Comparison of down-hole and laboratory shear wave velocities

1979 ◽  
Vol 16 (1) ◽  
pp. 152-162 ◽  
Author(s):  
T. J. Larkin ◽  
P. W. Taylor
Keyword(s):  
Shear Modulus ◽  
Soil Properties ◽  
Shear Wave ◽  
Torsion Test ◽  
Testing Procedures ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Seismic Surveying ◽  
Sample Disturbance

The method of down-hole seismic surveying is described. This method was successfully used to a depth of 50 m in a cased borehole and these results are presented. The method may be used to find the in situ low strain shear modulus for use in theoretical response studies.Structural changes and changes in the stress state of samples usually result from sampling, handling, and testing procedures. Large changes in soil properties may result from these processes. An assessment of the change in soil properties is presented, which is of importance for the use of laboratory derived soil properties in theoretical in situ dynamic response studies.The magnitude of sample disturbance is assessed by comparing in situ and laboratory measured shear wave velocities. In situ down-hole shear wave velocities are compared with low strain (1 × 10−6) laboratory dynamic torsion test results. The large differences found may be correlated with the in situ shear wave velocity.A procedure is presented to correct the laboratory established shear modulus–strain relation–ship for the effects of sample disturbance. The adjusted laboratory curve is then suitable for use in theoretical response studies and will be a more accurate representation of the in situ deformation characteristics.

A further comparison of shear-wave velocities

1982 ◽  
Vol 19 (4) ◽  
pp. 506-507 ◽  
Author(s):  
T. J. Larkin ◽  
P. W. Taylor
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Laboratory Apparatus ◽  
Wave Source ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Seismic Tests ◽  
Sample Disturbance

In a previous paper by the same authors the values of the shear-wave velocity in natural soils found from laboratory tests were compared with wave velocities measured in situ. Dynamic free-vibration torsion tests were carried out in the laboratory on undisturbed 150 × 75 mm soil samples. Downhole seismic tests were performed at the site to measure the velocity of propagation of low strain shear waves from a surface wave source. Differences between laboratory and field values of the shear-wave velocity were considered to be due to sample disturbance. Further work has established that, provided system compliance in the laboratory apparatus is allowed for, laboratory and field values agree reasonably well. The test results are analysed again with account being taken of the stiffness of the laboratory apparatus.

The Applicability of Existing Typical Liquefaction Evaluation Methods of Site Soils Based on Shear Wave Velocities for Bachu Earthquake

2011 ◽  
Vol 90-93 ◽  
pp. 1412-1418
Author(s):  
Jiang Hua Shi ◽  
Zhen Zhong Cao ◽  
Zhao Yan Li ◽  
Xiao Ming Yuan ◽  
Lin Dong
Keyword(s):  
Shear Wave ◽  
Shear Wave Velocity ◽  
Satisfactory Result ◽  
Evaluation Method ◽  
Evaluation Methods ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Testing Data ◽  
Critical Lines

Based on liquefaction survey of 2003 Xinjiang Bachu earthquake of Ms6.8 and in-situ shear wave velocity testing data, the feasibility and applicability of five typical liquefaction evaluation methods which use shear wave velocities as criteria are presented herein. Analysis showed that none of the five liquefaction evaluation methods can provide a satisfactory result in Bachu area. The successful judging rates are only 36% to 64%. The intensity method which is employed to evaluate liquefied and non-liquefied sites in Bachu area provides only 40% successful judging rate, and the method is risky in intensity VII area and conservative in intensity IX area. The critical lines of the five methods deviate greatly from the actual lines. In intensity VII area all the five methods incorrectly misjudge. Further work has to be conducted to research on the soil properties in Bachu area and to establish the regional liquefaction evaluation method in Xinjiang.

Horizontally Mounted Bender Elements for Measuring Shear Modulus in Soaked Sand Specimen

2014 ◽  
Vol 931-932 ◽  
pp. 496-500
Author(s):  
Keeratikan Piriyakul ◽  
Janjit Iamchaturapatr
Keyword(s):  
Shear Modulus ◽  
Shear Wave ◽  
Shear Waves ◽  
Side Wall ◽  
Bender Element ◽  
Bender Elements ◽  
High Quality ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Shear Strains

New horizontally mounted bender element devices capable of high-quality transmission and reception of horizontally propagated shear waves polarized in orthogonal planes across the mid-height of a sand specimen are described. Mounting of these bender elements is on the membrane, attaching on the side wall of the reactor container. This technique is suitable for use on samples down to 80 mm length. The effective fabrication procedures that have been developed are described. The instrumentation systems used to drive and receive signals are outlined, and estimates of the magnitude of the shear strains developed by the bender elements and the accuracy with which shear wave velocities can be determined are discussed. The sand specimen is treated by the solution then its strength is developed. These new bender elements enable shear modulus to be measured before, during and after the treatment.

Modulus reductions of dam embankment materials based on downhole array time series

2019 ◽  
Vol 36 (1) ◽  
pp. 400-421
Author(s):  
Tadahiro Kishida ◽  
DongSoon Park ◽  
Rita L. Sousa ◽  
Richard Armstrong ◽  
Young-Ji Byon
Keyword(s):  
Time Series ◽  
Shear Wave ◽  
Earthen Dam ◽  
Acceleration Time ◽  
Wave Velocities ◽  
Shear Wave Velocities ◽  
Shear Strains ◽  
Modulus Reduction ◽  
Core Materials

A database of three-component acceleration time series recorded at downhole arrays in earthen dam cores was published by the Japan Commission on Large Dams. This study reviews the acceleration time series in nine earthfill and rockfill dams in Japan. The apparent shear wave velocities between downhole sensors in each dam during strong shakes are determined by calculating the wave travel time between the recorded time series. Transient shear strains are calculated from the differences in the displacement time series between sensors through the double integration of filtered acceleration time series. The modulus reduction curves of the in situ core materials are constructed by combining the apparent shear wave velocities and shear strains. The modulus reduction data are then compared with empirical models. Observations show considerable uncertainties and dam-dependent characteristics in the extracted in situ shear modulus. Accordingly, this study proposes a methodology to update the empirical modulus reduction model for dam core materials on the basis of observed data on downhole time series.

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