As seamless steel pipes, being made of iron-based materials, are prone to electrochemical corrosion in their operating environment, it is essential to employ corrosion protection measures such as coatings and cathodic protection to extend their service life and ensure safety.

NPR rock bolt steel is a new type of reinforcing steel material, also known as negative Poisson's ratio. It possesses exceptional mechanical properties such as high constant resistance, large deformation, energy absorption, and impact and explosion resistance. Under tension, the material expands laterally within its elastic range; conversely, under compression, it contracts laterally. Traditional PR materials will break after reaching their ultimate load, while NPR structures can undergo large deformations without breaking after reaching a constant resistance value. Compared to PSB and HRB reinforcing bars, NPR rock bolt steel, due to its non-magnetic, high-strength, high-toughness, and highly uniform elongation characteristics, and its ability to adapt to large deformations, has broad application prospects in energy mines, transportation tunnels, earthquake-resistant buildings, and bridge engineering.

Self-drilling anchors and hollow grouting anchors differ significantly in their working principles.

1. Working Principle of Self-Drilling Anchors: Self-drilling anchors, also known as self-propelled anchors, rely on their own drilling ability to directly penetrate the soil or rock. During drilling, the anchor's special structural design allows it to gradually insert into the strata without the need for pre-drilling. The friction of the anchor and the bonding properties of the anchoring material work together to fix the anchor in the soil or rock layer. After construction, prestressing is applied to generate tensile stress in the anchor, compressing the surrounding soil or rock, thus achieving the anchoring effect.
2. Working Principle of Hollow Grouting Anchors: Hollow grouting anchors employ a different approach. The core of their design lies in the cavity inside the anchor. During construction, a hole is drilled first, then the anchor is inserted into the hole, and grout is injected into the surrounding soil or rock through the hollow portion. The grout forms a dense bonding layer between the borehole wall and the anchor rod, enhancing the anchoring force. This method not only solidifies the bond between the anchor rod and the soil but also improves the overall integrity of the soil, thus enhancing the anchoring effect.

Advantages and Disadvantages of Self-Drilling Anchor Rods
Advantages: Fast construction speed, eliminating pre-drilling time; simple equipment, easy to operate on-site; strong adaptability, capable of construction in confined spaces; does not rely on large amounts of grout, reducing construction material costs.
Disadvantages: Significantly limited by geological conditions, unsuitable for loose or fractured soil layers; prestress control is more difficult, potentially affecting the anchoring effect; drilling difficulty increases in hard rock or hard soil layers, raising construction costs.

Advantages and Disadvantages of Hollow Grouting Anchor Rods
Advantages: Adaptable to complex geological conditions, effectively improving borehole wall structure; grouting enhances the bonding and integrity of the anchor body, improving the anchoring effect; good adaptability, suitable for various soil and rock layers; allows for long-distance, multi-point grouting, enhancing overall stability.
Disadvantages: The construction process is complex and takes a long time; it requires high-level construction equipment and technology; the quality control of the grout affects the anchoring effect and requires strict management; the cost is relatively high, especially in large-scale projects.