Collapse pressure of perforated liner casing in CBM exploration based on plastic hinge model

WANG Tong-tao; YAN Xiang-zhen; YANG Xiu-juan

Abstract：The plastic hinge model of perforated liner casing was built up to calculate the collapse pressure according to the strength and deformation behavior of perforated liner casing subjected to extemal pressure. The calculation equa-tions of collapse pressure of perforated liner casing with initial ovalization were deduced by energy method. The influ-ences of phrase angle, diameter of perforation, shot density, initial ovalization, diameter-thickness ratio and yield stress on the collapse pressure of perforated liner casing were studied. The model and equations were used to calculate the collapse pressure of an actual perforated liner casing as example. The calculating results were compared with the test data in available literatures and FEM results. The research results show that the plastic hinge model is precise and cor-rect, which can satisfy with the actual engineering demands. The collapse pressure of perforated liner casing decreases with phrase angle,initial ovalization and diameter-thickness ratio increasing, and increases with the yield stress. The phrase angle and initial ovalization have greatly influence on the collapse pressure. The collapse pressure of perforated liner casing is slightly changed with the diameter and density of perforation when the diameter and density are smaller than 12 mm and 120 shots per meter, respectively. During the design of perforated liner casing, small phase angle and proper larger diameter and density of perforation are adopted and initial ovalization is constrained strictly in order to improve the collapse pressure and area of passage.