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Analysis of influencing factors of Rayleigh surface wave exploration depth
Published in Mohd Johari Mohd Yusof, Junwen Zhang, Advances in Civil Engineering: Structural Seismic Resistance, Monitoring and Detection, 2023
When the average speed remains unchanged, that is, the formation conditions remain unchanged, and the exploration depth is inversely proportional to the frequency of the Rayleigh wave used. In the process of Rayleigh surface wave exploration, the excitation mode of the transient surface wave source directly affects the frequency range, and source excitation has become one of the important links that restrict the depth of investigation. In other words, if the required exploration depth is small, then the main frequency of the seismic source should be higher; if the required exploration depth is larger, then the main frequency of the seismic source should be lower. We determine the best excitation method according to the exploration depth and the need to distinguish thin layers. In the surface wave engineering survey work, the commonly used seismic sources include hammering seismic source, falling weight seismic source, and explosive seismic source.
Subsurface exploration for foundation design
Published in An-Bin Huang, Hai-Sui Yu, Foundation Engineering Analysis and Design, 2017
The execution of seismic geophysical exploration methods generally involves the use of a seismic source and an array or receivers to detect the arrival of seismic waves. The seismic source can be as simple as a hammer striking the ground surface, a rifle shot, a harmonic oscillator, or an explosion. The receiver is a seismometer that converts ground shaking into an electrical response. Seismic methods introduced in the following sections include reflection method, refraction method, and surface wave method. These methods can be nonintrusive where the tests are conducted from the ground surface without the need of boreholes. Included also are the crosshole and the P-S logging methods, which are intrusive methods that require one or multiple boreholes to perform the test. Note that the shear wave velocity measurement in seismic cone penetration test described in Section 3.4 is also an intrusive seismic geophysical method.
2 storage
Published in Xia-Ting Feng, Rock Mechanics and Engineering, 2017
Land seismic surveys typically consist of a seismic source (or a group of seismic sources) moving over a pattern of source point locations and exciting seismic wavefields on each of these source points. An array of seismic receivers (vertical or three-component geophones) is deployed along profiles recording the wavefields emitted at the source point locations. Wherever possible, vibrator trucks are used as sources, having little environmental impact and allowing for relatively fast acquisition progress, but in areas of limited accessibility, explosives shot in shallow boreholes are used as an alternative. The receiver arrays typically consist of several lines with altogether several hundreds to thousands of single geophones. In areas with few obstacles and good infrastructure, several hundred source points may be acquired per day. This is still far beyond the efficiency of a marine seismic acquisition and is significantly reduced in topographically and logistically complicated areas (e.g., sand dunes, jungles, high mountains or densely populated areas).
Effects of Soil Characterization on the Seismic Input
Published in Journal of Earthquake Engineering, 2019
Stefania Viti, Marco Tanganelli, Vittorio D’intinosante, Massimo Baglione
In this test, both the source and the receptors are located on the surface. The soil profile is determined after the propagation velocities of the P and S waves, whose refraction properties are a function of the density of the soil they pass through. The seismic source is a pulse generated by a 15-kg mallet which has been fixed to the soil to generate the Love waves, and to a 2-m beam fixed to the soil along its entire length to generate the Rayleigh waves. Twenty-four 10-Hz geophones, spaced 5 m from each other, have been used as seismic receptors, with a global length equal to 115 m. A 24-channel 50-Hz seismograph (PASI, model 16S24), notch filter, having an Automatic Gain Control has been adopted as a spectrum analyzer.