基坑爆破临近砖砌体墙动力响应特征及安全控制OA

Controlling the vibration effects of foundation pit blasting is of great significance for ensur-ing the safety and stability of adjacent brick masonry structures.Based on a foundation pit blasting proj-ect of a subway in Wuhan,field tests and ANSYS/LS-DYNA numerical simulations were adopted to investigate the dynamic response characteristics of brick masonry walls adjacent to foundation pit blast-ing.Based on the principle of dimensional analysis,a blasting vibration prediction model was estab-lished,and a safety standard for blasting vibration of brick masonry walls was proposed.The results showed that the established numerical model results were consistent with the field test results and could be used for analyzing the dynamic response under blasting.The lower-order mode shapes of the brick masonry walls were transverse or longitudinal bending,while under higher-order modes,they exhibited coupled transverse and longitudinal bending.The dynamic response on the blast-facing side of the brick masonry walls was greater than on the opposite side,and the peak vibration velocity along the extension direction of the wall occurred at the ends,the middle,or near the middle,and changed with height.The blasting vibration of the brick masonry walls exhibited an elevation amplification ef-fect,which was more significant at locations farther from the blasting source,and the stress in different directions showed the characteristics of higher stress in the middle and lower stress at both ends.In-creasing the wall height and excavation depth caused the locations of significant elevation amplification effects and stress concentration to shift from the center of the wall toward both ends.A blasting vibra-tion prediction model was established,and combined with the ultimate strength theory,the safe blast-ing vibration velocity of brick masonry walls was determined to be 2.42 cm/s.A calculation formula for the safe charge of blasting was proposed,which can be applied to foundation pit blasting design.