Experimental Study And Numerical Simulation Of Chamber Stability In Interbedded Rock Mass

Layered composite rock mass is a very common form of stratum combination in rock mass engineering,which is formed by different components of cuttings through sedimentation,diagenesis,consolidation and other geological processes.Interbedding is one of the occurrence forms.The mechanical properties and constitutive relations of interbedded rock mass are different from those of single rock or weak interbedded rock mass due to its different structure and rock properties in different layers.Most of the related studies are based on interbedded rock mass or concentrate on the slope engineering of interbedded rock mass.In this paper,the interbedded chamber is taken as the research object,aiming at regularity exploration,focusing on basic research,not specific projects.Firstly,on the basis of similarity theory,the similarity criterion of model test is deduced by using equation analysis method and dimension analysis method.River sand,cement and gypsum were used as similar materials,and their proportions were adjusted to prepare sandstone and mudstone similar materials that meet the requirements of model experiments.The mechanical parameters such as elastic modulus,compressive strength and Poisson's ratio of each rock layer in model test are determined by uniaxial and triaxial conventional tests.A visual small-scale model experiment device has been developed.The device can be used not only as a fixture for model test pieces,but also as a model for model preparation.Based on the similar materials,the similar material model specimens of interbedded rock mass were prepared by using the above-mentioned devices,and the experimental study was carried out to explore the influence of the dip angle of interbedded rock mass and the thickness of interbedded rock mass on the stability of interbedded rock chamber.Through the overload test of model samples,it is concluded that the ultimate bearing capacity of rock mass models with different dip angles has obvious differences.The overall change rule is that the ultimate bearing capacity first decreases and then increaseswith the increase of dip angle.The ultimate bearing capacity decreases first and then increases when the inclination angle is 45°.When the inclination angle is 45 °,the ultimate bearing capacity is the smallest.When the inclination angle is 0 °,the model is mainly subjected to compressive stress,and the overall bearing capacity of the model is the largest.With the increase of thickness,the ultimate bearing capacity is increasing.Through the long-term loading test of model specimen,it is found that the displacement of surrounding rock increases first and then decreases with the increase of inclination angle.At the same time,because the whole chamber is in soft rock stratum and the two sides of the chamber are in weak zone,the displacement in the side of the chamber changes greatly relative to the roof position,and increases first with the increase of the inclination angle of the stratum.As the inclination increases,the bearing capacity of the interbedded rock mass model decreases first and then increases,so the displacement of key points increases first and then decreases.With the increase of the thickness of the stratum,the displacement of the surrounding rock of the chamber decreases,mainly because of the increase of the thickness of the stratum,which reduces the number of hard and soft layers within the scope of the project,reduces the soft and hard contact surface,and reduces the area of the weak area,making the overall stability of the model better.The deformation and creep law of the chamber are simulated when the depth of the chamber is 400 meters.The creep curves of the key points are analyzed by setting key points in the surrounding rock of the chamber.It is verified that the numerical simulation results are in good agreement with the model test.The conclusions in this paper can be used for reference in support and design of underground engineering.