Comprehensive Analysis of Rotary Drilling Rig Construction Technology and Precautions#drill rig tools#
Rotary drilling rigs, indispensable construction machinery in building foundation engineering, are widely used in municipal construction, highway bridges, and high-rise building foundation construction. With their powerful installed capacity, output torque, and axial pressure, rotary drilling rigs exhibit excellent mobility and construction efficiency. Furthermore, when used with different drilling tools, they can easily handle various drilling operations, including dry, wet, and rock drilling. However, to fully utilize the performance advantages of rotary drilling rigs, it is necessary not only to understand their construction technology but also to grasp some key precautions.
I. Construction Preparation
Before rotary drilling rig construction, thorough preparations must be made. This includes collecting site engineering geological and hydrogeological data, familiarizing oneself with the pile foundation engineering construction drawings and drawing review minutes. Simultaneously, a detailed investigation of underground pipelines, structures, and other hazards in the site and adjacent areas is required to ensure construction safety. In addition, the technical performance data of the main construction machinery and its supporting equipment, as well as the inspection and mix proportion tests of the required materials, are also indispensable preparatory work.
II. Construction Machinery and Equipment Rotary drilling rig construction involves various measuring instruments and machinery, such as theodolites, levels, and steel tape measures. These devices must have factory certificates of conformity to ensure stable and reliable performance. Meanwhile, small and medium-sized implements such as mixers, handheld power tools, and welding machines also require strict management to ensure their safe and effective operation.
III. Requirements for Small and Medium-Sized Implements For mixers, the machine body must be firmly and stably installed, and a rainproof operating shed must be erected. All clutches, brakes, wire ropes, and protective covers must be safe and reliable. Operators must be certified and ensure proper grounding. Handheld power tools must be equipped with individual leakage protection devices, and the protective covers must be safe and effective. The outer casing must be grounded or connected to neutral, and the rubber cord must not be damaged. Welding machines and other equipment also require strict management to ensure electrical safety during construction.
In summary, the construction process and precautions for rotary drilling rigs involve multiple aspects, requiring meticulous control from construction preparation to machinery and equipment management. Only by fully understanding and adhering to these requirements can we ensure that rotary drilling rigs exert their due performance advantages in foundation engineering, guaranteeing construction safety and efficiency.
(4) Gas Cylinder Safety Requirements
All types of gas cylinders must be equipped with clearly visible color markings and shock-absorbing rings, and prolonged exposure to direct sunlight is strictly prohibited. The distance between acetylene and oxygen cylinders should be greater than 5 meters, and acetylene cylinders must be equipped with flashback arrestors during use. Hose should be secured with clamps to ensure no leakage. Operators must hold relevant certificates before starting work.#drill rig tools#
IV. Drill Tool Installation and Selection
Drill tools should have sufficient rigidity to remain stable during drilling or other operations, without movement or shaking. Installation should follow the manufacturer's standards. During construction, appropriate rotary drilling rig bits can be selected according to different soil and geological conditions. For example, short auger bits are suitable for cohesive soils above the groundwater level, while core drill bits are suitable for weathered rock layers and cracked rocks.
V. Clear Water Construction Technology The clear water construction technology eliminates the need for mud slurry wall protection during hole formation, relying instead on the mud slurry generated during slow rotary drilling to stabilize the hole wall. During rotary drilling, the drill bit moves back and forth between the bottom of the hole and the ground surface, creating a relatively rough hole wall. This technology enhances the interlocking between the pile and the soil, better reflecting the interaction between the concrete pile and the loess and silty clay.
(2) Site Layout Principles The construction site should be carefully arranged according to the design requirements. First, the site should be leveled, debris removed, soft soil replaced, and compacted to ensure site stability. Next, professional surveying and layout personnel should be organized to accurately mark the pile positions, install cross-shaped protective stakes, and conduct measurement verification and data recording. When planning the driving route, it is necessary to ensure that the access road maintains an appropriate distance from the drilling location to maintain hole wall stability. If the construction site is dry land and the groundwater level is below the original ground level, the site should be leveled, compacted, and debris removed; if the site is located in a shallow water area, the island-building method should be used to ensure the drilling machine is installed securely. Meanwhile, the drilling rig chassis should not be placed directly on unstable backfill to prevent uneven settlement. Furthermore, the placement of the drilling rig should consider the ease of soil removal from the borehole.
(3) Pile Location Layout
Pile location layout is a crucial step in rotary drilling construction. Following the principle of "from the whole to the part," the pile foundation location should be accurately laid out. When laying out the drilling elevation, the elevation data should be checked promptly to ensure accuracy. A total station should be used to accurately lay out each pile point, ensuring that the positional error is within the allowable range specified in the standards.
(4) Drilling Rig Positioning
Before positioning the drilling rig, its performance status should be carefully checked to ensure normal operation. At the same time, attention should be paid to maintaining the stability and safety of the drilling rig.
(5) Steel Casing Installation
Based on accurate layout, steel casings should be installed according to relevant specifications. If drilling is carried out on land, a simple pit-digging method can be used for installation. The horizontal and vertical positions of the steel casing must be accurate, and the perimeter and bottom should be tightly sealed to prevent water leakage, ensuring construction safety and quality.
(8) When installing the steel casing: First, use the control stakes for positioning to mark the drilling position of the drilling rig at the bottom of the pit. Then, lower the steel casing into the pit, using crosshairs to determine its center position, and fine-tune the casing to align its center with the drilling center. Simultaneously, use a spirit level or plumb bob to ensure the steel casing is vertical. Afterward, backfill the steel casing evenly and symmetrically with clay of optimal moisture content, compacting it in layers to achieve optimal density, thus ensuring its verticality and preventing mud loss, displacement, and falling. If the soil layer at the bottom of the casing is not cohesive, it needs to be deepened or replaced, and a 300-500mm thick layer of clay should be backfilled and compacted at the bottom of the pit before installing the casing to prevent leakage and collapse at the bottom. During the compaction process, care must be taken to prevent the steel casing from tilting. In addition, wooden blocks should be symmetrically tied to the top of the casing to prevent it from sliding downwards.
(9) The fabrication and installation of steel casings must follow certain principles.
For steel casings less than 4m in length, steel plates with a thickness of 4-6mm should be used; for steel casings longer than 4m, steel plates with a thickness of 6-8mm should be used. If the steel casing needs to be buried deeper, multiple sections of steel casing can be connected. The connection points must be welded smoothly and meet the requirements for rigidity, strength, and leak prevention. The inner diameter of the steel casing should be slightly larger than the drill bit diameter; the specific dimensions should be selected according to the design requirements. The burial depth must also meet the design and specification requirements. In pile holes in rivers, the steel casing should be buried at a depth of more than 0.5m in hard, dense soil. Its top surface should be 1.5-2.0m above the construction water level or groundwater level and 0.3m above the construction ground surface. Before installation, accurate measurement and layout are required to ensure that the position deviation of the top surface of the steel casing does not exceed 5cm and the slope does not exceed 1%. During installation, a larger diameter drill bit should be used to pre-drill to the elevation of the bottom of the casing. Then, the drill bucket should be pulled out and used to press the steel casing into the predetermined position. Finally, coarse-grained soil should be used to backfill the area around the outside of the casing and compacted.
(10) During drilling, the drilling machine generally uses a clean water drilling process, without the need for mud slurry wall protection.
If groundwater is present and the borehole wall is unstable, wall protection mud or stabilizing liquid can be added into the borehole for wall protection. The following are the basic operations for rotary drilling rig construction:
During clean water drilling, the key switch of the rotary drilling rig should be set to the power position. At this time, its display will show the marking screen of the rotary drilling rig. Then, any key can be pressed to enter the working mode. The first step is to ensure the erection and vertical adjustment of the drilling mast, that is, to move the rotary drilling rig to the specific position of the drilling operation and observe the mast working screen on the display. In this screen, the displacement of the mast in the x-axis and y-axis directions can be monitored in real time.
The mast is raised from transport to working position by operating the electric handle of the rotary drilling rig. During this process, the rig's controller collects signals from the electric handle and tilt sensor. After mathematical calculation, the output signal drives the proportional valve of the hydraulic cylinder, thus achieving closed-loop mast erection control. This ensures the mast is erected smoothly and synchronously. Simultaneously, the system also collects signals from limit switches to protect the mast from tilting during erection.
Before drilling begins, the mast needs to be positioned. Typically, for straight hole drilling, the mast needs to be adjusted for verticality. This adjustment can be done manually or automatically. When the mast deviates from zero by ±5°, the automatic vertical adjustment button on the display can be used; otherwise, manual vertical adjustment is required using the jog button or the electric handle on the left control box. Throughout the process, the operator can monitor the mast's position on the display to ensure it reaches the preset working position.
Furthermore, in some cases, inclined hole drilling may be required. At this point, the operator needs to set the zero position using the automatic positioning button on the monitor before performing the vertical adjustment operation.
During water drilling, drilling operations can be completed directly through the main working interface. Before drilling, ensure the drill bucket is in contact with the ground and record the starting position of the drill bit using the zeroing button. The monitor will then simultaneously display the current drilling position information, including bar graphs and numbers, allowing the operator to monitor the actual drilling position, drilling depth, and hole depth in real time.
During drilling, the operator can monitor the hydraulic system's operating status using virtual instruments on the main interface, including power head pressure, pressurization pressure, and main winding pressure. The drill bit rotates to open the hole using its own weight and pressurization. Short bar graphs display the current drill bit depth, while long bar graphs dynamically show the drill bit's movement trajectory. Simultaneously, the total hole depth is displayed digitally for the operator's reference.
Once the drill bucket is filled with drill cuttings due to rotation and compression, it needs to be lifted to the surface, and the machine should be turned to the location of the waste disposal truck using the rotary operating handle. The drill cuttings are then loaded into the waste disposal truck. After completion, the machine can automatically or manually return to the drilling position, a status confirmed by the return indicator on the display.
Furthermore, during drilling, it is crucial to closely observe and record the borehole geological conditions, including soil layer changes and rock characteristics. This data is essential for subsequent geological analysis and design adjustments. Simultaneously, timely removal of cuttings from the borehole opening is essential to ensure construction safety and environmental protection.
After drilling to the predetermined depth, the drill rod must be lifted, and the borehole depth and loose soil thickness (the difference between the drilling depth and the borehole depth) must be measured to ensure the borehole quality meets design requirements. Finally, a borehole inspection is conducted to confirm that the borehole diameter, depth, and borehole wall quality meet the standards.
Once the borehole reaches the design elevation, a detailed inspection of the borehole depth, diameter, borehole wall thickness, and verticality is required. Any non-compliance should be addressed immediately to ensure borehole quality. The borehole inspection method will vary depending on the specific borehole diameter. For dry boreholes, we can use a heavy hammer to compact the loose soil inside the hole and directly measure using a measuring rope and borehole measuring instrument. If groundwater is present in the borehole, a pump-suction reverse circulation method is required for cleaning, while underwater concrete pouring is used for drilling and measurement. During this process, the viscosity and sand content of the drilling mud must be strictly controlled. Once the borehole quality is inspected and approved, concrete pouring should begin immediately.
Furthermore, borehole cleaning is a crucial step in bored pile construction. Its purpose is to ensure that the quality indicators of the borehole, the thickness of the sediment at the bottom of the hole, the amount of drill cuttings in the circulating fluid, and the mud on the borehole wall all meet the preset quality requirements. We use positive circulation rotary drilling technology for borehole cleaning. The specific steps include: after the borehole is completed, the drill string is raised to a certain height, then new drilling mud with qualified performance indicators is pumped in and positive circulation is maintained for at least 30 minutes. This is to remove sediment from the bottom of the hole and ensure that the mud content on the borehole wall and the sand content of the drilling mud are controlled below 4%. For engineering pile holes, due to the possibility of thick, loose, and easily collapsible soil layers, the final drilling operation cannot be carried out immediately after cleaning the hole. Instead, a reinforcing cage needs to be lowered into the hole, and the grouting pipe needs to be installed before a second cleaning operation is carried out. This ensures that the thickness of the sediment at the bottom of the hole meets the requirements before concrete pouring, thereby ensuring the quality of the concrete column.#drill rig tools#
