As part of the rock mass, both the mesoscopic and macroscopic flaws will affect the creep mechanical behavior of the rock mass with nonpersistent joints. This study focuses on this kind of rock mass and establishes a creep damage model to account for the effect of the joint on its creep mechanical behavior. First, on basis of analyzing the rock element creep mechanism and the typical creep deformation curve, a new creep damage constitutive model for the rock element is set up by introducing the damage theory and Kachanov damage evolution law into the classic creep constitutive model such as J body model. Second, the determination method of the proposed model parameters is studied in detail. Third, the calculation method of the macroscopic damage caused by the joint proposed by others is introduced which can consider the joint geometry, strength, and deformation parameters at the same time. Finally, the creep damage model for the rock mass with nonpersistent joints under uniaxial compression is proposed. The calculation examples indicate that it can present the effect of the joint on the rock mass creep mechanical behavior.
Natural gas is a kind of inflammable and explosive high-risk gas, and its transportation mainly depends on high-pressure pipelines. Serious pipeline leaks can cause fires and explosions. These accidents will cause loss of life and property to residents along the line. Therefore, it is very important to conduct risk analysis on high-pressure gas pipelines. In this paper, the Bow-tie model is used to conduct a strict logical reasoning on the causes and consequences of pipeline leakage, and a complete and clear risk evaluation index system for high-pressure gas pipelines is proposed. Secondly, the improved analytic hierarchy process (IAHP) is used to calculate the weight of each indicator and sort the weights. The calculation shows that the equipment plays a major role in the first-level indicators. Among the secondary indicators, the safety equipment, alarm system, natural disasters, operational misoperations, safety inspection errors, and design misoperations account for a significant weight ratio. The evaluation results of various factors are basically consistent with the actual situation. The research results can provide a reliable basis for the daily safety management of gas pipelines.
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