Views: 0 Author: Site Editor Publish Time: 2025-10-10 Origin: Site
In the process of foundation construction, the drilling depth and diameter of the rotary drilling rig are the key indicators determining the suitability of the project. These two capabilities are not fixed values but are the result of the combined effect of equipment model, geological conditions and construction techniques. The core logic lies in "matching as needed" rather than pursuing the extreme.
Rotary drilling rigs are typically classified into three types based on weight and torque: small, medium, and large. Each type corresponds to a different range of drilling capabilities. The small rigs are lighter in weight and have lower torque, suitable for drilling holes with diameters of less than 1.5 meters and depths of less than 30 meters. They are commonly used in rural self-built houses and for small municipal pile foundations. The medium rigs have a moderate weight and stronger torque, allowing the drilling diameter to expand to 1.5-3 meters and the depth to reach 30-60 meters. They are commonly used in urban residential buildings and ordinary factories. The large rigs weigh over 50 tons and have abundant torque, enabling the drilling diameter to exceed 3 meters and the depth to extend to over 60 meters. Some super-large equipment can even achieve drilling depths of over 100 meters, mainly serving major projects such as cross-river bridges and super-tall buildings.
The core components of the equipment directly affect the upper limit of its capabilities. The length and strength of the drill pipe determine the depth of the drilling. Extremely long drill pipes require high-strength materials to prevent bending and breaking during construction; the type of drill bit matches different requirements. Spiral drill bits are suitable for soft soil drilling, while rock-bit drill bits are used in hard ground layers, but they limit the drilling diameter. It is worth noting that when the drilling depth exceeds 100 meters, the drilling efficiency drops sharply and the accident risk significantly increases. Usually, other construction methods need to be considered.
Geological conditions are the natural limitations that determine the actual drilling capacity. In soft soil layers such as silt and silty clay, the drilling resistance is low, theoretically allowing the drill to approach the maximum depth specified by the equipment design. However, the hole walls are prone to collapse, and stabilizing techniques such as mud wall protection are needed to maintain stability. Otherwise, the drill hole diameter needs to be reduced. In hard soil layers such as granite and moderately weathered rock, the drilling resistance increases sharply, and torque becomes the main constraint. Even with medium-sized drilling rigs, the actual drilling depth may be reduced by more than half compared to soft soil layers. If encountering complex strata such as "upper soft and lower hard" layers or karst caves, both depth and diameter need to be conservatively designed. In such cases, it is necessary to address the stratum defects first before proceeding with the construction.
Complementary technologies and construction techniques can effectively expand the capacity boundaries. The mud wall protection technology forms a mud skin on the hole wall to enhance stability, allowing the drilling diameter in soft soil layers to be closer to the design value. The casing-following technique is used for extreme strata such as quicksand layers. By synchronously pushing in steel casing pipes to support the hole wall, it can break through the conventional depth limitations. The operational details during construction are also important. For example, in hard rock strata, drilling needs to be carried out slowly. If the speed is increased too quickly, it will lead to overload of torque and interruption of the drilling process. A drill bit that does not match the stratum will not only affect the depth but also damage the equipment.
In engineering practice, the selection of drilling capacity always revolves around the requirements. For small-scale projects such as rural self-built houses, the depth and diameter requirements are not high, and a small drilling machine can meet the needs, without the need to overly pursue large equipment to avoid cost waste. In urban 10-30 story residential buildings, medium-sized drilling machines combined with foundation casing technology can achieve an appropriate drilling scale, balancing efficiency and economy.
For large-scale infrastructure projects, more powerful equipment and technical combinations are required. For main piers of bridges across rivers, the pile foundations need to bear huge loads and require large drilling machines combined with ultra-long drill pipes to deal with hard rock strata beneath the riverbed; for onshore wind power foundations to resist wind loads, larger-diameter drilling holes are needed, and large drilling machines can efficiently complete the construction. For special large-scale projects such as cross-sea bridges and nuclear power projects, super-large drilling machines need to be combined with customized mud circulation systems or complete pipe technologies to achieve ultra-deep and large-diameter drilling in complex strata.
The drilling capacity of a rotary drilling rig is the result of the combined effect of the equipment's hardware, geological conditions, and construction techniques. When choosing a drilling rig, one must first clarify the load requirements of the project and the characteristics of the strata, and then match the corresponding model of the drilling rig and auxiliary technologies. Only in this way can efficient construction be achieved while ensuring safety and quality. With the development of intelligent technology, the new generation of rotary drilling rigs can automatically adjust the construction strategies by monitoring parameters in real time, making the capacity adaptation more precise. This provides more reliable technical support for various foundation projects.
