The adverse effects of vibration
The vibration of the ground during steel sheet piles will cause at least four adverse effects and should be noted:
① cause trouble to people's lives;
② damage to the outer surface or structure of the building;
③ make loose granular soil pressure and sedimentation;
④ cause slopes or excavation instability.
EN19935-1998 and the British norms, in particular, Yang 52284-1992, Ling 6472-1992 and 73852: 1993 in the first two aspects of the restrictions are clearly defined.
Interference with people's normal life Ground vibration may cause a series of chain reaction, from "slight sensation" to "feeling distress" to "restless" and finally to "anxiety". The vibration of the steel sheet pile does not harm the health of the body. The impact on the human body is generally spiritual. The subjective reaction is the result of the interaction between the vibration time and the vibration intensity. In BS472, the basic vibration curve and the magnitude of the vibration (VDV, 5), which may cause the least adverse reaction, may be reported in the range of aDV ¥, and the vibration level is low. It should be noted that the norm is only the possibility of predicting adverse reactions and does not have a legal effect.
Damage Structures There is little information on the fact that simply piling vibrations can cause minor damage to buildings with poor conditions (small cracks) on well-formed buildings. If the owner is worried that they will destroy their house, then before and after piling should be investigated to record all the defects on the building. But the contents of the two specifications are inconsistent. Impact piling will cause intermittent ground vibration, so as the instantaneous vibration vibration piling when the ground vibration is continuous, continuous vibration pp value of 50% of instantaneous vibration.
5228 and 5385 specified in the civil and industrial buildings of the intermittent vibration threshold of the vibration threshold ratio of 522 when the vibration value of more than 48 to large, for obvious defects in the building] 5228 vibration threshold can be reduced by 50%: the recommended vibration Threshold may occur when structural damage occurs.
The structure of the building should also be taken into account when the pp value is not damaged on the surface of the building. Rigid raft load-bearing recommended threshold, the norms of each country is also inconsistent. In the provisions of the vibration threshold of the base or rigid shear wall foundation, through the soil structure dynamic interaction, can greatly reduce the ground vibration. However, the flexible frame structure will fluctuate with passive interference. In addition, if the frequency and vibration frequency of the building is similar, the thinner suspension plate will amplify the dynamic disturbance. The mV value of the masonry retaining wall is controlled at 10mm / s at the bottom and 40mms at the top, and the pp limit of the underground facility is specified: intermittent vibration is 30mm / s, continuous vibration is 15mm / s, Shandong Binzhou Larsen steel sheet pile for the older river sewer to reduce 20% to 50%.
