Study On The Influence Factors Of Static Lateral Pressure Coefficient Of Loess And Its Effect On The Stability Of Cavern

With the promotion of urbanization,the rapid development of urban construction,water conservancy,transportation and other infrastructure construction in the western landlocked areas has been promoted.Coupled with the particularity of geographical location,underground engineering and retaining structure in the loess region have developed rapidly and their scale has become larger and larger.Due to the need of production and development,it is very important to explore the causes and rules of wall cracks in underground caverns of loess.One of the keys to the lateral stress calculation of cave walls is the static lateral pressure coefficient K₀.At present,there are few studies on the static lateral pressure coefficient of loess under the influence of environmental factors.Based on this,K₀consolidation tests under the influence of water content,freeze-thaw cycles and pore water chemical environment changes are conducted in this paper respectively from three aspects:water,temperature and pore water chemical environment.The contaminated liquid is mainly the typical landfill leachate with different molar concentrations of HCl and NaOH prepared manually in the laboratory.Furthermore,the evolution law of static lateral pressure coefficient under the influence of different environmental factors was explored by combining laboratory experiment,example analysis and numerical simulation,and the force and stability of underground caverns were analyzed.The main research contents are as follows:（1）In this paper,undisturbed loess with different water content gradients,different freeze-thaw cycles,different molar concentrations of HCl,NaOH and different concentrations of landfill leachate were controlled.Consolidation tests were carried out on GJY K₀consolidation instrument to study the static lateral pressure coefficient under the influence of the above environmental factors;（2）The results show that the K₀-σ_vcurve is strain-hardening,and the static lateral pressure coefficient increases with the increase of water content under the same vertical load.The static lateral pressure coefficient increases with the increase of freeze-thaw cycles.The static lateral pressure coefficient increases with the increase of molar concentration of HCl.The static lateral pressure coefficient decreases with the increase of NaOH molar concentration.The static lateral pressure coefficient increases with the increase of landfill leachate concentration;（3）Combined with the stress state analysis of cavern,the numerical example is discussed.It is found that the lower the water content is,the greater the maximum tangential stress in the tensile stress zone of the vault,and the larger the tensile stress zone is,the smaller the yield proximity is.When the number of freeze-thaw cycles increases,the maximum tangential stress in the tensile stress zone of the vault slightly increases,and the yield proximity decreases with the increase of the tensile stress zone.With the increase of HCl molar concentration,the maximum tangential stress of the vault in the tensile stress zone of the cavern increases,and the tensile stress zone remains basically unchanged,with a significant decrease in yield proximity.When the molar concentration of NaOH is too high,the maximum tangential stress of the arch in the tensile stress zone of caviar decreases,and the maximum tangential stress of the arch in the tensile stress zone increases,and the tensile stress zone increases.The yield proximity increases at low molar concentration and the structure is safe,while decreases at high molar concentration and the structure tends to be unsafe.With the increase of landfill leachate concentration,the maximum tangential stress in the tensile stress zone of cavern increases,the tensile stress zone decreases,and the yield proximity decreases;（4）The numerical simulation analysis of cavern shows that the increase of water content,the increase of freeze-thaw cycles,the increase of HCl molar concentration and the increase of typical landfill leachate concentration will increase the displacement value and the maximum equivalent strain value of cavern,and the structure tends to be unstable.With the increase of NaOH molar concentration,the displacement value of caviar decreases first and then increases,and the maximum equivalent strain value decreases first and then increases.The structural strength is improved within a certain range of molar concentration,and the structure tends to be unstable when the molar concentration is too high.