Research On Mechanical Properties Of Subway Tunnel Structure And Surrounding Rock Due To The Water Level Fluctuation Of Adjacent Water Body

With the rapid development of urban rail transit, subway tunnel inevitably pass throughsome complicated soil layer and landform. The complex engineering geological conditionsand environment can bring some disadvantage to the surveying, designing, construction andoperation of subway tunnel, some may endanger its security and stability. With the practicalexample of Caojiawan Station in Chongqing Metro Line6and as to the deformation anddisplacement caused by the effect of loading and unloading from the water level fluctuationsof adjacent reservoir, the paper analyzes the mechanics properties of tunnel structure andsurrounding rock by way of theoretical analysis, site tests and numerical analysis. Then somescientific conclusions and suggestions have been made. The main research results are asfollows:(i) Theoretical analysis has been carried out on the mechanics properties of tunnelstructure and surrounding rock, then the paper analyzes the mechanism of interaction betweentunnel and adjacent reservoir. The water level fluctuation has been equivalent to the effect ofloading and unloading, then summarize its effect factors.(ii) The buried depth boundary of the tunnel is determined, then discussing the theoreticcalculation method of stress and displacement of tunnel surrounding rock from the effect ofloading and unloading.(iii) Through the site tests and numerical simulation analysis, the paper studies theloading and unloading process as a whole. Research shows that the water level fluctuations ofadjacent reservoir has had a big effect on the stress and displacement of tunnel structure andsurrounding rock, and equating the process to the effect of loading and unloading isreasonable.(iv) The results of numerical simulation and the measured data are consistent, and thecurve trends are basically identical. On this basis, the major factors which effect tunnel stressand displacement from the water level fluctuations are summarized: the change value of waterlevel; the relative position of reservoir and tunnel, then analyze their change laws.(v) The contrastive analysis between loading and unloading effect shows that: due to thevalue of the unloading modulus and some residual deformation are beyond recovery, theeffect on mechanics properties of tunnel structure and surrounding rock in loading effect islarger than the unloading one.