At present, Measurement While Drilling (MWD) for detection of the roof rock stratum characteristics is mainly focused on numerical simulation and laboratory research, and the research results are somewhat different from the field experimental results. In order to achieve accurate prediction of the interface position of different rock layers, data acquisition of drilling displacement was performed by Laser displacement sensor in the field experiment. The sinusoidal model of MATLAB is used to fit the displacement, and the penetration rate model and the longitudinal vibration model are established by clustering to analyze the drilling response of different strength rock formations. Finally, the two models established were applied to investigate the position of rock interfaces in a drill hole by clustering. It is revealed that drilling process is cyclical, and the penetration rate processed in the field experiment is consistent with the laboratory and numerical simulation penetration rate. The dynamic response of penetration rate and longitudinal vibration for rock with different strength is an important indicator for identifying rock formations.

Measurement while drilling is an important part of the intelligent development of coal mines. The main purpose of this paper is to comprehensively analyze the response characteristics of borehole drilling parameters and find a better method to predict rock mechanical properties based on drilling parameters. Firstly, six concrete blocks and multiple specimens were prepared with different material ratios. Next, the concrete specimens were tested for mechanical properties in the laboratory. Meanwhile, the displacement, rotation speed, torque, and sound pressure level (SPL) were observed during the drilling of the concrete blocks. Finally, the response characteristics of drilling parameters such as rotation speed, rate of penetration (ROP), torque, and SPL were analyzed. Besides, multiple prediction models of rock mechanical parameters were obtained by data analysis. The research results indicate that the drilling process can be classified into the initial stage of drilling (fast speed) and the steady stage of drilling (slow speed). The torque work ratio accounts for more than 99%, which increases with the increase in rock strength. The penetration depth per revolution and torque work ratio are significantly related to rock uniaxial compressive strength, Brazilian tensile strength, cohesion, and elastic modulus. The ROP is the best choice for estimating rock mechanical parameters. This research provides an important reference for laboratory rock mechanics parameter testing and geological features detection based on drilling parameters.

Borehole imaging, one of the main methods of rock formation detection, is widely used in mining, tunnels, petroleum, and other fields of engineering. However, the method of manually identifying the characteristic of rock formation based on borehole imaging is greatly affected by subjective factors. For example, it should be noted that when the rock layer color is similar, the position of the rock interface may be different. In this paper, a method of quantitatively describing the characteristics of the rock formation is proposed, and the automatic recognition of the rock interface is realized. Firstly, the calculation method of rock dip angle and position based on borehole image with 360° wall surface development is proposed. Secondly, the three-dimensional distribution characteristics of the gray values of the rock layer are used to quantitatively describe the characteristics of the rock layer. Finally, an automatic recognition method of rock formation interface based on change-point detection algorithm is proposed. In addition, the recognition effect of the rock formation interface is analyzed by experiments and applied in the field. Research shows that, compared with method two, method one can determine the rock inclination. But its anti-interference ability is poor. Method two can better determine the position of the rock interface. The method is of great significance to the intelligent development of the borehole imaging system and promotes safe, efficient, and sustainable mining in coal mines.

Numerical simulation and field experiments were carried out to study the characteristics of reaming law, bottom-hole topography, and borehole volume in this paper that is a great significance to further understand the rock-breaking mechanism of the drill bit, modification of the calculation model of anchorage length and mechanical specific energy. Firstly, the numerical simulation was employed to analyze the characteristics of boreholes during drilling in different strength rock formations. Secondly, a series of two-wing Polycrystalline Diamond Compact (PDC) bits of different sizes were used for drilling in limestone, sandstone, sandy mudstone, and mudstone that was used to study the bottom-hole topography and reaming law. Finally, the collection of cuttings and recording displacements were carried out when drilling in sandy mudstone that was used to verify the proposed borehole volume calculation model. The results have shown that the reaming range is 0.273 ~ 2.056 mm when the uniaxial compressive strength of rock is between 25 and 98 MPa, and the bottom of the borehole is “bump-like.” The borehole volume calculation model considering the reaming law and the bottom shape of the borehole has improved flexibility. Furthermore, a new model for calculating the anchorage length is obtained in this paper.