Use Of Seismic Dilatometer For Design Infrastructures

The small-strain stiffness modulus G0 is not directly applicable to evaluate deformation in most practical engineering problems, and therefore, nonlinear soil behavior curves have been developed in terms of Young modulus E or shear modulus G. These curves were successfully obtained for sedimentary soils, while for residual soils, the available data from intertional community is still scarce. Residual soils are considered structured soils and often classified as problematic soils since they do not fit into the behavior of remolded or unstructured soils. In fact, the role of bonding and fabric affects both the strength and the stiffness of the soil. This article illustrates the use of the seismic dilatometer test (SDMT) for the determination of in situ stiffness decay curves with strain level (G-γ curves or similar) in a granitic residual soil of the Northeastern region of Portugal (Guarda), showing its adequacy to solve these kinds of problems. In situ and laboratory tests were performed on these granitic residual soils. The adopted approach relies on the ability of SDMT to provide a small-strain modulus G0 (from the shear wave velocity Vs) and a “working strain” modulus GDMT (derived from the constrained modulus MDMT in accordance with the theory of elasticity). Thus, in situ G-γ decay curves were tentatively constructed by fitting curves through these two points using a hyperbolic model. However, it was observed that the results obtained by the hyperbolic model for the cemented soils are not satisfactory. Based on the SDMT parameters, a logistic curve was derived for the reproduction of reference stiffness curves obtained from the triaxial test results.

Two high-resolution multi-offset vertical seismic profile (VSP) surveys were carried out in a permafrost mound near Umiujaq in northern Quebec, Canada, while performing seismic cone penetration tests (SCPT) to study the cryostratigraphy and assess the body waves velocities and the dynamic properties of warm permafrost. Penetrometer-mounted triaxial accelerometers were used as the VSP receivers, and a swept impact seismic technique (SIST) source generating both compressional and shear waves was moved near the surface following a cross configuration of 40 seismic shot-point locations surrounding each of the two SCPTs. The inversion of travel times based on a simultaneous iterative reconstruction technique (SIRT) provided tomographic images of the distribution of seismic velocities in permafrost. The Young's and shear moduli at low strains were then calculated from the seismic velocities and the permafrost density measured on core samples. The combination of multi-offset VSP survey, SCPT, SIST, and SIRT for tomographic imaging led to new insights in the dynamic properties of permafrost at temperatures close to 0 °C. The P- and S-wave velocities in permafrost vary from 2400 to 3200 m/s and from 900 to 1750 m/s, respectively, for a temperature range between –0.2 and –2.0 °C. The Young's modulus varies from 2.15 to 13.65 GPa, and the shear modulus varies from 1.00 to 4.75 GPa over the same range of temperature.Key words: permafrost, seismic cone penetration test, vertical seismic profiling, seismic tomography, dynamic properties.

Thirty-meter shear-wave velocity ( V S 30) is commonly used to estimate near-surface conditions for site classification, seismic site response, liquefaction analysis, and other geotechnical earthquake engineering application. Quantifying the uncertainty in V S 30 measurements is important for determining the accuracy and precision of this geophysical test. This study gathers existing available comparative and blind shear-wave velocity tests to evaluate the apparent or observable intra- and intermethod variability. Presented in this article are estimates of V S 30 uncertainty for the invasive methods of downhole, suspension logging, and seismic cone penetration testing, the noninvasive method of spectral analysis of surface waves, and the method of shear-wave velocity correlated geologic units. Discussed is the issue of soil disturbance with respect to invasive methods and how this may result in measurement bias. Results of this study indicate that uncertainty of shear-wave velocity measurements are on the order of 1%–3% coefficient of variation (standard deviation/mean) for downhole, suspension logging, and seismic cone penetration testing, 5%–6% coefficient of variation for spectral analysis of surface waves, and 20%–35% coefficient of variation for shear-wave velocity correlated geologic units. Presented here are procedures for propagating the uncertainty and/or bias in forward analyses.

The seismic cone penetration test (SCPT) is one of the most frequently used in situ testing methods for deriving the small strain shear modulus. Offshore SCPT results often present large scatter, in particular when data are obtained with different operational setups. No standard or industry consensus exist in terms of requirements to system key characteristics, operational testing procedures, interpretation and the numerical quality control of the traces obtained. Seismic sources currently deployed as part of the offshore industry practice have been developed individually by the various suppliers. This paper presents the findings of an onshore experimental study with the objective to increase the understanding of the influence of the offshore seismic source setup on SCPT results under controlled operational procedures. Accuracy and precision of the SCPT are investigated as part of the study.

The use of resistivity and seismic cone penetration tests for site characterization The use of resistivity and seismic cone penetration tests for site characterization. Recent application of cone penetration tests to geotechnical and environmental site characterization has generated a wide collection of new sensors. This paper presents methods of interpreting geotechnical in situ investigations carried out by electrical resistivity (RCPT) and seismic (SCPT) cones. It contains some fundamental equations and the description of in situ electrical resistivity and shear wave velocity measurements and presents the results of SCPT and RCPT investigations at the experimental Stegny site in Warsaw. The aim of the paper is to present the approach to determination of shear wave velocity and porosity of clayey soils. According to the test results obtained, it can be concluded that both applied techniques are very useful to estimate the distribution of clay deposits and some of their geotechnical parameters.

Based on the results of dynamic probing (DP), time-domain reflectometry (TDR/MUX/MPTS), resistivity cone penetration tests (RCPT), Marchetti dilatometer tests (DMT), and seismic dilatometer tests (SDMT), it is possible to develop a relationship to calculate the relative density (Dr) and degree of saturation (Sr) of selected sandy soils. Compiled databases from documented research points for selected sandy soils were used to construct and develop direct correlations between the measured pressures p0 and p1 from DMT and shear wave velocity (Vs) from SDMT, along with pore water pressures (u0) and atmospheric pressure (Pa). The results allowed us to make a preliminary prediction when evaluating the parameters. Further, they allowed limiting the use of an additional device, especially in the case of multilayer heavy preconsolidated subsoils. Moreover, soil physical and mechanical characteristics (temperature, humidity, pressure, swelling, salinity) measured from TDR/MUX/MPTS (laboratory/field-operated meter for simultaneous measurements of soil moisture, matric potential, temperature, and salinity—bulk electrical conductivity) were assessed. The main achievement of this paper is the original proposal of using a new nomogram chart to determine the relative density and degree of saturation based on DMT and SDMT tests.

Development of seismic CPT for evaluating in-flight soil properties in centrifuge model test

We conducted a high-resolution S-wave reflection survey using Land Streamer across a<br>buried part of an active fault at the western edge of the Niigata Plain, central Japan. The<br>survey line was set on a paved country road. The Land Streamer, which is featured by the<br>towing belts on which geophone units are mounted, provides high-quality data even at the<br>paved areas in spite of its soft coupling to the surface. However, it is hard to estimate the Swave<br>velocity of the surficial layer beneath the pavement, because of being masked by the<br>pavement of high velocity. We therefore carried out the seismic cone penetration tests<br>(SCPT) to clarify Vs profiles of the near surface. By means of the SCPT data, we<br>successfully determined the depths of reflectors. The reflection profile clearly delineates a<br>detailed structure of the surfrcial layers to a depth shallower than 60 m, and showed a<br>deformed structure in the Holocene layers, which is strongly inferred to be formed by<br>faulting of the existing active fault.

This paper provides details of two in-situ testing programmes performed to assess ore properties in the holds of ore carrying vessels. The first case comprised CPTs in the hold of an iron-ore carrying vessel - at both the ports of loading and discharge – enabling assessment of the ore properties after loading and the changes caused by the voyage. The second case comprised two CPTs and one Seismic Dilatometer Test (SDMT) in the hold of a coal carrying vessel shortly after loading – enabling assessment of the coal properties after loading, and direct comparison of CPT and SDMT interpretations.

Data-driven modeling for evaluating deformation of a deep excavation near existing tunnels

A new seismic dilatometer (SPDMT) has been developed to combine the measurements of the flat dilatometer (DMT) geotechnical parameters with both P- and S- waves velocities. This new SPDMT is composed of the traditional mechanical DMT and four sensors for measuring the body waves velocities placed above the DMT blade. This SPDMT device is presented here, and the test procedure and the interpretation of P- and S-wave measurements are discussed. Results of the application of this new instrument are reported in a test site located in Bondeno (Emilia Romagna, Italy). Here, challenging water table conditions offer the opportunity to evaluate the advantage of a combined measure of the two propagation velocities, together with DMT geotechnical parameters, with the same apparatus for the porosity evaluation and a more calibrated liquefaction assessment.

Shear wave velocity (V s ) is a key parameter for seismic amplification analyses, and for assessment of liquefaction potential of loose offshore sands. A number of methods are available to measure V s offshore, including seismic Cone Penetration Testing (CPT), Multichannel Analysis of Surface Waves, and Downhole methods. A marine investigation was carried out offshore Croatia for a new bridge connecting the Croatian mainland to the Peljesac peninsula. During the investigation, direct V s measurements were taken with the three methods outlined above. This paper presents the data acquisition, processing and results. Advantages and limitations of the three methods used for the survey are discussed.

Historically shear strain function and complex shear modulus based on geophysical methods were based on empirical relationship between Seismic Cone Penetration Test (SCPT) and Cone Penetration Test (CPT) method. New geological concept namely CPI model have been developed and applied in mathematical and engineering strains to study shear strain function. Modeling of the mathematical shear strain is done by halving the stratum index factor (SIF). The different types of responses of CPI model are discussed and classified based on numerical methods using degree of settlement and degree of consolidation. The results show that shear strain amplitude or mathematical shear strain is constant by using the modified CPI method where mathematical shear strain indicated is half of the stratum index factor and engineering shear strain indicated is equal to the stratum index factor. The other major al area. Last major finding involves the cyclic variation of Poisson Ratio which indicates the anisotropic properties of soft cohesive soil. © 2015, Int. J. of GEOMATE. All rights reserved.

Geotechnical and Geophysical Site Characterization

During reclamation projects huge amounts of sands are dredged and placed to create artificial land. To increase the density and therefore to mitigate the potential risk of liquefaction as well as to increase the stiffness and internal friction angle of the sand, it is often necessary to compact the reclaimed sand. The performance targets for compaction are frequently verified by means of achieving a particular relative density that is generally correlated from Cone Penetration Tests (CPT). For many reclamation projects, due to the non-availability of local quartz or silica sands, crushable, carbonate or calcareous sands are used. In these crushable sands, due to the very high stress concertation below the CPT cone, the particles tend to crush. The well-known published correlations between the relative density and cone resistance are established for non-crushable silica sands and are thus not applicable to these crushable sands and can result in over treatment costing time and money. Usually, the crushing effect is quantified in a calibration chamber test and a project specific correction factor is introduced. Alternatively, to avoid this costly and time-consuming procedure the use of measuring the shear wave velocity with seismic CPTs (SCPT) is possible. The Cyclic Stress Ratio (CSR) for liquefaction analysis and other soil parameters required for the design verification can be correlated without being influenced by the crushing of particles due to the non-invasive procedure. This paper gives an overview of the common practice for work verification in crushable sand and shows an approach to determine the required compaction parameters using seismic CPTs.