As a core high-efficiency construction technology for vertical shafts in underground engineering and mine construction, raise boring drilling differs from conventional top‑down drilling by adopting reverse upward rock breaking and shaft forming from bottom to top. It is mainly used for excavating mine raises, blind shafts, ventilation shafts, drainage shafts, and vertical connecting roadways in large‑scale underground projects. This process features high mechanization and automation, minimal surrounding rock disturbance, and significantly improved construction safety and operational efficiency compared with traditional manual shaft sinking. Its advantages are particularly prominent in the construction of deep shafts and steeply inclined shafts. At present, it has been widely adopted in coal mining, metal mining, water conservancy and hydropower, underground transportation, underground space development, and other engineering sectors.

According to shaft forming mechanisms and rock breaking modes, mainstream raise boring technologies are currently classified into full‑face raise boring and core barrel raise boring. Both feature mature technical systems, distinct equipment configurations, and different application scenarios and construction efficiencies. Their technical principles, construction procedures, and technical characteristics are detailed below.

1 Full‑Face Raise Boring Technology

Full‑face raise boring is the dominant technology for large‑diameter and large‑scale vertical shaft construction. Its core characteristic is that the drill bit cuts and breaks rock across the entire shaft section in one pass without retaining a central core, resulting in regular shaft profiles, strong construction continuity, and a wide adaptable diameter range. It is the preferred solution for deep ventilation shafts, ore passes, and large blind raises. Based on the rig force structure, drilling pressure application method, and process flow, it is divided into pull‑up and jack‑up processes.

1.1 Pull‑Up Full‑Face Raise Boring

Pull‑up raise boring is the most widely applied and technically mature mainstream process in engineering. It is suitable for medium‑to‑deep shafts, large diameters, and medium‑hard to hard intact or fractured rock formations, and is highly recognized in the industry for shaft accuracy and operational stability.

Standard Construction Procedure:

1. A small‑diameter pilot hole is drilled at the shaft collar from top to bottom and holed through to the lower roadway, forming a channel for drill string lowering and cuttings discharge.
2. The raise boring rig is installed on the surface. The drill string is lowered through the pilot hole to the lower roadway, where the large‑diameter reaming bit is assembled and connected.
3. The rotary mechanism of the rig provides cutting torque, and the hydraulic hoisting system tensions the drill string upward to generate stable axial bit pressure. The roller cutters on the bit break full‑face rock through combined extrusion, shear, and impact action.
4. Low‑pressure clean water or compressed air is used for cutter cooling, dust suppression, and cuttings conveyance. Rock cuttings fall into the lower roadway under gravity and are removed centrally by mechanized equipment.

Core Technical Advantages:

The drill string features a simple structure, high reliability, and low failure rate. Shaft verticality is precisely controlled by the pilot hole, ensuring strong controllability of borehole deviation. Cuttings discharge relies on gravity fall, making the system simple and efficient.

Through multiple generations of technical iteration, the maximum reaming diameter of this process can reach 7 m, and drilling depth has achieved a kilometer‑level breakthrough. Its lithology adaptability covers soft to extremely hard rock formations. Technologies such as intelligent monitoring, measurement while drilling (MWD), and automatic deviation correction have been gradually popularized, greatly improving the safety and efficiency of deep shaft construction.

1.2 Jack‑Up Full‑Face Raise Boring

Jack‑up raise boring is a pilot‑hole‑free raise construction process with high equipment integration. It eliminates the need for pre‑constructed surface pilot holes, reduces preliminary procedures, and offers strong mobility and flexibility. The drill bit is directly mounted on top of the rig, and axial bit pressure is applied by upward jacking via the built‑in hydraulic cylinder of the host, combined with rotary cutting to achieve rock breaking.

During construction, cuttings are collected into a side slag area of the rig through a special slag catching and diversion device. Cooling medium (water or compressed air) circulates and discharges along diversion channels, realizing integrated rock breaking, cooling, and slag removal. Constrained by hydraulic jacking stroke and bearing capacity, this process provides relatively low overall bit pressure and weak shaft wall stability control. It is mainly applicable to shallow shafts, well‑integrated rock formations, and special scenarios where pilot hole construction is unfeasible. It is commonly used for simple projects such as small emergency shafts and shallow connecting shafts, and is unsuitable for deep shafts, large diameters, or fractured and complex rock formations.

2 Core Barrel Raise Boring Technology

Core barrel raise boring is a refined, lightweight special raise process that adopts annular cutting with a central retained core. It fulfills dual functions of shaft forming and geological coring, serving as an important technical solution for construction in sections with integrated exploration and mining and complex geological conditions.

Originating in Europe and improved through domestic equipment upgrades, this technology has been widely used in small‑to‑medium diameter, shallow‑to‑medium depth shafts in soft to medium‑hard rock formations due to its lightweight design, low energy consumption, strong space adaptability, and low comprehensive cost. It can retrieve continuous and intact core samples, providing high‑precision basic data for surrounding rock classification, rock mass structure evaluation, hydrogeological analysis, and support design. It is suitable for mine exploration raises, small ventilation shafts, pipeline shafts, and similar scenarios.

2.1 Equipment Composition and Installation Process

The system adopts a fully suspended structure, requiring no surface fixed foundation or large underground concrete base, making it adaptable to narrow and low underground working spaces. Core equipment includes an annular cutting bit, drive motor, reduction mechanism, hydraulic core breaker, hoisting system, cable follower, and integral suspension mechanism.

The preliminary construction procedure is similar to that of the pull‑up process: a small‑diameter through pilot hole is first drilled, a steel wire rope is lowered from the surface to the lower roadway, and the rig and cutting assembly are suspended and installed as a whole. Installation is rapid with low requirements for underground space, highlighting convenient construction.

2.2 Rock Breaking and Core Breaking Mechanism

High‑strength cemented carbide cutting teeth are arranged circumferentially on the bit. The motor drives the bit to rotate via a reducer, realizing annular slot cutting and hole forming while retaining a continuous cylindrical core at the shaft center. After drilling to the designed footage, lateral thrust is applied via a hydraulic core breaker. Combined with core self‑weight and stress concentration, core fracture is achieved. The broken core and cutting cuttings fall together into the lower roadway for centralized mechanical or manual cleaning.

This process causes minimal disturbance to surrounding rock, produces regular and high‑integrity shaft walls, significantly reduces the difficulty of subsequent bolt‑shotcrete support, and improves the long‑term stability of the shaft.

2.3 Key Technical Parameters and Lithology Adaptability

The process features high standardization of parameters and clear adaptability. Core indicators are as follows:

● Common annular cutting diameters: 1.0 m, 1.2 m, and 1.5 m, meeting the construction needs of small‑to‑medium diameter shafts.

● Maximum drilling depth: up to 350 m, with the limit depth controlled by winch rope capacity, cable conveying length, and suspension system stability.

● Adjustable bit line speed in multiple gears to suit cutting conditions of different lithologies.

● Winch equipped with dual high and low speeds: low speed ensures stable drilling, while high speed enables rapid lifting of drilling tools, allowing controllable construction rhythm.

Lithology adaptability is mainly for soft to medium‑hard rock, with bit pressure precisely matched to rock mass strength. Drilling efficiency varies noticeably in typical strata, while overall construction continuity and stability are favorable, supporting refined shaft forming under complex geological conditions.

2.4 Technical Application Characteristics and Engineering Value

Verified through long‑term overseas engineering practice, such equipment features high annual effective footage per unit and stable operational reliability, and has been applied on a large scale in mines and underground projects across multiple European countries. The domestic version further optimizes lightweight and intelligent performance with stronger space adaptability. It delivers dual value of shaft construction and geological exploration, serving as an important supplement to full‑face raise boring. It possesses distinct promotion advantages in small‑to‑medium shafts and shallow‑to‑medium depth shafts under complex geological conditions.

3 Comprehensive Process Comparison and Technical Development Trends

At present, raise boring technology is generally developing toward larger diameters, greater depths, intelligence, low disturbance, and unmanned operation:

● Full‑face raise boring targets major projects such as kilometer‑class deep shafts and super‑large diameter shafts, with continuous iteration of technologies including measurement while drilling, automatic deviation correction, remote centralized control, and intelligent slag removal.

● Core barrel raise boring is evolving toward multifunctional integration, high‑precision coring, and rapid hole forming, with greater emphasis on integrated exploration and mining and synchronous acquisition of geological information.

The two processes complement each other to adapt to various vertical shaft projects, effectively resolving industry pain points of traditional manual raise construction such as high safety risks, high labor intensity, poor forming quality, and low efficiency. They have become the mainstream core technology for vertical shaft construction in modern underground engineering.