Experimental Comparison of Horseshoe Prefabricated and Spray Anchor Initial Support Structures

In order to study the mechanical deformation characteristics of the new horseshoe prefabricated initial support structure and compare its difference with the spray anchor initial support structure, the prototype loading tests of two types of structures were carried out. The structural design, lining prefabrication, test loading, and result analysis were introduced systematically, and the test results were deeply analyzed. The results show that the ultimate bearing capacity of the prefabricated initial support structure is 2.80 times the design load, and that of the spray anchor initial support structure is 1.32 times the design load. The ultimate bearing capacity of the former is about 2.10 times that of the latter. The prefabricated initial support structure is affected by the positive bending moment and negative axial force at the vault and the arch waist, as well as the negative bending moment and positive axial force at the arch shoulder and the arch bottom. The spray anchor initial support structure is similar. The maximum moment and the maximum axial force of the prefabricated initial support structure are about 1.39 and 1.45 times that of the spray anchor initial support structure near the destruction phase, respectively. The concave and convex deformation trend of the prefabricated initial support structure is basically the same as that of the spray anchor initial support structure. The right arch shoulder is convex, and the right arch waist is concave, with steel and concrete spalling when the structure is damaged, and the ultimate deformation capacity of the prefabricated initial support structure is about 1.20 times that of the spray anchor initial support structure.