Study On The Mechanical Properties Of The Key Parts In Xinzheng Portal Site

The earth site of Xinzheng Gate is located in Kaifeng city of Henan Province,the Nanzheng Gate village on the south side of Songcheng square.According to the present investigation and exploration,it is found that there are relics such as the ruins of the city gate of the Song Dynasty and the dwellings repaired in the Qing Dynasty.The Xinzheng gate is a city gate that used to eliminate hidden dangers of foreign invasion in the Northern Song Dynasty and lied in the south of the west wall in outer city.The ruins of the city gate are rectangular,the length from the north to the south is about one hundred and sixty meters,and the east-west direction is about 100 meters wide,which was made up of urn gates and city gates.The archaeological excavations have proved that 3 capitals,2 provincial capitals and 1 important town of central plains were covered here: the Kaifeng city of Qing Dynasty was built about 3 meters deep underground,the 5 meters to 6 meters belonged to the Ming Dynasty,the Bianjian city of Jin Dynasty was as deep as 6 meters,the Dongjing city of northern Song Dynasty was existed at bout 8 meters,and 10 meters down from the ground was the Bianzhou city of Tang Dynasty,the Daliang city which was the capital of Wei was at more than 10 meters deep.The scale is so huge and the layers are superimposed that have been judged to be unique in China's history of 5000 years by the archaeologists,it is the treasure of Chinese civilization.At present,the research on earthen sites' protection mainly focused on the deterioration mechanism and protection methods of the existing ground sites,the study on the soil mechanical properties of underground sites while excavating and after excavation is still blank.Moreover,the moisture content of the excavated soil sites varies greatly,which has great influence on the physical and mechanical properties of the ruins,and has many hidden dangers.If it is not protected,there will be a great possibly to have damages such as dry shrinkage,cracking,scattering,toppling and collapse on the surface of the earthen sites.Therefore,it is urgent to potect the earthen ruins of Xinzheng Gate.The main contents of this dissertation include:(1)In view of the mechanical properties of the key parts' soil of the Xinzheng Gate earthen site,this paper takes the internal mechanism of the destruction of the site as the starting point,clarified the engineering characteristics and geotechnical skills of the Xinzheng Gate earthen site in terms of climate,Stratigraphic lithology,hydrology and environment.(2)In order to meet the experimental requirements,the existing experimental instruments were modified,and the basic physical properties of the site,the uniaxial tensile strength,and the tensile strength of the soil under the confining pressure of 50,100,150 and 200 kPa were measured.After processing and analyzing the test results and data,the relationship among cohesive force,moisture content and water content were respectively fitted with MATLAB,it was also led into the Mohr-Koulomb model of soil,which laid the foundation for the study of this kind of soil.(3)By using the large numerical simulation and the finite element analysis software ABAQUS,the key pillars and the dangerous slope models in Xinzheng Gate are established separately,then the safety factors of the dangerous slope under different conditions are calculated,and compared with the slope stability safety factor calculated by Janbu method which belongs to the traditional limit equilibrium method,the stabilization of the slope under different conditions was determined.(4)The phenomenon of dry shrinkage cracking of the soil on the surface of the column was simulated by the temperature tension in ABAQUS,and the stress magnitude obtained from the simulation results was compared with the uniaxial tensile strength of soil which was measured by experiment,It reveals the inherent mechanics of dry shrinkage cracking of columns.The research results can help us to determine the trend of mechanical evolution of site soil and the foundation was laid for the excavation and protection of the earthen sites.