Stress And Deformation Analysis Of Frozen Wall In Deep Alluvium Considering Original Frost Heaving And Excavation Unloading

In deep alluvium,multi circle hole freezing method is often used in shaft sinking.During the forming process of freezing wall,the original stress state is obviously changed and the original frost heaving force is produced.After the shaft excavation and unloading,the freezing wall is deformed inward.When the stress and deformation of the freezing wall are large,the stability of the freezing wall and the safety of the freezing pipe will be adversely affected.For this reason,this article takes the freezing shaft sinking engineering of the second auxiliary shaft of Dingji Coal Mine as the background,and adopts the method of indoor experiment,theoretical analysis and numerical simulation to analyze the freezing of the deep alluvial layer under the conditions of original frost heave and excavation unloading,researching on wall stress and deformation characteristics.Firstly,through the inspection hole of the second auxiliary shaft of Dingji Coal Mine,the calcareous clay samples at 435m depth were selected to carry out the uniaxial creep test of frozen soil.The results show that the creep deformation can be divided into two stages:deceleration creep and stable creep.The burgers creep model is selected to identify the parameters of the test results,and the results are imported into FLAC3D for creep numerical simulation calculation.The results show that the simulation calculation and test results have a high consistency,which indicates that the burgers creep model can better describe the creep characteristics of calcareous clay 435m deep in Dingji second auxiliary shaft.At the same time,the sensitivity of creep parameters is analyzed,and the influence of different parameters on the development trend of frozen soil creep deformation is obtained.Secondly,based on the principle of interaction,considering the original frost heaving and excavation unloading effect of multi circle hole frozen wall,the analytical solution of the original frost heaving force,as well as the stress field and displacement field after the formation of frozen wall and excavation unloading are derived.Considering the rheological characteristics of frozen wall,burgers creep model is used to analyze the creep characteristics of frozen wall after excavation.Through the calculation of frost heaving deformation at the interface between deep clay layer and sand layer,the results show that there is a big difference between them,which reveals the mechanism of freezing pipe damage in freezing engineering.Then,based on FLAC3D calculation software,the thermal mechanical coupling numerical simulation analysis of frozen wall stress and deformation in deep alluvium considering original frost heave and excavation unloading is carried out.The results show that the temperature field simulation results are in good agreement with the field measured temperature during the formation of the frozen wall;after the formation of the frozen wall,the stresses inside the inner ring hole,between the middle ring hole and the outer ring hole,and outside the outer ring hole increase obviously,especially the radial stress at the inner ring hole increases greatly.At the same time,the inner unfrozen and a small part of the inner frozen wall displace to the center of the shaft,while the outer frozen wall basically displaces to the outside of the shaft center;when the shaft is excavated and unloaded,the frozen wall deforms and the stress is released,and then the frozen wall has creep deformation,which shows that the displacement of the middle and upper part of the excavation section is larger,and the maximum creep of the shaft wall is 58mm in 24h,which is the frozen wall in deep clay layer The main causes of instability and freezing pipe damage.Figure 85 table 7 reference 96...