Rock mass boreability plays a key role in the performance of tunnel boring machines (TBMs). The angle and orientation of the plane of joint are two factors which affect the boreability of the jointed rock masses. This paper is aimed at describing the combined effects of joint orientation and spacing on the boreability and presenting a new model and classification system to predict the boreability of the jointed rock masses, focusing on field studies. In this regard, a database of three water conveyance projects including the Queens Tunnel in USA, Kerman Tunnel in Iran, and Maroshi-Ruparel Tunnel in India has been employed. A total fracturing factor (presented by Bruland) has been applied as well. The results showed that the increase in the total fracturing factor will result in higher boreability. A model was developed for predicting the boreability of the jointed rock mass based on the total fracturing factor, and the convergence coefficient of this model was 0.7. The volumetric joint count classification system was also developed to analyze the relationship between the total fracturing factor and the volumetric joint count. In order to predict the boreability of the jointed rock mass in the Zagros Tunnel in Iran, the boreability was classified in three categories. The result showed a good agreement between the predicted and actual boreability of the jointed rock mass.

岩体的可钻性在隧道掘进机（TBM）的性能中起着关键作用。节理平面的角度和方向是影响节理岩体可钻性的两个因素。本文旨在描述节理方位和间距对可钻性的综合影响，并提出一种新模型和分类系统来预测节理岩体的可钻性，重点是现场研究。在这方面，已经使用了三个输水项目的数据库，包括美国的皇后区隧道，伊朗的克尔曼隧道和印度的马鲁西-鲁帕雷尔隧道。还应用了总压裂因子（由Bruland表示）。结果表明，总压裂因子的增加将导致更高的可钻性。建立了基于总压裂因子的节理岩体可钻性预测模型，该模型的收敛系数为0.7。还开发了体积联合计数分类系统，以分析总压裂因子与体积联合计数之间的关系。为了预测伊朗Zagros隧道中节理岩体的可钻性，将可钻性分为三类。结果表明节理岩体的预测和实际可钻性之间有很好的一致性。还开发了体积联合计数分类系统，以分析总压裂因子与体积联合计数之间的关系。为了预测伊朗Zagros隧道中节理岩体的可钻性，将可钻性分为三类。结果表明节理岩体的预测和实际可钻性之间有很好的一致性。还开发了体积联合计数分类系统，以分析总压裂因子与体积联合计数之间的关系。为了预测伊朗Zagros隧道中节理岩体的可钻性，将可钻性分为三类。结果表明节理岩体的预测和实际可钻性之间有很好的一致性。