Punching Metal Protective Screens Based on Elements Made of Rolled Sheets and Half Pipes

The object of the study is new design solutions for metal protective screens based on elements made of rolled sheets, half-pipes and guide pipes. Metal protective screens are used in the construction of underground transport structures using a closed method. The protective screen prevents deformations and subsidence of the surface of overlying soil layers, road and railway bed. During the construction of tunnel-type structures under existing transport communications, the conditions for the safe operation of roads and railways must not be violated. In this case, special attention is paid to subsidence of the overlying soil layers. The magnitude of subsidence affects the possibility to operate roads and reduce the speed or completely stop traffic on the railway. Therefore, the stress-strain state of the proposed metal protective screens was studied using a calculation model developed on the basis of the finite element method. To improve the accuracy of calculating internal for-ces on punching individual structural elements of a metal protective screen, the Romberg method was used. The proposed designs and technologies of protective screens retain the advantages of those currently used, while simultaneously reducing the costs of constructing a protective screen, since the design solutions under study require less effort to push through indivi-dual elements, and, as a consequence, use less powerful equipment. Calculations of the stress-strain state of the proposed designs of protective screens have shown their viability. As a criterion for checking the operability, the maximum stresses perceived by individual parts of the structures were considered; they do not exceed the yield strength of the selected steel, and the maximum vertical and horizontal displacements of individual parts of the screens were calculated, which do not exceed those specified in the requirements of the Rules for Technical Operation of Railways in the Republic of Belarus and the Instructions for Current Maintenance of Railway Tracks in the Russian Federation. This confirms the operability of the proposed metal protective screens.