scholarly journals A field test for dynamic soil properties

1971 ◽  
Vol 4 (2) ◽  
pp. 176-204
Author(s):  
G. L. Evans
Keyword(s):  
Earthquake Engineering ◽  
Soil Structure ◽  
Earth Pressure ◽  
Simple Wave ◽  
Wave Form ◽  
S Wave ◽  
Dynamic Moduli ◽  
Seismic Surveys ◽  
Wave Velocities ◽  
Dynamic Earth Pressure

The propogation velocity of waves through ground has been used for many years in the
seismic surveys for the detection of underlying strata. From a knowledge of the percussion (P) and shear (S) wave velocities in different materials, together with their bulk densities, it is possible to derive dynamic moduli and properties, such as the shear modulus (G) and poisson’s ratio (n), which are essential in
 the solution of problems relating to dynamic earth pressure, soil structure interaction and the dynamic analysis of foundation strata relating to earthquake engineering. The principle involved in finding the wave velocities in ground materials is the same as used in finding velocities in any material. A simple wave form or pulse is generated at one point and the travel time to several other
 points is detected with suitable signal receivers.

S-wave velocity measurements in deep soil deposit and bedrock by means of an elaborated down-hole method

1980 ◽  
Vol 70 (1) ◽  
pp. 363-377
Author(s):  
Y. Ohta ◽  
N. Goto ◽  
F. Yamamizu ◽  
H. Takahashi
Keyword(s):  
Wave Velocity ◽  
Earthquake Engineering ◽  
Underground Structure ◽  
P Wave ◽  
Velocity Measurements ◽  
S Wave ◽  
Deep Soil ◽  
Tokyo Metropolitan Area ◽  
Wave Velocities ◽  
P Wave Velocities

abstract Deep S-wave velocity measurements were planned at two separate sites in the Tokyo area from the earthquake engineering point of view, and actually carried out down to 2 to 3 km in depth using geophysical observation wells. S-waves were produced by means of ordinary small explosions and a specially designed SH-wave generator. A set of three component seismometers was installed in a capsule having a device that is clamped to the borehole wall. Measurements to the bottom of the wells were conducted at about 15 different depths at intervals of 100 to 500 m. The S-wave velocities are around 0.8 km/sec in Pleistocene soils, 1.2 to 1.6 km/sec in Miocene soils, and 2.5 to 2.7 km/sec in Cambrian rocks. The corresponding P-wave velocities are 2.0 to 2.3 km/sec, 2.6 to 3.0 km/sec, and 4.7 to 4.9 km/sec, respectively. These data show both S- and P-wave velocities in deep soil deposit increasing with depth. The greatest velocity difference is at the boundary above the pre-Tertiary rocks. The velocity structures completely agree with the known data such as sonic logs, density distributions, and geological sections. A comparison with velocity profiles at two separate sites was also made as the first step to visualize the three-dimensional underground structure in the Tokyo metropolitan area. The seismological and earthquake engineering importance of shear-wave velocity measurements for thick soil deposits was demonstrated by approximate calculations of the amplification of seismic waves between ground surface and bedrock.

Improved estimation method for dynamic bulk moduli of sandstones subjected to hydrostatic stress.

2021 ◽  
Author(s):  
Nazanin Nourifard ◽  
Elena Pasternak ◽  
Maxim Lebedev
Keyword(s):  
Hydrostatic Pressure ◽  
Wave Velocity ◽  
Hydrostatic Stress ◽  
Estimation Method ◽  
P Wave ◽  
S Wave ◽  
Dynamic Moduli ◽  
Fixed Rate ◽  
Wave Velocities ◽  
P Wave Velocity

<p>We designed and modified an experimental method to simultaneously measure the stress-strain (static moduli) and stress dependence of S and P-wave velocities of rocks (sandstone) under hydrostatic pressure by a Hoek’s cell. Dynamic moduli were calculated from the direct measurement of ultrasonic P- and S-wave velocities at a central dominant frequency of 1 MHz, while static moduli was recorded by strain gauges. The hydrostatic pressure was applied with a fixed rate at 1MPa/minute. We observed that the dynamic bulk moduli can be up to 44% higher than the static moduli in sandstones with porosity ranging from 8% to 24%. The results are in agreement with the existing empirical equations for soft rocks. Our experimental results demonstrate that the dynamic bulk’s modulus ranges from 4-13GPa, while the static bulk modulus ranges from 2-11GPa. We measured dynamic Young’s modulus and Poisson’s ratio at four different time periods (before applying the stress, right after the unloading, 20 days, and 60 days after the experiment) to investigate the effect of time on stress relaxation and eventually on the properties of the sandstones. All the samples showed an increase of Young’s modulus right after the stress application and then a gradual decrease of this value over time because of this relaxation; however, most of the samples could not reach the original state due to irreversible deformation at micro-level. Dynamic moduli show greater sensitivity to the irreversible deformations as compared to static moduli (even within the elastic limits). Dynamic moduli of porous material are also more sensitive to the microstructure than the static ones. Independent P and S-wave measurement for this study showed that the estimation of the S-wave velocity from the recorded P-wave velocity is not an accurate procedure and introduces a big error in the final calculation of the dynamic moduli. It also confirmed that by registering an accurate P-wave velocity the UCS (Unconfined Compressive Strength) value can be accurately estimated for sandstones. This demonstrates the great potential of dynamic studies as a non-destructive method to estimate this value for porous materials.</p>

The relation between seismic P‐ and S‐wave velocity dispersion in saturated rocks

Geophysics ◽  
1994 ◽  
Vol 59 (1) ◽  
pp. 87-92 ◽  
Author(s):  
Gary Mavko ◽  
Diane Jizba
Keyword(s):  
Wave Velocity ◽  
Large Scale ◽  
Velocity Dispersion ◽  
Seismic Velocity ◽  
Ultrasonic Velocities ◽  
S Wave ◽  
Local Flow ◽  
Wave Velocities ◽  
Shear Compliance

Seismic velocity dispersionin fluid-saturated rocks appears to be dominated by tow mecahnisms: the large scale mechanism modeled by Biot, and the local flow or squirt mecahnism. The tow mechanisms can be distuinguished by the ratio of P-to S-wave dispersions, or more conbeniently, by the ratio of dynamic bulk to shear compliance dispersions derived from the wave velocities. Our formulation suggests that when local flow denominates, the dispersion of the shear compliance will be approximately 4/15 the dispersion of the compressibility. When the Biot mechanism dominates, the constant of proportionality is much smaller. Our examination of ultrasonic velocities from 40 sandstones and granites shows that most, but not all, of the samples were dominated by local flow dispersion, particularly at effective pressures below 40 MPa.

Nonlinear behavior of soil sediments identified by using borehole records observed at the Ashigra Valley, Japan

1995 ◽  
Vol 85 (6) ◽  
pp. 1821-1834
Author(s):  
Toshimi Satoh ◽  
Toshiaki Sato ◽  
Hiroshi Kawase
Keyword(s):  
Shear Strain ◽  
Main Part ◽  
Nonlinear Behavior ◽  
Strong Motion ◽  
S Wave ◽  
Ground Shaking ◽  
Wave Velocities ◽  
The One ◽  
Soil Sediments ◽  
Strong Ground

Abstract We evaluate the nonlinear behavior of soil sediments during strong ground shaking based on the identification of their S-wave velocities and damping factors for both the weak and strong motions observed on the surface and in a borehole at Kuno in the Ashigara Valley, Japan. First we calculate spectral ratios between the surface station KS2 and the borehole station KD2 at 97.6 m below the surface for the main part of weak and strong motions. The predominant period for the strong motion is apparently longer than those for the weak motions. This fact suggests the nonlinearity of soil during the strong ground shaking. To quantify the nonlinear behavior of soil sediments, we identify their S-wave velocities and damping factors by minimizing the residual between the observed spectral ratio and the theoretical amplification factor calculated from the one-dimensional wave propagation theory. The S-wave velocity and the damping factor h (≈(2Q)−1) of the surface alluvial layer identified from the main part of the strong motion are about 10% smaller and 50% greater, respectively, than those identified from weak motions. The relationships between the effective shear strain (=65% of the maximum shear strain) calculated from the one-dimensional wave propagation theory and the shear modulus reduction ratios or the damping factors estimated by the identification method agree well with the laboratory test results. We also confirm that the soil model identified from a weak motion overestimates the observed strong motion at KS2, while that identified from the strong motion reproduces the observed. Thus, we conclude that the main part of the strong motion, whose maximum acceleration at KS2 is 220 cm/sec2 and whose duration is 3 sec, has the potential of making the surface soil nonlinear at an effective shear strain on the order of 0.1%. The S-wave velocity in the surface alluvial layer identified from the part just after the main part of the strong motion is close to that identified from weak motions. This result suggests that the shear modulus recovers quickly as the shear strain level decreases.

Jacobian matrix for the inversion of P- and S-wave velocities and its accurate computation method

2010 ◽  
Vol 54 (5) ◽  
pp. 647-654 ◽  
Author(s):  
FuPing Liu ◽  
XianJun Meng ◽  
YuMei Wang ◽  
GuoQiang Shen ◽  
ChangChun Yang
Keyword(s):  
Jacobian Matrix ◽  
Computation Method ◽  
S Wave ◽  
Wave Velocities ◽  
Accurate Computation

Shallow velocity structure and poisson's ratio at the Tarzana, California, strong-motion accelerometer site

1996 ◽  
Vol 86 (6) ◽  
pp. 1704-1713 ◽  
Author(s):  
R. D. Catchings ◽  
W. H. K. Lee
Keyword(s):  
Urban Areas ◽  
Velocity Structure ◽  
Strong Motion ◽  
P Wave ◽  
S Wave ◽  
Near Surface ◽  
Velocity Models ◽  
Wave Velocities ◽  
Poisson's Ratios ◽  
Poisson’S Ratios

Abstract The 17 January 1994, Northridge, California, earthquake produced strong ground shaking at the Cedar Hills Nursery (referred to here as the Tarzana site) within the city of Tarzana, California, approximately 6 km from the epicenter of the mainshock. Although the Tarzana site is on a hill and is a rock site, accelerations of approximately 1.78 g horizontally and 1.2 g vertically at the Tarzana site are among the highest ever instrumentally recorded for an earthquake. To investigate possible site effects at the Tarzana site, we used explosive-source seismic refraction data to determine the shallow (<70 m) P-and S-wave velocity structure. Our seismic velocity models for the Tarzana site indicate that the local velocity structure may have contributed significantly to the observed shaking. P-wave velocities range from 0.9 to 1.65 km/sec, and S-wave velocities range from 0.20 and 0.6 km/sec for the upper 70 m. We also found evidence for a local S-wave low-velocity zone (LVZ) beneath the top of the hill. The LVZ underlies a CDMG strong-motion recording site at depths between 25 and 60 m below ground surface (BGS). Our velocity model is consistent with the near-surface (<30 m) P- and S-wave velocities and Poisson's ratios measured in a nearby (<30 m) borehole. High Poisson's ratios (0.477 to 0.494) and S-wave attenuation within the LVZ suggest that the LVZ may be composed of highly saturated shales of the Modelo Formation. Because the lateral dimensions of the LVZ approximately correspond to the areas of strongest shaking, we suggest that the highly saturated zone may have contributed to localized strong shaking. Rock sites are generally considered to be ideal locations for site response in urban areas; however, localized, highly saturated rock sites may be a hazard in urban areas that requires further investigation.

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