Seismic Cone Penetration Test Research Articles

Stress-Based Model for Interpreting Shear Wave Velocity from Seismic Cone Penetration Tests in Unsaturated Soil

Shear wave velocity is an important parameter for estimating soil properties used in analyzing the dynamic response of soil to seismic loading. This paper focuses on developing a model for predicting shear wave velocity in unsaturated soils. The model was developed primarily for the interpretation of seismic cone penetration tests (SCPTs) in unsaturated soil to account for seasonal variations in moisture conditions. In practice, SCPTs typically occur over a period of days without the option of choosing a wet or dry period. The question becomes, if tests are conducted during a dry period, how can shear wave velocity corresponding to a wetter period be predicted, or vice versa? Answering this question was the primary motivation of this work. The work involved field testing with the seismic cone penetrometer during wet and dry periods and a focused study at three sites involving comparison between field and laboratory testing for shear wave velocity. The model presented in this paper is built upon the significant work of many other researchers with reference to new experimental data obtained by the authors. It is demonstrated that a stress-based model incorporating matric suction can provide reasonable predictions of shear wave velocity and provides a method to interpret the impact of changing moisture content on shear wave velocities determined with SCPTs.

Susceptibility to Liquefaction of Iron Ore Tailings in Upstream Dams Considering Drainage Conditions Based on Seismic Piezocone Tests

One of the critical challenges facing the mining sector is related to the prevention and mitigation of catastrophic incidents associated with its tailing dams. As mining tailings are very heterogeneous and field characterization is expensive and complex, geotechnical properties of these materials are largely unknown. The seismic cone penetration test (SCPTu) provides a field approach to estimate a large array of geotechnical information, including the liquefaction potential of tailing dams. Yet, the exploration of strain softening behaviors in geomaterials under undrained loading, utilizing the state parameter (ψ) inferred from SCPTu tests initially applied to soft soils, has been often used for mining tailings. This study is concerned with the implementation of a tailing classification system which uses the ratio between the small strain shear modulus and the cone tip resistance (G0/qt). A series of laboratory tests was executed, and three different methodologies were adopted to assess the effects of (partial) drainage conditions based on 531.26 m of SCPTu measurements conducted at three different upstream iron ore tailing dams in Brazil. Furthermore, the G0/qt ratio is integrated with ψ to assess the liquefaction tendencies of the investigated materials. The findings reveal the heterogeneous nature of the tailings, wherein indications of partial drainage are discernible across numerous records. Liquefaction analyses demonstrate that the tailings exhibit a contractive behavior in over 94% of the SCPTu data, confirming their susceptibility to flow liquefaction. Our findings are relevant for site characterization within iron ore tailing dams and other mining sites with similar geotechnical attributes.

Distributed acoustic sensing for seismic surface wave data acquisition in an intertidal environment

The application of distributed acoustic sensing (DAS) for shallow marine seismic investigations is assessed, in particular with respect to the collection of seismic surface wave data in an intertidal setting. Appropriate selection and directional sensitivity of fiber-optic cables is considered and the measured data is validated with respect to conventional seismic data acquisition approaches, using geophones and hydrophones, along with independent borehole and seismic cone penetration test (SCPT) data. In terms of cable selection, a reduction in amplitude and frequency response of an armored cable is observed, when compared with an unarmored cable. For seismic surface wave surveys in an offshore environment where the cable would need to withstand significant stresses, the use of the armored variant with limited loss in frequency response may be acceptable from a practical perspective. The DAS approach also has indicated good consistency with conventional means of surface wave data acquisition, and the inverted [Formula: see text] also is very consistent with downhole SCPT data. Observed differences in phase velocity between high tide (Scholte wave propagation) and low tide (Rayleigh wave propagation) are not thought to be related to the particular type of interface wave due to shallow water depth. These differences are more likely to be related to the development of capillary forces in the partially saturated granular medium at low tide. Overall, this study demonstrates that our novel approach of DAS using seabed fiber-optic cables in the intertidal environment is capable of rapidly providing near-surface S-wave velocity data across considerable spatial scales (multikilometer) at high resolution, which is beneficial for the design of subsea cables routes and landfall locations. The associated reduction in deployment and survey duration, when compared with conventional approaches, is particularly important when working in the marine environment due to potentially short weather windows and expensive downtime.

Applicability of soil‐type index for shear wave velocity‐based liquefaction assessment

AbstractThe current simplified liquefaction assessment method based on the shear‐wave velocity, Vs has uncertainties about how the fine contents change the Vs‐based liquefaction resistance. According to the simplified method, for a given Vs, the cyclic resistance ratio (CRR) increases with an increase in fine contents. However, field investigations recently revealed that for various silty sands, the correlation between CRR and Vs is soil‐type index dependent and not specific for all sand‐silt mixtures with the same fine contents. Therefore, a detailed experimental research program is performed in this study to clarify the effect of the soil‐type index on the shear wave velocity and CRR correlation. In the first part of the present study, the cyclic resistance of sand mixed with non‐plastic (NP) fines (dry weight of 0%, 5%, 15%, and 35%) was investigated using cyclic direct simple shear (CDSS) tests. Seismic cone penetration (SCPT) tests were performed inside the large‐scale box to facilitate normalized cone penetration resistance (qc1N) and shear wave velocity measurements on the soils used in the CDSS tests. A new correlation was proposed between the qc1N and normalized shear wave velocity (Vs1) using the soil‐type index Ic representing the behavior of soil. Then, CRR‐Vs1 correlation was obtained experimentally for four distinct ranges of soil‐type index. Finally, the results of this study and the proposed CRR‐Vs1 trends in other investigations were used to discuss the soil‐type dependent Vs‐based liquefaction susceptibility zones.

In-situ material damping measurements using the crosshole seismic method

Crosshole seismic testing is commonly used to determine detailed and reliable wave velocity profiles. Material damping measurements can also be performed in crosshole seismic testing, but these measurements require a window function to maintain similar amplitude shapes over the frequency range of interest for the calculation. In-situ seismic testing, including downhole and seismic cone penetration testing (SCPT), also requires a window function for the material damping calculations. However, the length of the window function has the largest influence on the material damping calculation. Therefore, the half-power bandwidth method is introduced to determine the material damping ratio without the window function in crosshole testing by replicating the unconfined, free-free, resonant column (Fr-Fr) test. To demonstrate the influence in the length of the window function, the first cycle of the signal is used in the material damping calculation. The half- power bandwidth method is verified using synthetic signals and field data. Two sets of crosshole and downhole tests were performed, one at a backfill test pad and the second at a Hornsby Bend research site operated by the University of Texas at Austin. The in-situ material damping ratio calculated from these two sets of crosshole tests using the half-power bandwidth method are compare with the Spectral Ratio Slope (SRS) method applied to the downhole testing at these sites. The material damping calculated from the half-power bandwidth method using the full signal results in a reliable and precise damping value compared to the SRS method applied to the downhole data.

Field and laboratory measurements of shear wave velocity in unsaturated soils

Shear wave velocity measurements in soil are important for assigning site soil profiles to seismic site classes and for calculating other dynamic soil properties. The seismic cone penetration test (SCPT) is commonly used to determine shear wave velocity profiles in the field. In the laboratory, bender elements provide an easy means to measure shear wave velocity of soil specimens from discrete depths. In this study, shear wave velocity measurements obtained from unsaturated soil profiles in the field and on field samples in the laboratory under similar stress conditions were analyzed and compared. Additionally, the influence of seasonal changes on the behavior of shear wave velocity was investigated. Comparisons of shear wave velocities from the field and laboratory were favorable for similar moisture and stress conditions. However, results showed that as the degree of saturation increases and suction decreases the shear wave velocity can decrease significantly.

Developments in the seismic CPT and links to the Ménard Pressuremeter Test

The seismic cone penetration test (SCPT) was developed in the early 1980s and significant developments have been made in its use and application. This paper provides a review of these developments with particular emphasis on its application to identify soil microstructure. The Ménard pre-bored pressuremeter test (PMT) is one of the most popular in situ tests in France and links between SCPT results and the PMT are suggested.

A database of ground motion recordings, site profiles, and amplification factors from the Groningen gas field in the Netherlands

A comprehensive database that has been used to develop ground motion models for induced earthquakes in the Groningen gas field is provided in a freely accessible online repository. The database includes more than 8500 processed ground motion recordings from 87 earthquakes of local magnitude ML between 1.8 and 3.6, obtained from a large network of surface accelerographs and borehole geophones placed at 50 m depth intervals to a depth of 200 m. The 5%-damped pseudo-acceleration spectra and Fourier amplitude spectra of the records are also provided. Measured shear-wave velocity (VS) profiles, obtained primarily from seismic Cone Penetration Tests (CPTs), are provided for 80 of the ∼100 recording stations. A model representing the regional dynamic soil properties is presented for the entire gas field plus a 5 km onshore buffer zone, specifying lithology, VS, and damping for all layers above the reference baserock horizon located at about 800 m depth. Transfer functions and frequency-dependent amplification factors from the reference rock horizon to the surface for the locations of the recording stations are also included. The database provides a valuable resource for further refinement of induced seismic hazard and risk modeling in Groningen as well as for generic research in site response of thick, soft soil deposits and the characteristics of ground motions from small-magnitude, shallow-focus induced earthquakes.

CPT-Vs correlations for post-glacial sediments in Metropolitan Vancouver

A comprehensive Seismic Cone Penetration Test (SCPT) database for post-glacial sediments in Metro Vancouver is compiled to assess and establish relationships between CPT parameters and shear-wave velocity (Vs). Five world-wide and one existing Fraser River Delta (FRD) specific empirical CPT-Vs correlations are examined and found to have limited applicability in predicting Vs from our SCPT database. Region-specific CPT-VS models are then developed from a training dataset using 4 different regression approaches and 6 different CPT parameters combinations. The regression approaches include multi-linear (MLR) and nonlinear (NLR) regressions, and Random Forest and Extreme Gradient Boosting supervised ensemble machine learning models. The performance of different models and CPT parameters combinations is assessed using a testing dataset. The machine learning models are found to perform slightly better than MLR and NLR models in predicting Vs. Based on performance and practicality, a final CPT-Vs model is selected and applied to predict Vs for 59 compiled CPTs in the region. The comparison between predicted CPT-Vs profiles and measured Vs profiles in similar geology units confirms accuracy of our developed model. The developed CPT-Vs prediction models can be employed to obtain Vs profiles for site response analysis, compare CPT- and Vs-based liquefaction evaluation methods, or map Vs30 in Metro Vancouver.

Verification of Seismic Cone Penetration Test Calibration Chamber Tests on a Sand

Abstract Calibration chambers are experimental apparatuses that allow the physical modeling of an in situ testing method, such as the cone penetration test (CPT), by performing laboratory experiments on soil samples with known stress, strain, and density characteristics. Over a series of development and improvements, more recent calibration chambers and laboratory cone penetrometers have become compact and less laborious than their predecessors. This includes the focus of this study where a miniature cone penetration testing (MCPT) calibration chamber previously designed and used at Western University is upgraded to measure shear wave velocity (VS) and enable anisotropic consolidation of soil specimens using a hydraulic piston. In addition to VS, MCPT can also measure cone tip resistance, sleeve friction, and excess pore water pressure developed behind the cone tip. A full test plan using the newly upgraded MCPT calibration chamber is presented in this study. These tests are performed on Fraser River sand at various relative densities and effective stresses. Results of this testing program are validated by comparison with a series of in situ seismic CPTs in the Fraser River delta, existing correlations between VS and cone tip resistance, and several other calibration chamber tests on different sands. Through these comparisons, the overall viability of the initial MCPT calibration chamber design, modifications made to the MCPT setup, and ultimately the results produced from this device are confirmed.

Influence of source-to-site distance and diagenesis on liquefaction triggering of 200,000-year-old beach sand

Liquefaction triggering of the outcropping 200,000-year-old Ten Mile Hill beds sand facies (Qts) near Charleston, South Carolina is characterized in this paper. The characterization includes evaluating the relative susceptibility to liquefaction of Qts assuming a uniform seismic load and using seismic cone penetration testing at 46 sites, the ratio of measured small-strain shear wave velocity to estimated small-strain shear wave velocity (MEVR), and the liquefaction potential index (LPI). The computed LPI values indicate a slight decrease in the liquefaction susceptibility of Qts moving away (5 to 30 km) from the likely source of the 1886 Charleston earthquake (Mw ~ 7). Also characterized is the liquefaction potential of Qts during the Charleston earthquake and a range of other earthquake loadings. The results for the range of other earthquake loadings are summarized in terms of liquefaction probability curves, which provide a method for mapping liquefaction potential in Qts. A back-calculated, lower-bound diagenesis correction factor of 1.11 for areas of Qts where liquefaction surface manifestations were not observed agrees well with the published data.

Laboratory-scale seismic CPT calibration chamber tests on Fraser River sand

Physical modeling of cone penetration testing (CPT) can be carried out under known stress, deformation, and density conditions using laboratory calibration chambers. This study presents the results of reduced-scale model CPTs (MCPT) on Fraser River sand using a calibration chamber that allows anisotropic consolidation of soil specimens, as well as the measurement of shear wave velocity (VS), using bender elements. In addition to VS, MCPT can also measure cone tip resistance (qc), sleeve friction (fs), and pore water pressure developed behind the cone tip (Δu2). The CPT model tests are performed on Fraser River sand at different effective stresses and relative densities. The CPT calibration chamber test results are comparable with those of in situ seismic cone penetration tests (SCPT) in the Fraser River delta, existing correlations between VSand qc, and calibration chamber tests on other sands. This confirms the overall feasibility of the MCPT calibration chamber design for the measurements of qc, fs, and VSin sandy soils.

A novel PSO-KELM based soil liquefaction potential evaluation system using CPT and Vs measurements

Evaluation of soil liquefaction potential is an essential step in geotechnical engineering design. This study presents a novel soil liquefaction potential evaluation system using cone penetration test (CPT) and shear wave velocity test (Vs) measurements. To this end, a new hybrid machine learning model called PSO-KELM model that combines the kernel extreme learning machine (KELM) with particle swarm optimization (PSO) is developed to assess soil liquefaction potential. Then, the PSO-KELM based searching technique is adopted to search the nonlinear relationship between CRR and CPT along with Vs measurements. Finally, a new probabilistic model is developed by considering the model uncertainty and sampling bias based on weighted maximum likelihood estimation. Results demonstrate that the performance of PSO-KELM model is significantly better than that of many other machine learning methods. The cyclic stress ratio, equivalent clean sand normalized cone tip resistance, normalized friction ratio, fines content, and soil behavior type are the recommended input variables for PSO-KELM model. The combined use of CPT and Vs measurements can significantly improve the prediction accuracy since it can more fully reflect soil liquefaction phenomenon. The proposed evaluation system can improve the performance of seismic CPT (SCPT) in soil liquefaction potential evaluation.

Assessment of small-strain characteristics for vibration predictions in a Swedish clay deposit

Environmental vibrations induced by human activities such as traffic, construction or industrial manufacturing can cause disturbance among residents or to vibration sensitive equipment in buildings. In Sweden, geological formations of soft clay overlying a stiff bedrock are soil conditions prone to ground vibrations that are encountered both in urban areas and along parts of the national railway network. This paper presents an extensive investigation of the small-strain soil properties for the prediction of environmental ground vibrations in a shallow clay where the bedrock is situated at 7.5 m depth. The small-strain properties are estimated using available empirical correlations, bender elements, seismic cone penetration tests, seismic refraction and inversion of surface wave dispersion and attenuation curves. The results are synthesised into a dynamic layered soil model which is validated by measurements at the soil's surface at source-receiver distances up to 90 m in the frequency range 1–80 Hz. Analyses of uncertainties in the estimated values of wave speeds and material damping are performed by model investigations, indicating that surface wave tests overestimate the damping compared to bender element tests. The properties of the topmost unsaturated part of the soil is found to have a significant influence on the response at large distances, caused by critically refracted P-waves resonating in the top layer.

Site Characterization of Swiss Strong-Motion Stations: The Benefit of Advanced Processing Algorithms

ABSTRACTSince 2009, 91 new strong-motion stations were built for the renewal of the Swiss Strong Motion Network. Another nine stations will be installed until 2022. For each new station, an extensive site characterization study is performed to model the 1D seismic-velocity profile and, for some sites, the liquefaction potential. Geophysical (passive and active surface-wave methods) and geotechnical cone penetration test (CPT) with additional pore-pressure measurement (CPTu) and seismic CPT (SCPT) methods are used. Analyzing the passive and active recordings with a variety of established and advanced methods, the fundamental frequency of the site, the polarization of the wavefield, the Love- and Rayleigh-wave phase-velocity dispersion curves, and the Rayleigh-wave ellipticity function are retrieved. The liquefaction potential is assessed using CPTu. SCPT measurements are sometimes used to determine the shallow underground structure. The benefits of the combination of different appropriate methods are shown for two examples—the borehole station SBUS in Buochs and the upcoming borehole station SCME in Collombey-Muraz. At both the sites, the CPTu measurements show an elevated liquefaction potential. Combining the passive and active data, the dispersion curves for Love and Rayleigh waves and Rayleigh-wave ellipticity curves are retrieved over a wide-frequency range and inverted for the S-wave velocity profile, in which the shallow part is constrained by the active or SCPT data, the intermediate part by the dispersion curves of the passive methods, and the deepest part by the ellipticity information. For Buochs, the 1D SH-wave amplification functions modeled for the velocity profiles are compared with the empirical amplification for earthquake recordings. Finally, an overview of the site characterization results for 52 of the newly installed seismic stations is given.

Relationship between Shear Velocities Recorded by Microtremor Observations and Seismic Cone Penetration Test Results

This research proposes a relationship between two methods such as a numerical approach by conducting a microtremor array observation and field survey by using the seismic cone penetration test unit (SCPTu). A database of shear-wave velocity (Vs) measurements was established using the microtremor array technique and seismic cone penetration test unit (SCPTu) on high-quality samples of rock and soft soil in Padang city, Indonesia. The study also demonstrates that the Vs values obtained from the different methods are consistent with the microtremor array technique. This technique may thus be deemed a valuable tool, as it can be used in engineering practice with confidence. Comparison of the Vs for different soils at the first layer between the microtremor array observation results and the SCPTu results exhibited the microtremor array method is unable to determine the Vs at the layer where its Vs changes dramatically, such as at the same layer as station UNP at 2 to 3.5m deep.

Insights from CPTu and Seismic Cone Penetration Testing in the Kathmandu Valley, Nepal

Seismic hazard assessment often relies on static piezocone penetration tests (CPTu) to estimate the cyclic resistance ratio (CRR) and for the evaluation of in situ soil behavior. This article presents CPTu data acquired in the Kathmandu valley sediments and makes use of established CPTu interpretation procedures to assess the soil in situ properties. Up to this point predominantly SPT data and limited shear wave velocity measurements have been relied upon to assess the variability and seismic response of soil deposits underlying Kathmandu. This article provides 1) additional data to add to the existing SAFER/GEO-591 database, 2) new shear-wave velocity measurements, and 3) initial estimates of CRR at the sites visited. Based on the work presented in this article, it is concluded that a more detailed methodology is needed for liquefaction assessment mainly due to the presence of saturated silts in the valley.

Liquefaction Potential Analysis in Bucharest City as a Result of the Ground Shaking during Strong Vrancea Earthquakes

Bucharest, the capital of Romania with about 2.5 million inhabitants, is frequently struck by intense, damaging earthquakes (2–3 events per century). The Collaborative Research Center 461 (CRC-461) entitled: “Strong Earthquakes - a Challenge of Geosciences and Civil Engineering” was established in July 1996 and ended in December 2007, but some projects continued until 2010. It was funded by the German Research Foundation and involved the University of Karlsruhe which today belongs to Karslruhe Institute of Technology. The CRC aimed strategic research in the field of strong earthquakes with regional focus on the Vrancea seismic events in Romania. Between 1995–2007 several research works were done in Romania, with the support of several Romanian research institutes and the University of Bucharest. One of the research questions was to study the occurring of liquefaction during strong earthquakes within the shallow sandy layers in Bucharest. In suitable conditions, strong earthquakes can cause, under certain geologic conditions, liquefaction and therewith ground failure as sand boils, lateral spreading, or differentiated subsidence. In the present paper we analyze the liquefaction risk for Bucharest. For this purpose, at 10 representative sites in Bucharest, Seismic Cone Penetration Tests (SCPTu) were executed. An area-wide evaluation of the liquefaction probability in Bucharest was established. The factor of safety (FS) against liquefaction and the probability of liquefaction (PL) were computed from the obtained test-data. For the first time, maps of the liquefaction potential index (Li) for Bucharest were outlined. This map shows how severe the liquefaction phenomena might be during strong Vrancea earthquakes in Bucharest, amplifying the site effects. Keywords: hydrogeologic conditions, liquefaction probability, liquefaction hazard, Bucharest city, strong Vrancea earthquakes

СПОСОБ ГЕОТЕХНИЧЕСКОГО МОНИТОРИНГА ПОРОД ТАШТУНСКОГО РАЗЛОМА ЮГО-ЗАПАДНОГО БОРТА КАДЖАРАНСКОГО КАРЬЕРА

A method has been suggested for geotechnical monitoring of tectonic fault rock mass of the south-west wall in Qajaran open-pit mine by applying the pseudo-static method of CPTu (Cone Penetration Test with in-situ pore water pressure measurements) which gives an opportunity to define the root parameters of soils such as: pore water pressure, unit weight, drained and undrained shear strength. The versatile in-situ CPTu methods allow to profile simultaneously the geotechnical properties of each soil strata with permanent penetrating speed, and also while using the SCPTu (Seismic Cone Penetration Test with in-situ pore water pressure measurements) method, as well as determine horizontal and shear seismic wave velocities from the given geomechanical environment. At that, it also becomes possible to pull out independently intact samples from tectonic-fault-soils for future laboratory testing. Two different approaches for geomechanical proposition of the south-west wall stability of Qajaran open-pit mine based on the limit equilibrium theory and outputs from the proposed in-situ geotechnical seismic monitoring (SCPTu) have been analysed. The difference of the results from the two analyzed approaches (USA vs ESA) was about 8 to 10% in estimating the slope stability. Based on the analyzed results of the stability of the south-west wall of Qajaran open-pit mine, it is recommended to apply undrained strength analysis for undrained tectonic-fault soils (USA – Undrained Strength Analysis) instead of the effective drained strength analysis (ESA – Effective Strength Analysis) for drained rocks by taking into account the developed excess pore water pressure when saturated clayey soils sheared in undrained conditions.

Study of mining tailings geotechnical parameters obtained from SCPTu tests carried on dry and saturated layers

The correct interpretation of in situ and laboratory test results is an important step in the design of mining tailing containment structures. This study aims to analyze the Seismic Cone Penetration Test (SCPTu) results obtained into a mining tailing reservoir composed of two material layers: a thick-dry and a tick-saturated. It is possible to observe that in a same tailing reservoir, the CPTu test interpretation can lead to a classification of each layer as a different soil with specific behavior and properties. This condition demonstrates that tailings with intermediate permeability (10-5 m/s < k < 10-8 m/s) may present partial drainage conditions during a standard cone penetration test (CPTu) (v=20 mm/s), if saturated conditions are verified. The effects of partial drainage can affect test results, and can induce to errors in the prediction of soil behavior and geotechnical parameters. To evaluate the possible effects of partial drainage, in situ test results were compared to laboratory tests results. It was possible to verify that estimated behavior of dry layers, obtained from in situ tests results, present more similarity to the results from laboratory tests. Probably, the partial drainage effects verified through the interpretation of dissipation tests, distorted the estimated behavior of the saturated layer material.