Abstract: It is significant to study the stability of ancient city wall for its conservation and restoration under the environmental and human destruction conditions. In this study, the current preservation situation of Yulin City Wall (YCW) were investigated, and the mechanical properties of masonry structures and rammed soil in city wall were tested by in-situ tests and laboratory experiments. The overall stability and stress-strain state of the city wall were analysed with numerical method when the brick-clay structures turned degraded, and the embedded buildings were demolished. The research results show that: 1) The safety factor is smaller than the design value of 1.3 when the average water content of the rammed soil is larger than 11.5% during the rainfall infiltration stage or the denudation length of rammed soil at the top of the city wall larger than 2.5 m. However, the degradation of masonry structures has little effect on the stability of the city wall, which indicates that the strength of the rammed soil plays a determining role on the overall stability of the city wall. 2) The plastic zone almost extends to the top of the city wall, when 2 or 3-storey high buildings embedded 3.0 m depth or 1-story high buildings embedded 2.5 m depth in the bottom of the city wall are demolished. 3) The plastic zone may extend to the top of the city wall and will collapse, when the penetrative door with the width larger than 4.0 and 1-storey high building with the width larger than 2.5 m are demolished, respectively. It has no influence on the stability of the city wall, when the penetrative buildings with the section size smaller than 2.0 m×2.0 m are demolished.

Key words: Yulin City Wall (YCW), stability, mechanical property of brick-clay structure, numerical analysis