Investigation On The Anti-penetration Effects Of Steel-tube-confined Concrete Shield Structures

The rapidly development and extensive application of earth penetrator in morden warfare promote the development of shelter technology.The steel-tube-confined concrete shield structures turn to be extensively application in protective engineering because of its superior anti-penetration performance.Based on the existing study of single steel-tube-confined concrete targets(structural unit),the performance and mechanisms against penetration of hexagon steel-tube-confined concrete integral structure are studied by making use of experiment methods,numerical simulation and engineering modeling.The mechanisms against penetration of steel-tube-confined concrete seven-unit model structure are revealed and an engineering model to predict the depth of penetration for confined-concrete integral structure is developed.The results in this paper can provide important instruction for engineering application of steel-tube-confined concrete in protective structure.The mainly works can be summarized as follows:1.Experiments of 12.7mm hard core bullets penetrating into steel-tube-confined concrete seven-unit model structure are conducted,with the comparative test of penetration into single targets,layered targets and semi-infinite targets.The influence factors of anti-penetration resistance are studied,such as the size and the thickness-diameter matching of steel tube,steel ration of the target and so on.The failure modes and mainly damage parameters are obtained.The results show that: the steel-tube-confined concrete seven-unit model structure has superior anti-penetration performance,which work better in penetration resistance with reduction of depth of penetration by 16% compared with the same-size single target.The well matched integral target is better than the semi-infinite target with reduce the penetration depth of 16%-22%.Compared with the same-size integral target,the penetration depth of layered target increases by about 14%.There are many factors that have influence on target anti-penetration resistance such as impact velocity,thickness and diameter and thickness-diameter matching of steel tube and the steel ratio of the target.The optimization of thickness-diameter matching can effectively improve the anti-penetration resistance of steel-tube-confined concrete shield structures.2.Using finite element software LS-DYNA and based on the FEM-SPH coupling method,the FEM/CSC-SPH/HJC coupling method is established where the CSC model adopted in the finite element mesh area,and the HJC model used in the smooth particle region.The FEM/CSC-SPH/HJC coupling method is proposed for simulating concrete penetration experiments,and the anti-penetration mechanism for steel-tube-confined seven-unit model structure is analyzed.The results show that: Numerical results match the experimental results well.The concerete and steel-tube surrounding provid constraint effect to the impacted unit,and the concrete in the impacted unit damaged obviously while the concrete in the surrounding unit stay intact.3.Taking the elastic constraint effect of surrounding concrete into consideration,the quasi-static cylindrical cavity-expansion engineering model for integral structure and the formula to predict the depth of penetration are established in this paper.Based on quasi-static cylindrical cavity-expansion model for the single-unit target,the model is proposed on the assumption that response modes of target are “cracked-comminuted” and concrete is treated yielding according to the H-B(Hoek-Brown)criterion in comminuted region.The rationality of the formula is verified with the analysis of the penetration resistance in the experiment.