Study on bearing failure characteristics and parameters of pipe roof support in super shallow buried tunnel in soft surrounding rock

Through theoretical analysis, laboratory test and numerical simulation, this paper studies the bearing failure characteristics and support parameters of pipe roof support in super shallow buried double track railway tunnel crossing soft surrounding rock. Based on the analysis of the load and load range of the pipe roof in the super shallow double track railway tunnel, Pasternak double parameter model is selected as the mechanical analysis model of the pipe roof. Based on this, 11 groups of laboratory tests of pipe roof grouting steel pipes are proposed and designed, and the influence of pipe diameter, wall thickness, grouting fullness and reinforcement cage measures of pipe roof grouting steel pipes on the change law of bearing capacity of pipe roof grouting steel pipes is analyzed. The bearing capacity of pipe roof grouting steel pipes under different parameters was obtained and compared with the numerical simulation results of ABAQUS for verification. Based on the analysis and summary of the bearing failure characteristics of pipe roof support and the test results, it is concluded that the grouting steel pipe with full grouting, wall thickness of 4 mm and pipe diameter of 108 mm without reinforcement cage can meet the support capacity requirements of most super shallow buried double track railway tunnels crossing soft surrounding rock. At the same time, in the actual engineering, the grouting fullness of the pipe roof should be focused on to prevent the pipe roof steel pipe from separating from the internal grouting body, and the wall thickness of the steel pipe can be reduced and no reinforcement cage can be set up if unnecessary.

Automated summary

This paper investigates the bearing failure characteristics and support parameters of pipe roof support in super shallow buried double track railway tunnel crossing soft surrounding rock through theoretical analysis, laboratory tests, and numerical simulation. Based on the analysis of load and load range, the mechanical analysis model of the pipe roof is selected. Laboratory tests are conducted to analyze the influence of pipe diameter, wall thickness, grouting fullness, and reinforcement cage measures on the bearing capacity of pipe roof grouting steel pipes. The results are compared with numerical simulations for verification, leading to the conclusion that a fully grouted steel pipe with a wall thickness of 4 mm and a diameter of 108 mm without reinforcement cage can meet the support capacity requirements for most super shallow buried double track railway tunnels crossing soft surrounding rock.