Primary Wave Velocity Research Articles

Determining the Geotechnical Characteristics of Some Sedimentary Rocks from Iran with an Emphasis on the Correlations between Physical, Index, and Mechanical Properties

Geotechnical characteristics were assessed to correlate physical, index, and mechanical properties of twelve sedimentary rock samples of four rock types collected from northern and northwestern parts of Damghan, northern Iran. Mineralogical and physical properties of the rocks were determined from prepared specimens in the laboratory after the field investigations. Also, the selected rock samples were subjected to index and mechanical tests including P-wave velocity, Schmidt rebound hardness, slake durability, point load, Brazilian, block punch, and uniaxial compressive strength. Mineralogical studies by thin section and X-Ray diffraction methods indicated that the selected rock samples with different textures are mainly composed of quartz and calcite. The studied rocks had low to high dry unit weight, low to medium porosity and low to very high P-wave velocity. The rocks were classified as durable and very durable based on the slake durability index. They were very strong to extremely strong in point load index, weak to moderate in block punch index, and weak to strong in uniaxial compressive strength. So they were classified in different strength categories. The obtained correlations between different rock properties from regression analyses indicated that specific gravity and unit weights are affected by mineral content while the other characteristics including water absorption, primary wave velocity, Schmidt rebound hardness, slake durability index, point load index, Brazilian tensile strength, and block punch strength are controlled by the porosity of the rocks.

Modified pseudo-dynamic bearing capacity analysis of shallow strip footing considering total seismic wave

The seismic bearing capacity analysis is a very important study for the safe design of underground structures in earthquake-prone areas. The earlier pseudo-dynamic methods provide the methodology of seismic analyses without considering the effects of Rayleigh waves though it contributes about 67% of the total seismic energy. So, in this paper, an attempt has been made to evaluate the seismic bearing capacity of shallow strip footing using modified pseudo-dynamic approach. This approach simultaneously considers the effect of Rayleigh wave along with primary wave and shear wave velocity. Limit equilibrium method is used to solve this problem of seismic bearing capacity of shallow strip footing resting on c–Φ soil. Along with that single seismic bearing capacity, coefficients are presented under simultaneous resistance of unit weight, overburden and cohesion and detailed analyse w.r.t different parameters. Also, results are thoroughly compared with the existing values in the literature and the significance of the present methodology for designing the shallow strip footing is discussed.

Strong near-surface seismic anisotropy of Taiwan revealed by coda interferometry

We report the near-surface (<400 m) primary wave velocity (Vp), shear wave velocity (Vs), Vp/Vs ratio, Poisson's ratio and Vs anisotropy of Taiwan by applying seismic coda interferometry to 34 borehole-surface station pairs. We find clear characteristic cos⁡2θ dependence of Vs in all the determinations, and about half of the amplitudes of anisotropy are larger than 10%, with the largest amplitudes up to 34%. The patterns of anisotropy fall into two categories, OPA (Orogeny-Parallel Anisotropy) and SAA (Stress-Aligned Anisotropy). Both types of anisotropy fit well the local geological fabrics and/or the ambient stress, and show strong correlation with the Poisson's ratios at the borehole sites. With these new findings and reported tomographic results, we infer that the SAA are likely confined to the uppermost portion of the crust, in particular to the fluid-saturated late-Quaternary deposits. The strong near-surface anisotropy also implies that delay times contributed by the shallow crust might have been underestimated in studies of shear-wave splitting measurements using the direct arrivals of earthquake waves.

Regression-based models for the prediction of unconfined compressive strength of artificially structured soil

Unconfined compressive strength (UCS) of soil is a critical and important geotechnical property which is widely used as input parameters for the design and practice of various geoengineering projects. UCS controls the deformational behavior of soil by measuring its strength and load bearing capacity. The laboratory determination of UCS is tedious, expensive and being a time-consuming process. Therefore, the present study is aimed to establish empirical equations for UCS using simple and multiple linear regression methods. The accuracy of the developed equations are tested by employing coefficient of determination (R 2), root mean square error (RMSE) and mean absolute percentage error (MAPE). It has been found that the developed equations are reliable and capable to predict UCS with acceptable degree of confidence. Among all the developed models, model-I consist of lime content, curing time, plastic limit, liquid limit, potential of hydrogen, primary ultrasonic wave velocity, optimum moisture content and maximum dry density as independent parameters shows highest prediction capacity with R 2, RMSE and MAPE are 0.96, 25.89 and 16.59, respectively.

Combination of the Physical and Ultrasonic Tests in Estimating the Uniaxial Compressive Strength and Young’s Modulus of Intact Limestone Rocks

Geo-mechanical parameters of intact rocks like uniaxial compressive strength (UCS) and young’s modulus (E) have been essentially evaluated for many objects. These parameters are obtained by standard UCS tests that are destructive, expensive, and time-consuming task. By using nondestructive methods such as the ultrasonic or physical tests, the parameters can be indirectly predicted. Consequently, presentation of multiple linear regression equations between destructive and nondestructive parameters is proposed in this paper. In order to predict the UCS and E in terms of density (ρ), porosity (n), primary wave velocity (Vp) and shear wave velocity (Vs), 482 rock samples’ data of five sedimentary rock types (in range from limestone to marl) from five different dam sites (located in Asmari formation, southwest of Iran) were analyzed. After regression analysis of the test results, the best fit equations are selected–equations with four independent variables (ρ, n, Vp, Vs) and high coefficients of determination (R2) on levels of 0.91 for UCS and 0.88 for E. These equations are simple, practical, and accurate enough to apply. They also can be used in practice for prediction purposes with acceptable accuracy.

Evaluation of Geotechnical Parameters using Geophysical Data

The financial implications and the time required for carrying out a comprehensive geotechnical investigation to characterize a site can discourage prospective private residential building developers, especially where a large area of land is to be investigated for construction purposes. Also, most of the geotechnical test procedures utilized during site investigation only provide information on points tested in the subsurface. This research method suggests an approach of investigating the subsurface condition of a site in order to obtain key subsoil geotechnical properties necessary for foundation design for proposed engineering facilities. Seismic wave velocities generated from near surface refraction were combined with percussion drilling and cone penetration tests to obtain a comprehensive geotechnical investigation. From the results of the seismic refraction method, the bulk density of the soil, Young’s modulus, bulk modulus, shear modulus and allowable bearing capacity of a competent layer that can bear structural load at the particular study site were determined. The most competent layer was found within the depth observed by geotechnical methods. In addition, regression equations were developed in order to directly obtain the bulk density of the soil, Young’s modulus, bulk modulus, shear modulus and allowable bearing capacity from the primary wave velocities.

Laboratory measurement of elastic waves in Basalt rock

Abstract This paper reports the laboratory measurement of compression and shear waves in Basalt rock. Compression or primary waves were produced using a standard ultrasonic pulse velocity tester. However, it is well accepted that the production of pure shear waves in rock is difficult because of which suitable assumptions are made in the testing. Since bender elements have traditionally been used to produce pure shear at very small strains in soft materials, their use has been extended in this study to Basalt rock. The fabrication and setup of bender element tests is first discussed. The transducers were accommodated in pre-drilled slots at the two flat ends of the samples, the effect of which was carefully investigated using experimental and numerical studies. For 10–12 mm long piezoceramic plates, the shear wave velocity was found to reduce by about 5% because of the slots. The shear wave velocity was estimated using the first arrival method after removing the near field and the crosstalk effects from the output signal. The shear wave velocity ranged between 1.15 and 3.31 km/s and was nearly equal to one-half of the primary wave velocity. The results also show that the ratio of the shear wave velocity and the compression wave velocity was independent of the density and porosity of the Basalt rock. Because most of the rock was unweathered and compact and, its cavities filled with secondary minerals such as zeolites, calcites and silicates, it is unlikely that the high overburden pressures would affect the observed wave velocities.

Experimental investigation of primary-wave velocities and constrained moduli of quartz sand subjected to extender element tests and stress anisotropy

The measurement of primary wave velocities (Vp) of geo-materials is an essential step for the geophysical and dynamic characterization of sediments. Advances in experimentation have established in recent years the use of the extender element test method in laboratory research and practice. This method is applicable for the measurement of Vp of geo-materials applying a high-frequency pulse excitation, typically between 5 and 20 kHz. In the study, extender elements inserted in a stress path triaxial apparatus were used for the measurement of primary-wave velocities of quartz sands of variable grain morphologies. During the dynamic tests, the samples were subjected to a deviatoric compressive load, which allowed the study of the effect of stress anisotropy, expressed through the stress ratio, on Vp. To overcome difficulties of poor signal output of P-waves, which may occur when the sample is fully saturated, the samples were prepared and tested in a dry state. Measurements of sample volumetric strains were conducted from local strain sensor attached to the sample which captured radial deformations during the isotropic and anisotropic stress paths and a vertically positioned LVDT which captured the axial strains of the samples. Accordingly, based on the measured P-wave velocities and the density of the samples, the constrained modulus (Mmax) was quantified. The results indicated that for a given mean effective confining pressure, the sensitivity of Vp and Mmax to the magnitude of the applied stress ratio was controlled, markedly, by the morphology of the grains; for sands of fairly rounded and spherical grains, this effect was relatively small, but for sands of irregular in shape grains, the stress ratio affected markedly the behavior of the samples.

Thermally induced variation of primary wave velocity in granite from Yantai: Experimental and modeling results

This work analyzes the results from experiments for studying the effect of high temperature on primary wave velocity of granite. Test samples are preheated to different temperatures (from 25° to 900 °C) and then cooled down by air. The primary wave velocity test is performed on the heated samples. Lastly, the microstructure test is carried out to study the mechanism of thermal damage and development process of micro cracks. The results show that the primary wave velocity reduces gradually while the temperature increases, i.e. the higher the heating temperature is, the faster the wave velocity reduces. Basing on the waveform, the quality factor (Q) of primary wave velocity is calculated and is decreased with the increase of heating temperature. From the thermal damage factor (D(T)) model of primary wave velocity and the measured data, the D(T) of granite samples is found to increase with heating temperature rising following the S-logistic function. Then, according to the change of microstructure, the formation mechanism of thermal damage is analyzed and the damage process of rock verified by the deterioration of mechanical parameters. For rock heated to different temperatures and then cooled down, the main reason for damage at lower temperature is dehydration and that at higher temperature is the increase of cracks which destroy the structure and weaken the bonding between particles.

Temperature effect on microstructure and P-wave propagation in Linyi sandstone

In order to study the effect of high temperature on the sandstone, scanning electron microscope (SEM) experiments and primary wave (P-wave) velocity tests have been carried out on sandstone specimens heated to different temperature. The results showed that: (1) the mass loss rate increases exponentially with the increase of temperature and reaches 2.97% at 900°C; (2) the P-wave velocity change rate increases exponentially with the increase of temperature while there is some fluctuation before 500°C; (3) the damage threshold temperature of sandstone samples is 300°C and the limit temperature is 900°C; (4) there is a good linear relationship between the mass loss rate and the P-wave velocity change rate, and the correlation coefficient (R) of the fitting line is 0.989; (5) the damage caused by high temperature can be reflected better by the mass loss rate than P-wave velocity change rate. The results obtained in this paper will be good for predicting the properties of sandstone when exposed to high temperature.

Effect of Gym Ball Exercise on Primary Dysmenorrhea and Pulse Wave Velocity of Lower Limbs in Young Women

Background/Objectives: Gym Ball can be used as an exercise therapy program for prevention of low abdominal pain. Accordingly, the purpose of this study was to investigate the effect of gym ball on primary dysmenorrhea pain and arterial pulse wave velocity of lower limbs in young women. Methods/Statistical analysis: The subjects are 16 (age 19.81 ± 0.83years, height 161.48 ± 1.69cm, weight 56.33 ± 3.27kg, menarche 15.49 ± 0.28years) college female students. Gym Ball exercise was performed with a frequency of three times a week (Monday, Wednesday, Friday), by 50 minutes at a time for 10 weeks. Comparison of related variables before and after gym ball exercise was verified by paired t-test. Findings: The present study shows that left PWV and right PWV of lower limbs were significantly decreased after gym ball exercise. Cardiac Output and Stroke Volume were significantly increased after gym ball exercise. In addition, dysmenorrhea pain index such as VAS and VRS were each showed a significant decrease. Application/Improvements: In conclusion, gym ball exercise represents that it improves blood flow circulations of the lower limbs and reduce the pain of the lower abdomen during menstrual period. Therefore, gym ball exercise program can be used in the prevention of primary dysmenorrhea.

Experimental Determination of Crack Initiation and Crack Damage of Two Granites

Mineralogical composition and microstructural features influence rock strength and their failure mechanisms. Crack initiation (CI) and crack damage (CD) are important processes of the failure mechanisms of rocks. Since CI is the lower limit of the long term strength of rocks at low confinement, this study is mainly concerned with triaxial tests and the determination of CI and CD using different methods. A triaxial cell has been designed to examine spalling behavior of magmatic rocks under low confinement, at minor principal stresses up to 2.5MPa. Two granites with different grain sizes were tested. Methods to determine CI and CD include the calculation of circumferential, volumetric and crack volumetric strain. In addition, acoustic emission monitoring provides the onset of CI and CD. Uniaxial compressive tests including primary wave velocity measurements as well as acoustic emission were used to supplement the dataset. The wave velocities also give an indirect determination of CI and CD as the initiation of cracks reduces the speed of the waves. This study aims to compare the different methods determining CI and CD and to connect the results with mineralogical and microstructural features. Orientated thin sections were prepared to identify the mineralogical composition. Furthermore, the growing influence of confining pressure from 0.1 to 2.5MPa on rock strength was analyzed.

A study of wave velocities and poisson ratio of recycled concrete aggregate

The dynamic properties of two uniform recycled concrete aggregates (RCA) were investigated with a focus on shear wave velocities (Vs), primary wave velocities (Vp) and Poisson ratio (ν). The geotechnical characterization of these materials, one RCA with a fraction of 1.18–2.36mm and the other with a fraction of 0.60–1.18mm, was implemented through the quantification of particle shape descriptors, monotonic drained triaxial tests and one-dimensional compression tests. The grain damage of the RCA was quantified by examining the grading curves of the samples before and after the performance of the one-dimensional compression tests. Bender and extender element tests were carried out on dry samples under isotropic conditions of the confining pressure in order to investigate the dynamic properties of the RCA and comparisons were implemented between bender/extender elements and resonant column tests in torsional and flexural modes. The laboratory test results indicated that during the isotropic compression of the samples, Vs showed slightly higher sensitivity to pressure than Vp and the Poisson ratio was found to be dependent on pressure. However, during the isotropic unloading stage, Vs and Vp showed similar sensitivity to pressure and the Poisson ratio was found almost to be independent of pressure change. An empirical-type model proposed in the literature for crushed rock of irregular-shaped grains predicted within satisfactory limits the small-strain shear modulus of the RCA. The small-strain material damping in shear and the strain-dependent modulus and material damping were investigated and are discussed for a limited number of tests.

In Situ Methane Hydrate Morphology Investigation: Natural Gas Hydrate-Bearing Sediment Recovered from the Eastern Nankai Trough Area

The hydrate morphology of natural gas hydrate-bearing (GH) sediments recovered from the eastern Nankai trough area was investigated under hydrostatic pressurized conditions that prevent dissociation of gas hydrates in a sediment. We developed a novel X-ray computed tomography system and an attenuated total reflection infrared (ATR-IR) probe for use in the Instrumented Pressure Testing Chamber for our set of Pressure-Core Nondestructive Analysis Tools (PNATs), which can measure the sediment structure, primary wave velocity (PWV), density, and shear strength under pressurized conditions. The hydrate saturation values estimated using the ATR-IR absorption bands of H2O molecules strongly correlate with PWV. Assuming homogeneity of hydrate distribution in the planes perpendicular to the sample depth direction, the hydrate morphology of natural GH sediments in the eastern Nankai trough area demonstrated a load-bearing morphology type. The predicted hydrate morphology results are in good agreement with data repo...

Application of near-surface seismic refraction tomography and multichannel analysis of surface waves for geotechnical site characterizations: A case study

In this case study two geophysical methods based on seismic waves were employed to evaluate the geotechnical properties of the soil deposits at a site for a planned wind farm. Regional geological information shows that the study area is mainly covered by recent alluvium, which is classified as a mixture of fine sand and gravel. Twenty five seismic refraction surveys were carried out in the study area. The acquired shot gathers were processed, from which primary wave (P-wave) and shear wave (S-wave) velocities were derived. The P-wave velocities were obtained by using the Seismic Refraction Tomography method (SRT) while the S-wave velocities were extracted by utilizing the Multichannel Analysis of Surface Waves (MASW) technique, which is established based on the dispersion characteristics of Rayleigh waves. Seismic hazard at the site was evaluated according to the Iranian code using the measured S-wave velocities, and the friction angles of the soil deposits were approximated using an empirical method and by making use of Jaky's formula for earth pressure at rest, which yielded similar values. The deformation properties of the foundation soil were also estimated based on the correlations between seismic wave velocities and elastic properties of soil as well as Janbu's formula for soil modulus. The findings of this study may serve as references for economic and non-destructive geotechnical site characterizations using seismic-wave methods.

Determination of the Geotechnical Characteristics of Hornfelsic Rocks with a Particular Emphasis on the Correlation Between Physical and Mechanical Properties

Geotechnical characteristics and relationships between various physical and mechanical properties were assessed for eight types of hornfelsic rock collected from southern and southwestern parts of the city of Hamedan in western Iran. Rock samples were subjected to mineralogical, physical, index, and mechanical laboratory tests and found to contain quartz, feldspar, biotite, muscovite, garnet, sillimanite, kyanite, staurolite, graphite, and other fine-grained cryptocrystalline matrix materials. Samples had a porphyroblastic texture, and the mineral contents and physical properties influenced various rock characteristics. Some rock characteristics were affected by mineral content, while others were affected by porosity. Dry unit weight, primary and secondary wave velocities, and slake-durability index were noteworthy characteristics affected by mineral content, while porosity had the greatest influence on water absorption, Schmidt hardness, point load index, Brazilian tensile strength, and uniaxial compressive strength. Empirical equations describing the relationships between different rock parameters are proposed for determining the essential characteristics of rock, such as secondary wave velocity, slake-durability index, point load index, Brazilian tensile strength, and uniaxial compressive strength. On the basis of these properties, the studied rocks were classified as being strong or very strong.

Pseudo-Dynamic Bearing Capacity of Shallow Strip Footing Resting on c-Φ Soil Considering Composite Failure Surface

The evaluation of bearing capacity of shallow strip footing under seismic loading condition is an important phenomenon. This paper presents a pseudo-dynamic approach to evaluate the seismic bearing capacity of shallow strip footing resting on c-F soil using limit equilibrium method considering the composite failure mechanism. A single seismic bearing capacity coefficient (N?e) presents here for the simultaneous resistance of unit weight, surcharge and cohesion, which is more practical to simulate the failure mechanism. The effect of soil friction angle(F), soil cohesion(c), shear wave and primary wave velocity(Vs, Vp) and horizontal and vertical seismic accelerations(kh, kv) are taken into account to evaluate the seismic bearing capacity of foundation. The results obtained from the present analysis are presented in both tabular and graphical non-dimensional form. Results are thoroughly compared with the existing values in the literature and the significance of the present methodology for designing the shallow strip footing is discussed.

Soil Velocity Profile on Soft Soil Using Seismic Refraction

Soil velocity profile often used as subsurface characterization by using geophysical technic. Seismic refraction is one of geophysical technique to determine primary wave (p-wave) velocity of soil profile. In this paper, seismic refraction technique has been performed on two different types of soft soil (peat soil and RECESS clay) for comparison of its p-wave velocity soil profile. From p-wave velocity soil profile comparison, its show the peat soil has soil velocity range from 211 m/s – 534 m/s at depth of 0 – 4 m while the soft clay show soil velocity range from 248 m/s – 1842 m/s at depth of 0 – 5.5 m. The profiles of peat soils and RECESS clay have been verified using peat samplers and existing borehole data. Both of velocity soil profiles, indicated that peat soil have lower velocity compare with soft clay due to its unique and soft soil characteristics. The difference of p-wave velocity soil profile between peat soil and soft clay are clearly showed both soils have different soil p-wave velocity with different soils characteristics.

Experimental study of the effect of high temperature on primary wave velocity and microstructure of limestone

To study the effect of high temperature on the microstructure and velocity of primary wave (P-wave) propagation in rocks, scanning electron microscope (SEM) experiments, mercury injection experiments and P-wave velocity tests were conducted on limestone samples which had been heated at high temperature (from 25 to 900 °C), and then the variations of P-wave velocity and microstructure were analyzed. Consequently, a P-wave velocity-based damage model was established to evaluate the damage level of limestone. The experimental results showed that: (1) the internal defects of limestone started to develop at 300 °C, and the range of 300–600 °C was the main development stage; (2) the porosity increased slowly with the rising of temperature below 200 °C, and rapidly increased above 300 °C; and (3) the P-wave velocity grew a little below 100 °C and decreased tardily in 100–300 °C, and then sharply decreased in 300–600 °C. The P-wave velocity damage model also shows that damage of the samples occurred above 300 °C. This study suggests that 300 °C should be the damage threshold temperature of limestone, and in 300–600 °C, significant damage of limestone would occur.

Pseudo-dynamic analysis for bearing capacity of foundation resting on c–Φ soil

Estimation of seismic bearing capacity of foundation in earthquake prone area is an important parameter in the design of any substructure. This paper presents a pseudo-dynamic approach for calculating the seismic bearing capacity of shallow strip footing resting on c–Φ soil using limit equilibrium method. Considering the Coulomb failure mechanism, the effect of wall friction angle and soil friction angle, soil cohesion, shear wave and primary wave velocity, and horizontal and vertical seismic accelerations are taken into account to evaluate the seismic bearing capacity of foundation. In this paper, the seismic bearing capacity presents in a single coefficient (Nγe) for the simultaneous resistance of unit weight, surcharge, and cohesion, which is reasonable and easy to use. The results obtained from the present analysis thoroughly compared with the existing values in the literature and the significance of the present methodology for designing the shallow strip footing is discussed.