For rock and soil layers with good adhesion, dry or clean water drilling techniques can be used without the need for mud wall protection. For loose and prone to collapse formations or underground water distribution, as well as unstable borehole walls, static mud wall protection drilling technology must be used to inject wall protection mud or stabilizing fluid into the borehole for wall protection.
1.The construction process of rotary drilling rig mainly consists of the following seven steps
□ Pile foundation positioning: Based on the leveling points and measurement control network provided by the surveying unit, points are made on the extension line of the axis. During the pile construction process, the on-site measurement control points are checked and effectively protected.□ Buried casing: Align the centerline of the casing with the center of the measured pile position, strictly protect the verticality of the casing, and ensure that its centerline coincides with the center of the pile; After fixing the casing in the correct position, backfill and compact it with clay to ensure its verticality.
□ Pile driver in place: After the drilling rig is installed in place, align the center of the drill bit with the center of the pile position to ensure that there is no hole displacement during construction. (Rotary drilling rigs generally have a locking function after positioning. As long as the drilling rig does not shift as a whole, the drill rod can rotate freely. With the operation of the operator, it will still be aligned with the original pile center.)
□ Drilling: Using a mud box and mud pit in combination, manual (using a mud pump to mix and make mud, using sodium based or calcium based bentonite, and the dosage can be converted according to the mud density requirements or controlled by a mud density meter) is used to mix and protect the wall for drilling. The mud density should be determined according to the specific bottom conditions, and the drilling parameters under various geological conditions should be determined based on pile testing and construction experience (the mud density selection range is generally between 1.05 and 1.10); After drilling, check various indicators such as aperture, depth, sediment, and mud density. The biggest advantage of rotary drilling is that the mud can be reused repeatedly. After the first slurry production, appropriate supplementation can be made in the future
□ Placement of steel cage: Use a crane to vertically lift the steel cage into the hole, place it at the design elevation, and fix it in place.
□ Installation of conduit: Use a crane to insert the conduit. The diameter and length of the conduit should match the depth of the hole, with a distance of 0.3m from the bottom of the hole. The initial pouring amount should ensure that the conduit is buried at a depth of not less than 1m after the concrete has diffused.
□ Pouring concrete: After injecting a certain amount of concrete, use a crane to pull up the pipe to ensure the diffusion and compaction of the concrete, and repeat this process until the top surface. The minimum burial depth cannot be less than 0.5m, and the maximum burial depth can reach 10m or more. This is mainly because rotary excavation construction requires less mud density, less sediment, and a significant weight difference between concrete and mud.
Drilling characteristics of rotary drilling rig
By comparing with traditional drilling pile drivers, we can conclude that rotary drilling machines have significant advantages in the drilling process, and their main advantages are summarized as follows:□ The drilling speed is fast, more than 5 times that of ordinary drilling machines, effectively ensuring the progress of the project. The drill rod of the rotary drilling rig is a telescopic drill rod, which has a fast drilling speed and strong adaptability to different geological conditions, making it widely applicable.
□ Convenient to move, rotary drilling rigs are mostly hydraulic tracked telescopic chassis, which can easily move the rig to the desired position, unlike ordinary drilling rigs that are as cumbersome to move, while ensuring the stability and good maneuverability of the entire machine.
□ Fast positioning speed and high positioning accuracy. Before drilling, align the center of the drill bit with the pile position, and then set the corresponding coordinates as the axis coordinates by the robotic arm. During the construction process, the operator can use advanced electronic equipment in the cab to accurately achieve alignment, allowing the drilling rig to reach the optimal drilling state.
□ The drilling depth and verticality can be automatically detected and controlled. Due to the high degree of automation of the drilling rig itself, the drilling depth and verticality can be controlled by an electronic system and displayed in real-time on the screen. Compared with traditional bored piles, the bearing capacity of rotary excavation piles is significantly improved, and the construction quality of bearing piles is guaranteed.
□ The safety and environmental protection features are prominent. The whole machine adopts full hydraulic transmission, and the leveling and walking displacement of the whole machine are all assisted by hydraulic motors or cylinders. It not only has good overload protection, smooth operation, safety and reliability, flexible and light operation, low vibration and noise, greatly reducing the workload of the operator, but also has safety protection devices such as height limit and boom amplitude limit of the main and auxiliary winches, as well as hydraulic control switches in the cab, which promote civilized construction and safe production; The mud used in the drilling process can be recycled, and the drilling slag can be separated from the mud and transported away by lifting the rotary excavator bucket, reducing pollution and making the construction site relatively clean and tidy.
□ After drilling, there is less sediment. The rotary drilling rig uses static mud to protect the wall during drilling, and the drilling slag is extracted through the rotary bucket, so the amount of sediment is very small; And other drilling rigs discharge drilling debris through the circulation of mud, so it is common to have more sediment.
Rotary drilling rig has the characteristics of high power, fast drilling speed, high degree of automation, flexible and convenient movement, accurate positioning, labor saving, production safety, convenient work, good environmental performance, low noise, high work efficiency, time saving, and reduced construction costs. But it also has some problems caused by its own reasons. Due to the multiple construction process links, if one link is not careful, quality problems may occur. This requires construction and supervision personnel to have a serious work attitude, strong sense of responsibility, good technical level, and rich on-site handling ability.