| With the continuous progress of urbanization in China,the development,transformation and demolition of various types of buildings are increasing.As the main material of urban construction,concrete usually brings many problems,such as dust and noise,during the demolition construction.Therefore,it is necessary to develop safer and environment-friendly crushing methods to achieve comprehensive benefits in all directions.Static crushing is a silent crushing method,which has been widely used in various fields.Unlike mechanical demolition and blasting demolition,this silent crushing mode greatly reduces the noise and environmental pollution problems generated in the project.However,due to its long action time,uncertain hole arrangement,uncontrollable fracture,large impact of working environment temperature,and easy occurrence of blowhole,it reflects that the technology still has great room for progress.Therefore,it is of great significance for engineering practice to deeply understand the expansion failure characteristics of soundless chemical demolition agent(SCDA)and the failure mechanism of static crushing.This paper probes into the best use conditions of SCDA,and analyzes the crack propagation law of the whole process of SCDA crushing concrete.The accuracy of the physical experiment was further verified by the numerical model established by RFPA2 D software,and the progressive observation of crack growth was realized by using acoustic emission and stress monitoring.The main research contents are as follows:(1)The expansion performance of SCDA was tested by the volume change of soundless chemical demolition agent before and after the experiment.The volume expansion rate under different water agent ratio and mixing water temperature was compared to obtain the best water agent ratio and mixing water temperature.At the same time,the temperature change during the soundless chemical demolition agent reaction was recorded.A thick-walled cylinder system specially used to measure the expansion pressure was made,and a variety of apertures were selected to measure the expansion pressure of the soundless chemical demolition agent.The results show that the expansion pressure increases almost linearly with increasing hole diameter.(2)Several groups of concrete test blocks with different hole diameters and hole spacing were prepared,and the whole crushing process of concrete was compared and analyzed.At the same time,measured the acoustic emission number and stress change from the beginning to the end of the soundless chemical demolition agent reaction to obtain a more detailed crack growth gradual change process.From the final test results,it can be seen that the crack propagation state will be different under different aperture spacing.(3)The rock fracture analysis system RFPA was used to endow the mechanical properties of different regions of the model,and to build the numerical model of the same aperture and hole spacing used in the physical test process.Through the analysis and calculation of the model,the test results of the static broken concrete physical test are verified.It was found that there was a certain correlation between the two,which proved the reliability of the numerical model.The deformation and failure mechanism of the static crushing process was analyzed from the crack width,crack propagation direction and crack number of the numerical model.(4)The validated RFPA numerical model was used to extend,and a large number of full-scale model data with different hole diameters,hole spacing and tensile strength were calculated.The relationship between hole diameter,hole spacing and tensile strength was deeply analyzed,and the concept of effective crack area was proposed,and a fitting formula of hole spacing and tensile strength was established.In addition,the influence of the hole layout on the static crushing efficiency was also considered,and the optimal hole spacing was selected to support the hole diameter,hole spacing and tensile strength of the impact of effective fracture area. |
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