The characteristics of the particle size distribution (PSD) are an important reflection of energy consumption during rock drilling and drilling efficiency. A new approach incorporating both fine and coarse fractions of the PSD to supplement the typical approach of merely utilizing D50 (50% passing diameter) to index drilling resistance and efficiency is reported in this paper. A series of drilling experiments are conducted on limestone with variable rotation rate and with measured response of both penetration rate and PSD. The PSD organizes into a bimodal distribution with two distinct peaks corresponding to fine (Peak I) and coarse (Peak II) fractions. The mean size of Peak I is mainly conditioned by the rock property and the contact angle of the drilling tool. Peak II results from the effects of grinding and comminution and is conditioned by operational drilling parameters of rotation speed and the penetration rate of the bit. With an increase in bit penetration rate, the mean particle size of Peak II increases and its volume percentage decreases. With an increase in rotation rate, the mean particle size of Peak II initially decreases before slightly increasing at higher rates, while sympathetically, its volume percentage initially increases before decreasing. Such mechanistic analyses applied to define the resulting form of the PSD suggest operational changes that may be used to control the resulting PSD and optimize drilling.

中文翻译：

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一种评估凿岩机粒度分布的新方法：双峰特征分析

粒度分布（PSD）的特性是岩石钻探过程中能耗和钻探效率的重要体现。本文报道了一种新的方法，该方法结合了PSD的细颗粒和粗颗粒，以补充仅利用D50（通过直径的50％）来提高抗钻性和效率的典型方法。在石灰石上进行了一系列钻探实验，这些石灰石具有可变的旋转速度，并且测量了穿透速度和PSD的响应。PSD组织为双峰分布，具有两个不同的峰，分别对应于精细（峰I）和粗糙（峰II）馏分。I峰的平均尺寸主要取决于岩石的性质和钻具的接触角。峰II是由磨削和粉碎作用产生的，并由转速和钻头的钻进速度等可操作的钻井参数调节。随着钻头钻入速率的增加，峰II的平均粒径增大，而体积百分数减小。随着旋转速率的增加，峰II的平均粒径开始减小，然后以较高的速率略微增加，而令人同情的是，其体积百分比在减小之前开始增大。用于定义PSD的最终形式的这种机械分析表明可用于控制所得PSD和优化钻探的操作更改。峰II的平均粒径增加而体积百分比减小。随着旋转速率的增加，峰II的平均粒径开始减小，然后以较高的速率略微增加，而令人同情的是，其体积百分比在减小之前开始增大。用于定义PSD的最终形式的这种机械分析表明可用于控制所得PSD和优化钻探的操作更改。峰II的平均粒径增加而体积百分比减小。随着旋转速率的增加，峰II的平均粒径开始减小，然后以较高的速率略微增加，而令人同情的是，其体积百分比在减小之前开始增大。用于定义PSD的最终形式的这种机械分析表明可用于控制所得PSD和优化钻探的操作更改。