(1. China Railway Siyuan Survey and Design Group Co.，Ltd.，Wuhan，Hubei 430063，China；
2. National and Local Joint Engineering Research Center of Underwater Tunnel Technology，Wuhan，Hubei 430063，China；
3. State Key Laboratory of Geomechanics and Geotechnical Engineering，Institute of Rock and Soil Mechanics，Chinese Academy of Sciences，Wuhan，Hubei 430071，China；4. University of Chinese Academy of Sciences，Beijing 100049，China)
Abstract：In order to validate the calculation model and safety factor calculation method for the combined spray-anchor support in the total safety factor method，this paper developed a large-scale tunnel structure model test system from the perspective of structural test，and carried out the loading test of the spray-anchor combined support structure under the unsupported tunnels and the different anchor spacing. The triaxial test of surrounding rock and fine sand material，and the tensile and pull-out test of anchor material were used to clarify the physical and mechanical parameters of each material in the model test，simulate the whole process of loading and damage of the spray-anchor combination support under different anchor spacing and unsupported tunnels，and monitor the stress and strain of the surrounding rock，anchor strain，inner and outer strain of the spray layer，and the displacement of the spray layer with the external load. Based on this，the design bearing capacity，ultimate bearing capacity，and deformation force characteristics of the unsupported tunnels and the combined spray-anchor support with different anchor spacing were analyzed and compared with the theoretical calculation results of the total safety factor method. The results show that：sprayed concrete and anchor can effectively carry the surrounding rock，improve the lateral limiting force of the surrounding rock，play the supporting role of the anchor rock bearing arch，and improve the deformation and bearing capacity of the surrounding rock；the bearing capacity and damage characteristics of the spray-anchor combination support obtained from the test are more in line with the results of theoretical calculations，which shows that the total safety factor method of spray-anchor combination support calculation method is reasonable and the method is on the safe side.
