What does this research mean for the field?

Heating and rapid cooling treatments significantly alter the thermal shock damage and strength of granite, with higher temperatures and liquid nitrogen cooling leading to greater damage, smaller fragment sizes, and shifting the primary drilling challenge from increasing the rate of penetration to improving cleaning efficiency. Novelty: ClaimNovelty.INCREMENTAL. Consensus alignment: ConsensusAlignment.NEUTRAL.

What question did this study set out to answer?

This research aims to investigate how different thermal treatments affect the failure characteristics of granites under impact load during drilling.

May 30, 2026Open Access

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Experimental research on failure mechanism and evolution characteristics of thermal-treated granites under action of impact load with PDC cutter

HWHao-Yu WangBeijing University of Technology YXYan XiChina University of Petroleum, Beijing WLWei LianChina University of Petroleum, Beijing

Key Points

This research aims to investigate how different thermal treatments affect the failure characteristics of granites under impact load during drilling.
Conducted drillability tests and SHPB tests on thermally treated granites.
Analyzed dynamic rock-breaking performance using a SHPB system equipped with a PDC cutter.
Utilized 3D contour scanning and fractal theory to assess impact craters and fragments.
Granites heated to 600 °C produced fragments about 45% smaller than those at room temperature.
Liquid nitrogen-cooled specimens exhibited greater damage degree compared to other treatments.
As temperature increased, challenges for drilling tools shifted from maximizing rate of penetration to enhancing cleaning efficiency.

Abstract

High rock temperatures and complex engineering environments are the most significant problems in enhancing the rate of penetration (ROP) and drilling tool efficiency for hot dry rocks (HDR). Studying the failure characteristics of different thermal-treated granites by PDC cutters during percussive drilling has profound significance in enhancing the compatibility between drilling teeth and rock during HDR mining and optimizing the drilling toolʼs efficiency in breaking rocks. Through drillability tests and SHPB tests, the present study explored the relationship between drillability and the dynamic behavior of granites. In addition, granites with different heating temperatures and cooling methods were subjected to dynamic rock-breaking tests by the SHPB system installed with the PDC cutter. Furthermore, the impact crater was quantified by 3D contour scanning technology, and the fractal theory was utilized to analyze the fragments. Then, the equations for the dynamic magnification factor of intrusion, fractal dimension, and specific rock-breaking energy of granite upon impact loading are discussed. According to the results, the impact crater size is closely associated with the heating temperature of the rock. Heating and rapid cooling treatments will affect the thermal shock damage and strength of rock, and then change the penetration depth, damage volume, and area of impact craters generated from the PDC cutter. The granite at 600 °C exhibits about 45% smaller fragment size than that at room temperature, while the damage degree of the liquid nitrogen-cooled specimen will be greater. According to the variation of dynamic magnification factor, fractal dimension, and specific rock-breaking energy of rock with thermal shock damage, it can be found that with the temperature increasing, the problems drilling tools need to solve gradually shift from increasing ROP to improving cleaning efficiency. The experimental results are expectedly to lay the ground for high compatibility between drilling tools and formation in HDR.

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Cite This Study

Wang et al. (Fri,) studied this question.

synapsesocial.com/papers/6a1a7e6a0307b785094311ee https://doi.org/https://doi.org/10.1016/j.petsci.2026.05.034

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