阶梯式钻头挤土机理的有限元分析

为了分析阶梯钻头冲击挤密作用下土体的变形机理,将土体视为DP材料,服从Drucker-Prager屈服准则,通过钻具与土体之间的接触以及施加冲击载荷来模拟钻进过程,建立了潜孔锤冲击挤密钻进的有限元模型。以非线性瞬态动力学有限元分析为手段,利用有限元软件ANSYS9.0对阶梯钻头冲击挤密作用下土体的变形机理进行了模拟分析。结果表明,在冲击载荷作用下,冲击功主要用于竖向压缩土体,水平方向的挤压作用相对较小。阶梯钻头对土体的破坏作用可以看作是每个台阶的微剪切作用,当台阶布置合理时,土体沿等效锥面整体破坏,破坏后的土体在等效锥面的作用下被挤向孔壁四周,挤密效果较好。

Finite element analysis of soil displacement mechanism of step bit

In order to analyzes the soil deformation mechanism under the impact load of the step-bit, the finite element model of impact and displacement drilling with down the hole hammer (DTH) is established on the basis of adopting Drucker-Pager yield criterion, taking soil as DP materials and simulating the drilling process by applying the impact load on soils. Based on the finite element method of non-linear transient dynamics, the soil deformation mechanism is studied with the commercial finite element code ANSYS9.0 which has the capability of simulating large-strain frictional contact between two or more solid bodies. Research results show that the impact energy is mainly used to compress soils in vertical direction while the compress effect is smaller in horizontal direction. The behavior of step-bit acting on soil can be considered as mini-shear effect which destroys soils along the equivalent cone surface when the bit’s step is disposed appropriately. Then the failure soil is compacted around the hole-wall.