Study of Tower Structure of the Octagonal Tower Based on GPR

Manghong Octagonal Tower (MOT) was built in the Qing dynasty Kangxi period (BC 1662~ BC 1722). The tower's architectural style and tower pattern blend Confucianism, Taoism and Buddhism culture. It has been the spiritual ballast of the local residents since its completion and plays an important role in sacrificial activities. The tower also has important archaeological value for studying the architectural characteristics and economic culture of Qing Dynasty in China. We can't obtain internal structure information of MOT, which is formed by the verrucano stone. However, because of some reasons such as age, geological subsidence and erosion, the tower tilts. Tower structure has been reformed in maintenance work. It's difficult to obtain the changes of tower structure on the surface. The structure of the tower is an important factor affecting the force change and tilt of the tower, so it is an urgent problem for the protection of cultural relics and archaeological research to analyze the structural characteristics of the tower and the existence of hidden defects without damaging the body of the tower. In this paper, we use GPR to detect the structure of stony MOT in different heights. We set up a dense detection lines with a line distance of 0.20 m to detect the structure of stone in high resolution and analyze the distribution characteristics of the tower so as to provide guidance for the protection of historic building architectural relics. The results show that the body of MOT forms mainly composed of two layers of crossed stone and the south wall is thicker. There is no darkroom or empty in tower foundation. The tilt of the tower, which has a great harm, will further cause unequal force to cause cracks in the tower body, so the protection measures should be taken on the premise of avoiding the man-made destruction of the tower.