Technologies for improving the accuracy of coordinate transfer through a vertical borehole in tunnel construction

To justify the junction of oncoming tunnels satisfying the accuracy requirements, it is required to create an initial geodetic base in the tunnel. For this purpose, it is necessary to transfer coordinates, heights and azimuths of the reference geodetic network on the Earth's surface to the tunnel via vertical or inclined boreholes. In case the vertical boreholes are used, this is termed as orientation via vertical boreholes. When observing the verticality of the project in construction of large-size buildings, the traditional solutions have proved to be inefficient and in many cases inappropriate for the construction requirements. The article deals with the transfer of topocentric coordinates through a vertical borehole during tunnel construction and monitoring of vertical structures using the GNSS technology and topocentric coordinates. An example of implementation is shown at a particular site in Vietnam. The technical solution tested in the first metro line of Vietnam can be applied to similar types of operations. The following conclusions are made: 1 - the use of a laser device to replace the plumbing lines when transferring coordinates to the tunnel through vertical boreholes meets the technical requirements for tunnel construction; 2 - the topocentric coordinate system has very convenient characteristics for controlling the verticality of buildings using the GNSS technology data; 3 - the GNSS technology overcomes disadvantages of the conventional methods in determining the verticality of a building during construction, especially for multi-storey buildings.