Interpretation of Core Parameters of Rotary Drilling Rigs: How Torque, Drilling Depth, and Power Affect Construction Efficiency?

        As the core equipment for pile foundation construction, the performance of a rotary drilling rig directly determines the construction progress, hole quality, and engineering cost. Torque, drilling depth, and power, as the three core parameters, are interrelated and work in synergy to collectively influence construction efficiency. The following will elaborate on their parameter definitions and specific impacts on construction.

        Torque is the torsional force output by the rotary drill string of a rotary drilling rig when driving the drill bit to rotate, with units typically in kN·m. It is crucial for overcoming formation resistance and achieving cutting and breaking of rock and soil. The magnitude of torque directly determines the rig's adaptability to complex formations, thereby influencing drilling speed and hole stability.

        In easily drillable formations such as soft soil and cohesive soil, low to medium torque can meet construction requirements, and torque is not a bottleneck for efficiency at this time. However, in hard formations such as gravel layers, rock layers, and strongly weathered rock layers, sufficient torque is required to break rock and soil and prevent drill bit jamming. If torque is insufficient, the drill bit speed will drop, cutting power will be weak, which not only significantly reduces drilling efficiency but may also cause problems such as hole wall collapse and accelerated drill bit wear, increasing rework costs and construction risks. Conversely, torque parameters matched to the formation can achieve efficient cutting, reduce stop-drilling failures, and improve hole-making efficiency.

        Drill depth refers to the maximum drilling depth that a drill rig can achieve under standard configuration, measured in meters (m). It is divided into maximum drill depth and effective drill depth, which directly determine the equipment's adaptability to different pile foundation depth requirements. The drill depth parameter is not necessarily better when larger; it needs to be reasonably selected in combination with actual engineering requirements. Otherwise, it may cause performance waste or construction restrictions.

        For shallow foundation projects (such as small building pile foundations and municipal pipeline pile foundations), it is sufficient for the drill depth to meet the foundation design requirements. Over-pursuing a large drill depth will increase equipment procurement and operating costs. However, for deep pile foundation projects such as high-rise buildings and bridges, insufficient drill depth will result in an inability to complete construction tasks, requiring equipment replacement or measures such as secondary drilling, which seriously delays the project schedule. In addition, drill depth is also related to the number of drill rods and drill rig stability. During deep drilling, the rigidity of the drill rods and the stability of the machine body need to be ensured; otherwise, it will affect the verticality of the borehole and indirectly reduce construction efficiency.

        Power typically refers to the rated power of the drilling rig's engine, measured in kW. It serves as the core energy source for driving torque output, drill pipe lifting and lowering, and machine body movements, directly determining the rig's working intensity and continuous operation capability. Power has a positive correlation with torque (at a fixed speed, greater power results in stronger torque output) and also affects the equipment's working rhythm. 

        When power is insufficient, the drilling rig not only experiences limited torque output but also reduced drill pipe lifting/lowering speed and drill bit rotation speed, slowing down the overall working rhythm. This is particularly evident during deep drilling and heavy-load operations, where issues such as engine overload and shutdown for cooling are prone to occur, interrupting the construction process. Sufficient power ensures the drilling rig can operate continuously and stably under high-load conditions, enhancing the coordination efficiency of drill pipe lifting and drill bit cutting, and shortening the single-hole construction cycle. It should be noted that higher power does not necessarily mean greater economy; excessively high power increases fuel consumption and equipment wear. Therefore, energy balance needs to be achieved by considering torque requirements and drilling depth demands.

        Torque, drilling depth, and power are not independent of each other but form a collaborative system of 'energy-capability-range'. Power provides energy support for torque, torque determines the drilling capability suitable for the formation, and drilling depth limits the construction range. The higher the matching degree among the three, the higher the construction efficiency.

        In actual construction, parameters need to be optimized in combination with formation conditions and pile foundation design requirements: For hard formations, equipment with high torque and sufficient power should be prioritized, while ensuring that the drilling depth meets the design requirements. For soft formations, torque and power output can be appropriately reduced to balance efficiency and economy. For deep drilling, sufficient power and torque need to be matched on the premise of ensuring drilling depth to avoid affecting construction stability due to excessive load. In addition, the hydraulic system of the equipment and the quality of the drill string will also indirectly affect the performance of the parameters, so comprehensive consideration is needed to maximize construction efficiency.