In horizontal directional drilling (HHD), the reamer drilling in soft and hard sandwiching has occurred the excessive wear, broken cutting teeth, swapped cone and even catastrophic buried wells accidents and other engineering problems. This paper involves elastic-plastic mechanics and rock mechanics, using the Drucker-Prager criterion as the rock constitutive relation and the plastic strain as a failure criterion of rock broken. And it establishes a nonlinear dynamics finite element model which is composed of a diameter of 601 mm cone reamer entity and a three-dimensional rock by the finite element method. The goal of the paper is for a comparative study of the reamer's lateral, axial and torsional vibration intensity in the former soft-hard formation and former hard-soft formation and homogeneous formation. And it still studies the influence of the construction parameters for the reamer's vibrations characteristics in the soft and hard sandwiching. The study results show that the severe lateral vibration of the reamer is the root cause of the reamer's premature failure, the adverse effects of which are much larger than the axial vibration and torsional vibration on the reamer's premature failure. And the unreasonable reaming parameters exacerbate the lateral vibration. In addition, the reamer's lateral vibration intensity in the former soft-hard formation and former hard-soft formation reaches a homogeneous formation several times the original magnitude. Especially in the former hard-soft formation, the lateral vibration amplitude peak, acceleration peak and acceleration RMS respectively achieve the homogeneous formations of 4.2 times, 6.6 times, 7.1 times. This paper is based on the baker Hughes BHA vibration grading standards, which recommend the optimum construction parameters in soft and hard sandwiching, and the field application case demonstrates the correctness of the recommendation. The study conclusions provide a scientific basis for the preferable construction parameters, which has an important significance for slowing down the reamer's quick failure, and improving work safety when the reamer drills in soft and hard sandwiching. (C) 2013 Elsevier Ltd. All rights reserved.
