What about tunnel construction survey?

(1) It is generally stipulated that 1) The accuracy of control measurement should be measured by the medium error, and the maximum error (tolerance) is stipulated to be twice the medium error. 2) During tunnel construction, the following work should be done well: ① Regularly check the datum points and leveling points of the precision triangulation network or precision traverse network laid in the long tunnel; (2) The leveling points and centerline points outside the tunnel shall be determined according to the longitudinal plane of the tunnel and the length of the tunnel. Regular review, hole control points should be set according to the construction progress. 3) The pile points in tunnel construction survey must be stable, reliable and have good visibility. Benchmarks should be located in places that are not easy to be damaged and properly protected. Measuring instruments and tools should be calibrated before use, so as to ensure that the technical conditions of the instruments and tools meet the use requirements. When using photoelectric rangefinder, it should be carried out according to its use requirements. (4) The accuracy of tunnel plane control survey, the tolerance of two opposite construction center lines in the tunnel on the penetration surface, the influence of control survey errors inside and outside the tunnel on the penetration error of the penetration surface, the accuracy of traverse angle measurement and ranging in the tunnel, and the difference of leveling point height between the two tunnels shall all conform to the provisions of the current Standard for Highway Tunnel Survey (JTJ 063) of the Ministry of Communications. 5) After the completion of the tunnel, the technical achievements of breakthrough measurement, the measured results and explanations of breakthrough errors, the measured results and schematic diagrams of clearance section measurement and permanent center line points and leveling points shall be submitted. (2) Construction survey in the tunnel 1) The wires in the tunnel shall extend into the tunnel according to the entry point, and the entry point shall be included in the control network. The angle measurement error of the connection angle transmitted by the entry point should not exceed the requirements of the measurement grade, the length of the rear view direction should not be less than 300m m, the traverse points should be laid along the center line of the route as far as possible, and the length of the traverse side should not be less than 200 m in a straight line; The curve segment should not be shorter than 70m. For the single conductor that does not have the closing condition, two groups of independent observations should be made and checked with each other: ① For the tunnel measured in the tunnel by the midline method, the straight line part of the centerline point spacing should not be shorter than100m; The curve part should not be shorter than 50m. (2) When the extended center line point is detected by straight line extension method or curve deflection angle method, the lateral deviation of the point shall not be greater than 5mm ... 2) The tunnel constructed by extra-long tunnel, long tunnel and large roadheader shall be guided by laser equipment. 3) The temporary point of pilot tunnel extension and excavation can be calibrated by midline method, and its extension length should not be more than 30m in a straight line; The curve part should not be more than 20m, and the distance between two messenger wires in string method should not be less than 5m. When calibrating the center line of excavation face with chord method, the distance can be measured with tape measure. 4) Before the excavation, the dimension line of the design section shall be marked on the excavation section, and the section drawing shall be measured in time after the excavation is completed. For tunnels constructed by upper and lower pilot tunnels, after the middle line of the upper pilot tunnel extends for a certain distance, it should be jointly measured with the middle line of the lower pilot tunnel to check the middle line point of the upper pilot tunnel or the pilot point of the upper pilot tunnel. 5) The temporary center line point of lining must be determined by theodolite, and its spacing should be properly encrypted for visual lofting, but it should not be greater than 10m. 6) Before installing lining formwork, check the midline and elevation, mark the elevation of vault, side wall bottom and arching line, and control the installation of arch formwork and wall formwork by designing the offset of lining section. After the model is established, it must be checked and corrected to ensure its correctness. 7) Scattered routes in the hole should be laid from the elevation control points in the hole to the outside of the hole. Combined with the construction situation in the hole, it is advisable to set the height distance of the measuring point at 200 ~ 500 m. According to the leveling points set inside and outside the hole and the construction needs, increase the leveling points for the construction in the hole. For the convenience of construction, a temporary leveling point shall be set every 100m at the arch of the pilot tunnel and the side wall construction section, and it shall be checked regularly. (3) Measurement and adjustment of penetration error 1) The measurement of penetration error should be carried out according to the following requirements: (1) When precise traverse is used for measurement, a temporary point is set near the penetration surface, and the coordinates of the point are measured from two directions, and the obtained closure difference is projected onto the penetration surface and its vertical direction, so as to obtain actual horizontal and vertical penetration errors, and then placed at the temporary point. (2) When the midline method is used for measurement, two opposite directions should be extended to the penetration surface respectively, and a temporary point should be taken to measure the horizontal and vertical distance between two points, so that the actual penetration error of the tunnel can be obtained. (3) The leveling route enters the hole from both ends and reaches the same leveling point or the center line point near the penetration surface, and the measured elevation difference is the actual elevation penetration error. 2) The adjustment of the through error should be carried out according to the following steps: ① Adjust the center line of the straight hole with the broken line method. (2) Curve tunnel, according to the actual penetration error, adjust the center line from both ends of the curve to the penetration surface according to the length ratio. (3) When precise traverse method is used for measurement, the through error is adjusted by coordinate increment adjustment. (4) When adjusting the error of elevation breakthrough, the leveling point elevation near the breakthrough point should take the average elevation measured at the entrance and exit respectively as the adjusted elevation. ⑤ After the tunnel is completed, the actual completion error of the construction centerline and elevation should be adjusted in the unlined 100m section (i.e. the line adjustment section). The excavation and lining of this section should be set out with the adjusted centerline and elevation. (4) Completion Survey 1) After the completion of the tunnel, the actual tunnel clearance based on the route centerline shall be measured every 50m for the straight section and 20m for the curved section, and the vault height, the width of the protruding line and the horizontal width of the pavement shall be marked. 2) The permanent center line point of the tunnel shall be embedded with metal marks in the concrete after completion survey. Permanent midline points should be set every 200-250 m on the straight line, and the curve should be set at the beginning and end of the transition curve; The middle of the curve can be appropriately increased according to the visibility. After the establishment of the permanent center line point, a sign should be drawn on the side wall of the tunnel. 3) A leveling point should be buried every kilometer in the tunnel, and at least one tunnel shorter than lkm should be set up, and signs should be drawn on the side wall of the tunnel. (5)GPS survey Compared with the traditional survey, GPS survey has a remarkable advantage that GPS survey does not need mutual visibility between points and points, and is not limited by graphic intensity, thus making the point selection work very flexible, especially in tunnel survey in areas with dense trees and difficult visibility. 1) When laying the GPS tunnel control network, each hole has at least one GPS point on the tunnel axis (that is, the position of the hole), and the two ends of the hole are connected by the simplest graph, but free baseline vectors are not allowed, so that the GPS network forms a closed graph for verification. 2) Although 2)GPS points do not require mutual visibility, in order to provide the direction of entering the tunnel, each hole is required to have at least one direction of mutual visibility, and it is better to add a checking direction when the visibility conditions permit. 3) When designing the drawings, full consideration should be given to strengthening the inspection of asynchronous rings, so as to check the influence of field observation factors such as centering, leveling error and atmospheric change on the results, and avoid the existence of gross errors. 4) For long tunnels, due to the long distance between points, vehicles and traffic routes must be considered when making dispatching plans, so as to ensure that operators have enough time to reach each point and make preparations before observation. 5) Due to poor survey conditions, GPS observation is greatly limited. However, the height angle and azimuth angle of obstacles at each control point are different, which easily leads to different observation time of the same satellite at each station. Therefore, it is required to make a highly accurate plan before observation to ensure that the observation work is carried out as planned and the observation is successful. (6) Construction process control survey 1) Monitoring survey should achieve the following purposes: ① Grasp the dynamic information of surrounding rock and support and give timely feedback to guide the construction work; (2) Modify the design of the support system by measuring the displacement and stress of the Zhou Yan and the support. 2) The composite lining tunnel shall meet the requirements in Table 9 of Technical Specification for Highway Tunnel Construction (JTJ 042- 1994). 2。 1 Select the measurement item. 1 ~ 4 in the table is required; The selection and measurement of item 5 ~ 1 1 shall be determined according to the surrounding rock conditions and surface subsidence requirements. 3) After blasting excavation, engineering geology and hydrogeology shall be observed and recorded immediately, and geological description shall be made. Geological changes and important locations should be recorded with photos. After the initial support is completed, the surface of spray layer should be observed and recorded, and cracks should be checked; 4) After tunnel excavation, the surrounding rock, initial support and vault subsidence shall be measured in time; After the anchorage is installed, the pullout test of the anchorage should be carried out. When the surrounding rock is poor, the cross section is large or the surface subsidence is strictly controlled, displacement measurement and other measurements should be carried out in the surrounding rock. For tunnels located in Ⅲ ~ Ⅰ grade surrounding rocks and with the thickness of overburden less than 40m, the surface settlement should be measured.