Construction Scheme And Modell Test Study On Horizontal Freezinig Method Of Water Rich Gravel Stratum

With the continuous advancement of the construction of urban underground space,the strata that the project needs to cross are more special,especially in the soft water rich area in the East and South.The horizontal freezing method has gradually becrome one of the widely used effective construction methods because of its advantages of fast speed of soil reinforcement,short time of strength improvement.high overall stability of the soil after reinforcement,and strong waterproof effect.However,due to the complex and changeable strata conditions,there is a great difference between the construction depth and the force condition,the freezing parameters can not fully learn from previous experience.Therefore,it is of great significance to carry out the design research and stability analysis of the horizontal freezing method in the urban underground engineering.This paper takes Nanning Metro Line 1 National University to Qingchuan interval subway connecting passage as the engineering background.The change laws of mechanical parameters and thermodynamic parameters of the soil under the action of low temperature are obtained through laboratory test.Bascd on the interaction betweenn the frozen wall and the surrounding gravel layer,a mechanical model for the contact passage before masonry is establi shed,The radial deformation of the internal and external sides of the frozen wall and the variation law of the thickness of the frozen wall under external loads are calculated,and the stability of the frozen wall is verified numerically.The similarity criterion of the horizontal freezing method applied to the construction of the Nanning subway interval connection channel is deduced,a model system with similar ratio at 1:20 is established,the freezing temperature measurement scheme,displacement measurement scheme and stress measurement scheme are designed.The distribution law of freezing temperature field,the evolution law of displacement field of frozen wall and ground surface during freezing,excavation and melting stages,and freezing pressure evolution law of frozen wall and different strata are obtained through experiments.According to the test data,the stress and deformation in the freezing wall forming process are analyzed,the change trend of the thickness of the frozen wall is obtained,and the stability of the frozen wall in the construction process is verified.Through the comparison and analysis of the model test results and the numerical results,the feasibility of the construction of the water rich gravel stratum using the horizontal freezing method is verified,and the factors affecting the freezing method construction are summarized.It is expected that this method can play a good role in guiding the design of excavation and the selection of construction plans in the actual horizontal freezing method.