牙轮钻头动静耦合碎岩机理及旋挖成桩应用

Rock Fragmentation Mechanism of Roller Bit under Coupling Dynamic and Static Loads and the Application of Rotary Drilling Bored Piles

摘要:

总结了在不同高温状态下冷却、不同加载速率及随机裂隙发育状态下花岗岩动态抗拉力学特性的变化规律；结合牙轮钻头孔底碎岩过程，分析了动静载荷耦合作用下岩石破碎的载荷-侵深特性曲线，认为动、静载荷耦合作用的加载点（即动载的施加点）应是在静载处于卸载阶段；并根据加载能量大小讨论了不同动静耦合工况下产生的岩石破裂深度及破碎体积，表明通过一定范围内增大静载荷及冲击力、预加静压对岩石进行预应力损伤、加载—卸载—加载的破碎循环模式，有利于高效碎岩及裂纹的发育。嵌岩桩基础工程实践表明，通过改造牙轮钻头等钻具结构形式及布齿方式，利用动静耦合加载方式及对钻头冷却处理，可实现牙轮钻头在微风化花岗岩高效钻进的目的，为牙轮钻头的旋挖钻进成桩应用提供了重要的技术支撑。

关键词:嵌岩桩基础;牙轮钻头;动静耦合载荷;碎岩机理;旋挖钻进;花岗岩

Abstract:

The variation rules of granite dynamic tensile mechanical properties are summed up, which are under the conditions of being cooled under different high temperatures, different loading rates and random fracture development; according to the process of down-hole rock cracking by roller bits, analysis is made on the curve of loading-fracturing depth under the coupling dynamic and static loads, the loading point of coupling dynamic and static loads should be at unloading stage of static load. Fracturing depth and volume of rock mass under dynamic and static loads are discussed based on the different pressure values, it is indicated that the efficient rock fragmentation and crack development could be carried out through enhancing static load and impact force, preloading static pressure to make pre-stress damage on rock and loading unloading loading fracturing circular mode. By the rock-socket pile foundation engineering practice, it is showed that by optimizing the structure and teeth arrangement, applying dynamic and static loading mode and cooling treatment of bit, the roller bit can realize high efficiency drilling in slightly weathered granite, which provides import technical support for the application of roller bit in rotary drilling bored piles construction.

Key words:rock-socket pile foundation; roller bit; coupling dynamic and static loads; rock fragmentation mechanism; rotary drilling pile; granite