Rock drilling projects have to face a variety of complex rock geological structures. Some rocks have undergone long geological structure changes, natural weathering, and human activities, resulting in various geological defects. In the natural state, these rocks may be in a relatively stable equilibrium state, but when they are affected by natural disasters or large external forces such as drilling and blasting during engineering construction, the original stress field of the rock will be redistributed, thereby making the rock the deformation, collapse, landslide, ground subsidence, and other geological disasters will directly affect the progress of the project and the safety of personnel. Therefore, in engineering construction, it is necessary to use a rod that can withstand high tensile stress to drill and embed in the rock mass to adjust and improve the rock’s strength and self-stabilization performance. This construction is called anchoring engineering. The member tool used is the anchor.
Development of a self-drilling anchor systems
Self-drilling anchor systems are one type of many anchor drilling tools. At the end of the 1980s, in response to the slow construction process caused by complex strata in large-scale underground projects, Austrian Maishi Rock and Soil Anchor Tools Co., Ltd., which specializes in the development and sales of rock and soil anchoring technology and special tools, launched the NATM and designed a new type of anchor drilling tool that integrates drilling, grouting, and anchoring functions to ensure rapid anchoring in broken rock layers, soft rock soil layers, and complex geological structures. Because it is more efficient and easier to operate than the previously used casing wall anchor drill, it will soon be popularized and applied in large-scale engineering projects.
In 2002, Atlas Copco of Sweden acquired Maishi Rock and Soil Anchor Tools Co., Ltd. of Austria and established Atlas Copco MAI Gmbh. Since then, with the continuous deepening of the construction field’s understanding of the role of rock anchoring and mechanism, the application field and market demand for self-drilling anchor systems have continued to grow and soon became a new type of anchor drilling tool with high-quality, high-efficiency, and complete functions. Now, Atlas Copco MAI Gmbh not only introduces a large number of self-drilling anchor systems to the market but also mass-produces supporting hollow grouting bolts, GFRP bolts, Swellex expansion bolts, and high-pressure grouting equipment, forming a comparative a complete production system of geotechnical anchoring tools.
Self-drilling anchor systems combine drilling, grouting, and anchoring functions, and compared with the traditional anchoring system, it has the characteristics of easy installation, applicable to rock formations with various geological conditions, and applied to rock and soil and rock anchoring in a variety of engineering fields.
Application fields of self-drilling anchor system
In railway construction projects, it can meet the safety and fast anchoring construction of complex geological structure section tunnels and apply to over-advance support of tunnels and rescue treatment of geologic disasters, as well as fast anchoring of loose and broken rock section of the road slope. Usually, the anchoring depth is 4-10 meters.
In highway projects, it can be used for stabilized foundation anchoring of slopes, road moats, and foundation pits, and rapid anchoring of soft and broken rock sections of road slopes. The usual anchoring depth is 20 meters, and the maximum depth can reach 30 meters.
In the underground powerhouse of the hydropower station and the surface anchoring project, it can be used as a small-aperture anchor pile to strengthen the rock mass. It has the characteristics of good tensile and compressive anchoring strength, small displacement, simple construction, and stable supporting structure. The anchoring depth is 10-20 meters.
In the foundation reinforcement project, prestressing can be applied through the matching pad and nut on the full-length waveform or trapezoidal threaded drill rods to make them into prestressing anchors, which are used in the anchoring project of slope stabilization and foundation reinforcement, with an anchoring depth of 15-30 meters.
With the increase in the mechanization of underground drilling and shoveling equipment and the continuous improvement of supervision in engineering construction projects, the requirements for production efficiency and project quality are getting higher and higher. Self-drilling anchor systems are also increasingly used in construction sites such as anchoring support, slope management, pit retaining wall, large underground mine tunnel, and underground projects.
