Experimental platform development of rock mass rotary cutting system for estimating mechanical parameters of rock mass

In geotechnical engineering, the fundamental parameters of rock mechanics serve as essential data for various projects such as mining, water conservancy, highways, railways, and national defense endeavors, including rock slope engineering, underground cavern engineering, rock excavation, support, and reinforcement. The swift and precise acquisition of rock mechanics parameters, a pivotal research focus in geotechnical engineering, has long garnered the attention of scientists. Presently, two primary approaches are employed for obtaining these parameters: empirical estimation and field testing. However, the reliability, scientific validity, and accuracy of empirical methods are not guaranteed, while field testing methods are time-consuming (typically requiring several weeks to months), costly (often amounting to tens of thousands to hundreds of thousands for a set of parameters), and may lack representativeness.

To fulfill the demands of integrating intelligence into rock engineering education and bolster students’ practical innovation capabilities, a teaching experimental platform for rock-cutting probing is developed. This platform facilitates continuous monitoring of field rock mechanics parameters during the drilling process. Field rotary cutting probing tests are performed on 25 types of rocks, and precise data on parameters such as torque, rotation speed, drilling speed, and pressure were obtained. Additionally, relationship curves between torque, pressure, and drilling increment per rotation are accurately derived. The discrete distribution characteristics of drilling pressure and torque obtained through along-drill monitoring during the rotary cutting drilling process are also analyzed.

The rock-cutting probing teaching experimental platform comprises several systems, including the electrical control system, hydraulic system, oil pump transmission system, along-drill monitoring system, and human–machine interaction interface. The equipment’s control system employs a programmable logic controller to achieve integrated control of drilling, data acquisition, storage, and real-time display. High-precision drilling pressure and torque sensors are utilized for real-time monitoring, as they offer a wide measuring range, high accuracy, excellent stability, robust signal strength, and wireless reception capability. The major feature is the capability to control the load and drilling speed of the rock mechanics parameter probe without interference between the two control modes. The dynamic display of drilling speed, rotation speed, drilling pressure, torque, and other test parameters on the digital display window, plotted against time and displacement, provides a real-time depiction of data values for generating relationship curves between any two test parameters. At different drilling speeds of 300 and 400 rpm, the torque gradually increases as the drill bit initially penetrates the rock formation. As the drilling process continues, the torque remains relatively constant with drilling depth, forming a nearly straight line. A higher drilling speed correlates with greater monitored torque of the drill bit. However, when the rotation speed is set at 450 and 500 rpm, torque exhibits a discrete distribution with drilling depth under different drilling speeds, with the discrete distribution becoming more pronounced at higher rotation speeds. Under varying rotation or drilling speed, the relationship curve between drilling pressure and torque approximates an overlapping state, indicating a proportional relationship between drilling pressure and torque. According to its discrete characteristics, the drilling and rotation speeds can be adjusted in real time to minimize errors arising from instrument and drill rod vibrations. During the rotary cutting drilling process, the relationship curves between drilling pressure and torque exhibit nearly linear overlap, irrespective of drilling speed and rotation speed. Both drilling pressure and torque increase linearly with drilling increment per rotation, and the conclusions drawn are largely consistent with indoor test results.

The equipment effectively addresses the challenges of in-situ testing of rock properties and provides a reliable experimental basis for investigating rock-cutting characteristics. Moreover, the equipment is versatile, finding utility not only in scientific research, exploration, and design for obtaining engineering rock mechanics parameters but also in the educational fields of civil engineering, mining engineering, and engineering geology. This versatility underscores the considerable application value of the system.