Study On Mechanical Properties And Hypoplastic Constitutive Model Of Frozen Saturated Sand

The artificial freezing method is widely used in the construction of mine construction,subway engineering,tunnel engineering and other fields.It is also the main technical means for mining and tunnel excavation through water-rich sand layer.A comprehensive understanding of the mechanical properties of frozen saturated sand and the stress-strain relationship under complex stresses can provide important guidance for the construction of artificial freezing methods.Under the influence of natural factors such as in-situ stress,frost heave and pressure rise,as well as artificial excavation and surcharge,underground frozen soil may be in various dimensional stress states,and the intermediate principal stress also has a significant impact on the strength and deformation characteristics of frozen soil.Therefore,studying the strength and deformation characteristics of saturated frozen sand under different loading conditions and establishing the frozen soil constitutive model with simple structure and clear physical meaning of parameters can provide theoretical reference for the construction of artificial freezing method in water-rich sand layer and provide a new direction for the establishment of frozen soil constitutive model.In this paper,the strength and deformation characteristics of frozen saturated sand under different stress states are studied by combining laboratory test,numerical simulation and theoretical analysis,and the corresponding constitutive model is established based on the hypoplastic theory.The main research contents and results are as follows:(1)Conduct triaxial shear tests at 3 temperatures,3 confining pressures,and 5 medium principal stress coefficients to analyze the effects of various factors on the strength and deformation characteristics of saturated frozen sand.The results show that a decrease in temperature significantly enhances the strength and shear expansion of frozen saturated sand;Increasing confining pressure increases strength and weakens shear shrinkage;As the coefficient of principal stress increases,its strength first increases and then decreases,and its shear dilatancy increases.(2)A critical state model for frozen sand is established by introducing a cohesion tensor and relative density state variable into the hypoplastic model proposed by Wu and Lin.Comparing the predicted values of the model with the experimental values,it was found that the model has good performance under different temperature,initial confining pressure,and medium principal stress coefficient conditions,and can better describe the strength and deformation laws of saturated frozen sand.(3)Based on Wu et al.’s basic idea of anisotropic hypoplastic modeling,establish an anisotropic hypoplastic model for frozen soil.We simulated the stress-strain response of static water compression tests and conventional triaxial compression tests under different deposition angle conditions,analyzed the influence of anisotropy coefficient and deposition angle on the model prediction results,and verified the effectiveness and feasibility of establishing an anisotropic hypoplastic model of frozen soil using this method.(4)Combined with damage mechanics and the conservation principle of strain energy,the cohesion tensor and correction function are introduced on the basis of Wu Bauer’s hypoplastic model to establish a one-dimensional sub plastic damage constitutive model of frozen sand considering pore compaction,and a parameter determination method is proposed.The model can well reflect the initial pore pressure and strain softening characteristics of frozen saturated sand during loading,and accurately describe the full stress-strain curve of frozen sand under uniaxial compression stress state.Figure[44]Table[8]Reference[95]...