Monitoring of Transport Tunnel Deformation at the Construction Stage

The analysis of normative documents related to geodetic support of transport tunnel construction showed that for now there are no integral monitoring methods providing surface tunnel structure observation. Therefore, the authors substantiate a new technological scheme of geodetic monitoring of portal parts of a tunnel under construction. To collect data about displacements of tunnel portal structures it is suggested that control points should be fixed by reflective tape or rotating prisms, and their coordinates should be located in an object's coordinate system. It is suggested that an original geodetic base should be fixed as geodetic points of forced centering out of zone of virtual deformations. Deformation control benchmarks heights should be measured by trigonometric leveling. It is shown that RMS error in measuring the heights of points of geodetic monitoring network should not exceed 4 mm. It is found that required accuracy in network building can be provided by III class leveling. To collect data about the depth of weak soils, located close to tunnel portals, as well as the borderlines of their sliding, it is for the first time suggested that surveys should be conducted using borehole inclinometer. The research proves that on pre-portal sites boreholes should be placed close to the group of deformation control benchmarks.