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Wave Propagation 2011 Part 19

Tham khảo tài liệu 'wave propagation 2011 part 19', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Field Experiments on Wave Propagation and Vibration Isolation by Using Wave Barriers 515 a b c Fig. 2. Electrodynamic shaker and accelerometers placed on the foundations a Electrodynamic shaker placed on the foundation b Electrodynamic shaker and accelerometer c Measurements recorded foundation d Accelerometers placed on the foundation. d Material Mass density p t m3 Pressure wave velocity Cp m s Shear wave velocity Cs m s Poisson s ratio V Geometry Depth of trench Ht m Width of trench Bt m Bentonite softer trench 1.65 400 100 0.35 Rectangular 2.5 1.0 Concrete stiffer barrier 2.40 5000 2400 0.20 Rectangular 2.5 1.0 Water filled trench 0.98 - - 0 Rectangular 2.5 1.0 Table 3. Material properties and geometric parameters of the in-filled trench barrier. between 2ẰR and 7ẰR from the wave barrier. The trench width has to be built between 0.12R and 0.5ẤR to accomplish such remarkable reduction in vertical soil vibrations 21-23 . The predominant values of the applied excitation frequencies in these experimental studies and the related Rayleigh wavelengths are given in Table 4 in order to determine the optimum 516 Wave Propagation in Materials for Modern Applications geometrical parameters of the rectangular trench barrier an average for an effective protection and to avoid the difficulties in their practical applications such as instability of soil high water table levels and high costs. Frequency of exciter f Hz Wave length of Rayleigh waves ZR m Trench width Bt min.0.1zR m Active isolation Passive isolation Trench depth Ht min.0.6ZR m Measurement point from trench Lt min. 10zR m Trench depth Ht min.1.33ZR m Measurement point from trench min.2Z.R m 25 7.92 0.79 4.75 79.2 10.53 15.84 50 3.96 0.40 2.37 39.6 5.26 7.92 75 2.64 0.26 1.58 26.4 3.51 5.28 100 1.98 0.20 1.19 19.8 2.63 3.96 All All 1.00 2.50 20.0 2.50 5.00 Table 4. Rayleigh wavelength and minimum conditions for the screening effectiveness of an open trench barrier. Four types of trench barriers are used to obtain