风化花岗岩地层旋转钻进中的能量分析

旋转钻进是岩土工程钻探的主要钻进方式,从能量守恒原理出发,对旋转钻进的能量进行分析。同时,在R-20液压式回转钻机上安装数字式钻孔过程监测（DPM）系统,在风化花岗岩地基工程中进行试验,并在监测数据的基础上对钻进能量进行分析计算。研究结果表明,钻进过程中用于破碎岩石的能量主要来自钻进系统的动能,钻进系统用于破碎岩石的能量分配与地层强度特性有关。在风化程度较低或新鲜岩层中钻进时,破碎岩石98%以上的能量来自系统的动能,而轴压力推动钻头位移所给出的能量不到2%;在土层或全风化岩层中,轴压力所做的功达到22%以上,且明显随风化程度的增高而增大,说明钻进系统动能与轴力功可用以表征地层的可钻性,这为实时钻进能量用于地层的识别提供理论依据。

ANALYSIS OF ENERGY FOR ROTARY DRILLING IN WEATHERED GRANITE FORMATION

Rotary drilling is a dominant way in geotechnical engineering borehole surveying.Based on the principle of conversation of energy,the energy for rotary drilling has been analyzed.Besides,a hydraulic rotary drill R-20 instrumented with a drilling process monitoring(DPM)system has been used for site investigation on weathered granite formation;and drilling energy is further analyzed based on the monitored data.The result shows that the penetrating energy in drilling is mainly kinetic energy dependant.The distribution of energy for rock failure is related with the strength characteristics of the penetrated formation.The kinetic energy is more than 98 percent and energy from effective thrust force is less than 2 percent when drilling in slightly weathered rock or fresh rock.However,the energy from the effective thrust force reaches to more than 22 percent,apparently increases with the increase in weathered degree of rock when drilling in soil or very strongly weathered rock.It shows that kinetic energy of drilling system and energy of effective thrust force can reflect the characteristics of the penetrated formation,which can provide theoretical foundation for identification of formation using penetrating energy in real-time.