A surface settlement monitoring method suitable for bridge jacking process

Abstract

The present application relates to a method for monitoring ground settlement applicable to bridge jacking process, mainly to the technical field of methods for monitoring ground settlement, which includes the following steps: cleaning and cleaning the side wall of the bridge load-bearing column; setting a reference line on the side wall of the bridge load-bearing column at the same height in the horizontal direction; installing a slide rail on the side wall of the bridge load-bearing column in a direction perpendicular to the horizontal plane; temporarily fixing a settlement module on the slide rail, and temporarily fixing a measurement module on another slide rail; adjusting the relative position of the settlement module and the measurement module, and then fixing the settlement module and the measurement module; recording the difference between the settlement module and the measurement module in the vertical direction; and repeating steps 5-7. The present application has the advantages of high measurement accuracy and is conducive to improving the quality of bridge jacking construction.

Description

Technical Field

[0001] The present application relates to the technical field of methods for monitoring ground surface settlement, and in particular to a method for monitoring ground surface settlement applicable to a bridge jacking process. Background Art

[0002] The bridge jacking process refers to a construction method in which the beam is cast or assembled in sections at the bridge head, and then pushed longitudinally with a jack so that the beam is in place through the temporary sliding bearing surface on the top of each pier. The bridge jacking method has been rapidly promoted because of its advantages such as small construction area, uninterrupted construction process, good structural integrity, and the equipment and formwork can be reused, and there is no noise during the construction process. With the increasing number of reinforced concrete and other cross-section continuous beam bridges and cable-stayed bridges built in my country, the application scenarios of the bridge jacking process are also gradually expanding.

[0003] Due to the construction characteristics of the bridge jacking process, the bridge load-bearing columns bear loads in a sequential manner, so the surface settlement process that accompanies the load bearing also occurs in a sequential manner. This will cause the end faces of the bridge load-bearing columns to have height differences in the vertical direction, that is, uneven settlement. Due to the existence of height differences, construction personnel need to continuously adjust the steel guide beams installed at the ends of the steel box beams to ensure that the jacking process can proceed smoothly. This phenomenon is particularly obvious during the jacking construction of continuous truss-stiffened steel box beams with large widths, large spans, and large deadweights, which may have an adverse impact on the on-time delivery of the jacking construction.

[0004] With respect to the above-mentioned related technologies, the inventors believe that when the existing bridge jacking technology is used to deal with the construction scenario of continuous truss-stiffened steel box girders, the uneven settlement of the bridge load-bearing columns may have an adverse effect on the construction progress. Summary of the invention

[0005] In order to alleviate the impact of uneven settlement of bridge load-bearing columns on the construction progress during the jacking construction of continuous truss-stiffened steel box girders, the settlement of bridge load-bearing columns is visualized and digitized in advance. This application provides a surface settlement monitoring method suitable for bridge jacking technology.

[0006] The present application provides a surface settlement monitoring method applicable to bridge jacking technology, which adopts the following technical solution:

[0007] A surface settlement monitoring method applicable to a bridge jacking process comprises the following steps:

[0008] S1, cleaning and cleaning the side walls of the bridge bearing columns;

[0009] S2, set reference lines on the side walls of the bridge bearing columns at the same height in the horizontal direction;

[0010] S3, installing a slide rail on the side wall of the bridge load-bearing column in a direction perpendicular to the horizontal plane, wherein one end of the slide rail close to the ground is at the same height as the reference line;

[0011] S4, temporarily fixing the sedimentation module on the slide rail, and temporarily fixing the measurement module on another slide rail, wherein the slide rail on which the sedimentation module is installed is adjacent to the slide rail on which the measurement module is installed;

[0012] S5, adjusting the relative position of the sedimentation module and the measurement module so that the sedimentation module and the measurement module are located at the same height, and then fixing the positions of the sedimentation module and the measurement module;

[0013] S6, starting the bridge jacking construction, and stopping the construction when the centroid of the bridge deck box girder reaches the bridge load-bearing column where the settlement module is installed;

[0014] S7, leaving it to stand for 24 hours, and recording the difference between the settlement module and the measurement module in the vertical direction;

[0015] S8, sequentially move and install the settlement module and the measurement module according to the forward direction of the bridge pushing construction and repeat steps S5-S7 until the bridge pushing construction is completed.

[0016] By adopting the above-mentioned technical scheme, the slide rail in the present application plays a role of supporting and limiting the settlement module and the measuring module. The settlement module can be displaced in the direction vertical to the ground together with the settlement process of the bridge support column, thereby generating a height difference with the upper surface of the measuring module leveled in the static initial state. The present application converts the difficult-to-observe overall settlement distance of the bridge load-bearing column into an easy-to-observe and measurable height difference between the settlement module and the measuring module. Repeating the measurement steps can obtain a linear change relationship diagram between the settlement distance of the bridge load-bearing column and the bridge jacking distance, thereby providing reference data for predicting the settlement value that will be generated by the bridge load-bearing column that has not yet borne the load, facilitating on-site construction personnel to adjust the bridge jacking distance, jacking height and holding angle of the steel guide beam in advance, promoting the efficient progress of the bridge jacking construction, and achieving the purpose of alleviating the impact of the uneven settlement of the bridge load-bearing column on the construction progress during the jacking construction of the continuous truss stiffened steel box girder, and realizing and digitizing the settlement of the bridge load-bearing column in advance.

[0017] Optionally, the slide rail includes a track fixed on the side wall of the bridge load-bearing column in the vertical direction and a limit block fixed on one end of the track close to the ground.

[0018] By adopting the above-mentioned technical scheme, the track structure in the slide rail plays a role of auxiliary support and position reference in the position adjustment process of the sedimentation module and the measuring module, facilitates the centering process of the sedimentation module and the measuring module, simplifies the installation process of the present application, and the limit block fixedly installed at the bottom end of the slide rail plays a role of position limitation for the sedimentation module and the measuring module, which can avoid the sedimentation module and the measuring module slipping off the slide rail.

[0019] Optionally, a limiting groove is provided on the upper surface of the limiting block along the direction of the bridge jacking construction.

[0020] By adopting the above-mentioned technical solution, the grooves opened on the upper surface of the limit block along the jacking construction direction can provide more stable support for the settlement module and the measurement module, reduce the irregular shaking and movement of the settlement module and the measurement module during the measurement process, reduce the measurement error of the present application, and further improve the accuracy of the present application.

[0021] Optionally, the settlement module includes a first positioning slider slidably connected to the slide rail, a settlement arm fixedly connected to the first positioning slider at one end, and a wedge block arranged on the settlement arm away from one end of the first positioning slider; the first positioning slider is provided with a plurality of bolt holes along a direction perpendicular to the side wall of the bridge load-bearing column.

[0022] By adopting the above technical solution, the sliding connection structure between the first positioning slider and the slide rail in the settlement module enables construction personnel to adjust the vertical height of the settlement module according to the on-site conditions, so that it can be aligned and leveled with the measuring module. The settlement arm serves to connect the first positioning slider and the wedge block. The sliding connection structure between the wedge block and the measuring module can generate a height difference between the measuring module and the measuring module after vertical settlement occurs, thereby converting the settlement degree caused by the bridge support column into an easily measurable height difference.

[0023] Optionally, the measuring module includes a second positioning slider slidably connected to the slide rail, a measuring arm fixedly connected to the second positioning slider at one end, and a comparison block arranged on the measuring arm away from one end of the second positioning slider; a dovetail groove is provided on a side plane of the comparison block close to the wedge block in a direction perpendicular to the horizontal plane; the wedge block is slidably connected to the comparison block.

[0024] By adopting the above technical solution, the sliding connection structure between the second positioning slider and the slide rail in the measuring module enables construction personnel to adjust the vertical height of the measuring module according to the on-site conditions, so that it can be aligned and leveled with the settlement module. The measuring arm serves to connect the second positioning slider and the comparison block. The dovetail groove on the comparison block can form a snap-on and sliding connection structure with the wedge block, thereby converting the settlement caused by the bridge support column into an easily measurable height difference.

[0025] Optionally, a support ring is sleeved on the settlement arm; a reinforcing rod is rotatably connected to the upper surface of the support ring; and the reinforcing rod is fixedly connected to the side wall of the bridge load-bearing column.

[0026] By adopting the above technical solution, the support ring and the reinforcing rod structure can provide auxiliary support and connection to the settlement arm, which can increase the posture stability of the settlement arm during the settlement process, further reduce the measurement error of the present application, and improve the use accuracy of the present application.

[0027] Optionally, an extension plate is provided on the upper surface of the comparison block, and a detection rod is sleeved on the extension plate; the extension plate is parallel to the upper surface of the comparison block, and one end of the detection rod abuts against the upper surface of the comparison block.

[0028] By adopting the above technical solution, the extension plate arranged on the upper surface of the comparison block cooperates with the detection rod structure sleeved on the extension plate to facilitate the staff to detect whether the sedimentation module and the measurement module are leveled by sliding the detection rod, thereby simplifying the use process of the present application.

[0029] Optionally, one end of the detection rod close to the comparison block is tapered, and the cross-sectional area of ​​the detection rod gradually decreases along the direction close to the comparison block.

[0030] By adopting the above technical solution, the conical structural design of the contact end of the detection rod and the comparison block can reduce the contact area between the detection rod and the plane to be detected, reduce the influence of other factors on the measurement accuracy of the detection rod, and reduce the resistance encountered by the detection rod during movement.

[0031] Optionally, a clamping block is provided at one end of the extension plate away from the comparison block; the clamping block is detachably connected to the extension plate.

[0032] By adopting the above technical solution, the clamping block fixedly arranged at one end of the extension plate away from the comparison block plays a role in position limiting the movement of the detection rod, which can prevent the detection rod from falling off the extension plate during use.

[0033] Optionally, the wedge block is provided with scale lines along a direction perpendicular to the horizontal plane.

[0034] By adopting the above technical solution, the scale lines arranged on the wedge block along the vertical horizontal plane direction can make it convenient for construction workers to calculate the specific settlement value of the bridge load-bearing column by reading the scale.

[0035] In summary, the present application includes at least one of the following beneficial technical effects:

[0036] 1. The slide rails in the present application play a supporting and limiting role for the settlement module and the measuring module. The settlement module can be displaced in the direction vertical to the ground together with the settlement process of the bridge support column, thereby generating a height difference with the upper surface of the measuring module leveled in the static initial state. The present application converts the difficult-to-observe overall settlement distance of the bridge load-bearing column into an easy-to-observe and measurable height difference between the settlement module and the measuring module. By repeating the measurement steps, a linear change relationship diagram between the settlement distance of the bridge load-bearing column and the bridge jacking distance can be obtained, thereby providing reference data for predicting the settlement value that will be generated by the bridge load-bearing column that has not yet borne the load, facilitating on-site construction personnel to adjust the bridge jacking distance, jacking height and holding angle of the steel guide beam in advance, promoting the efficient implementation of the bridge jacking construction, achieving the purpose of alleviating the impact of the uneven settlement of the bridge load-bearing column on the construction progress during the jacking construction of the continuous truss stiffened steel box girder, and realizing and digitizing the settlement of the bridge load-bearing column in advance.

[0037] 2. The sliding connection structure between the first positioning slider and the slide rail in the settlement module of the present application enables construction personnel to adjust the vertical height of the settlement module according to the on-site conditions, so that it can be aligned and leveled with the measuring module. The settlement arm plays the role of connecting the first positioning slider and the wedge block. The sliding connection structure between the wedge block and the measuring module can generate a height difference between the measuring module and the vertical settlement, thereby converting the settlement degree generated by the bridge support column into an easily measurable height difference.

[0038] 3. The sliding connection structure between the second positioning slider and the slide rail in the measuring module in the present application enables construction personnel to adjust the vertical height of the measuring module according to the on-site conditions, so that it can be aligned and leveled with the settlement module. The measuring arm serves to connect the second positioning slider and the comparison block. The dovetail groove on the comparison block can form a snap-on and sliding connection structure with the wedge block, thereby converting the settlement caused by the bridge support column into an easily measurable height difference. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It is a structural schematic diagram of a surface settlement monitoring method suitable for a bridge jacking process disclosed in an embodiment of the present application.

[0040] Figure 2 It is a structural schematic diagram of the sedimentation module in the embodiment of the present application.

[0041] Figure 3 It is a schematic diagram of the structure of the measurement module in the embodiment of the present application.

[0042] Explanation of the accompanying drawings: 1. slide rail; 11. track; 12. limit block; 2. sedimentation module; 21. first positioning slider; 22. sedimentation arm; 23. wedge block; 24. support ring; 25. reinforcement rod; 3. measurement module; 31. second positioning slider; 32. measuring arm; 33. comparison block; 34. extension plate; 35. detection rod; 341. card block. DETAILED DESCRIPTION

[0043] The following is combined with Figure 1 -Attached Figure 3 This application is described in further detail.

[0044] The bridge jacking construction process is a new type of construction process that uses hydraulic equipment to jack cast-in-place beams or pre-installed beams onto temporary supports in the horizontal direction. Due to the various advantages of the temporary equipment used in the process, such as the ability to reuse them and the good overall continuity of the project, the application of jacking construction has been widely promoted. However, in the jacking construction of continuous truss-type stiffened steel box girders with large deadweight and wide span, the uneven settlement of the bridge load-bearing columns will have an adverse effect on the smooth progress of the construction. In order to alleviate the impact of the uneven settlement of the bridge load-bearing columns during the jacking construction of continuous truss-type stiffened steel box girders on the construction progress, the settlement of the bridge load-bearing columns is visualized and digitized in advance. This application provides a surface settlement monitoring method suitable for bridge jacking technology.

[0045] The present application embodiment discloses a surface settlement monitoring method applicable to a bridge jacking process, comprising the following steps:

[0046] S1, clean and tidy up the side walls of the bridge's load-bearing columns.

[0047] In this step, the side walls of the bridge load-bearing columns need to be polished until the verticality of the sides of the bridge load-bearing columns meets the measurement requirements to minimize the measurement errors caused by the installation process.

[0048] S2, set reference lines on the side walls of the bridge bearing columns at the same height in the horizontal direction.

[0049] In this step, the setting of the reference line can provide a position reference for the installation of the slide rail 1 , and significantly reduce the height installation error of the slide rail 1 .

[0050] S3, a slide rail 1 is installed on the side wall of the bridge load-bearing column in a direction perpendicular to the horizontal plane, and the end of the slide rail 1 close to the ground is at the same height as the reference line.

[0051] In this step, after the installation process of the slide rail 1 is completed, a laser rangefinder, a total station or other equipment should be used to assist in correcting the installation position of the slide rail 1 to reduce the error caused by the installation process.

[0052] S4, temporarily fixing the sedimentation module 2 on the slide rail 1, temporarily fixing the measurement module 3 on another slide rail 1, and the slide rail 1 on which the sedimentation module 2 is installed is adjacent to the slide rail 1 on which the measurement module 3 is installed.

[0053] In this step, during the temporary fixing process, the settlement module 2 and the measuring module 3 need to be placed at the same level to reduce the displacement of the settlement module 2 and the measuring module 3 during the centering and leveling process.

[0054] S5, adjusting the relative position of the sedimentation module 2 and the measurement module 3 so that the sedimentation module 2 and the measurement module 3 are located at the same height, and then fixing the positions of the sedimentation module 2 and the measurement module 3.

[0055] In this step, after the sedimentation module 2 and the measuring module 3 are fixed, it is necessary to recheck whether the upper surfaces of the sedimentation module 2 and the measuring module 3 are in the same horizontal plane, so as to eliminate the measurement error caused by the installation process.

[0056] S6, start the bridge jacking construction, and stop the construction when the centroid of the bridge deck box girder reaches the bridge load-bearing column where the settlement module 2 is installed.

[0057] In this step, attention should be paid to the impact of the vibration generated during the jacking construction process on the relative position of the settlement module 2 and the measurement module 3. If a position offset occurs, it should be recorded, and offset should be performed during the final data measurement and recording to reduce errors.

[0058] S7, let it stand for twenty-four hours, and record the difference between the sedimentation module 2 and the measurement module 3 in the vertical direction.

[0059] In this step, after recording and calculating the difference, the equipment should be left standing for 1 hour, and then the settlement before and after standing should be compared. The previous data can be recorded only when the error is less than or equal to 1 mm. If the error is greater than 1 mm, the subsequent measurement data should be used as the standard, and the equipment should be left standing until the error size meets the standard for continuing construction.

[0060] S8, sequentially move and install the settlement module 2 and the measurement module 3 according to the forward direction of the bridge jacking construction and repeat steps S5-S7 until the bridge jacking construction is completed.

[0061] In this step, after obtaining the data, the horizontal axis is the horizontal distance from the bridge construction end point to the measurement point, and the vertical axis is the settlement, and a linear relationship curve between the bridge jacking distance (or the bridge load-bearing columns at different positions from near to far) and the settlement is obtained. The linear relationship curve is used as reference data to obtain the expected settlement value of the bridge load-bearing column that has not yet been loaded, so as to pre-adjust the angle of the steel guide beam installed on the continuous truss stiffened steel box girder during the jacking construction, so as to improve construction efficiency, shorten the construction period, and facilitate on-time delivery.

[0062] Reference Figure 1 The embodiment of the present application discloses a surface settlement monitoring method suitable for bridge jacking process, which includes a slide rail 1, a settlement module 2 and a measurement module 3. The slide rail 1 is installed on the side wall of the bridge load-bearing column in a direction perpendicular to the horizontal plane. The settlement module 2 and the measurement module 3 are slidably connected to the slide rail 1.

[0063] Reference Figure 1 The slide rail 1 includes a track 11 and a limit block 12. The track 11 is detachably fixedly connected to the side wall of the bridge load-bearing column by bolt connection along the direction of the vertical horizontal plane. The limit block 12 is fixedly connected to the end of the track 11 close to the ground by welding. A limit groove is provided on the upper surface of the limit block 12, and the length direction of the limit groove is the same as the forward direction of the bridge jacking construction. Two slide rails 1 are symmetrically installed on the side wall of each bridge load-bearing column. The installation heights of all slide rails 1 are on the same horizontal plane. The lower end surface of the slide rail 1 is flush with the upper edge of the reference line drawn during the installation process.

[0064] Reference Figure 1 and Figure 2 The settlement module 2 includes a first positioning slider 21, a settlement arm 22, a wedge block 23, a support ring 24 and a reinforcing rod 25. Among them, the first positioning slider 21 is installed on the slide rail 1 by a sliding connection, and the first positioning slider 21 can slide in a direction perpendicular to the ground. The settlement arm 22 is arranged in the horizontal direction, one end of the settlement arm 22 is fixedly connected to the first positioning slider 21, and the other end of the settlement arm 22 is fixedly connected to the wedge block 23. The wedge block 23 can be a solid metal block with a wedge-shaped portion, and the side of the wedge block 23 is provided with scale lines in a direction perpendicular to the horizontal plane by engraving. The support ring 24 can be a solid metal ring sleeved on the settlement arm 22. The reinforcing rod 25 is installed on the support ring 24 in a hinged manner, and the other end of the reinforcing rod 25 is installed on the side wall of the bridge load-bearing column by bolt connection.

[0065] Reference Figure 1 and Figure 3The measuring module 3 includes a second positioning slider 31, a measuring arm 32, a comparison block 33, an extension plate 34 and a detection rod 35. The second positioning slider 31 is installed on the slide rail 1 by a sliding connection, and the second positioning slider 31 can slide in a direction perpendicular to the ground. The measuring arm 32 is arranged in the horizontal direction, one end of the sinking arm 22 is fixedly connected to the second positioning slider 31, and the other end of the measuring arm 32 is fixedly connected to the comparison block 33. The comparison block 33 can be a solid metal square with a dovetail groove, and the dovetail groove provided in the comparison block 33 is consistent with the wedge-shaped part of the wedge block 23. The upper surface of the comparison block 33 is provided with an extension plate 34 by welding, and the extension plate 34 is arranged in the horizontal direction. The length of the extension plate 34 is greater than the length of the comparison block 33. The detection rod 35 is sleeved on the extension plate 34 and is slidably connected to the extension plate 34. The end of the detection rod 35 close to the ground abuts against the upper surface of the comparison block 33. The end of the detection rod 35 close to the comparison block 33 is tapered, and the cross-sectional area of ​​the detection rod 35 gradually decreases in the direction close to the comparison block 33. The end of the extension plate 34 away from the comparison block 33 is detachably fixed with a clamping block 341 by means of a threaded connection. The clamping block 341 can be a solid metal block with a threaded hole and a cross-sectional area larger than that of the extension plate 34.

[0066] The above are all preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. Therefore, any equivalent changes made according to the structure, shape, and principle of the present application should be included in the protection scope of the present application.

Claims

1. A surface settlement monitoring method suitable for bridge jacking process, characterized in that: The following steps are involved: S1, cleaning and cleaning the side walls of the bridge load-bearing columns; S2, set reference lines on the side walls of the bridge bearing columns at the same height in the horizontal direction; S3, installing a slide rail (1) on the side wall of the bridge load-bearing column in a direction perpendicular to the horizontal plane, wherein an end of the slide rail (1) close to the ground is at the same height as the reference line; S4, temporarily fixing the sedimentation module (2) on the slide rail (1), and temporarily fixing the measurement module (3) on another slide rail (1), wherein the slide rail (1) on which the sedimentation module (2) is installed is adjacent to the slide rail (1) on which the measurement module (3) is installed; S5, adjusting the relative position of the sedimentation module (2) and the measuring module (3) so that the sedimentation module (2) and the measuring module (3) are located at the same height, and then fixing the positions of the sedimentation module (2) and the measuring module (3); S6, starting the bridge jacking construction, and stopping the construction when the centroid of the bridge deck box girder reaches the bridge load-bearing column installed with the settlement module (2); S7, leaving it to stand for 24 hours, and recording the difference between the sedimentation module (2) and the measurement module (3) in the vertical direction; S8, sequentially moving and installing the settlement module (2) and the measurement module (3) in the forward direction of the bridge pushing construction and repeating steps S5-S7 until the bridge pushing construction is completed.

2. The surface settlement monitoring method applicable to bridge jacking process according to claim 1 is characterized by: The slide rail (1) comprises a track (11) fixedly arranged on the side wall of a bridge load-bearing column in a vertical direction, and a limit block (12) fixedly arranged on one end of the track (11) close to the ground.

3. The surface settlement monitoring method applicable to bridge jacking process according to claim 2 is characterized in that: The upper surface of the limit block (12) is provided with a limit groove along the direction of bridge jacking construction.

4. The surface settlement monitoring method applicable to bridge jacking process according to claim 1 is characterized in that: The settlement module (2) comprises a first positioning slider (21) slidably connected to the slide rail (1), a settlement arm (22) one end of which is fixedly connected to the first positioning slider (21), and a wedge block (23) provided on the settlement arm (22) at one end away from the first positioning slider (21); the first positioning slider (21) is provided with a plurality of bolt holes in a direction perpendicular to the side wall of the bridge load-bearing column.

5. The surface settlement monitoring method applicable to bridge jacking process according to claim 4 is characterized in that: The measuring module (3) comprises a second positioning slider (31) slidably connected to the slide rail (1), a measuring arm (32) one end of which is fixedly connected to the second positioning slider (31), and a comparison block (33) provided on the measuring arm (32) at one end away from the second positioning slider (31); a dovetail groove is provided on a side plane of the comparison block (33) close to the wedge block (23) in a direction perpendicular to a horizontal plane; and the wedge block (23) is slidably connected to the comparison block (33).

6. The surface settlement monitoring method applicable to bridge jacking process according to claim 4 is characterized by: A support ring (24) is sleeved on the settlement arm (22); a reinforcing rod (25) is rotatably connected to the upper surface of the support ring (24); and the reinforcing rod (25) is fixedly connected to the side wall of the bridge load-bearing column.

7. The surface settlement monitoring method applicable to bridge jacking process according to claim 5 is characterized by: An extension plate (34) is provided on the upper surface of the comparison block (33), and a detection rod (35) is sleeved on the extension plate (34); the extension plate (34) is parallel to the upper surface of the comparison block (33), and one end of the detection rod (35) abuts against the upper surface of the comparison block (33).

8. The surface settlement monitoring method applicable to bridge jacking process according to claim 7 is characterized by: One end of the detection rod (35) close to the comparison block (33) is tapered, and the cross-sectional area of ​​the detection rod (35) gradually decreases in a direction close to the comparison block (33).

9. The surface settlement monitoring method applicable to bridge jacking process according to claim 7 is characterized by: A clamping block (341) is provided at one end of the extension plate (34) away from the comparison block (33); the clamping block (341) is detachably connected to the extension plate (34).

10. The surface settlement monitoring method applicable to bridge jacking process according to claim 4 is characterized in that: The wedge-shaped block (23) is provided with scale lines along a direction perpendicular to the horizontal plane.

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