NUMERICAL SIMULATION OF ROCK BREAKING MECHANISM WITH HIGH-PRESSURE WATER JET

109Journal of Hydrodynamics, Ser. B, 1(2004),109-110 .China Ocean Press, Beiing- Printed in ChinaNUMERICAL SIMULATION OF ROCK BREAKING MECHANISM WITHHIGH-PR ESSURE WATER JETPh. D. Candidate:NI Hong jianCollege of Petroleum Engineering， University of Petroleum ( East China)， Dongying 257061， China, e-mail: hj. ni @ 163. comSupervisor:The first part is to study the coupling style andWang Rui-he ( University of Petroleum ( East mechanism between rock and water jet during wa-China) )ter jet rock breaking. The results of numerical cal-Members of Dissertation Defense Committee :culation and experiments show that the primary iShen Zhong-hou ( University of Petroleum teraction is the interface coupling， the impacting(East China) )，Chairmanload and static pressure exerted by the water jet toGu Xin-yi (Drilling Technology Research Insti- break rock. The process of rock breaking can be di-tute, Shenli Oilfield)vided into two stages. In the initial stage, the stressGe Hongkui ( University of Petroleum (East wave is the primary load and most of rock breakingtakes place， while in the later stage the existingHan Zhi- yong (University of Petroleum (East rock damage, for instance, microholes and microc-racks etc. ，is secondly developed. .Guan Zhi-chuan ( University of PetroleumThe second part includes， the rock damage( East China) )model and the damage coupling model, suitable forLiu Ting cheng ( Beiing University of Science the whole water -jet rock breaking process, estab-and Technology)lished with continuous damage mechanics and microYu Wen ping (China Petroleum and Chemical damage mechanics on the basis of analyzing experi-Corporation)mental results. And the numerical method was developed with the continuum mechanics and the FEMTime of Dissertation Defense: Nov. 24, 2002theory.The third part is numerical study on rockABSTRACT: Based on the analysis of experimental results,breaking mechanism with high -pressure water jetthe rock damage model and the damage coupling model suit-with nonlinear FEM and dynamic rock damage mod-able for the whole rock breaking process with water jet wereel. The results show that most of rock damage andestablished with continuous damage mechanics and micro dam-age mechanics, and the numerical method was developed withbreakage take place in several milliseconds, the pri-continuum mechanics and the FEM theory. The rock breaking mary damage behavior under the general continualmechanism with water jet was studied systematically with nu- water jet is tensile damage caused by the rock unloa-merical simulation for the first time in the field of waterjet ding and the jet impacting, and the evolvement ofrock breaking. The mumerical results agree with the experi- rock damage is step changed. The rock breakingmental ones which shows that the presented method is reason-process of pulse water jet is basically identical with .able and can reflect the reality of water jet rock breaking. Thethe general continual water jet. Because the dura-conclusion can be applied in practice.tion中國煤化工s short comparatively,the rYHCN M H Grgy of rock is greaterKEY WORDS: water jet, rock fragment, rock damage mod-el, FEM, experimental studyrelatively, and the rock breaking efficiency is higherthan the general continual water jet apparently dur-BRIEF INTRODUCTION OF THE PAPER: This ing pulse water jet unloading. The energy dissipa-thesis incAue數據ree parts:tion and frequency of rock elastit vibration obviously110affect the breaking process. When the elastic vibra- rock surface. The rock breaking process with swirtion direction is same with that of jet impact, the ling water jet is to break out an annular on rock sur-rock breaking effect will be getting better, while if face firstly, and then the annular develops along theopposite, it will be getting worse. The rock break- radial and axial directions, and the find bottom forming ability of swirling water jet is stronger. Because of rock broken hole is protruding aw1. The advan-the jet particle velocity is three -dimensional and its tage of swirling water jet rock breaking is the highimpacting rock is mainly sloping during the breaking breaking efficiency， large breaking area and lessrock, the interference of returning fluid is less, and rock breaking energy per unite volume so the swir-all these aspects make it easy to draw and shear the ling water jet can drill out large-diameter rock hole.中國煤化工MHCNMHG