Research On Static And Dynamic Constitutive And Road Explosion Damage Effect Of Cement-Stabilized Steel Slag

At present,the international situation is turbulent,and terrorism has a high incidence,which makes local conflicts and even wars imminent,and once war begins,airport runways,war readiness roads and major transportation roads transporting troops and materials will become the primary targets of attack.therefore,it is of great strategic significance to study the dynamic response process and damage mechanism of roads under explosive loads.Because steel slag has good anti-wear and impact resistance,its porous and flexible properties can absorb a large amount of explosion energy and weaken the explosion damage effect.Therefore,as a road base material,cement-stabilized steel slag can greatly improve the explosion resistance,integrity and impact resistance of the structure,so it is a potential excellent road construction material.At present,the research on cement-stabilized steel slag is mainly focused on macro-static mechanical behavior,but there are few studies on its microstructure,damage mechanism and macro-micro dynamic mechanical response.Therefore,firstly,this paper makes a systematic research on the mechanical properties and static and dynamic constitutive relationship of cement-stabilized steel slag by means of the combination of theory and experiment,macro and micro.Then,based on the above theory,and taking a cement-stabilized steel slag base highway in Xinjiang as the research object,the explosion damage effect of the highway is deeply analyzed by using the method of mathematical model and numerical simulation.the main research contents and results are as follows:（1）The basic properties such as chemical composition,phase composition,physical properties and expansibility of steel slag in Xinjiang are analyzed,and the feasibility of steel slag as pavement base material is demonstrated.At the same time,through the tests of unconfined compressive strength,XRD,SEM,EDX and NMR,the relationship between mechanical strength and microstructure of cement-stabilized steel slag at different ages is discussed and compared with cement-stabilized macadam.The results show that the mechanical properties of steel slag aged for more than one year can fully meet the road requirements of base materials.Compared with cement-stabilized macadam,the compressive strength of cement-stabilized steel slag at 7 d,14 d and 28 d age increased by 15.4%,22.0%and 23.7%.Due to hydration and pozzolanic reaction,the C-S-H content of cement-stabilized steel slag ITZ is higher,but the Ca（OH）₂ and AFt content are lower.The internal curing effect of steel slag reduces the ITZ width of cement-stabilized steel slag by9.4%and 31.0%,respectively.With the increase of curing time,the adsorption pore amount of cement-stabilized steel slag increased,while the seepage pore volume and migration pore volume decreased obviously,in which the pore span and total porosity decreased by 47.7%and 7.29%,respectively.（2）Based on the three-dimensional scanning technology,the discrete element model of cement-stabilized steel slag with real steel slag shape is constructed by Particle Flow Code 3D,the sensitivity between macro and micro parameters of the sample is explored,and the nonlinear regression equation between them is established.The uniaxial compression simulation tests were carried out on the samples with 0%,10%,30%and 50%steel slag stone content,and the macro and micro mechanical properties and the evolution law of microcracks in the failure process were analyzed from the aspects of strength,energy and fracture damage.The results show that with the increase of steel slag stone content,the strength of the sample increases,the number of microcracks increases,and the brittle failure is significant.The failure process of cement-stabilized steel slag can be divided into five stages,in which there is a lag between the peak AE intensity and the stress peak in the peak explosion stage.when the content of steel slag is 0%,10%,30%and 50%,the lag percentage is 20.8%,14.3%,15.5%and 11.6%,respectively.The content,particle size,roughness and interfacial tensile strength of steel slag have great influence on the crack initiation stress of cement-stabilized steel slag.When the content of steel slag stone is 0%,10%,30%and 50%,the shape of steel slag stone is irregular and the interfacial tensile strength is 9.0,13.0,17.0 and 21.0 MPa,the crack initiation stress of cement-stabilized steel slag increases by 91.1%,13.5%and 123.8%,respectively.With the increase of the particle size of steel slag,the crack initiation stress decreases,but the peak stress increases.（3）Based on the elastoplastic theory and generalized Hooke law,and considering the strain rate effect and random damage characteristics of cement-stabilized steel slag,the elastoplastic dynamic damage constitutive model of cement-stabilized steel slag under complex stress is established.The program for solving the constitutive model is developed by using the subroutine interface VUMAT provided by ABAQUS,and the uniaxial compression,true triaxial and SHPB tests of cement-stabilized steel slag are simulated.The results show that in the uniaxial compression test,the peak stress error between the theoretical and experimental results is only 3.4%.In the true triaxial test,the average error between the theoretical results and the experimental results is less than±5.0%.By comparing the theoretical and experimental results of the SHPB test,it can be seen that the model has the best fit when predicting the instantaneous failure with strain rate above 13s^-1,while the relative error increases when the strain rate is lower than 13s^-1,but it still has good applicability.Generally speaking,the constitutive model can accurately describe the static and dynamic characteristics of cement-stabilized steel slag under real stress state,and the VUMAT subroutine developed enriches the ABAQUS material library,which plays an important role in improving and popularizing the constitutive model.（4）Based on the synergistic theory,the deformation and failure mechanism of multilayer media under the action of explosion wave are deeply analyzed,and the blasting cavity expansion and crack driving effect of explosive gas are considered.At the same time,a full-stage road explosion damage prediction model is established based on thermodynamics,explosion mechanics,material dynamics and stress wave theory.Then,the prediction model is verified and analyzed by using public test data and numerical simulation method.The results show that under different blasting point depths,the blasting funnel volumes of the prediction model,numerical simulation and field test are basically the same.The maximum relative error is less than 11.2%,which shows that the prediction model has good rationality and accuracy.（5）The effects of different charge quantity and blasting point depth on the blasting damage effect of cement-stabilized steel slag base road are studied by using numerical simulation and prediction model,and the quantitative relationship between charge quantity,blasting point depth and blasting funnel volume is put forward.Through the study,it is found that when the blasting point is located in the surface layer,the blasting funnel volume is small and can not cause obvious damage to the structure;When the blasting point is located at the bottom of the base,the blasting funnel volume is the largest and the spallation phenomenon occurs at the interface;When the blasting point is located in the cushion layer,the blasting funnel volume obviously decreases and presents a double-layered“V”shape;With the increase of the blasting point depth,the blasting funnel volume gradually tends to the“hidden explosion”state.At the same time,when the blasting point is fixed on the base to increase the charge,the blasting funnel volume increases at first and then tends to be stable.At this time,there must be an optimal charge corresponding to the maximum blasting funnel volume.In addition,this paper also discusses the influence of different base materials on road explosion damage effect.Through comparative analysis,it is found that cement-stabilized steel slag has better explosion resistance,integrity and impact resistance than cement-stabilized macadam.