Study On Simulation Method Of Surrounding Rock Pressure Of Micro-Expansive Rock Tunnel

The expansive rock is a soft rock,which has the characteristics of significant water swelling and water shrinkage.In the tunnel in this lithology,the surrounding rock will have a large deformation under the condition that the expanded surrounding rock has its own water content or engineering-induced water content increase,and the lining structure will bear a large surrounding rock pressure.It poses a threat to the construction of the tunnel and the safety of the lining.In the simulation calculation of such tunneled surrounding rock,the load structure model is often used.According to the expansion force measured by the geological survey report,as part of the surrounding rock pressure,the radial action acts on the lining structure,so that the internal force of the lining is often calculated more than the actual The internal force in the structure is much larger.At the same time,in the actual geological conditions,the thickness of the expansive rock formation is usually limited,and the range of the width far exceeds the thickness,so that the horizontal expansion effect is much larger than the vertical direction,so it is more difficult to simulate the calculation in the load structure model.The calculation of the influence of the expansion force on the safety of the lining by the above method is challenged,especially in the three-dimensional rock mechanics model,it is more difficult to simulate the known expansion force,and the three-dimensional rock mechanics model is used to simulate the tunnel structure during construction.It is especially important to pay attention to the deformation stability of surrounding rock during this period.For this reason,a new solution is proposed in this paper: the temperature field of the surrounding rock is determined by the analog load structure model and the internal force of the lining control section in the plane rock mechanics model,and then This temperature field is used in the three-dimensional rock mechanics model to simulate the expansion pressure of the surrounding rock,and this method can also simulate the local surrounding rock expansion.The paper uses the above principle to simulate and analyze the construction of the gypsum surrounding rock section of the Jinyunshan tunnel of a certain expressway.Firstly,the temperature field of the surrounding rock is determined by the analog load structure model and the internal force(axial force)of the lining control section in the plane rock mechanics model;this temperature field is used in the tunnel using theGuantian Ota(non-clay)yield criterion.In the three-dimensional finite element model,excavation simulation is carried out according to the tunnel excavation step.The deformation of the gypsum micro-expansion surrounding rock during the construction process and the influence of the force on the lining structure are numerically simulated.The internal force and displacement of the lining structure are analyzed.According to the variation law of the progress of the excavation,the stability of the surrounding rock during the construction process is determined.According to the relationship between the location of the micro-expansion surrounding rock and the tunnel in the actual tunnel,the expansion force of the micro-expansive rock at different local locations is analyzed in detail.The stability of the surrounding rock and the influence of the support structure are also affected.In addition,according to the calculation results of the above various working conditions,the safety of the lining structure is analyzed.The calculated values??of the deformation and stress of the surrounding rock and lining are monitored on site.The data was compared and analyzed,and the consistency of the results showed the correctness of the method.