Experimental and numerical study on protective effect of RC blast wall against air shock wave

Prototype experiments were carried out on the explosion-proof performance of the RC blast wall.The mass of TNT detonated in the experiments is 5 kg and 20 kg respectively.The shock wave overpressure was tested in different regions.The above experiments were numerically simulated,and the simulated shock wave overpressure waveforms were compared with that tested and given by CONWEP program.The results show that the numerically simulated waveform is slightly different from the test waveform,but similar to CONWEP waveform.Through dimensional analysis and numerical simulation under different working conditions,the equation for the attenuation rate of the diffraction overpressure behind the blast wall was obtained.According to the corresponding standards,the degree of casualties and the damage degree of the brick concrete building at a certain distance behind the wall can be determined when parameters are set.The above results can provide a reference for the design and construction of the reinforced concrete blast wall.

Abrasion Resistance of Cement Paste with Granulated Blast Furnace Slag and Its Relations to Microhardness and Microstructure

The abrasion resistance of cement pastes with 30 wt%,40 wt%and 50 wt%granulated blast furnace slag(GBFS),and its relations to microhardness and microstructure like hydration products and pore structure were studied.Results indicated that GBFS decreased the abrasion resistance of paste,and among the pastes with GBFS,the paste with 40 wt%GBFS showed the highest abrasion resistance.The microhardness of GBFS was lower than that of the cement,and the microhardness of the hydration products in paste with GBFS was also lower than that of the hydration products in paste without GBFS,so that the abrasion resistance of paste decreased when GBFS was incorporated.The reason for the decrease of microhardness of pastes with GBFS was that the contents of Ca(OH)_(2)in pastes with GBFS was significantly lower than that in the paste without GBFS,while large amounts of calcium aluminate hydrates and hydrotalcite-like phases(HT)in pastes with GBFS were generated.Furthermore,among the pastes with GBFS,the paste with 40 wt%GBFS showed the lowest porosity which was the main reason for its highest abrasion resistance.

Safety assessment for buried drainage box culvert under influence of underground connected aisle blasting:A case study

Blasting engineering in complex urban environments is considered to influence the safety and stability of the overlying drainage box culvert structure owing to vibration.Therefore,field blasting and vibration tests were performed on the blasting engineering of the Wuhan Metro Line 8 connected aisle,and the LS-DYNA software was used to analyze the dynamic response characteristics of an underground drainage box culvert during the blasting test.The vibration response evolution law of the buried drainage box culvert under blasting vibration was investigated,and a safe surface control standard for the blast vibration of a drainage box culvert is proposed.The results reveal that the maximum tensile stress of the box culvert structure was 0.33 MPa.The peak particle velocity(PPV)and peak tensile stress(PTS)of the drainage box culvert decreased as the water level in the box culvert increased.Based on the relationship between the tensile stress of the box culvert,PPV of the box culvert,and PPV of the surface,it is proposed that the surface control velocity of the buried drainage box culvert is 1.36 cm/s.