Layered rock strata are observed to be common during the excavation of tunnels or cavities,and may significantly affect the deformation and failure characteristics of surrounding rock masses due to various complex for...Layered rock strata are observed to be common during the excavation of tunnels or cavities,and may significantly affect the deformation and failure characteristics of surrounding rock masses due to various complex forms and mechanical properties.In this paper,we propose a three-dimensional axisymmetric velocity field for roof collapse of shallow cavities in multi rock layers,by considering the influences of roof cross-section shapes,supporting pressure,ground overload,etc.The internal energy dissipation rate and work rates of external forces corresponding to the velocity field are computed by employing the Hoek-Brown strength criterion and its associated flow rule.Further,the equations of the collapse surfaces and the corresponding weight of collapsing rock masses are derived on the basis of upper bound theorem.Furthermore,we validate the proposed method by comparing the results of numerical calculations and existing research findings.The change laws of the collapse range under varying parameters are obtained for the presence of rectangular and spherical cavities.We also find that the three-dimensional mechanism is relatively safer for engineering designing actually,compared with the traditional two-dimensional mechanism.All these conclusions may provide workable guidelines for the support design of shallow cavities in layered rock strata practically.展开更多
基金funded by National Natural Science Foundation of China(Nos.51704177,51809159)A Project of Shandong Province Higher Educational Science and Technology Program(No.J16LG04)+2 种基金Open Research Fund of State Key Laboratory of Geomechanics and Geotechnical Engineering(No.Z018005)Shandong Co-Innovation Center for Disaster Prevention and Mitigation of Civil Structures(No.XTP201911)the Doctoral Research Fund of Shandong Jianzhu University(No.XNBS1501).
文摘Layered rock strata are observed to be common during the excavation of tunnels or cavities,and may significantly affect the deformation and failure characteristics of surrounding rock masses due to various complex forms and mechanical properties.In this paper,we propose a three-dimensional axisymmetric velocity field for roof collapse of shallow cavities in multi rock layers,by considering the influences of roof cross-section shapes,supporting pressure,ground overload,etc.The internal energy dissipation rate and work rates of external forces corresponding to the velocity field are computed by employing the Hoek-Brown strength criterion and its associated flow rule.Further,the equations of the collapse surfaces and the corresponding weight of collapsing rock masses are derived on the basis of upper bound theorem.Furthermore,we validate the proposed method by comparing the results of numerical calculations and existing research findings.The change laws of the collapse range under varying parameters are obtained for the presence of rectangular and spherical cavities.We also find that the three-dimensional mechanism is relatively safer for engineering designing actually,compared with the traditional two-dimensional mechanism.All these conclusions may provide workable guidelines for the support design of shallow cavities in layered rock strata practically.
