylinders, 500 mm.

[0034] Compared with the prior art, the present application has the following characteristics and beneficial effects.

[0035] 1、The present application sets the positioning target point along the center line of the curved bridge, and sets a short stroke pushing method formed within 500 mm, repositions the target point coordinates after each small stroke pushing, uses the calculation method proposed by the present application to calculate the radial correction distance, and sequentially corrects according to the deviation situation in 2-3 strokes; the present application provides a scientific correction method in the bridge pushing process, so that the position of the pushed beam segment is more accurate, and solves the technical problems that the traditional correction method in the pushing process is usually based on the experience of the site team, and the method lacks accuracy and increases the risk of installation stress.

[0036] 2, the ramp bridge of the application, ramp bridge jacking construction, using differential jacking + transverse correction method realizes the integral jacking of curve bridge, it is a major breakthrough of step-by-step jacking technology, and promotes the progress of bridge construction technology. BRIEF DESCRIPTION OF DRAWINGS

[0037] The application will be further described in detail below with reference to the drawings.

[0038] Figure 1 It is the structural schematic diagram of the beam segment of the application arranged on the jacking system.

[0039] Figure 2 It is the structural schematic diagram of the step-by-step jacking equipment of the application arranged on the temporary pier.

[0040] Figure 3 It is the connection structure schematic diagram of the guide beam and the beam segment in the application.

[0041] Figure 4 It is the end point coordinate layout diagram when the design centerline of the curve bridge in the application is divided into several arc segments.

[0042] Figure 5 It is the position diagram of the end point coordinate after jacking and the actual positioning target point in the application.

[0043] The reference signs: 1-temporary pier, 2-step-by-step jacking equipment, 3-guide beam, 4-assembly support, 5-assembly platform, 6-beam segment. DETAILED DESCRIPTION

[0044] In the embodiment, the steel box girder is jacked to the design position by the jacking method, the steel box girder segment is jacked forward by 15.1m, differential jacking method is used for jacking, the jacking speed of the curve inner and outer jacking equipment is 100:121, the outer equipment jacks 300mm at a time, the inner equipment jacks 248mm at a time, in the jacking process, in order to ensure that the box girder and the guide beam web are always within the range of ±50mm of the longitudinal center line of the jacking equipment; the radial position is corrected once every 2-3 strokes of jacking, after jacking to the position, the steel box girder segments of 12#-14# are assembled on the assembly support 4; after assembly is completed, jacking construction is continued; the steel box girder segments of 3 segments are jacked once.

[0045] In the jacking process, the dynamic jacking correction construction method of the large curvature bridge includes the following steps:

[0046] Step one, layout of jacking system: the step-by-step jacking equipment in the jacking system is symmetrically laid along the design centerline of the curve bridge, so as to ensure that the longitudinal jacking cylinder of each step-by-step jacking equipment is along the tangential direction of the bridge stroke, and the transverse jacking cylinder is along the radial direction of the bridge stroke.

[0047] Step two, extract the design centerline trajectory of the curved bridge and divide the design centerline of the bridge into several arc segments; the endpoint coordinates of the travel arc segment on the design centerline are (x1, y1), (x2, y2),...., (x i , y i ),...., (x n , y n ); linear regression fitting is performed on each arc segment by using a straight line, and the radian and radius of each arc segment are θ i and r i respectively; wherein i and n are positive integers, and i < n.

[0048] Step three, set the positioning target points on the beam segment to be jacked: select at least two endpoint coordinates A(x j , y j ) and B(x k , y k ) on the design centerline of the curved bridge below the beam segment to be jacked, and project the endpoint coordinates A and B on the beam segment to be jacked to form positioning target points A'(x j ', y j ') and B'(x k ', y k '); wherein j and k are positive integers less than or equal to n, and j≠k.

[0049] Step four, optimize the jacking direction to the direction of the linear regression fitted straight line, and the horizontal jacking cylinder and the longitudinal jacking cylinder of the corresponding walking jacking equipment each time jacking component is Δx i and Δy i .

[0050] θ i =2×arcsin(500 / 2r i ).

[0051] Δx i =r i (1-cosθ i ).

[0052] Δy i =r i ×sinθ i .

[0053] Step five, calculate the entire set of jacking components {Δx i , Δy i} at all endpoint coordinates in the entire curved bridge.

[0054] Step six, according to the entire set of jacking components {Δx i , Δy iThe horizontal pushing cylinder and the longitudinal pushing cylinder of the step-by-step pushing equipment corresponding to the pushing distance Δx and Δy below the beam segment to be pushed are arranged respectively i and Δy i The short-stroke pushing is sequentially performed.

[0055] After every 2-3 times of short-stroke pushing, the pushing components Δx and Δy of the horizontal pushing cylinder and the longitudinal pushing cylinder are combined i and Δy i The end point coordinates C(x j+m , y j+m ) and D(x k+m , y k+m ) of the current positioning target point on the design center line of the bridge are calculated, and the current position coordinates A'(x j+m ', y j+m ') and B'(x k+m ', y k+m ') of the positioning target point are recalibrated. When the pushing is performed twice, m=2; when the pushing is performed three times, m=3.

[0056] In step eight, the dynamic deviation correction calculation is performed. The dynamic deviation correction coordinate calculation method is as follows: the positioning target point deviation correction calculation stroke S j and S k are calculated

[0057]

[0058]

[0059] In step nine, the dynamic deviation correction is performed: according to the positioning target point deviation correction calculation stroke S j and S k calculated in step eight, the horizontal pushing cylinder of the step-by-step pushing equipment at the corresponding position is used to push the displacement S j and S k , so as to approach the target coordinate, and the beam is lowered after accurate pushing.

[0060] In step ten, when S j '<L / 2000 and S k '<L / 2000, the next stroke pushing is performed, and steps six to nine are repeated until the linear regression fitting line segment pushing is completed.

[0061] In step eleven, the guide beam is removed, the remaining beam segment is installed on the assembled support by using the hoisting equipment, and the whole bridge construction is completed.

[0062] In the embodiment, the walking top pushing device is arranged at the bottom of each beam segment to be pushed, and at least two groups of the walking top pushing device are arranged along the bridge center line at intervals, and each group of the walking top pushing device is symmetrically arranged along the bridge center line. The interval between the walking top pushing devices adjacent in the radial direction is adapted to the width of the beam segment to be pushed. The end point of the travel arc segment on the design center line is arranged at the midpoint of the line connecting the walking top pushing devices.

[0063] In the embodiment, the curvature of the curved bridge is greater than or equal to 1 / 60.

[0064] How to ensure the overall stability and torsional resistance of the steel box girder and realize the pushing of the steel box girder along the curve is a key technical difficulty in engineering. In step one, the top pushing system comprises a temporary pier 1, a walking top pushing device 2, a guide beam 3 and an assembling support 4. The temporary pier 1 is arranged at intervals along the center axis of the designed bridge. The assembling support 4 is arranged between the adjacent temporary piers 1, and an assembling platform 5 is arranged at the top of the assembling support 4. The beam segment 6 to be pushed is assembled and formed on the assembling platform 5, and directly pushed to the designed position by the walking top pushing device 2. The walking top pushing device 2 is installed at the top of the temporary pier 1. The beam segment 6 to be pushed is placed at the top of the walking top pushing device 2. The guide beam 3 is installed at the front end of the beam segment 6 to be pushed, and the welding of the guide beam and the beam segment 6 to be pushed is also completed on the assembling support. The beam segment 6 to be pushed is a steel box girder segment.

[0065] In the embodiment, 10 walking top pushing devices 2 of 300T are put into use. The walking top pushing device 2 adopts a distributed control system combined with a man-machine interaction interface to realize remote monitoring, and utilizes displacement feedback to realize multi-point synchronous pushing closed-loop control. The synchronous precision of the device action is less than 2mm. The electromagnetic proportional reversing valve is combined with displacement feedback to realize stepless speed regulation and proportional action control in the pushing process. In order to reduce the cantilever negative bending moment of the beam body in the pushing process, a guide beam 3 with a length of 27m and a circular curvature radius of 60m is arranged at the front end of the bridge, and three assembling supports 4 are arranged in the C17-C18 and C14-C15 intervals to meet the requirements of the pushing process and the lifting and installation of the first and last beam segments 6.

[0066] In step two, the length of the straight line segment linearly regressed and fitted with each arc segment is not greater than 500mm.

[0067] In the embodiment, the specific method for approaching the target coordinate in step nine is as follows.

[0068] In step 1, for the j position, the lateral pushing oil cylinder of the outer walking top pushing device is arranged to move S towards the target direction. j The lateral pushing oil cylinder of the inner walking top pushing device is arranged to move S towards the target direction. j .

[0069] Step 2, for k position, set the lateral pushing oil cylinder of the outer walking pushing device to move to the target direction S k , set the lateral pushing oil cylinder of the inner walking pushing device to move to the target direction S k .

[0070] Step 3, start to perform radial pushing rectification for the j position and k position of the to-be-pushed beam section at the same time.

[0071] Step 4, recheck and reacquire the position coordinates of the positioning target points of the to-be-pushed beam section after rectification as A'(x j+m ”, y j+m ”) and B'(x k+m ”, y k+m ”),

[0072] and calculate the rectification calculation stroke S j ' and S k ' of the positioning target points in combination with the rectification calculation stroke formula of each walking pushing device:

[0073]

[0074]

[0075] Step 5, judge whether S j ' > L / 2000 and S k ' > L / 2000 are true, if true, repeat step 9 to rectify again until the requirements are met, and then proceed to the next pushing; wherein L is the length of the pushing section between oil cylinders, 500 mm.

[0076] In this embodiment, the specific method for calculating the end point coordinates C(x j+m , y j+m ) and D(x k+m , y k+m ) in step 7 is as follows:

[0077] x j+m = x j+m-1 + Δx j+m-1 ; x j+m-1 = x j+m-2 + Δx j+m-2 ;

[0078] y j+m = y j+m-1 + Δy j+m-1 ; y j+m-1 = y j+m-2 + Δy j+m-2 .

[0079] x k+m = x k+m-1 × Δxk+m-1 ; x k+m-1 = x k+m-2 + Δx k+m-2

[0080] y k+m = y k+m-1 + Δy k+m-1 ; y k+m-1 = y k+m-2 + Δy k+m-2 .

[0081] The current position coordinates A'(x j+m ', y j+m ') and B'(x k+m’ , y k+m ') of the positioning target points on the to-be-determined pushing beam segment and A'(x j+m ", y j+m ") and B'(x k+m ", y k+m ") are measured by a measuring method.

[0082] In the embodiment, the walking top pushing device integrates vertical jacking, longitudinal pushing, transverse deviation rectification and return functions in one space, the longitudinal pushing function is realized by taking the walking top pushing process as the soul, and richly providing mechanical walking, hydraulic transmission, construction control and monitoring alarm functions, the whole system of the device is controlled by a computer to realize multi-point synchronous operation, the beam body can be adjusted in six degrees of freedom, and the vertical curve and the horizontal curve of the beam body can be adapted. The walking top pushing device utilizes the self-balancing principle, the pushing force and the friction force generated by the sliding surface of the device are balanced with each other, the horizontal force construction during pushing is realized, the problem of large horizontal force in the traditional pushing and pulling type pushing is overcome, and the amount of temporary works for pushing construction is effectively reduced. Since the device has vertical jacking function, the adaptability to the settlement of the support is strong, and a smooth slide is not needed. Since the size of the support return force of each working surface can be actively adjusted, the stress of each working surface can be actively adjusted according to the stress condition of the pushing beam segment, and the stress of the pushing beam segment during the pushing process is more reasonable. The whole system is controlled by a computer, the pushing conditions of each pushing point are reflected in real time, the attitude during pushing can be controlled, adjusted and visualized, and the construction precision and safety are ensured.

Claims

1. A dynamic pushing rectification construction method for a large-curvature bridge, characterized in that, The steps include the following: Step one, the layout of the pushing system: the step-by-step pushing equipment in the pushing system is symmetrically laid along the design center line of the curved bridge, ensuring that the longitudinal pushing cylinder of each step-by-step pushing equipment is tangent to the bridge stroke, and the transverse pushing cylinder is radial to the bridge stroke; Step two: Extract the design centerline trajectory of the curved bridge and divide the design centerline into several arc segments; the endpoint coordinates of the arc segments on the design centerline are (x1, y1), (x2, y2), ..., (x... i y i ), ..., (x n y n Linear regression fitting is performed on each arc segment using a straight line, where the radius and curvature of each arc segment are θ, respectively. i and r i Where i and n are positive integers, and i < n; Step three, setting positioning target points on the beam segment to be jacked: selecting at least two end point coordinates A(x j , y j ) and B(x k , y k ) on the curve bridge design center line below the beam segment to be jacked, and projecting the end point coordinates A and B on the beam segment to be jacked to form positioning target points A'(x j ', y j ') and B'(x k ', y k '); wherein j and k are positive integers less than or equal to n, and j≠k. Step four, the direction of pushing is optimized to the direction of the straight line of linear regression fitting, and the corresponding transverse pushing oil cylinder and longitudinal pushing oil cylinder of the walking pushing device each time pushing component is Δx i and Δy i ; θ i = 2 x arcsin(500 / 2r i ); Δx i = r i (1 - cos θ i ); Δy i = r i x sin θ i ; Step 5: Calculate the set of jacking components {Δx} at all endpoint coordinates of the entire curved bridge. i Δy i }; Step six, according to the total set of pushing components {Δx i , Δy i} calculated in step five, the corresponding horizontal pushing cylinder and longitudinal pushing cylinder of the walking pushing device under the beam segment to be pushed are respectively set to push the distance Δx i and Δy i , and short-stroke pushing is sequentially performed; Step seven, after every 2-3 times of short distance pushing, the pushing component of the transverse pushing oil cylinder and the longitudinal pushing oil cylinder is calculated as Δx i and Δy i , the end point coordinates of the target point in the design center line of the bridge are calculated as C(x j+m , y j+m ) and D(x k+m , y k+m ); and the current position coordinates of the target point are recalibrated as A'(x j+m ', y j+m ') and B'(x k+m ', y k+m '); when pushing 2 times, m=2; when pushing 3 times, m=3; Step eight, dynamic deviation correction calculation is carried out, and the dynamic deviation correction coordinate calculation method is as follows: calculating the positioning target point deviation correction calculation stroke S j and S k : Step nine, performing dynamic correction: according to the positioning target point correction calculated in step eight, the stroke S is calculated j and S k , using the displacement of the transverse pushing cylinder of the walking top pushing device at the corresponding position, to approach the target coordinate; j and S k ​ Step ten, wait for S j ′ < L / 2000, and S k ′ < L / 2000 to push the next trip, repeat steps six to step nine, until the completion of all linear regression fitting line segment push.

2. The method according to claim 1, wherein the method is characterized by: The step-by-step pushing equipment is provided at the bottom of each segment of the beam to be pushed, and at least two groups of step-by-step pushing equipment are provided, and the at least two groups of step-by-step pushing equipment are spaced along the bridge center line, and each group of step-by-step pushing equipment is symmetrically laid along the bridge center line; the spacing between the radially adjacent step-by-step pushing equipment is adapted to the width of the beam segment to be pushed.

3. The method of claim 1, wherein the method further comprises: providing a plurality of jacks positioned on the bridge deck; and positioning a plurality of jacking pads on the bridge deck, wherein the jacking pads are positioned between the jacks and the bridge deck. The curvature of the curved bridge is greater than or equal to 1 / 60.

4. The method of claim 1, wherein the method further comprises: providing a plurality of jacks; and positioning the plurality of jacks on the bridge deck at a plurality of locations along the bridge deck. In step one, the pushing system includes temporary piers (1), step-by-step pushing equipment (2), guide beams (3) and assembly supports (4); the temporary piers (1) are provided in one group and are spaced along the center axis of the designed bridge; the assembly support (4) is provided between the adjacent temporary piers (1), and the assembly platform (5) is provided at the top of the assembly support (4); the step-by-step pushing equipment (2) is installed on the top of the temporary pier (1); the beam segment (6) to be pushed is placed on the top of the step-by-step pushing equipment (2); the guide beam (3) is installed at the front end of the beam segment (6) to be pushed.

5. The method of claim 1, wherein the method further comprises: providing a plurality of jacks positioned on the bridge deck; and positioning a plurality of jacking pads on the bridge deck, wherein the jacking pads are positioned between the jacks and the bridge deck. In step two, the length of the straight line segment linearly regressed and fitted with each arc segment is not greater than 500 mm.

6. The method of claim 1, wherein the method further comprises: The specific method for approaching the target coordinate in step nine is: Step 1, for j position, set the lateral pushing oil cylinder of the outer side walking pushing device to move S to the target direction j , set the lateral pushing oil cylinder of the inner side walking pushing device to move S to the target direction j ; Step 2, for k position, set the lateral pushing oil cylinder of the outer side walking pushing device to move S to the target direction k ; set the lateral pushing oil cylinder of the inner side walking pushing device to move S to the target direction k ; Step 3, simultaneously starting to push and correct the position of the beam segment to be pushed in the j position and the k position in the radial direction; Step 4, again, review, re-acquire the position coordinates of the positioning target point of the rectified beam segment to be jacked as A'(x j+m ”, y j+m ”) and B'(x k+m ”, y k+m ”), And combined with each step by step pushing device deviation correction formula, calculation of positioning target point deviation correction stroke S j ′ and S k ′: Step 5, judging S j ′>L / 2000 and S k ′>L / 2000 is true, if true, repeat step nine again to correct the deviation until the requirements are met, and then proceed to the next step of pushing; wherein L is the length of the pushing section between the oil cylinders 500mm.

Images