The stressed state and stress relaxation in rocks

Journal of Mining Science -     

气动凿岩机钎杆应力波弯曲振动分析

介绍了气动凿岩机钎杆在工作过程中所产生的应力波及其特性,阐明了钎杆噪声是钎杆在工作过程由于偏心撞击和钎杆本身弯曲而产生的。     

Circulation system of a pneumatic drill with central drilling mud removal

The article describes experimental testing of a pneumatic drill tool with reverse circulation of drill fluid. The authors assessed suitable clearance between downhole packer and drill hole walls and propose engineering design aimed for higher performance of the pneumatic drill circulation system.     

岩石在静应力状态下的循环冲击试验及破坏模式研究

在冬瓜山深部采集四种岩石,并进行了单轴压缩变形试验,测得平均单轴抗压强度。以单轴抗压强度为依据,轴压选取三个级别,在中南大学SHPB动静组合加载实验机上对岩石试样进行等幅循环冲击。通过对试验数据和现象进行分析,揭示岩石在循环冲击过程中的能量传递变化规律,并从峰值应力和弹性模量的变化两个方面进行分析。对岩石的破坏模式进行分析,得到不同类型岩石的破坏失稳机理和破坏模式,为现场施工提供理论依据。     

Assessment of stress state in rocks by deformation characteristic of borehole zone with hydrofracture

The authors propose the method of stress state assessment in permeable rocks. The method is numerically studied as the relationship between cross-section area of borehole length interval with a hydrofracture and the loading pressure on the borehole walls. The test data processing algorithm and the practical application of the method are considered.     

岩层破裂状态与钻削机构振动响应特性研究

针对煤巷顶板煤岩的复杂性及顶板岩层破坏难以有效控制、预测问题,考虑钻头与煤岩相互作用产生耦合振动,通过分析锚杆钻头的受力及其振动特性,以煤岩硬度f=4.2,3.5,2.55为例研究钻削机构钻削完整岩石与破碎岩石时的耦合振动特性。利用最小二乘法原理拟合振动曲线,消除趋势项,并对曲线进行平滑处理。研究表明:在相同钻削条件下随煤岩硬度的增加,钻削机构横向振动半径有所增大;钻削相同硬度煤岩的完整岩石和破碎岩石时钻削机构横向振动半径随煤岩破裂程度的增加而减小。可据此来判断煤巷锚孔内煤岩破碎的范围,进而预测顶板是否存在冒顶隐患及冒顶隐患的程度,亦可据此判断煤巷锚孔内稳定岩层的位置和厚度,为顶板支护参数的设计提供技术支持。     

Stressed state of rocks of block structure

Conclusions 1. The stressed state of rock masses depends to a considerable extent on their block structure. There is no clear dependence for stresses on block geometric dimensions and shape.2. A block nature for the rock mass increases the proportion of the largest ratio of principal stresses ₂/₁ compared with a homogeneous rock mass at the same points. In other words in block masses the maximum tangential stresses are greater than in a homogeneous rock mass which promotes movement of blocks in relation to each other on a background of general equilibrium for a structure of a larger scale level.3. A block structure for rock mass promotes reorientation of the principal stresses compared with a homogeneous rock mass.Translated from Fiziko-Tekhnicheskie Problemy Razrabotki Poleznykh Iskopaemykh, No. 5, pp. 38–47, September–October, 1994.     

Stress state of rocks in subduction zone

The authors use the boundary element method in the 2D elastic problem to investigate the regularities of the principal stress distribution in the subduction of the oceanic plate under the continental plate under different boundary conditions. The investigation covers the cases when the fault zone has irregularities and the fault zone boundary is smooth. The point displacements at the boundaries of the continental and oceanic plates are analyzed. It is shown that the anticlimax induced by an instantaneous failure along the fault zone irregularities can generate an earthquake with M _s = 7.5 and higher magnitude, with 2?C7-meter shears of the oceanic and continental lithospheric plates.