An anchor drill is a specialized drilling device used for drilling anchor holes in geotechnical engineering. It is widely used in mining, tunneling, slope engineering, and water conservancy projects, and is essential for ensuring structural stability and construction safety. Its core function is to drill anchor holes that meet design requirements in rock, soil, or mixed formations. Anchor rods (such as metal rods or fiberglass rods) are then installed in the holes and an anchoring agent (such as cement slurry or resin) is injected. This secures the anchor rods to the surrounding rock and soil, forming an integrated "anchor-anchor-rock and soil" support system. Ultimately, this system prevents rock and soil collapse and landslides (such as tunnel roof collapse and slope instability), controls rock and soil deformation (such as surrounding rock displacement in mining areas), and improves the bearing capacity of engineering structures (such as strengthening water conservancy dams and foundation pit sidewalls).

   I. Core Operating Principles of Anchor Drilling Rigs (General Process)

   Regardless of the type of anchor drilling rig, the basic operating principles revolve around three core steps: power-driven drill rotation, axial pressure-driven formation crushing, and hole cleaning using a slag removal system. The specific process is as follows:

   First, power transmission: The power unit (pneumatic, hydraulic, or electric motor) converts power into torque, which drives the drill pipe and drill bit through the drive shaft. Next, axial pressure is applied: The propulsion mechanism (outriggers, guide rail cylinders, and air cylinders) applies axial pressure to the drill bit, forcing the drill bit into the formation. Next, formation crushing occurs: The rotating drill bit (select the appropriate type depending on the formation) breaks the rock or soil into rock or soil debris through cutting, impact, or grinding. Finally, slag removal and hole cleaning occur: The slag removal system removes the debris from the hole (pneumatic drills use "compressed air slag removal," hydraulic or electric drills use "air-water combined slag removal" or "slag removal"). "Mud removal" (debris removal) prevents debris from clogging the hole. Finally, hole depth control is performed using a depth gauge (such as a dial or sensor) on the drill body to ensure the drilling depth meets the design requirements. Upon completion, the drill tool is removed.

   II. Main Classifications of Anchor Drilling Rigs (Classified by Three Major Dimensions)

   Anchor drilling rigs can be classified in various ways, with the core classification based on power source, structure, and applicable strata. Different types of equipment are suitable for different engineering scenarios.

  1. Classification by Power Source (The Most Core Classification)

   ① Pneumatic anchor drilling rigs: Powered by a pneumatic motor and driven by compressed air. They offer excellent explosion resistance, simple structure, low cost, and light weight, but they have low power and efficiency, and require an air compressor. They are primarily suitable for use in underground coal mines (high-gas environments, where explosion protection is mandatory) and small tunnels.

   ② Hydraulic anchor drilling rigs: Powered by a hydraulic motor and driven by hydraulic oil. They offer powerful power, high torque, and high drilling efficiency, making them suitable for hard rock formations. However, they are complex and expensive, requiring a hydraulic power station. They are commonly used in metal mines, hard rock tunnels (such as railway tunnels), and deep hole drilling operations.

   ③ Electric anchor drill rigs: Powered by a three-phase asynchronous motor or DC motor, they offer advantages such as low noise, environmental friendliness (no smoke or oil pollution), and low energy consumption. However, they require an external power supply and have poor explosion resistance (special design is required for explosion-proof applications). They are suitable for use in non-explosion-proof environments, such as subway tunnels, surface slopes, and foundation pits.

   ④ Internal combustion anchor drill rigs: Powered by a gasoline or diesel engine, they offer high maneuverability and require no external power supply. However, they are noisy, polluting, and fuel-intensive, and have poor explosion resistance. They are primarily used for temporary surface projects, such as emergency slope reinforcement and in areas without power or gas sources.

   2. Classification by Structure

   ① Handheld anchor drill rigs: Small and lightweight (typically between 5 and 15 kg), they are manually operated and are only suitable for shallow holes (≤ 2 m deep) and soft soil and rock formations, such as small foundation pit support projects.

   ② Outrigger anchor drill rigs: Equipped with retractable outriggers (pneumatically or hydraulically powered), these outriggers support the machine body to provide axial drilling pressure. They offer superior stability compared to handheld models and are suitable for medium- to shallow-hole operations (2 to 5 m deep). They are commonly used in applications such as initial tunnel support and mine excavation.

   ③ Rail-mounted anchor drill rigs: The machine body is mounted on a rail (or drill rig), which allows for precise advancement and positioning of the drill tool. They offer high drilling depths (5 to 20 m) and high accuracy, making them suitable for deep-hole anchor bolting and cable anchor holes (cable anchors are thicker anchors used for stronger support), such as in slope construction and large tunnels.

   ④ Vehicle-mounted anchor drill rigs: These drill rigs are integrated into construction vehicles (such as crawlers or trucks). They offer high mobility and automation, making them suitable for large-scale operations, such as roadbed slope reinforcement and open-pit mine slope projects.

   3. Classification by applicable strata

   ① Soft rock/soil anchor drill rigs: These drill tools primarily utilize a "cutting + crushing" method. The drill bits are typically alloy-toothed and are equipped with a spiral drill rod (to facilitate slag removal). They are suitable for formations such as clay, sand, and weathered rock.

   ② Hard rock anchor drill rigs: These drill tools primarily utilize an "impact + rotary" method and are equipped with high-hardness drill bits (such as diamond composite drill bits and ball-tooth drill bits). They are suitable for drilling in hard formations such as granite and quartzite.

  III. Typical Application Scenarios for Anchor Drilling Rigs

   Anchor drilling rigs are primarily used in geotechnical reinforcement and support projects, as follows:

   In mining projects, they are commonly used in underground coal mine excavation faces, metal mine stopes, and mine tunnels. Pneumatic (explosion-proof) and hydraulic anchor drills are commonly used. Their primary function is to support roof and sidewalls and prevent surrounding rock collapse. In tunnel and underground engineering projects, such as railways/ Hydraulic outrigger or rail-mounted anchor bolters are commonly used in highway tunnels, subway tunnels, and underground pipeline corridors (for initial support) to reinforce tunnel surrounding rock, control tunnel deformation, and ensure construction safety. Vehicle-mounted or rail-mounted hydraulic anchor bolters are used in slope engineering projects, such as roadbed slopes, foundation pit slopes, open-pit mine slopes, and mountain slopes, to prevent landslides and collapses and protect surrounding buildings and roads. In water conservancy and construction projects, electric or hydraulic anchor bolters are often used for operations such as dam reinforcement, high-rise building foundation pit support, and underground garage sidewall reinforcement. They improve the stability of dams and foundation pits and resist lateral soil pressure.

   Anchor bolters are the "pivotal equipment" of geotechnical engineering support systems, and their performance directly determines the quality of anchor support and project safety. When selecting a model, it is necessary to consider three core factors: the project scenario (explosion-proof/non-explosion-proof), the formation hardness (soft rock/hard rock), and the drilling parameters (depth/diameter) to choose the appropriate model. At the same time, through standardized operation and regular maintenance, ensure the efficient and safe operation of the equipment.