Upper Bound Solutions Of Earth Pressure And Structure System Reliability For Deep Cavity

Abstract:Underground engineering, an important research topic of geotechnical engineering, plays a significant role in the field of traffic engineering, mining and national defense. The stability of deep cavity is the core issue of the research of underground engineering. Therefore, how to accurately assess the safety of deep cavity is the hot issue that geotechnical engineers focus on, and how to precisely obtain collapse pressure of deep cavity is a difficult problem for the geotechnical engineering. Limit analysis based on plastic mechanics is a kind of effective manner to conduct the stability research of geotechnical engineering. Limit analysis based on plastic mechanics is of strict theoretical basis. The limit analysis assumes the soil as an ideal elastic-plastic model and considers the relationship between the stress and strain of soil in an ideal way, which ignores elastic-plastic period during soil deformation which results in the complicated and difficult calculation. Within the scope of this hypothesis, the limit analysis has a lot of advantages, such as rigorous theory, clear concept, simple analysis method and concise calculation. By establishing the kinematically admissible velocity field and the statically admissible stress field, limit analysis can use the principle of virtual power to obtain the upper bound solution and the lower bound solution of the collapse pressure of deep cavity. So it is one of the effective methods in the stability research of geotechnical engineering.With respect to the safety assessment of the deep cavity, the reliability is more scientific and rigorous in contrast to the factor of safety. Therefore, this article combines the limit analysis with reliability theory to study the collapse pressure and stability for the deep cavity, which can provide theoretical basis on the support design and stability assessment for the deep cavity. The main innovative achievements in this paper are as follows:(1) A failure mechanism composed of the translational and rotational blocks, namely the collapsing wedge block, rotating circular block, and multi-translational triangular blocks, is established to analyze the collapse pressure for the deep cavity. The analysis shows that, when the number of the triangular blocks increases, upper bound value of the supporting force of the rock becomes equable and the accuracy of the calculation also becomes higher. When n=3, the accuracy of the calculation is enough. In addition, based on the presented failure mechanism (n=3), the results of this paper calculating by the limit analysis is compared with the result by Platts theory and numerical simulation and the maximum difference is less than30%, which demonstrates that the failure mechanism in this paper is reasonable.(2) Based on the presented failure mechanism for the deep cavity, analytically upper bound solutions subjected to the linear Mohr-Coulomb criterion as well as the nonlinear Mohr-Coulomb criterion are obtained separately. Then, the influence of the nonlinear coefficient and geotechnical parameters on the collapse pressure is analyzed.(3) Based on the presented failure mechanism for the deep cavity, analytically upper bound solutions subjected to the Hoek-Brown failure criterion are obtained, and then the influence of the parameters related to the Hoek-Brown failure criterion and geotechnical parameters on the collapse pressure is analyzed.(4) The general structure system reliability models of multiple failure modes, with single function and multiple functions, are established separately. The calculating method using the Monte Carlo simulation method to programme directly is proposed, and the specific calculation procedures and flow charts are also given. Besides, relatively accurate value of structural system reliability is gotten based on different models(5) Based on Mohr-Coulomb failure criterion and Hoek-Brown failure criteria, reliability models of structural system for deep cavity with the multiple correlated failure modes are established separately. Using Monte Carlo simulation method to calculate the reliability of the model, the main factors influencing the structure system reliability for deep cavity is obtained via Parameter Sensitivity Analysis.(6) Taking the Jiangyuanling Tunnel in the Tongping highway and the transportation roadway of21128mining area in Shanjiaoshu mine for example, the limit analysis upper bound method is utilized to calculate the collapse pressure. The accuracy of the proposed approach in this paper is then validated by comparison with numerical simulations and field measurement results. This paper contains99pictures,61tables, and204references.