## 1 Introduction  
As one of the key technologies in the field of geotechnical engineering, the bolt support system plays an irreplaceable role in the support of roadway and tunnel engineering. Its application has spread all over the world and achieved remarkable engineering results. In terms of mechanical mechanisms, geotechnical anchoring technology realizes the synergistic effect of a supporting system and the surrounding rock medium by optimizing the distribution of the soil stress field, thus significantly improving the structural integrity and overall stability of the rock and soil [1]. This technology not only reflects the transformation of modern geotechnical engineering from passive support to active reinforcement, but it also provides reliable technical support for underground engineering under complex geological conditions. Under the unfavorable geological conditions such as a soft clay layer and a loose sedimentary layer, or in an engineering environment with high requirements for the deformation control of rock and soil mass, the effect of the application of a traditional grouting bolt in roadway and tunnel support reinforcement is significantly limited. The specific performance is as follows: the overall deformation of the bolt exceeds the allowable range, the structural bearing capacity is insufficient, and the waterproof performance is poor. These limitations not only affect the reliability of the supporting structure but also pose a potential threat to the safety of the project, which needs to be solved through technological innovation. However, a large number of experimental data and theoretical studies [2; 3; 4; 5; 6] show that there is an obvious nonlinear relationship between the ultimate bearing capacity of ordinary anchors and the length of the anchorage section; with an increase in the length of the anchorage section, the bearing capacity increases rapidly and then tends to be stable. This phenomenon shows that the method of increasing the bearing capacity only by extending the length of the anchorage section has an obvious diminishing effect, and it is difficult to fundamentally solve the technical problem of an insufficient bearing capacity. With the rapid development of material science and geotechnical engineering technology, the bolt support system has shown a significant diversified development trend. Based on different engineering requirements and technical parameters, a modern bolt system can be systematically divided according to multiple classification criteria: from the perspective of the anchoring mechanism, it can be divided into grouting type and friction type; according to the type of grouting material, it can be divided into cement-based and resin-based categories; according to the material properties of the rod body, it can be divided into traditional steel and new polymer composite materials. The prestressing method can be divided into active support and passive support systems; in addition, it can also be divided into special supporting structures, such as conventional anchors and energy-absorbing anchors, based on the energy dissipation characteristics [7; 8; 9; 10; 11; 12; 13]. This diversified technical development not only enriches the theoretical system of bolt support but also provides reliable technical support for precise support under complex engineering conditions. At the same time, through systematic research, scholars at home and abroad have innovatively proposed the new supporting structure of an expanded head bolt and developed and applied it [14]. An enlarged head bolt is a support technology that expands the diameter of the bottom of the borehole through a specific process and forms an end expansion structure with a diameter significantly larger than the rod body after grouting. This technology significantly improves the uplift bearing capacity of the bolt by increasing the contact area between the anchoring end and the rock and soil mass.