ESTIMATING MODAL PARAMETERS FOR A SIMPLE SOFT-SOIL SITE HAVING A LINEAR DISTRIBUTION OF SHEAR WAVE VELOCITY WITH DEPTH

1996 ◽  
Vol 25 (2) ◽  
pp. 163-178 ◽  
Author(s):  
J. X. ZHAO
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
Modal Parameters ◽  
Linear Distribution ◽  
Soil Site

Analysis on the Bias of Seismic Ground Motion Prediction in a Shallow Stiff-Soil Site by LSSRL-1 Program

2014 ◽  
Vol 915-916 ◽  
pp. 18-21
Author(s):  
Zhuo Shi Chen ◽  
Xiao Ming Yuan ◽  
Shang Jiu Meng
Keyword(s):  
Shear Wave ◽  
Ground Motion ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Dynamic Parameters ◽  
Ground Motion Prediction ◽  
Blind Prediction ◽  
Soil Site ◽  
Parkfield Earthquake ◽  
Stiff Soil

The main causes of the ground motion blind prediction bias are the variability of the adopted program, the shear-wave velocity of the site, and the soil nonlinear dynamic parameters. By considering the variability of shear-wave velocity and the dynamic parameters, this essay used LSSRLI-1 Codes and Mw6.0 seismic record of Parkfield earthquake to calculate ground responses of 9 different conditions at Turkey Flat site. The authors believe that the variability of shear-wave velocity caused the dominant impact to the blind prediction of this shallow stiff-soil site. That impact is much greater than that of the dynamic parameters. LSSRLI-1 program may either underestimate the ground response of the shallow stiff-soil site or may overestimate it, so we should combine the specific site conditions and a large amounts of data to do the further analysis.

Shear Wave Velocity Investigation for Ten Representative Sites of National Capital Territory, New Delhi, India

2011 ◽  
Vol 2 (1) ◽  
pp. 29-43 ◽  
Author(s):  
A.K. Mahajan ◽  
A.K. Shukla ◽  
Ajit Pandey ◽  
Mukesh Chauhan ◽  
Neetu Chauhan ◽  
...  
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
River Sediments ◽  
Soil Classification ◽  
New Delhi ◽  
Site Class ◽  
Class B ◽  
Masw Method

In this paper, shear wave velocity (Vs) investigations are carried out using Multichannel analysis of surface waves (MASW) method at ten representative sites in the NCT region, New Delhi. The analysis shows that the Vs obtained from the sites located on Alwar quartzites of Delhi Super Group ranges from 770 m/s to 2800 m/s, whereas on other sites located on lake/river sediments (Nazafgarh, Balsava and Akshar Dham) have Vs less than 180 m/s. The sites located on thick sediments shows Vs of the order of 180 m/s to 250 m/s. According to the soil classification, the sites covered can be classified under three categories: Class ‘B’ (Vs30 as >760m/s; JNU site and Asola site), class ‘D’ (Vs30>180 m/sec-360; Bhavana, Suhalpur, Ghazipur and Kirbi cantt. sites), whereas the sites located near lake/river sediments are classified as class ‘E’ (with very soft soil) and will be prone to liquefaction potential during strong earthquake shaking.

scholarly journals Validation of spatial autocorrelation (SPAC) method with L-shape array in Jyoso City, Japan

2011 ◽  
Vol 42 ◽  
pp. 101-105
Author(s):  
Prithvi Lal Shrestha
Keyword(s):  
Phase Velocity ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Equilateral Triangle ◽  
Velocity Structure ◽  
Soft Soil ◽  
The Other ◽  
Side Length ◽  
Ps Logging

This study is aimed to validate the efficiency of an L-shape array for SPAC method using microtremor in estimating the shear wave velocity (V,) structure. The experiment for validation was conducted in the Toyota Community Baseball Ground, Jyoso City, Ibaraki Prefecture, Japan in March 2009 with an equilateral triangle array with side length of 40 m and in June 2010 with an equilateral triangle array with side length of50 m, together with an L-shape array of the similar size. Multichannel Analysis of Surface Waves (MASW) was also performed simultaneously in June 20I 0. In the same lot PS-logging data are available from nearby LBRH IO station of the K.IK-NET (NTED, Japan) that shows soft sediment of about 20 m thick with V, of 110 m/s in the geological column of the site. The comparison of the determined phase velocity and that calculated from PS logging data shows close matching of two sets of curves separately. One is between PS logging and the triangle array (40 m), and the other is between the triangle array (50 m) and the L-shape array (50 m). Former two are of the almost same place whereas other two arrays are deployed about 200 m away from the other set. Some discrepancy between two sets is shown. This seems due to lateral variation of underground velocity structure which is consistent with the result of MASW. Based on the results of analysis one can say that a L-shape array can be applied to estimate shear wave velocity for shallow depth so it can be layout in urban areas to determine phase velocity information from microtremors. Therefore, it may be feasible to apply it in the Kathmandu Valley, Nepal that is based upon the soft soil with high possibility of liquefaction or earthquake hazard.

scholarly journals Study of VCM Improved Soft Soil Properties Using Non-Destructive and Destructive Techniques

Geosciences ◽  
2020 ◽  
Vol 10 (8) ◽  
pp. 300
Author(s):  
Diandri Fakhri Alditra ◽  
Susit Chaiprakaikeow ◽  
Suttisak Soralump
Keyword(s):  
Soil Properties ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
Soil Improvement ◽  
Prefabricated Vertical Drain ◽  
Soil Settlement ◽  
Pump Pressure ◽  
Non Destructive

In Bangkok, the demand for housing is extensively high due to the city growing rapidly, so some swampy areas are filled with soil. A Prefabricated Vertical Drain (PVD) with the Vacuum Consolidation Method (VCM) is required to make the soil applicable for construction. However, it is difficult to monitor the soil strength during the process because the airtight sheet will be broken. This research aims to study the possibility of using the Spectral Analysis of Surface Waves (SASW) test to monitor the effectiveness of the VCM method and to study the development of shear-wave velocity over the consolidation period. Multiple instruments were installed on site, namely, vacuum gauges, settlement plates, and a piezometer, as well as a borehole to monitor the pump pressure, settlement, porewater pressure, and soil properties. Ten SASW tests were taken to measure the change in shear-wave velocity (Vs) over 7 months. The results showed an increment in the Vs along with increments in the settlement and undrained shear strength (Su), as well as a decrement in pore pressure during the consolidation period. The correlation between Vs and soil settlement was developed to predict the amount of settlement using Vs. These all indicated the potential of using the SASW method for soil improvement monitoring purposes.

scholarly journals Observation and synthesis of spatially-incoherentweak-motion wavefields at Alfredton basin, New Zealand

1997 ◽  
Vol 30 (1) ◽  
pp. 14-31 ◽  
Author(s):  
A. J. Haines ◽  
Jaishun Yu
Keyword(s):  
New Zealand ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Soft Soil ◽  
Seismic Energy ◽  
Wave Impedance ◽  
3 Dimensional ◽  
Scale Experiment ◽  
Random Nature

To observe and model the detailed pattern of ground motion amplification in a small soft-soil basin an experiment was conducted at Alfredton, New Zealand. 19 seismometers were deployed for 5 weeks at closely spaced sites in and around a 400-500 m diameter, sediment-filled depression in soft, sandstone basement. During this period 112 earthquakes, with "weak" ground motions, were detected by at least some of the instruments, and 15 well-recorded events were selected for detailed analysis. Geotechnical data obtained to provide the parameters for the 3-dimensional modelling included measurements of the shear-wave velocity. Across the basin this is 60 m/s at the surface, increasing steadily to 300+ m/s at the bottom of the basin, and the shear-wave velocity in the basement is 850 m/s. Thus, there are no boundaries where the contrast in shear-wave impedance is especially large. In contrast to situations where there are large contrasts in shear-wave impedance to trap seismic energy in soft-soil layers, the amplifications observed in the basin at Alfredton were small. The small amplifications are confirmed by the 3-dimensional modelling. Another feature of the observed wavefields is that in all cases the incident motions, recorded at the basement sites around the basin, were spatially incoherent. In other words, the wavefields arriving at the basin were of a complex, seemingly random nature. This is the first occasion that the spatial coherency of wavefields has been measured in a fine-scale experiment in New Zealand. Apart from the small amplications and the observed lack of coherency between the basement sites, the most striking result, which was obtained from both the observations and the modelling of similarly incoherent wavefields, is that for short-duration events in which the main motions last for no more than a second, the amplifications in the basin are larger than for events in which the motions are of longer duration; that is, the extent to which differently propagating incoherent wave packets interfere destructively inside the basin increases with the duration of the wavefields.

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