Study On Stability Of Qanat Culvert Considering Soil Spatial Variability

Qanat is an artificially excavated irrigation system in desert areas.It is distributed in North Africa,the Middle East,and Central Asia,such as Iran,Afghanistan and Xinjiang region,China.The background of the project in this article is the Tehran-Qom-Isfahan high-speed railway built by China for Iran in the “Belt and Road” project.There are a large number of Qanat structures along the high-speed railway.Under the action of high-speed railway subgrade and train operation load,the unreinforced Qanat culvert(artificial soil cave)may collapse,cause damage to the connected foundation,and affect the stability of the upper highspeed railway subgrade and train operation safety.At present,there is a lack of relevant research on the stability of Qanat under load,especially considering the spatial variability of soil,so it is urgent to carry out relevant research work.Therefore,considering the spatial variability of the foundation soil where the Qanat is located,this paper analyzed the overlying load influence on the stability of the Qanat under different parameters.The main research contents and results are as follows:(1)According to the basic physical and mechanical parameters and in-situ test data of the foundation soil along the Tehran-Qom-Isfahan high-speed railway,the regression fitting method was used to analyze the correlation between the laboratory test results of the soil and the correlation between the in-situ test and the laboratory test results,and compared with the previous empirical formula,the fitting formula of the above correlation was obtained.(2)Based on a large number of laboratory test data,the statistical characteristics of physical and mechanical parameters(dry density,void ratio,liquid limit,plastic limit,cohesion,internal friction angle,compression modulus and compression coefficient)of CL and SC soils,which are the two main types of foundation soils along the Tehran-Qom-Isfahan high-speed railway,were analyzed from the aspects of variability statistical analysis and probability density distribution.(3)Based on the assumption that the foundation soil of Qanat is a uniform soil layer with the same parameters,finite element limit analysis method and model test method were used to explore the influence of Qanat culvert depth on the stability of Qanat in homogeneous space.(4)Based on the results of homogeneous space analysis,using random adaptive finite element limit analysis,starting from the depth of the culvert,the variability of strength parameters,and the spatial correlation length of the strength parameters,the stability of Qanat culvert(Soil Cave)considering the spatial variability of the soil was studied.