Damage Effect Study On Concrete Contact Blast

Concrete is the most widely ?sed building material in the world and plays an important role in civil and military fields.Accidental explosions and regional terrorist attacks occur from time to time in life,which make buildings strongly impacted and destroyed,and serio?sly threaten people's lives and property security.Therefore,the research on the damage effect of concrete contact explosion can provide suggestions and reference for the anti-explosion design of national defense engineering and civil buildings,and has high practical value.In this paper,the concrete model strength is C40,the diameter is 1m,and the model thickness and charge weight are taken as variables to carry on the concrete contact explosion test,and combined with the numerical value.The damage effect is simulated and analyzed.The results are as follows:(1)By means of 12 physical model tests,the distribution of cracks in concrete subjected to contact explosion is analyzed statistically,and the fragmentation of concrete after explosion is analyzed.The type of crack is defined.The experimental results show that the concrete cracks are randomly distributed under contact explosion,the number of fragments is smaller than that of middle pieces,and the mass of fragments is smaller than that of large pieces,and the radial cracks are dominant in the type of cracks.(2)Through the analysis of concrete contact explosion crater shape and earthquake collapse effect,it is found that the concrete crater shape is irregular cone shape under contact explosion.When the thickness of the model is constant,the diameter and depth of the crater increase with the increase of the dosage of the explosive,and the collapse phenomenon becomes more and more obvio?s with the increase of the dosage of the explosive.When the dosage is constant,the diameter and depth of the crater increase with the increase of the position of the explosive point,and are limited by the change of the model thickness.The diameter and depth of the crater decrease non-linearly with the increase of the thickness of the model.When the thickness of the model increases,the larger the dosage,the faster the attenuation.(3)The prediction formulas of crater diameter D and depth h are obtained by dimensional analysis combined with measured data fitting,And compared with the current prediction formula,the accuracy has been improved by 30% and 32%,respectively.(4)Through the numerical simulation of the collapse and collapse of the contact explosion,the whole failure process of the concrete slab is completely reconstructed,and the research shows that the explosion-proof surface of the anti-explosion surface is mainly formed by compression failure,and the back-and-explosion surface is mainly controlled by the reflected tensile stress wave.The explosive stress wave propagates inside the concrete in the form of a spherical wave front,and the energy utilization rate of the contact explosion energy of the test is 1.7% by the stress peak attenuation law of the adjacent unit.At the same time,it is found that the closer the explosive source,the greater the strength of the stress wave,the faster the attenuation.(5)With the help of the definition of concrete contact explosion failure grade,the test phenomenon is divided into explosion into pit,explosion collapse and explosion through grade 3.Based on the calculation formula of collapse failure coefficient and numerical simulation,the relationship between failure grade and failure coefficient is obtained: the smaller the failure coefficient,the higher the failure grade.When the failure coefficient k > 5.75,the failure order is order 1,when the failure coefficient is between 4.78<k?5.75,the failure level is 2(a),and when the failure coefficient is between 3.24<k? 4.78,The failure level is 2(b),and when the failure coefficient is k?3.24,the damage level is 3.