THE ROLE OF ASTRO-GEODETIC IN PRECISE GUIDANCE OF LONG TUNNELS |
Paper ID : 1139-SMPR-FULL |
Authors: |
میراحمد میرقاسم پور *1, علی یاسر جعفری2 1لویزان خیابان شعبانلو دانشگاه تربیت دبیر شهید رجایی دانشکده عمران 2کهریزک، خیابان مصطفوی، پلاک 38، واحد یک |
Abstract: |
ABSTRACT: One of main aspects of surveying projects is guidance of paths of a long tunnel from different directions and finally ending all paths in a specific place. This kind of underground surveying, beacause of particular condition, has some different points in relation to the ground surveying, including Improper geometry in underground transverse, low precise measurement in direction and length, distinct gravity between underground point and corresponding point on the ground (both value and direction of gravity) and etc. To solve this problems, astro-geodetic that is part of astronomy science in geodesy, can help surveying engineers. In this article, the role of astronomy is defined in two subjects: 1- Azimuth determination of directions from entrance and exit nets of tunnel and also calibration of gyrotheodolite to use them in Underground transvers: By astronomical methods, azimuth of directions can be determine with an accuracy of 0.5 arcsecond, whereas, nowadays, no gyroscope can measure the azimuth in this accuracy; For instance, accuracy of the most precise gyroscope (Gyromat 5000) is 1.2 cm over a distance of one kilometre (2.4 arcsecond). Furthermore, the calibration methods that will be mention in this article, have significance effects on underground transverse. 2- Height relation between entrance point and exit point is problematic and needs long time; For example, in a 3 km long tunnel ( in Arak- Khoram Abad freeway), to ralate enterance point to exit point, it is necessary to do leveling about 90 km. Other example of this boring and longtime leveling is in Kerman tunnel. This tunnel is 36 km length, but to ralete the entrance point height to exit point, 150 km leveling is needed. This paper also discuss application of astro-geodetic and determination of vertical deflection by digital zenith camera system TZK2-D. These two elements make possible to define geoid profile in terms of tunnel azimuth in entrance and exit of tunnel; So by doing this, surveying engineers are able to transfer entrance point height to exit point of tunnels in easiest way. |
Keywords: |
Astro-geodetic, TZK2-D, Underground surveying, vertical deflection |
Status : Paper Accepted (Poster Presentation) |