Study On The Performance Of Composite Material Structure Made Of Armor Plate, Supporting Rebar And Polyurethane Foam And Its Application In Underground Prevention Engineering

According to the international research trends,along with the appearance and application of new materials and new types of structures,aiming at meet the needs of new materials and structures applying to future defending project(especially in cold region of tableland),a kind of composite material structure composed of armor plate, supporting rebar and polyurethane foam is studied and developed.By means of systematic load bearing experiments(including dead load and live load),field chemical blast test and numerical modeling,the mechanical properties of this new material structure is studied.Then,the simplified mechanics model regarding the new material structure is established.Furthermore,the mechanical properties of shallow buried basket type work made of the new material under the effect of chemical blast are also studied.Finally,the specific design and construction methods are discussed. All of these research results may provide a theoretic basis for practical application of the new material structure.The composite material structure composed of armor plate,supporting rebar and polyurethane foam and its molding techniques are brought forward.This composite structure is made of two layers of armor plate(one on the top,the other on the bottom), supporting rebar which connect the two layers of armor plate and polyurethane foam filled in the interspace of the structure.According to the test results,compared with the interlayer structure used in the past,this new structure has higher loading capacity, better ductility,better capacity of absorbing energy,and stronger antidetonating ability.Three problems are studied by numerical modeling analysis,including the mechanical property of the structure which is composed of armor plate and supporting rebar under various load cases,the influence of the relative stiffness of armor plate and supporting rebar to the mechanical behavior of the structure and the influence of the arrangement pattern(crossed or uncrossed)of the two rows adjacent rebar to the mechanical behavior of the structure.The results show that the supporting rebar acts as compression bar and it is constrained by the armor plate.The constrained effect affects the ultimate compression load magnitude and the average axial stress distribution of the supporting rebar.The less the space between two rows adjacent rebar is,the more the ultimate compression load will be.The relative stiffness of the armor plate and the supporting rebar should be compatible.Based on the compression bar and thin plate stability theory,formulas used to calculate the critical shear resistant load of the framework corresponding to two conditions are deduced.The interaction between inner foam and outer thin metal shell is studied by test. The test results show that the interlayer composite structure can prevent rebar and armor plate from inflecting untimely and enhance its carrying capacity and stiffness because the inner polyurethane foam can help to restrict the supporting rebar and the armor plate from deforming.The polyurethane foam can not only stop the rebar and armor plate from inflecting untimely,but also restrict the deformation of the rebar and the armor plate latterly so as to ensure the structure still retain a relatively higher residual carrying capacity.The field blast test results show that the composite material structure has good deformation resistant capacity and can endure repetitious blast.The composite structure may have two types of failure mode which are three plastic hinge and four plastic hinge failure framework.The test results may become test references for further research in composite material structure.And the further study also shows that the undergoing stress intensity of the composite material structure is smaller than that of the reinforced concrete plate or concrete plate that means the composite structure has better anti detonation ability.On the basis of perpendicular anisotropy thick slab theory,a kind of simplified method used to analyze the anti detonation property of the composite material structure is developed.The analysis model,the stiffness constant and the basic equation for internal force are all developed.The simplified method can provide a theoretical basis for the application of this new composite material structure.Based on one dimensional plane wave theory,a method that beam model is applied to analyzing the stress status of shallow buried box shaped work made of composite material structure.In this model,the top slab of the underground box shaped structure is treated as a buried beam which is simple supported on the elastic foundation;the beam is divided into some finite thick beam elements(displacement components include vertical displacement w,rotation angel of sectionβand horizontal displacement u);transverse shear deformation of beam is considered.Then, geometrical nonlinearity calculation is performed for this model.In this model,both the mass motion of the framework and the distortion of the top slab are all considered. Consequently,this model may be used to analyze the stress status of the shallow buried box shaped structure made of composite material effectively.How to design package type field operations works with compound material is studied in this paper.Application design of work depends on technical requirement of strategy.Top slab is always destroyed at first in low-buried package type field operations.This paper brings forward using a beam model to calculate and check top slab,and eccentric compression bar to analyze side wall.That coveting over and joining-up in series binding bolt are mainly considered to deal with the connection of work,and in this way,the entire resistance to deformation of the work can be fully used.Construction technical requirements for package type field operations made of composite material are brought forward.Digging flat bottom pit is very important for constructing field operations.There are two methods to dig flat bottom pit,which are by machine and by blasting,and the choice of the method depends on practical situation.According to the test which provides the relative method and datum of digging flat bottom pit by blasting,the installation of the work is introduced which may contribute to the actual application of the work.