Study On Optimized Hole Of Static Cracking Of Concrete Based On XFEM

Static cracking is a special blasting method with a lot of advantage,such as environmental,safety,convenience and so on,it has got a wide range of applications in demolition.To further improve the efficiency of static blasting demolishing of concrete,maximize the expansion capability of the Soundless Cracking Agent(SCA),firstly,the expansion tests of SCA were conducted to determine the suitable reaction conditions,such as water-agent ratio and water temperature,and maximum expansion pressures that SCA can generate for different hole diameters at preferred reaction conditions.Moreover,the concrete block model with different holes was built by using ABAQUS,and the numerical simulation and analysis of the static crushing process of the concrete was carried out by the Extended Finite Element Method(XFEM),couple with the experment verification.The specific research work of this paper and the main conclusions obtained are as follows:(1)The expansion rate test at the ratio of the water-changing agent and the mixing water temperature were carried out,by testing the height difference during the SCA reaction process,and then found the suitable water-agent ratio and water temperature,based on this,the expansion pressure test of thin-walled steel pipes with different inner diameters was carried out.it was found that the maximum expansion pressure tends to increases linearly with a growth in inner diameter of the hole,found out the optimal hole diameter.(2)Explain the theoretical basis of the XFEM and the fracture,the concrete block model with holes(24 mm,26 mm,28 mm,30 mm diameters)in the center was established by ABAQUS software and XFEM,the gradual surface load based on the swelling pressure test is applied to the hole,analysis the whole process of the crack initiation,expansion,and crack-through in different hole diameter,the energy release rate theory is used to further analyze the crack growth process.(3)Numerical model verification of standard concrete block crushing with single hole.Concrete test block consistent with the numerical model was prepared,and the static cracking test of the concrete was carried out,The similarities and differences between the crushing effect and the numerical simulation results were observed,it is found that the hole diameter of the two crushable holes are the same,and the number of penetration cracks and the direction of crack propagation also have a certain correlation.This shows that the extended finite element method is reliable in simulating static concrete crushing.(4)On the basis of the expansion pressure test,the ABAQUS software is used to further establish concrete test block models of different sizes and different hole distances with a hole diameter of 45 mm.The fracture simulation analysis is carried out based on the XFEM,The results show that a concrete cube with a side length of350 mm can be broken by a broken hole with a hole diameter of 45 mm,and a suitable hole distance is 300 mm when the hole diameter is 45 mm.The research can provide a basis for the selection of hole diameter and hole distance in actual static crushing engineering.