Analysis Of Disease Classification And Stability Of Ganzhou Ancient City Wall

Ganzhou ancient city wall is one of the larger and more complete brick walls of Song Dynasty in China.However,with the passage of time,the ancient city wall has been constantly damaged and eroded by various human and nature,resulting in many diseases threatening the safety of the ancient city wall.In order to understand the current disease details and overall stability of Ganzhou ancient city wall,based on the detailed disease investigation and research analysis of Ganzhou ancient city wall,according to the in-situ rebound detection results,fuzzy mathematics and analytic hierarchy process are used to evaluate the disease status of Ganzhou ancient city wall.Finally,the finite element software ANSYS is used for simulation,The stability of ancient city wall under different working conditions is analyzed.The main conclusions are as follows(1)Through the field investigation of Ganzhou ancient city wall,it is found that the main diseases are cracks,plants(tree roots,root plants and mosses),wall deformation(bulge,depression),efflorescence,brick weathering(denudation,dissolution and decolorization)and mortar loss.There are differences in the distribution of the disease,the west section of the wall disease is the most serious,the east section of the wall disease is the lightest,the inner wall disease is more serious than the outer wall disease.Among the three gun cities,xijinmen gun city has the most serious disease,with many cracks and weathered bricks and stones.Among the four gates,Jianchun gate has the most diseases,not only has many cracks,but also has a large distribution area of alkali and moss.According to the investigation and analysis of the disease,the main causes of the disease are water damage,plant growth,wind erosion and harmful media in the air,such as sulfate and sodium ion.(2)Through the in-situ rebound test,it is found that the compressive strength of the brick and mortar in the city wall section which has been repaired recently is relatively high,but the brick and mortar in the city wall section which has not been repaired are seriously deteriorated,and the overall strength is relatively low.In the serious deterioration area of the ancient city wall,the compressive strength of the brick and mortar is very low.(3)Based on the first-hand data obtained from the field investigation of the ancient city wall,the paper evaluates the disease status of the ancient city wall by using the method of fuzzy mathematics and analytic hierarchy process.The results show that the disease level of the western and Northern sections of the city wall is grade C,which belongs to moderate damage.It should be detected in medium density and considered to be repaired.The disease grade of the eastern section of the city wall is a,which belongs to weak damage and does not need to be repaired.(4)The two-dimensional plane stress-strain model of the ancient city wall is established by using the finite element software ANSYS to analyze the stability of the ancient city wall under four different conditions(rainwater infiltration,masonry deterioration,cracks and tree roots)under peak crowd load.The results show that the crowd load has little effect on the stability of the ancient city wall;When the moisture content of rammed earth is 16% and 32%(saturated state),the stability of the city wall will be unstable.After calculation,when the moisture content of rammed earth is greater than 12.5%,the stability safety factor of the city wall will be less than 1.3;The deterioration condition of masonry has little influence on the stability of the ancient city wall,and the rammed earth and its state play a leading role in the stability of the ancient city wall;The typical cracks in the west section have little influence on the overall stability of the ancient city wall,and the wall is in a safe range;When the big tree roots are distributed at the bottom of the inner wall,the wall is still in the elastic state,which is relatively safe.When the big tree roots are distributed at the middle of the inner wall,the plastic zone will appear at the bottom of the rammed earth of the inner wall,which is a potential safety hazard.