Study On Deterioration Of The Rock Block And The Entire Stability Of Feifengguan(Hailongtun Site)

Hailongtun Site is a Tusi City Site in the Chinese Tusi Heritage of the World Cultural Heritage.It is one of the well-preserved ancient military castles in China and even Asia.As time goes on,there are different types and degrees of disease characteristics in the Guan body and the wall of the site.The deterioration effect of rock masonry is remarkable,and the structural stability problem is also increasing.It threatens theretention time of stonemasonry siteseriously.Therefore,investigating the disease characteristics of the city wall sites,and exploring the deterioration of rocks and structural stability,they are in the hope of seeking targeted protection and reinforcement measures.It can provide some reference value for the protection of similar stone ancient buildings in China.This paper takes Feifengguan of Hailongtun ruin as the research object.By field testing,the deterioration index and surface strength parameters of rock blocks are obtained.Combined with indoor accelerated deterioration simulation experiment and rock mechanics experiment,the key mechanical parameters of deteriorated fossils are determined,and the evolution law of deterioration degree with time is revealed.It provides data support for the stability study of ancient stone masonry buildings.On this basis,the stability analysis system of ancient stone masonry buildings considering structural defects is further established.Combined with the field geophysical experiment and deformation monitoring data,the interaction between material deterioration and structural deformation is analyzed,and the instability mechanism is discussed.It is in hope of putting forward a method for systematically evaluating the stability of ancient masonry structures with defects,and providing a scientific basis for the reinforcement and protection of ancient stone masonry buildings.By investigating and analyzing the diseases of Feifengguan Guan body,utilizing the in-situ testing and indoor simulation experiments to study the deterioration characteristics of rock blocks.Using seismic CT and crack deformation monitoring to analyze the structural stability of the Guan body.The main research results are as follows:(1)At present,the main existing diseases of Feifengguan are swelling,collapse,arch instability,crack development,block aging,rain leakage and biological diseases seven diseases.Among them,the structural instability of Feifengguan Guan body is the most harmful,and it threatens the survival time of Feifengguan Guan body,directly.(2)By means of surface hardness test,acoustic wave test,surface rebound hammer test and Karsten flask method,a large number of on-site Guan body rock blocks are tested.Among the three rock blocks of Feifengguan,the surface water absorption rate of sandstone blocks inserted in the wall is higher,the surface hardness,rebound value and P-wave velocity value are lower,and the deterioration degree is the most serious.(3)By comparing the field test of different lithologic rock blocks with indoor simulated deterioration test results,it is found that the quality loss of sandstone blocks is serious under different influencing factors,but the strength loss is small.the surface deterioration rate of limestone and marl blocks in acid environment is faster,it is because that the internal mineral components are easily corroded by reaction in acid environment.(4)Through field geophysical test and real-time deformation monitoring,the whole stability of Feifengguan before reinforcement is analyzed.The internal velocity of Feifengguan is low,and there must be a certain gap.The crack monitoring data show that the crack width changes very little after temporary support of the Guan body,so reinforcement measures should be taken as soon as possible to control the diseases existing in the Feifengguan.