Impact Analysis Of Subway Construction On Adjacent Historic Buildings

The vibration induced by the subway has become a kind of vibration hazard. At present, domestic and international studies focus more on the vibration induced by the subway operation than that induced by the subway construction. There is a lot of work to do for foundation pit vibration safety of adjacent buildings. By the observation of Subinterval8, Block5, Nanchang Subway Line1, foundation pit vibration problem caused by underground continuous wall construction during the subway construction stage is studied, and some significant and practically applicable results are obtained.First, vibration of the Memorial of August1st Nanchang Uprising caused by underground continuous wall construction is measured. Results show that the building’s maximum responsive velocity of the vibration caused by subway construction is largest in vertical direction, second largest in horizontal direction that is vertical to the foundation pit, and the least in horizontal direction that parallels the foundation pit; With the storey increases, the building’s maximum responsive velocity also increases. Building vibration maximum responsive velocity shall not exceed the permitted vibration velocity according to Technical specifications.Second, the point that impact load’s form caused by impact drill is triangular load and the peak value of impact load calculation formula are proposed.Third, Use the finite element software MIDAS/GTS to set up subway construction site-Memorial of August1st uprising coupling finite element model to imitate actual working conditions. Compare the measured results with the finite element calculation results to verify the feasibility of the model as well as the load calculation formula. Based on the model, load which impacts different depths of soil layers and the multiple impact load combination impacts are analyzed, and conclusion is also arrived:The measured data are basically consistent with the calculated results; with the depth of soil layer increasing building vibration response decreases first and then increases. Multiple impact load combination impacts will cause superposition of structure vibration response.Fourth, the ground vibration velocity attenuation formula caused by subway construction is proposed. Through finite element analysis and data regression analysis by using Origin software, conclusion is drawn: Ground vibration attenuation caused by impact load is fastest in vertical direction, second fastest in the horizontal direction that parallels the foundation pit, and slowest in the horizontal direction that is vertical to the foundation pit. The attenuation formula parameter α does not change with the vibration direction or the load level, and will keep close to constant0.4. Safe distance from the source of vibration at the underground continuous wall construction stage for adjacent buildings is also suggested.