The Four Major Construction Techniques of Rotary Drilling Rigs Have Been Summarized for You!

Foundation Drilling

The four major construction technologies are dry hole forming technology, slurry static pressure technology, casing technology, and concrete wall-making technology.

The rotary drilling rig is a construction machine suitable for drilling operations in construction foundation projects. It is widely used in foundation construction projects such as municipal construction, highways and bridges, high-rise buildings, etc. It is suitable for dry (short spiral) or wet (rotary bucket) and rock formation (core drill) drilling operations with different drilling tools. The drilling rig has the characteristics of large installed power, large output torque, large axial pressure, flexible maneuverability, high construction efficiency, and multi-function.

Rotary drilling rigs are adapted to the soil geological conditions in most areas of our country and have a wide range of uses. They can meet the needs of bridge construction, foundations of high-rise buildings, and other projects. At present, rotary drilling rigs have been widely used in various bored pile projects. Therefore, it is of great significance to technically discuss the construction technology of rotary drilling rigs.

Dry Hole Forming Process

1. Characteristics of Dry Pore Formation

Because the geology is solid and dense, no other auxiliary hole-forming materials or equipment are needed during drilling, and it can be drilled directly. The dry hole forming process is the simplest process in rotary excavation construction, and its characteristics are simple to process and low construction cost.
The dry hole forming process is aimed at hard plastic and solid geology and can be used with or without groundwater, but it is best to have no groundwater. Before adopting the dry hole forming process, it is necessary to understand the geotechnical and groundwater conditions to ensure that the hole does not collapse.

2. Advantages and Disadvantages of Dry Hole Formation

Disadvantages of dry drilling: Although there is no need to worry about hole collapse, due to the loss of lubrication, softening, cooling, and buffering of water and mud, the drilling resistance of some formations increases, especially in dense dry soil and coarse sand layers, and slag collapse occurs. Difficulty, aggravating drill tooth wear, and drill pipe vibration.
Advantages of dry drilling: In addition to the simple process and low construction cost, under certain geological conditions, due to the softening of mudstone when exposed to water and lubrication of mud, slippage, tooth jamming, and lake bottom phenomena will occur. Dry pore formation can eliminate the above phenomena and improve shearing and crushing efficiency.

Mud Static Pressure Process

Mud Static Pressure

The mud pressure supports the hole wall and prevents construction quality problems and accidents such as hole shrinkage, hole collapse, and buried drilling.

Three Indicators of Mud

1. Mud pressure

2. Mud wall protection

3. Sand content

4. Three-piece mud set: mud hydrometer, mud viscometer, and sand content meter.

Other Functions of Mud

Mud-specific gravity, viscosity, and sand content are important parameters in mud action and are the guarantee for protecting the quality of hole formation and the safety of equipment personnel. But in addition to supporting and wall protection, mud also has many other functions, which play different roles under different geological and groundwater conditions, including suspension, lubrication, cooling, shock absorption, buoyancy, softening, etc.

Mixing Ratio of Pulping Materials

1. Mud mix ratio: bentonite is used as the slurry wall protection process, and the raw materials are water, bentonite, cellulose, and caustic soda; the mix ratio is 100:8:0.05~0.1:0.1~0.5.

2. Solid-free drilling fluid: Polymer mud is a synthetic electrolyte based on a variety of monomers or copolymers, and is an organic polymer material. Common polymer mud product forms are divided into solid and liquid. The liquid form is mainly inverse emulsion material; the solid form is divided into granular and powdery; according to the dissolution speed, it is divided into ordinary type and instant type. Polymer mud becomes a translucent paste after being fully dissolved in water. The dosage is very small. It is a light mud with a specific gravity generally less than 1.08. It has a high viscosity and strong penetration. It can effectively adjust the rheology of the mud and quickly settle drilling cuttings in the hole. , a thin transparent paste protective layer is formed around the hole wall through penetration and adhesion, which can effectively increase the drilling speed, prevent well leakage and hole wall collapse, reduce drilling tool wear, and maintain well-diameter rules.

Different Types of Mud Applications

Due to the diversity of geological types, changes in layer thickness and burial depth, and the abundance of groundwater levels, different geology and groundwater requirements require different mud.

Casing Process

1, Steel Casing

1. The function of the casing: is to protect the safety of pile holes, equipment, and personnel. The length of the casing is determined according to the rock soil and groundwater conditions. Generally, the length of the casing is between 2M and 4M, and the diameter of the casing is usually 200MM larger than the pile diameter;

2. Lower casing method: reamer, drill bucket, special tooling, vibrating hammer;

3. Control requirements: verticality and center deviation of the buried casing.

2, Segmental Casing

The casing driver, pipe scrubber, or full-rotation drilling rig, as well as the vibrating hammer bury the casing, and the rotary drilling bucket drills the pipe in the casing. The casing technology can replace the slurry wall protection static pressure technology and is suitable for bite piles, inclined piles, unstable strata, and outdoor construction, limited resources (no water and electricity), urban environmental protection construction, etc.

1. Casing function: The same strength supports the hole wall to prevent hole collapse; the length of the casing enables forced guidance to prevent deviation holes; the sealing of the casing protects groundwater.

2. Casing structure:

① Drive plate: The drive plate is connected to the bottom of the power head drive sleeve through bolts to achieve structural transition, and its function is to transmit torque and pressure.

②Connecting plate: The connecting plate is connected to the driving plate through a pin, and a pin is reserved for connecting with the casing driver.

③ Casing driver: The upper part of the casing driver is connected to the connecting plate through a pin, and the lower part is connected to the casing. The diameter of the casing driver must match the diameter of the casing; the lower part of the casing driver has a positioning groove and a stop to facilitate docking with the casing. The function of the sleeve driver is to transmit torque and pressure to the sleeve and sleeve shoe.

④ Casing: The upper end of the casing can be connected to the casing driver or casing through the pin, and the lower end of the casing can be linked to the casing or barrel shoe.

⑤Connecting pin: The tapered ring and the wire ring are fixed on the casing. After the casing is docked and positioned, the supporting ring is installed with a sealing ring and twisted into the wire ring and the tapered ring to realize the connection.

⑥Column shoe: The front end of the cylinder boot is inlaid with alloy drill teeth. Through rotation and axial pressure, it can circumferentially cut various strata and rocks, reduce the resistance of buried casing, and improve the casing drilling ability.

3. Casing running methods: casing driver, pipe rubbing machine, full-rotation drilling rig

4. Applicable working conditions: urban construction, outdoor construction

5. Applicable geology: silt layer, loose stratum, large-sized boulders, unfilled caves, special foundations (biting piles, inclined piles)

Concrete Wall Building Technology

The concrete wall-building process of rotary drilling rigs is not a formal rotary excavation process. This passive safety process lags behind the active safety of mud static pressure and casing processes and has certain operational risks.

1. Concrete Wall-Building Effect

Usually when constructing on plateaus, mountainous areas, backfill soil, and karst caves, due to insufficient or no groundwater, or lack of water resources, when dry hole forming technology is used for construction, deviation holes and partial collapse holes will appear in the holes, and C15 concrete will be backfilled into the holes. , backfill the abnormal parts in the hole, and use a Core barrel to drill the core after the concrete reaches the initial setting strength.

Backfilling concrete into the deviated hole can repair the deviated hole, backfilling concrete into the local collapsed hole position, and locally generating a protective wall layer; backfilling the hollow cave with concrete, filling the karst hole and drilling the guide to prevent the drill from jamming and deviating the hole.

2. Application of Concrete Wall Building

Cave geology
Offset hole
Partial hole collapse

3. Things to Note When Building Concrete Walls

1. Lag: Concrete wall protection has certain advantages when dealing with karst caves and offset holes. However, when dealing with local collapse holes, due to the lag problem, if the drill bucket collapses at the bottom of the hole, it is likely to cause a buried drill. Similar incidents have also occurred in actual construction. ACCIDENT. Therefore, when using concrete wall protection, you should be fully prepared for precautions, fully understand the geology and the conditions inside the hole, and only use this process when you are sure.

2. Cost: Due to the large amount of concrete used, when the contract is signed, the backfill concrete and excess pouring will be borne by Party A’s project department.

3. Construction efficiency: When using concrete wall protection, it takes time to reach the initial setting state, which results in intermittent construction of single holes and reduces construction efficiency.

Preparation for Construction

1. Technical preparation: Before the start of the project, the project chief engineer will organize all construction personnel to conduct technical briefings, put forward specific requirements for key processes, main technical requirements, quality standards, and quality objectives, and conduct pre-job safety training for important personnel.

2. Construction guarantee

①. Before starting work, make preparations for equipment arrival, installation, and debugging.

②. Before drilling, the coordinates of each pile should be reviewed. Only after the review is correct can the measurement and setting-out work be carried out.

③. Prepare water supply, power supply, construction access roads, temporary facilities, and materials in advance according to the overall layout of this bid section.

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