掘进机刀盘滚刀间距对北山花岗岩破岩效率的影响实验研究

掘进机(TBM)开挖隧道过程中,其刀盘上滚刀间距设计的合适与否关系着破岩效率的高低。由于岩石非均匀、非连续、各项异性的特性,使用数值模拟方法研究滚刀破岩过程存在局限性。现场掘进实验主要是针对特定的掘进机做出机械运行参数优化,无法研究不同刀间距对破岩的影响。全尺寸滚刀破岩实验可以人为调整刀间距,且实验中采用大体积岩石可以避免尺寸效应的影响,因此受到了广泛的关注。采用北京工业大学自制的机械破岩试验平台,安装17英寸(432 mm)盘形滚刀,选取尺寸为1000 mm×1000 mm×600 mm的北山完整花岗岩试样,进行了5组刀间距的线性切割试验。实验中采集滚刀三向力,分层收集岩片且对其进行称重。对不同刀间距作用下的平均法向力、平均滚动力和比能进行了分析研究。当贯入度较小时,刀间距对平均法向力和平均滚动力的影响都不明显,随着贯入度的增加,刀间距对平均法向力和平均滚动力的影响增加。对于所有的刀间距而言,增加贯入度会产生更多的岩片,但并不一定会提高破岩效率,对于北山花岗岩而言,当刀间距与贯入度的比值为30左右时,比能值最低,此时破岩效率最高。

Influence of different cutter spacings on rock fragmentation efficiency of Beishan granite by TBM

In tunnel construction by tunnel boring machine (TBM), the excavation efficiency is highly related to cutter spacing. Due to the inhomogeneous, discontinuous and anisotropic characteristics in rocks, there are limitations to study rock fragmentation process by using numerical simulation. The purpose of in-situ penetration tests is to optimize the operational parameters for a specific TBM, thus this kind of tests cannot consider the effect of different cutter spacings on rock breaking process. The full-scale cutting experiment can minimize the size effect by using a large rock sample and the cutter spacing is able to be adjusted during the experiment, therefore the full-scale cutting experiment has been widely used in recent years. In order to study the influence of different cutter spacings on excavation efficiency by TBM cutter, the mechanical rock fragmentation experimental platform of Beijing University of Technology is used to conduct a series of rock cutting tests with five sets of cutter spacings. In these tests, the diameter of the disc cutter with a constant cross section is 432 mm. The size of test granite rock sample is 1000 mm×1000 mm×600 mm, taken from Beishan, Gansu Province of China. During the experiments, the three dimensional forces acting on the rolling cutter are recorded, and the rock chips collected after each cutting pass are weighed respectively. The impact of cutter spacing on excavation efficiency is analyzed by use of the obtained average normal force, average rolling force and specific energy. The results show that when penetration is small, the cutter spacing has no obvious effect on the average normal force and rolling force. However, with the increasing penetration, the cutter spacing has significant impact on both the average normal force and the rolling force. For all of the cutter spacings arranged in the tests, the increase in penetration will produce more rock chips but not always improve the efficiency of rock fragmentation at the same time. For Beishan intact granite, when the ratio of spacing to penetration is around 30, the specific energy reaches the minimum value, which means that the highest rock fragmentation efficiency can be expected under this condition.