P-wave Velocity Measurements Research Articles

Evaluation of Static and Dynamic Residual Mechanical Properties of Heat-Damaged Concrete for Nuclear Reactor Auxiliary Buildings in Korea Using Elastic Wave Velocity Measurements.

The main objectives of this study are (1) to investigate the effects of heating and cooling on the static and dynamic residual properties of 35 MPa (5000 psi) concrete used in the design and construction of nuclear reactor auxiliary buildings in Korea; and (2) to establish the correlation between static and dynamic properties of heat-damaged concrete. For these purposes, concrete specimens (100 mm × 200 mm cylinder) were fabricated in a batch plant at a nuclear power plant (NPP) construction site in Korea. To induce thermal damages, the concrete specimens were heated to target temperatures from 100 °C to 1000 °C with intervals of 100 °C, at a heating rate of 5 °C/min and allowed to reach room temperature by natural cooling. The dynamic properties (dynamic elastic modulus and dynamic Poisson’s ratio) of concrete were evaluated using elastic wave measurements (P-wave velocity measurements according to ASTM C597/C597M-16 and fundamental longitudinal and transverse resonance tests according to ASTM C215-14) before and after the thermal damages. The static properties (compressive strength, static elastic modulus and static Poisson’s ratio) of heat-damaged concrete were measured by the uniaxial compressive testing in accordance with ASTM C39-14 and ASTM C469-14. It was demonstrated that the elastic wave velocities of heat-damaged concrete were proportional to the square root of the reduced dynamic elastic moduli. Furthermore, the relationship between static and dynamic elastic moduli of heat-damaged concrete was established in this study. The results of this study could improve the understanding of the static and dynamic residual mechanical properties of Korea NPP concrete under heating and cooling.

Laboratory observations of frequency-dependent ultrasonic P-wave velocity and attenuation during methane hydrate formation in Berea sandstone

SUMMARYKnowledge of the effect of methane hydrate saturation and morphology on elastic wave attenuation could help reduce ambiguity in seafloor hydrate content estimates. These are needed for seafloor resource and geohazard assessment, as well as to improve predictions of greenhouse gas fluxes into the water column. At low hydrate saturations, measuring attenuation can be particularly useful as the seismic velocity of hydrate-bearing sediments is relatively insensitive to hydrate content. Here, we present laboratory ultrasonic (448–782 kHz) measurements of P-wave velocity and attenuation for successive cycles of methane hydrate formation (maximum hydrate saturation of 26 per cent) in Berea sandstone. We observed systematic and repeatable changes in the velocity and attenuation frequency spectra with hydrate saturation. Attenuation generally increases with hydrate saturation, and with measurement frequency at hydrate saturations below 6 per cent. For hydrate saturations greater than 6 per cent, attenuation decreases with frequency. The results support earlier experimental observations of frequency-dependent attenuation peaks at specific hydrate saturations. We used an effective medium rock-physics model which considers attenuation from gas bubble resonance, inertial fluid flow and squirt flow from both fluid inclusions in hydrate and different aspect ratio pores created during hydrate formation. Using this model, we linked the measured attenuation spectral changes to a decrease in coexisting methane gas bubble radius, and creation of different aspect ratio pores during hydrate formation.

Non-Embedded Ultrasonic Detection for Pressure Cores of Natural Methane Hydrate-Bearing Sediments

An apparatus for the analysis of pressure cores containing gas hydrates at in situ pressures was designed, and a series of experiments to determine the compressional wave response of hydrate-bearing sands were performed systematically in the laboratory. Considering the difficulties encountered in performing valid laboratory tests and in recovering intact hydrate bearing sediment samples, the laboratory approach enabled closer study than the marine environment due to sample recovery problems. The apparatus was designed to achieve in situ hydrate formation in bearing sediments and synchronous ultrasonic detection. The P-wave velocity measurements enabled quick and successive ultrasonic analysis of pressure cores. The factors influencing P-wave velocity (Vp), including hydrate saturation and formation methodology, were investigated. By controlling the initial water saturation and gas pressure, we conducted separate experiments for different hydrate saturation values ranging from 2% to 60%. The measured P-wave velocity varied from less than 1700 m/s to more than 3100 m/s in this saturation range. The hydrate saturation can be successfully predicted by a linear fitting of the attenuation (Q−1) to the hydrate saturation. This approach provided a new method for acoustic measurement of the hydrate saturation when the arrival time of the first wave cannot be directly distinguished. Our results demonstrated that the specially designed non-embedded ultrasonic detection apparatus could determine the hydrate saturation and occurrence patterns in pressure cores, which could assist further hydrate resource exploration and detailed core analyses.

Estimating porosity and hydraulic conductivity for hydrogeology on the basis of reservoir and elastic petrophysical parameters

The aim of paper was to show how petrophysical parameters measured in laboratory or as well logging outcomes can be used to determine hydrogeological quantity - porosity and combine it with hydraulic conductivity. Bulk density and acoustic waves velocity were applied to calculate porosity besides of laboratory mass measurements applied as standard in hydrogeology. Anisotropy question was touched because petrophysical parameters measured in two perpendicular directions revealed different results.Upper Jurassic carbonate samples from two regions of South Poland were used in laboratory measurements of elastic and reservoir properties to determine open/effective-interconnected and total porosity, bulk density and hydraulic conductivity. Petrophysical measurements of bulk density and elastic P-wave and S-wave velocities were used for total porosity determination. The obtained results were also basis for the dynamic elastic moduli calculations. Laboratory measurements and analyses were done separately for the samples cut horizontally and vertically to bedding to underline possibility of anisotropy recognition. The main goal of investigations was to determine porosity from various methods and show that well logging results can be used rather than laboratory results. Hydrogeological parameters determination from well logs might be crucial in deep aquifers prospection.

Laboratory ultrasonic measurements: Shear transducers for compressional waves

The ultrasonic measurements technique is well established to measure the elastic properties of rocks in the laboratory for seismic and well-log data interpretation. The key components of every laboratory ultrasonic setup are piezoelectric transducers, which generate and register elastic waves in rock samples. The elastic properties of rocks are determined through the velocities of elastic waves, which are measured by the times of the waves' travel from the source to the receiver transducer. Transducers can be specifically designed to generate P-waves (P-transducers) or S-waves (S-transducers). In limited studies, the measurement of P-wave velocities with S-transducers is mentioned. Such measurement is possible due to specific aspects of the operation of S-transducers. Namely, S-transducers are known to emit parasitic low-energy P-waves, which travel faster than high-energy S-waves and hence can be registered. However, no justification or elaboration of this method of measuring P-wave velocities was reported. To fill this gap, we first compare P-wave velocities measured with S-transducers against P-wave velocities measured with P-transducers in different rocks and materials. We show that the discrepancy between velocities measured with the two methods in homogeneous materials is less than 1% and can be up to 4% for natural rocks. Second, we numerically simulate the operation of S-transducers, show that parasitic P-waves have a dipole structure, and explain how the receiver transducer can register this compressional dipole. Finally, we use laser doppler interferometry to measure the displacement of the free surface of a sample caused by elastic waves emitted by the source S-transducer. We observed the dipole structure of the sample's surface displacement upon P-wave arrival on the surface.

Petroacoustics and composition of presalt rocks from Santos Basin

The deposition of the presalt section from Santos Basin began when Gondwana started to break up and South America and Africa were separating. Initial synrift carbonate deposits affected by relatively severe tectonic activity evolved to a lacustrine carbonate environment during the later stages of basin formation. Although the reservoirs are composed of carbonate rocks, the occurrence of faults and the intense colocation of igneous rocks served as a source of chemical elements uncommon in typical carbonate environments. Consequently, beyond the presence of different facies with complex textures and pore geometries, the presalt reservoir rocks present marked compositional and microstructural variability. Therefore, rock-physics modeling is used to understand and interpret the extensive laboratory measurements of P-wave velocities, S-wave velocities, and density that we have undertaken on the presalt carbonate cores from Santos Basin. We show that quartz and exotic clay minerals (such as stevensite and other magnesium-rich clay minerals), which have different values of elastic moduli and Poisson's ratio as compared to calcite and dolomite, may introduce noticeable “Poisson's reflectivity anomalies” on prestack seismic data. Moreover, although the authors concentrate their attention on composition, it will become clear that pore-space geometry also may influence seismic rock properties of presalt carbonate reservoirs.

Mechanical anisotropy of coal with considerations of realistic microstructures and external loading directions

This paper investigates the anisotropy of coal under uniaxial compression conditions using both experimental and numerical methods. Primary wave (P-wave) velocity measurements, X-ray micro-computed tomography (CT) scanning, and uniaxial compression tests were conducted to assess the anisotropic characteristics of selected coal samples. Based on the experimental results, comprehensive analyses were carried out to study the influences of different contributing factors on the anisotropic properties of coal. A three-dimensional (3D) finite difference model was then built to further investigate the effects of failure initiation, stress redistribution and the presence of microstructures on the anisotropy of coal. The experimental and numerical results of uniaxial compression tests indicate that the coal strength anisotropy is affected by the directional distribution of the microstructures. Bedding planes directly control the uniaxial compressive strength of coal, and face cleats have a greater influence on the mechanical properties than butter cleats. The presence of mineral inclusions increases the heterogeneity of coal because of the significant differences in strength and deformation in the mineral inclusion zones. The mechanical and seismic anisotropies are both directly related to the directional distribution of the microstructures, which is demonstrated by the variations in the anisotropic strength and P-wave velocity of the coal. The correlations between the uniaxial compressive strength (UCS) and P-wave velocity are different when the coals are loaded in different directions, and an exponential correlation was suitable for defining this relationship.

Sound velocity and density of liquid Ni68S32 under pressure using ultrasonic and X-ray absorption with tomography methods

A new experimental setup for simultaneous P-wave velocity (VP) and density (ρ) measurements for liquid alloys is developed using ultrasonic and X-ray absorption methods combined with X-ray tomography at high pressures and high temperatures. The new setup allows us to directly determine adiabatic bulk moduli (KS) and to discuss the correlation between the VP and ρ of the liquid sample. We measured VP and ρ of liquid Ni68S32 up to 5.6GPa and 1045K using this technique. The effect of pressure on the VP and ρ values of liquid Ni68S32 is similar to that of liquid Fe57S43. (Both compositions correspond to near-eutectic ones.) The obtained KS values are well fitted to the finite strain equation with a KS0 value (KS at ambient pressure) of 31.1GPa and a dKS/dP value of 8.44. The measured VP was found to increase linearly with increasing ρ, as approximated by the relationship: VP [m/s]=1.29ρ [kg/m3] – 5726, suggesting that liquid Ni–S follows an empirical linear relationship, Birch's law. The dVP/dρ slope is similar between Ni68S32 and Fe57S43 liquids, while the VP–ρ plot of liquid Ni–S is markedly different from that of liquid Fe–S, which indicates that the effect of Ni on Birch's law is important for understanding the VP–ρ relation of planetary and Moon's molten cores.

Correlation of ultrasound velocity with physico-mechanical properties of Jodhpur sandstone

Abstract The aim of this study is to determine the correlation of ultrasound velocity with the physico-mechanical properties of sandstonefrom Jodhpur, India. The relationship between dry density, the Schmidt hammer rebound number, the point load strength index, and uniaxial compressive strength with ultrasound velocity are investigated. Ultrasonic P-wave velocity measurement is a simple, portable, and a non-destructive technique which can be carried out in situ as well as in the laboratory without the availability of core samples. Sandstone specimens were collected from various locations in Jodhpur, India and tested in the laboratory. The empirical equations depicting the relationship between physico-mechanical properties and ultrasound velocity were derived by regression analysis yielding reasonably good correlations. To check the sensitivity of the correlations, a t-test was performed which also confirms the validity of the equations proposed.

Comparison of thermal and elastic properties of sandstones: Experiments and theoretical insights

We measured P-wave velocity, thermal conductivity and thermal diffusivity on 26 sandstone samples under dry and water-saturated conditions. Subsequently, we compared these measurements with predictions by frequently used models.Overall, these three properties decrease with porosity and increase with water saturation. Comparing data sets and models, we distinguish three main groups of sandstone samples: From the difference in the intrinsic elastic and thermal properties of the dominant mineral, two tendencies attributed to either quartz or another rock forming mineral are identified, which separate class 1 sandstone and samples from class 2 sandstones. Within class 1 clean sandstones, a sub-class (sub-class 1a) consists of similarly porous samples having different elastic and thermal properties. Based on elasticity, we attribute this effect to microcracks or grain contacts in the samples. While this feature does not affect the total porosity, it affects all of three physical properties strongly and in a similar way. Additionally, we define a second sub-class (sub-class 1b) for Fontainebleau sandstone with porosities above 13%. For these four samples, the effect of water saturation on the elastic and thermal properties is different.

Effect of coupled triaxial stress-perforation on fracture mechanism and acoustic wave velocity of limestone

Perforation with shaped charges establishes the hydraulic communication between cased wellbore and reservoir. Higher DoP1 is one of the most important goals of perforation. Performance of a perforation is greatly influenced by confining pressure, which was mostly anisotropic, around the target. Therefore, it is necessary to consider the triaxial confining pressure on the target to achieve the actual results. In this study, a new triaxial perforation machine designed and constructed to investigate the effect of anisotropic in-situ stress on the DoP and failure pattern of limestone targets. The number of tests was optimized by Taguchi's method and ANOVA2 was used to determine the cross effect of the different combination of applied in-situ stresses on DoP. The ultrasonic P-wave velocity was measured before and after perforation under different conditions of anisotropic loading. The results show that the Measured DoP is more controlled by the off plane stresses (stresses normal to shooting axis) than the stress in the direction of penetration. The created fractures by perforation are more oriented along the maximum horizontal stress, which is less propagated around a hole with increasing the maximum to the minimum off plane stress ratio. The measured p-wave velocity showed that VP increases along the perforation hole from the beginning of the hole toward the block boundaries. It was found the loading conditions control the VP values along the shooting axis. In anisotropic loading mode, the velocity of P-waves in direction of the maximum stress was greater than minimum horizontal stress. In the isotropic loading condition, VP values were same along the direction perpendicular to the firing axis.

Extraordinary rocks from the peak ring of the Chicxulub impact crater: P-wave velocity, density, and porosity measurements from IODP/ICDP Expedition 364

Joint International Ocean Discovery Program and International Continental Scientific Drilling Program Expedition 364 drilled into the peak ring of the Chicxulub impact crater. We present P-wave velocity, density, and porosity measurements from Hole M0077A that reveal unusual physical properties of the peak-ring rocks. Across the boundary between post-impact sedimentary rock and suevite (impact melt-bearing breccia) we measure a sharp decrease in velocity and density, and an increase in porosity. Velocity, density, and porosity values for the suevite are 2900–3700 m/s, 2.06–2.37 g/cm3, and 20–35%, respectively. The thin (25 m) impact melt rock unit below the suevite has velocity measurements of 3650–4350 m/s, density measurements of 2.26–2.37 g/cm3, and porosity measurements of 19–22%. We associate the low velocity, low density, and high porosity of suevite and impact melt rock with rapid emplacement, hydrothermal alteration products, and observations of pore space, vugs, and vesicles. The uplifted granitic peak ring materials have values of 4000–4200 m/s, 2.39–2.44 g/cm3, and 8–13% for velocity, density, and porosity, respectively; these values differ significantly from typical unaltered granite which has higher velocity and density, and lower porosity. The majority of Hole M0077A peak-ring velocity, density, and porosity measurements indicate considerable rock damage, and are consistent with numerical model predictions for peak-ring formation where the lithologies present within the peak ring represent some of the most shocked and damaged rocks in an impact basin. We integrate our results with previous seismic datasets to map the suevite near the borehole. We map suevite below the Paleogene sedimentary rock in the annular trough, on the peak ring, and in the central basin, implying that, post impact, suevite covered the entire floor of the impact basin. Suevite thickness is 100–165 m on the top of the peak ring but 200 m in the central basin, suggesting that suevite flowed downslope from the collapsing central uplift during and after peak-ring formation, accumulating preferentially within the central basin.

A pressure core ultrasonic test system for on-board analysis of gas hydrate-bearing sediments under in situ pressures.

The enormous potential as an alternative energy resource has made natural gas hydrates a material of intense research interest. Their exploration and sample characterization require a quick and effective analysis of the hydrate-bearing cores recovered under in situ pressures. Here a novel Pressure Core Ultrasonic Test System (PCUTS) for on-board analysis of sediment cores containing gas hydrates at in situ pressures is presented. The PCUTS is designed to be compatible with an on-board pressure core transfer device and a long gravity-piston pressure-retained corer. It provides several advantages over laboratory core analysis including quick and non-destructive detection, in situ and successive acoustic property acquisition, and remission of sample storage and transportation. The design of the unique assembly units to ensure the in situ detection is demonstrated, involving the U-type protecting jackets, transducer precession device, and pressure stabilization system. The in situ P-wave velocity measurements make the detection of gas hydrate existence in the sediments possible on-board. Performance tests have verified the feasibility and sensitivity of the ultrasonic test unit, showing the dependence of P-wave velocity on gas hydrate saturation. The PCUTS has been successfully applied for analysis of natural samples containing gas hydrates recovered from the South China Sea. It is indicated that on-board P-wave measurements could provide a quick and effective understanding of the hydrate occurrence in natural samples, which can assist further resource exploration, assessment, and subsequent detailed core analysis.

Crack tensor-based evaluation of inada granite behavior due to damage under true-triaxial testing condition

In the present work, wave velocity measurements were implemented to assess the state of damage in specimens of Inada granite. The specimens were first loaded under true-triaxial testing conditions for which different levels of major principal stress with respect to ultimate strength were applied. Christoffel's stiffness equation was used to derive elastic properties of the domain via P-wave velocity measurements. The compliance matrix arrays in the strain-stress relationship were then calculated in the most heterogeneous case which involved 21 constants. Furthermore, determination of second and fourth rank crack tensors enabled convenient judgment for the degree of anisotropy expected during permeability and dispersivity studies which are very important in environmental studies. It was found that while more attempt to model granitic rocks in their real form is useful, the orthorhombic symmetry assumption for the rock under study would eventually render best outcome for realistic simulation purposes of mechanical properties. Finally, areas of application for the proposed development are discussed and prospects of future work by the researchers are outlined.

Seismic and strain detection of heterogeneous spatial distribution of CO2 in high- permeable sandstone

In this study, we attempt to clarify the heterogeneous CO2 distribution in homogeneous and high-permeability porous sandstone (Mt. Simon sandstone: 105 mD) using both physical rock experiments and fluid mechanical analyses. In particular, the experiments involve CO2 injection into porous sandstone with measurements of P-wave velocity (Vp) and strain under low capillary number (Ca) flow conditions. We set three Vp-measurement lines and two strain gauges (vertical and horizontal) at the center of the core. We also monitor changes of flow rate, volume, and differential pressure between the two pumps during CO2 injection. The Vp values of all channels show slight changes (under 4%). By contrast, the strain measurements indicate a substantial expansion in both directions. It is proposed that the injected CO2 reaches the counter end of the core specimen immediately and forms few large-percolation clusters in porous sandstone. The CO2 that follows flows only through clusters as pathways without capillary resistance. These CO2 flows produce spatially heterogeneous distributions of CO2 in the porous sandstone and make it difficult to monitor and detect CO2 by seismic wave velocities only.

Methods for Characterizing Cracks Induced in Rock

A detailed understanding of how induced cracks form and propagate in rock is important in many fields, particularly in mining where size reduction of material is a major cost. This contribution provides a comprehensive review of previously published methods for characterizing rock cracks. The existing methods generate one of the two types of data: crack-related changes in bulk rock properties or the nature of the actual cracks, such as aperture, location, morphology and mineralogical boundaries. However, no single technique provides both types of information. Using a suite of granodiorite specimens which were cracked under microwave irradiation, this contribution illustrates how multiple nondestructive and destructive techniques can be integrated to provide both types of data on cracks induced in rock. Rock property changes were quantified using P-wave velocity measurements and uniaxial compressive strength tests. The cracks were characterized qualitatively and quantitatively using a combined approach of micro-computed tomography, optical microscopy and automated mineralogical analysis of scanning electron microscopy images. The resulting dataset provides information on the mechanical and mineralogical effects of the cracking. The microwave irradiation led to a significant reduction in rock strength, caused by networks of intergranular and intragranular cracks in granodiorite, disproportionately associated with biotite. Based on the strengths and limitations of each method as illustrated by the granodiorite results, recommended protocols are provided for evaluating cracks in four different types of studies: (1) quick assessments of damage; (2) geotechnical investigations; (3) mineralogical investigations and (4) comprehensive evaluations of the effects of cracking, requiring data on mechanical properties and the characteristics of the cracks.

An Experimental Study Among P-wave Velocity of Sandstones, Pressures and Water Saturation in Hami, Xinjiang, China

Seismic velocity of rocks have a wide range of applications in regional tectonic research and shallow seismic exploration. Hami area is one of the important production bases for oil and gas in China, but there is short of seismic velocity. This paper contributes to the measurement of Pwave velocity of sandstones from Hami under different conditions by applying AutoLab 2000 computer-controlled servo hydraulic triaxial test system. Specifically, it shows the variation of seismic wave velocity of sandstones with respect to the water saturation under various pressures. The results show that P-wave velocity of sandstones is remarkably correlated linearly with the increasing water saturation and the correlation coefficient is over 0.9. Besides, the change rate between P-wave velocity and water saturation will decrease with the increasing pressure. The fitting formulas among pressures, water saturation and P-wave velocity are suitable for Hami region. Finally, we get a new method to predict water saturation by combining the experimental result with logging curve in Hami area.

Depositional constraints and diagenetic pathways controlling petrophysics of Middle Miocene shallow-water carbonate reservoirs (Leitha limestones), Central Paratethys, Austria-Hungary

Middle Miocene shallow-water limestones, the so-called Leitha limestones, comprise a widespread Middle Miocene lithological unit of the Central Paratethys Sea. It includes mainly limestones composed of corallinacean algae and other fossil debris and were deposited in shoals of various basins such as the Vienna, Eisenstadt-Sopron and Styrian basins of Austria where they form potential hydrocarbon reservoir rocks. Petrophysical parameters including porosity, permeability, density, P-wave velocity and magnetic susceptibility measurements were performed and evaluated. The sampled sites of Mannersdorf and Wöllersdorf quarries and drill-hole Bruckneudorf are located in the Vienna Basin and share the same principal limestones depositional facies that is massive, closely-packed rudstone facies. This facies has low porosities below 10%, low permeability lower than 1.2 mD except one samples at 68.5 mD, high bulk density of dry samples up to 2.64 g/cm3 and high P-wave velocity up to 6761 m/s. In Mannersdorf, a second facies type of soft porous coarse-grained rudstone shows significantly higher porosity (up to 47%), higher permeability up to 124.3 mD, lower bulk density of dry samples less than 1.8 g/cm3 and lower P-wave velocity less than 2798 m/s. This latter facies retains primary porosity and secondary porosity enhanced by dissolution. In contrast, the former facies type suffered intensive cementation, which destroyed the primary porosity, and in some cases, subsequent later dissolution and karstification enhanced secondary porosity partly.Kummer (Austria) and Fertőrákos (Hungary) quarries are located within the Eisenstadt-Sopron Basin. The well-sorted grainstone facies has high porosity up to 50%, extremely high permeability up to 31238 mD, low bulk density of dry samples less than 1.71 g/cm3 and low P-wave velocity less than 3219 m/s. The poorly-sorted massive rudstone facies recorded only in Kummer quarry is less porous (porosities range from 22 to 31%) and less permeable. The role of dissolution predominates in these limestones besides compaction and pressure solution in the massive rudstone facies. Limestones from the Rosenberg quarry of the Styrian Basin show two facies types: (1) wackestone to packstone facies with lower porosity (up to 16.4%) and lower permeability ranges from 0.16 to 0.91 mD, compared to (2) the packstone facies with higher porosity (21%) and higher permeability of 1.83 mD. The influence of diagenesis on both facies is similar, represented by early marine cementation followed by partial dissolution and finally meteoric blocky cementation.The depositional influence on petrophysics of Leitha limestones, for instance, packing, sorting and grain size represents the basis for the differences in facies types in the same locality and among various localities. This depositional influence controls the subsequent stepwise diagenetic evolution the facies. Local depositional environments and their spatial evolution play a significant role on reservoir properties such as, at Mannersdorf the two facies types are varied due to the primary depositional characteristics and hence, the diagenetic evolution. Diagenetic pathways are principally similar in the different localities and basins; however, different stages of diagenesis are recorded due to different burial and exhumation histories.

A Method to Identify Blasting-Induced Damage Zones in Rock Masses Based on the P-Wave Rise Time

Abstract Blasting-induced damage zones in rock masses are commonly identified by changes in the ratio of the P-wave velocities before and after blast. In ultrasonic tests, water is usually adopted as the coupling medium. As the ultrasonic wave propagates in the aqueous medium, the measured P-wave velocity will be affected by the water coupling distance between the transducer and the wall of the test hole. However, compared to the rock material, due to the lower dispersivity of the aqueous medium, the P-wave rise time is nearly unaffected by water coupling distance. The method based on P-wave rise time is as simple and feasible as the method based on P-wave velocity while employed in field testing. Furthermore, when P-wave rise time is used to detect blasting-induced damage zones, the measured data are in less variability and greater reliability than that acquired from the method based on P-wave velocity. As a result, while the P-wave velocity data are highly variable, the damage zone is difficult to discriminate, but it can be relatively easily discriminated using the P-wave rise time.

Response of Partially Saturated Non-cohesive Soils

Abstract This paper analyses and discusses experimental results of undrained triaxial tests. The tests were performed on non-cohesive partially saturated soil samples subjected to monotonic and cyclic loading. The tests were aimed at determining the influence of saturation degree on soil’s undrained response (shear strength, excess pore pressure generation). The saturation of samples was monitored by checking Skempton’s parameter B. Additionally, seismic P-wave velocity measurements were carried out on samples characterized by various degrees of saturation. The tests clearly showed that liquefaction may also take place in non-cohesive soils that are not fully saturated and that the liquefaction potential of such soils strongly depends on the B parameter.