Seismic Cone Research Articles

Seismic Flat Dilatometer Tests in Connecticut Valley Varved Clay

Abstract Downhole shear wave velocity measurements have been incorporated within a “Marchetti” flat dilatometer by placing a velocity transducer in a connecting rod just above the blade. The hybrid of combining downhole seismic with flat dilatometer, termed the seismic dilatometer test (SDMT), has the superior advantages of determining both the routine estimates of soil properties and stratigraphic information, while also measuring the small-strain stiffness within a single sounding. The SDMT is rapid, simple, and cost effective, requiring essentially no more time than a conventional dilatometer sounding. Results of seismic dilatometer testing in clays at the National Geotechnical Experimental Test Site (NGES) in Amherst, Massachusetts are presented and compare favorably with results from companion series of seismic cone penetrometer tests.

A Case Study for Characterizing Undrained Cyclic Deformation Properties in Young Sand Deposit from In-Situ and Laboratory Tests

ABSTRACT This paper describes a case study in which undrained cyclic deformation properties of a recent sand deposit in use for seismic response analysis was investigated through a comprehensive site investigation, coupled with cyclic loading tests in the laboratory. The test site comprised a loose sand deposit in Tokyo Bay which was reclaimed in I960’. The objective of this investigation was to examine the applicability of profiling small-strain shear modulus and damping characteristics of the recently reclaimed sand deposit by performing undrained cyclic triaxial and/or torsional shear tests on disturbed sand samples retrieved by ordinary tube samplers, and also on fully reconstituted samples prepared with a void ratio similar to the in-situ subsoil. Two types of sand sample with high and low quality were obtained by means of in-situ ground freezing technique and by ordinary tube samplers, respectively. The quality of the samples was evaluated by comparing the pseudo-elastic shear modulus, Gmax, from the laboratory cyclic loading tests to Gf from an in-situ downhole seismic cone test, which was involved with little disturbance to the original subsoil. On the basis of the test results, it was concluded that for this loose sand deposited only thirty years ago, the aging and structural effects were not significant with respect to the undrained cyclic deformation properties at small strains. It was also demonstrated that the undrained cyclic deformation properties can be evaluated with laboratory tests on isotropically consolidated specimens using disturbed or even fully reconstituted samples when the density profile with depth is pre-determined by means of appropriate in-situ tests.

Use of in situ measurements of ground inclination for determining shallow elastic parameters

We present the application of high-resolution ground inclination measurements to estimate some elastic properties in shallow stratified terrain. The direct problem for the solution of vertical and radial displacements under static loads is illustrated by means of the well-known Boussinesq problem for the elastic half-space. More realistic (stratified) configurations are taken into account by means of the stiffness matrix method proposed by Kausel and Roesset. In order to test our procedure some inclination surveys were performed in the virgin Texcoco Lake zone in Mexico City. Results are presented for the shear wave velocity and depth of the uppermost strata. A good fit between theoretical and observed inclinations was obtained. This leads to improved estimates of the ground parameters studied. Comparisons with results from independent seismic wave refraction profiles and cone resistance values validate our procedure. The agreement between the results from measurements of the ground surface inclination and results from other common, established techniques shows that the former technique provides a good estimate of ground elastic parameters. Nous montrons comment des mesures à haute résolution du pendage permettent d'estimer certains paramètres d'élasticité de couches superficielles stratifiées. Le probléme direct de la résolution des déplacements verticaux et radiaux sous l'effet de charges statiques est illustré à l'aide de la formule bien connue de Boussinesq pour la masse élastique semi-infinie. On tient compte de configurations stratifiées plus réalistes en utilisant la matrice de rigidité proposée par Kausel et Roesset (1981). Pour Vérifier notre méthodologie, nous avons effectué des relevés de pendage dans la zone vierge du lac Texcoco à Mexico. Nous présentons les résultats obtenus pour la vitesse de l'onde de cisaillement et la profondeur des couches superficielles. Les valeurs théoriques du pendage concordent bien avec les valeurs observées, ce qui veut dire que notre méthode permet d'estimer avec plus de précision les paramétres du terrain étudié.Elie est validée par des comparaisons avec les résultats d'études ind6pendantes de profils de réfraction des ondes sismiques et des valeurs de résistance en pointe. La concordance entre les résultats des mesures du pendage des couches superficielles et les résultats d'autres techniques bien établies montre que les premiéres offrent une bonne estimation des paramétres d'élasticité du sol.

Estimate of Elastic Shear Modulus In Holocene Soil Deposits

ABSTRACT An empirical equation in use for estimating the pseudo-elastic shear modulus, Gf, of subsoil, associated with shear strains less than 0.001% is proposed in this paper. In a series of in-situ seismic cone tests performed nationwide, the profiles of both Gf and the in-situ void ratio, e0, with depth were successfully characterised at five sites, each comprising a soft clay layer deposited in the Holocene era. The database which comprised the original data from the field and laboratory tests, coupled with similar information on well-documented Holocene clay deposits in Europe, was statistically analyzed in attempts to determine a generalised relationship with which Gf of soft clay may be reasonably estimated only from routinely available borehole data; that is e0 and the current geostatic effective overburden pressure, σv′An empirical relationship, G f = 5 , 000 e 0 − 1.5 σ v ′ kP a , was derived from the statistical analysis applied to data from seven different clays worldwide, for which e0 extended over a range between 1 and 5, and the overconsolidation ratio ranged roughly between 1 and 2. The applicability of the proposed relationship was evaluated for two case records, each in which the clay exhibited unusual behavior; i.e., the undrained shear strength remained more or less constant with depth due to the existence of artesian pressure at one site, and, at the other, Gf decreased, whereas e0 increased, σv′ with depth. It was demonstrated that even in these clay deposits exhibiting exceptional profiles, the proposed relationship was capable of predicting Gf with a reasonable accuracy by determining the profiles of e0 and σv′ with depth. In addition, the prediction when compared to Gmax from carefully performed laboratory cyclic tests, yielded a better estimate of Gf from the in-situ seismic survey. Despite the fact that the empirical relationship was initially designated to estimate Gf of soft clays, it may be equally applicable to sandy deposits. This was verified by comparing it to similar, and well-established, relationships developed for sands. A case record as such is also described for a loose sand deposit at Higashi-Ohgishima in Tokyo Bay which was placed in 1960’s by land reclamation.

Small- and High-Strain Measurements of In Situ Soil Properties Using the Seismic Cone Penetrometer

Seismic cone penetration tests provide an economical and expedient means of assessing small-strain properties (low-amplitude shear modulus, GMAX) and large-strain behavior (shear strength, τmax) of soil deposits from a single sounding. That measurements are taken at complete opposite ends of the strain spectrum permits development of the entire stress-strain-strength representation of soil layers with depth. A modified hyperbola is shown to be appropriate in a modulus degradation scheme for application to static monotonic loading of soils. Also, a global correlation of mass density (ρ) with shear wave velocity (Vs) for all types of geomaterials is presented, which facilitates the calculation of GMAX = ρVs2.

Small- and High-Strain Measurements of in Situ Soil Properties Using the Seismic Cone Penetrometer

Seismic cone penetration tests provide an economical and expedient means of assessing small-strain properties (low-amplitude shear modulus, GMAX) and large-strain behavior (shear strength, τmax) of soil deposits from a single sounding. That measurements are taken at complete opposite ends of the strain spectrum permits development of the entire stress-strain-strength representation of soil layers with depth. A modified hyperbola is shown to be appropriate in a modulus degradation scheme for application to static monotonic loading of soils. Also, a global correlation of mass density (ρ) with shear wave velocity (Vs) for all types of geomaterials is presented, which facilitates the calculation of GMAX = ρVs2.

Evaluation of in situ anisotropy from crosshole and downhole shear wave velocity measurements

Downhole and cross hole shear wave velocity determinations are becoming a routine part of dynamic site evaluation studies. The in situ measurements are frequently performed in boreholes using a variety of techniques. A seismic cone system has been developed for determining both downhole and crosshole shear wave velocity. The system consists of a source and two receivers, all embodied in penetrometers. At any depth three different polarized sets of shear wave signals can be generated and are recorded by both receivers, located at different distances from the source. It has been suggested from laboratory tests in large chambers that the measured shear wave velocities can be used to evaluate the in situ stress conditions. Tests have been performed at research sites in Vancouver to evaluate the in situ stress dependence of the measured shear wave velocities. The results of this study suggest that variations in structural anisotropy are the predominant factors controlling the directional shear wave velocities, and almost mask the effect of stress-induced variations. Les mesures de vitesse des ondes transversales, le long et entre les trous, font partie intégrante de la routine des études dynamiques d'évaluation des sites. Les mesures in-situ sont trés souvent réalisées dans des trous de forages à l'aide de diverses techniques. Le système développé permet de mesurer la fois, à l'aide d'un cône sismique, les vitesses le long et entre les trous. Ce système est constitué d'une source et de deux récepteurs intégrés à des pénétromètres. Quelle que snit la profondeur, trois différents trains d'ondes polarisées peuvent être générés puis enregistrés par les deux récepteurs situés à une distance variable de la source. Les essais de laboratoire à grande échelle laissent à supposer que les vitesses mesurées permettent d'évaluer les conditions de contrainte in-situ. Des essais ont été réalisés dans des sites d'étude à Vancouver pour évaluer la relation de la vitesse des ondes transversales à la contrainte in-situ. II ressort de cette étude que cette vitesse est principalement fonction des variations de l'anisotropie structurale qui masquent de ce fait les effets dus aux variations de la contrainte in-situ.

Evaluation of liquefaction resistance of sand by maximum shear modulus

Abstract Laboratory tests and in‐situ seismic cone penetration tests are conducted to evaluate the liquefaction resistance of Lanyang sandy soils. Resonant column tests and cyclic torsional shear tests are performed on remolded samples to establish the relationship between the maximum shear modulus and the liquefaction resistance. The relationship is used to predict the in‐situ liquefaction resistance. Test results show that liquefaction resistance predicted by CPT‐qc is consistent with the one predicted by maximum shear modulus. From the comparisons, the maximum shear modulus is found to be a good index in assessing in‐situ liquefaction resistance.

Practical aspects of in situ measurements of material damping with the seismic cone penetration test : Stewart, W P; Campanella, R G Can Geotech JV30, N2, April 1993, P211–219

Practical aspects of in situ measurements of material damping with the seismic cone penetration test : Stewart, W P; Campanella, R G Can Geotech JV30, N2, April 1993, P211–219

Digital filtering techniques for interpreting seismic cone data : Baziw, E J J Geotech Engng Div ASCEV119, N6, June 1993, P998–1018

Digital filtering techniques for interpreting seismic cone data : Baziw, E J J Geotech Engng Div ASCEV119, N6, June 1993, P998–1018

Earthquake response at Grangemouth

The Grangemouth industrial zone in Scotland is on an area of deep soft clay. Extensive site investigations related to industrial development which included seismic cone testing enabled accurate numerical calculations to be carried out to assess the response of this soft site to earthquake excitation. The site is surrounded by the permanent LOWNET seismological array, which together with a temporary seismic station at the site enabled comparison between numerical predictions and instrumental experimental evidence. The comparisons confirmed the predominance of the site dynamic response in earthquake ground surface motions. They also enabled a site-specific design response spectrum to be developed with greater confidence. La zone industrielle de Grangemouth (Ecosse) est située sur une argile molle profonde. Les études extensives réalisées in-situ en vue d'un développement industriel comprenent des essais sismiques au cône. Elles permettent de réaliser des calculs numériques précis afin de connaître la réponse de ce sol mou aux excitations sismiques. Le site est entouré par le dispositif sismique permanent Lownet qui, associé à une station sismique temporaire, permet de comparer les prévisions numériques aux résultats expérimentaux et instrumentaux. Les comparaisons confirment la prédominance des réponses dynamiques du site dans les mouvements sismiques de surface du sol. Elles permettent également de déterminer avec une plus grande fiabilité un modèle de spectre de réponse spécifique du site.

Development of electric static cone penetration testing in Great Britain from 1972–1992 : Erwig, H Ground EngngV26, N3, March 1993, P30–34

This paper reviews the progress of electric static cone penetration testing (CPT) in the UK during the past 20 years. It describes in detail the reasons for its development and associated advances in equipment. The use of the electric cone penetrometer, which is an on-site testing device, has increased steadily in the UK. Both onshore and coastal marine penetrometers have been developed, together with a variety of CPT equipment for special conditions. Considerable improvements have been made to cone penetrometer tip design. A range of additional sensors have become commercially available, including the piezocone and conductivity, seismic and temperature cones. The thrust of CPT equipment can be used to push a variety of devices into the ground, of which soil samplers are currently most used. Relevant research has been conducted by the Building Research Establishment, Science & Engineering Research Council, and three British universities. Reasons for the increased use of CPT in the UK include: (1) profiling; (2) reliability; (3) speed; (4) cost effectiveness; (5) considerable improvements to correlation between CPT data and soil parameters. Operators will continue to try to improve equipment strength and durability. The cone pressuremeter and seismic cone are now commercially available. Cone penetrometer equipment can be used successfully for environmental site investigations.

Real time evaluation of shear wave velocity during the seismic cone penetration test : Piccoli, S; Smits, F P Proc 3rd International Symposium on Field Measurements in Geomechanics, Oslo, 9–11 September 1991V1, P159–166. Publ Rotterdam: A A Balkema, 1991

Real time evaluation of shear wave velocity during the seismic cone penetration test : Piccoli, S; Smits, F P Proc 3rd International Symposium on Field Measurements in Geomechanics, Oslo, 9–11 September 1991V1, P159–166. Publ Rotterdam: A A Balkema, 1991

Seismic cone penetration test for evaluating liquefaction potential under cyclic loading : Robertson, P K; Woeller, D J; Finn, W D L Can Geotech JV29, N4, Aug 1992, P686–695

Seismic cone penetration test for evaluating liquefaction potential under cyclic loading : Robertson, P K; Woeller, D J; Finn, W D L Can Geotech JV29, N4, Aug 1992, P686–695

Digital Filtering Techniques for Interpreting Seismic Cone Data

Seismic cone penetration testing (SCPT), a relatively new in situ technique, records the arrival of seismic waves generated at the surface using velocity or acceleration transducers installed in an electric piezocone. To distinguish the different seismic arrivals, instruments with fast response times are required, i.e., accelerometers. The fast response time of an accelerometer results in a very sensitive instrument with corresponding noisy time‐domain characteristics. One way to separate events is to apply digital filters, which characterize the signal frequencies and then isolate frequency spectrums of interest. The digital filter introduced in this paper is based on frequency‐domain filtering using cross‐correlation algorithms. The cross‐correlation filter concepts are synthesized by a computer program referred to as PS CrossCor, whose performance was evaluated by interpreting both synthetic and real data. Data from three sites is presented to compare the PS CrossCor and the established crossover method. The results from the analysis indicate that PS CrossCor is an accurate and reliable tool that greatly assists in determining seismic velocities, and has potential for determining other seismic parameters.

Practical aspects of in situ measurements of material damping with the seismic cone penetration test

The downhole seismic cone penetration test (SCPT) procedure has been extended to allow the measurement of material damping at small strains at minimum expense while one is measuring shear wave velocity. The nature of damping, the required equipment characteristics, and the recommended procedure and calculation methodology are presented in a practical way. SCPT results from four different sites give results that are in general agreement with laboratory measurements of damping for sands and clays and with values recommended by other authors. It appears, however, that previously reported measurements of damping by borehole methods are higher, by a factor of two or more, when compared with SCPT and laboratory results. Key words : in situ, damping, seismic, shear wave, cone penetrometers, procedures.

Seismic cone analysis using digital signal processing for dynamic site characterization : Campanella, R G; Stewart, W P Can Geotech JV29, N3, June 1992, P477–486

Seismic cone analysis using digital signal processing for dynamic site characterization : Campanella, R G; Stewart, W P Can Geotech JV29, N3, June 1992, P477–486

G max-qc Relationships for Clays

Abstract Data are compiled from 31 clay sites where in-situ measurements of initial tangent shear modulus (Gmax) and cone tip resistance (qc) were available. Values of Gmax were obtained from either seismic cone penetration (SCPT), crosshole (CHT), downhole (DHT), or spectral analysis of surface wave (SASW) tests, and readings of qc were taken either by regular cone penetration (CPT) or piezocone (CPTU) tests. Multiple regression analyses indicate that in-situ values of Gmax depend on void ratio (eo), overburden stress (σ′vo), and stress history (OCR), as previously established from laboratory resonant column tests. Since qc also depends on σ′vo and OCR, a moderate association between Gmax and qc is possible, despite their incompatible strain levels. For preliminary correlative purposes, a power function relates in-situ Gmax, qc, and eo in clay deposits having a wide range in plasticity, sensitivity, stress history, and consistency.

Evaluation of sediment properties in the Lower Hutt and Porirua areas by means of cone and seismic cone penetration tests

Cone and Seismic Cone Penetration Tests (CPT and SCPT) have been carried out at a total of 101 sites in the Porirua and Lower Hutt regions of New Zealand, initially (from 1975 to 1987) as government-funded public- good science, and later as part of a multi-disciplinary microzoning project under contract to Wellington Regional Council. The shear wave velocities and depths determined in the study were successfully used to predict small-signal resonant frequencies for two sediment-filled basins, and the inferred cohesions were used qualitatively to predict the importance of nonlinearities in limiting ground motion amplification. The major results were the identification and shear wave characterisation of a surface layer (depth 12 m, diameter 600 m) of cohesive flexible sediment in the Porirua basin and a successful prediction of the associated basin resonant frequency, identification and shear wave characterisation of a thick surface layer (depth 30 m, length 2 km, width 500 m) of cohesive flexible sediment in the Wainuiomata basin which explained an observed resonance, identification and shear wave characterisation of a wedge of flexible sediment, cohesive below and uncohesive above, in the lower part of the Hutt Valley, and identification of a pocket of flexible sediment in the Naenae area.

Seismic cone penetration test for evaluating liquefaction potential under cyclic loading

Impressive progress has been made in the last 25 years in recognizing liquefaction hazards, understanding liquefaction phenomena, and analyzing and evaluating the potential for liquefaction at a site. Recent findings related to the application of the seismic cone penetration test (SCPT) for the evaluation of liquefaction potential under cyclic loading are presented and discussed. The SCPT provides independent measurements of penetration resistance, pore pressures, and shear-wave velocity in a fast, continuous, and economic manner. The current methods available for evaluating liquefaction using penetration resistance are presented and discussed. Recent developments in the application of shear-wave velocity to evaluate liquefaction potential are discussed, and a new method based on normalized shear-wave velocity is proposed. Limited case-history data are used to evaluate and support the proposed correlation. A worked example is presented to illustrate the potential usefulness of the SCPT for evaluating liquefaction potential at a site. Key words : liquefaction, in situ tests, seismic.