Seismic Piezocone Penetration Tests Research Articles

Characterization on the correlation between SPT-N and small strain shear modulus Gmax of Jiangsu silts of China

Small strain shear modulus plays a fundamental role in the evaluation of site response parameters. Only few authors used measured density and shear wave velocity (Vs) to estimate small strain shear modulus. In this study, an attempt has been made to develop the regression relationship between standard penetration test (SPT) N values and the small strain shear modulus (Gmax). For this purpose, field investigations SPT and seismic piezocone penetration test (SCPTU) data from locations in Su-Xin Expressway of China, have been used, which were also used for ground improvement project. The in situ density of soil layer was estimated using undisturbed soil samples from the boreholes. The Vs profiles with depth were obtained for the locations close to the boreholes. The values for small strain shear modulus have been calculated by measured Vs and in situ soil density. About 50 pairs of SPT-N and Gmax values were used for regression analysis. The differences between measured and corrected values which were used in fitted regression relations were analyzed. Most of the existing correlations were developed based on the studies carried out in Japan and in India, where N values are measured with hammer energy of 78%, which may not be directly applicable for other regions because of the variation in SPT hammer energy which in China is about 55%. A new correlation has been generated using the measured values in silts of China. From this study, it is found that uncorrected values of N and modulus gives the best fit regression relations when compared to corrected N and corrected modulus values. With most equation was used for sand and clay, the regression relations between corrected values of N and modulus gives the equation of silts in China.

In-situ evaluation of undrained shear strength from seismic piezocone penetration tests for soft marine clay in Jiangsu, China

Abstract Undrained shear strength, s u is an important geotechnical parameter of soft clay. The seismic piezocone test (SCPTU) can provide valuable information regarding in-situ soil behavior and stratigraphy in geotechnical site investigation. Therefore, the relationships of s u with the data obtainable in SCPTU testing have long been a topic of research interest. The objective of this paper is to evaluate the su of marine clay from Lianyungang in Jiangsu Province of China. First, existing methods for obtaining the su values of clay soils from basic SCPTU penetrometer readings are reviewed. The relationships between su and SCPTU parameters at the Lianyungang site are then determined. su values derived from field vane testing and CPTU results are also discussed. The relationship between su and the pore pressure cone factor is proposed and the pore pressure cone factor is shown to be approximately about 8.03, providing a means to estimate su. A previously developed method of using maximum excess pore pressure is also utilized here for the overconsolidated clays within the stratigraphic sequence. Additionally, a relationship between su and shear wave velocity is proposed, linking stiffness with strength in a stiffness-strength correlation. The derived correlations are in accordance with those previously reported in the literature, and the results also showed that SCPTU tests can be used comprehensively to estimate the su of Jiangsu marine clay.

Assessment of Ground Improvement by Vibro-compaction Method for Liquefiable Deposits from In-Situ Testing Data

Seismic piezocone penetration tests, resistivity piezocone penetration tests, and standard penetration tests (SPT) were conducted to quantitatively assess the effects of soil improvement by vibro-compaction. The differences of piezocone penetration test (CPTU) basis readings, improvement index for densification, electrical resistivity of soils, and state parameters before and after ground treatment were analyzed, and the effect of the increase in stiffness on the site response was also analyzed for the effect of densification. A combination of shear wave velocity, Vs, and cone tip resistance, qc, was used for the interpretation of the changes of coefficient of earth pressure at rest, K0, and mean grain size, D50, before and after compaction. The dissipation process of excess pore pressures during vibro-compaction has been presented to show the effect of drainage. In addition, liquefaction potential was also estimated by CPTU and SPT for its effect of reinforcement. The results showed that the liquefied soil was densified and the use of a combination of in-situ tests could be used for ground improvement needed to mitigate liquefaction.

Determination of Bearing Capacity of Single Pile based on Seismic Piezocone Penetration Tests

Based on the similar characteristics of installation about the penetrometer of seismic piezocone penetration tests(SCPTu) and the single pile, a theoretical relationship between ultimate bearing capacity of single pile, time-effect of shaft bearing capacity of single pile, excess pore water pressure around the pile during pile driven and the data measured from SCPTu is developed according to the cavity expanded theory, the Terzaghi one-dimensional consolidation theory and effective stress theory. The result of field test in KunShan and the calculated result which used the theoretical relationship mentioned above are compared. The results indicate that the analytical solutions agree well with the in-situ tests, which show that the applications of seismic piezocone penetration tests have wide range in the design of pile foundation.

Evaluation of geotechnical parameters of a lagoonal clay deposit in Jiangsu Lixia River area of China by seismic piezocone tests

The use of the Seismic Piezocone Test (SCPTU) in geotechnical site investigation offers field assessment on stratigraphy and soil behavior. Compared with some traditional investigation methods such as drilling, sampling and field inspecting method or laboratory test procedures, SCPTU can greatly accelerate the field work and hereby reduce corresponding operation cost. The results of a site investigation on the soft, normally to slightly overconsolidated, Lixia River lagoonal clay deposit underlying several expressway lines, including a seismic piezocone penetration test, undisturbed sampling from an adjacent borehole, and laboratory testing, are reported. The determination of soil profile and the main geotechnical properties is facilitated by the use of seismic piezocone penetration test that can provide up to four independent reading with depth from a single sounding. The coupled use of normalized cone resistance and pore pressure parameter provides a simple and quick soil classification for highly interbedding of Lixia River lagoon ground. Comparison of the results reveals the validity of SCPTU tests to interpret the engineering properties of Lixia River lagoonal clay. These data will also be particularly useful for future local construction work.

Assessment of Stress History of Jiangsu Clay Deposits from Seismic Piezocone Penetration Testing (SCPTU) Data

The stress history as indicated by the profile of overconsolidation ratio (OCR) or preconsolidation pressure of a soil deposit is one of the dominant factors that influence the engineering behavior of soils. A commonly used method to obtain the parameter is a laboratory oedometer test, which is of low accuracy and time consuming because of inevitable sample disturbance. The purpose of this article is to assess the capability of existing interpretation methods and develop new methods to reasonably predict the OCR of clayey soils utilizing the seismic piezocone penetration test (SCPTU) data. Seven sites in Jiangsu province of China were used for this study. At each site, in situ SCPTU tests were performed and soundings of cone tip resistance (q c ), sleeve friction (fs), pore pressures (u 2), and shear wave velocity (Vs) were recorded. High-quality Shelby tube samples were collected close to the SCPTU tests and used to conduct laboratory oedometer consolidation tests to evaluate the reference OCR values. The predicted OCR values from different methods were compared with the laboratory OCR values. The results showed that all the investigated SCPTU methods overpredict the laboratory-calculated OCR. The collected data were further used to develop two new SCPTU methods that can estimate the OCR reasonably.

Gmax of Reclaimed Ground on the Western Coast of Korea Using Various Field and Laboratory Measurements

The maximum shear modulus of soil is a principal parameter for the design of earth structures under static and dynamic loads. In this study, the statistical data of the maximum shear moduli of reclaimed ground in the Songdo area on the western coast of Korea were evaluated using various field and laboratory tests, including the standard penetration test (SPT), piezocone penetration test (CPTu), self-boring pressure meter test (SBPT), down-hole seismic test (DHT), seismic piezocone penetration test (SCPTu) and resonant column test (RCT). Soils were classified variously by using a conventional unified soil classification system and classification charts for CPTu data. For the soils containing mostly sand and silt, the soil classifications using the classification charts for CPTu data show good agreement with the unified soil classification. Based on the statistical analysis on various maximum shear moduli, new site-specific empirical correlations between the shear moduli and SPT and CPTu values were proposed. Predictions of the maximum shear moduli using the proposed correlations were compared with the data obtained from the DHT, which is comparatively exact in evaluating the maximum stiffness of soils. The good agreement confirmed that the proposed correlations reasonably predicted the maximum shear moduli of soils in western coastal area of Korea.

Liquefaction assessments using seismic piezocone penetration (SCPTU) test investigations in Tangshan region in China

Shear wave velocity (Vs) measurements from seismic piezocone penetration (SCPTU) soundings have been increasingly used for site characterization and liquefaction potential assessments. Several sites in Tangshan region, China liquefied during the Tangshan earthquake, Mw=7.8 in 1976 and these sites were characterized recently using the SCPTU device. Other sites in the same region where liquefaction was not observed are also included in the present field investigations. Three liquefaction assessment models-based on measured shear wave velocity, shear modulus and tip resistance parameters of SCPTU are evaluated in this paper for their accurate predictions of liquefaction or non-liquefaction at the test sites. Analyses showed that the shear wave velocity—liquefaction resistance model with normalized overburden vertical stress have yielded a success rate of 78% in predicting liquefied site cases and another similar approach with mean stress based normalization has a success rate of 67%. The correlation of qc/Go-CRR7.5 based on geological age has correctly assessed the liquefaction potential at most sites considered in this research. Overall, all three models based on shear wave velocity, shear modulus and cone tip resistance are proven valuable in the assessments of liquefaction at the present test sites in the Tangshan region.

Assessment of soft clay ground improvement from SCPTU results

Some in situ seismic piezocone penetration tests (SCPTU) were performed in undisturbed soils and the inter-pile soils between T-shaped, bidirectional, soil–cement deep mixing columns at lacustrine clay sites to quantitatively assess the effects of ground improvement. The difference of cone resistance and sleeve friction of soils among the columns after cement column construction was analysed. From pore pressure dissipation tests, the consolidation characteristics of the inter-pile soils were evaluated. The effect of the deep mixing column on the behaviour of the inter-pile soils is discussed. Preconsolidation pressures were estimated using some methods based solely on net cone tip resistance, excess pore pressure, effective cone resistance and a multiple regression based on cone tip resistance and shear wave velocity. Cement columns increase the lateral stress locally within the zone of influence of the column. Soils initially appear to be normally consolidated to slightly overconsolidated, and a significant increase in preconsolidation pressure was noticed in clay layers after treatment.

Research on Application of Seismic Piezocone Penetration Tests in Pile Foundation

According to the characteristics of installation about the penetrometer of seismic piezocone penetration tests (SCPTu) and the pile, a theoretical relationship between ultimate bearing capacity of single pile, time-effect of shaft bearing capacity of single pile, excess pore water pressure around the pile during pile driven and the data measured from SCPTu is developed based on the cavity expanded theory, the Terzaghi one-dimensional consolidation theory and effective stress theory. The result of field test in KunShan and the calculated result which used the theoretical relationship mentioned above are compared. The results indicate that the analytical solutions agree well with the in-situ tests, which show that the application of seismic piezocone penetration tests have wide range in the pile foundation.

Assessment of the Coefficient of Lateral Earth Pressure at Rest (K o) from In Situ Seismic Tests

Abstract The coefficient of the earth pressure at rest (Ko) is an important soil parameter that influences shear strength, stress-strain behavior, and compressibility characteristics of both cohesive and cohesionless soils. This paper presents a research study in which the Ko values of natural soil deposits are interpreted on the basis of seismic shear wave velocity measurements made at two research sites in Jiangsu province of China. Seismic piezocone penetration tests and cross-hole seismic logging tests were performed at both sites and these results have been used in two existing Ko-shear wave velocity models for prediction of Ko. The predicted Ko at both sites are compared with values determined utilizing Jaky’s formula via laboratory measured strength parameters. Certain variations between predictions and measurements are noted for soils at shallow depths, which are attributed to stress history and desiccation in these layers. Further analysis developed correction factors that accounted for both soil types and overconsolidation ratio effects. These factors can be used with original models for better interpretation of Ko for overconsolidated clays. This approach showed a reasonable match between interpreted Ko properties from both models and those that utilize laboratory test results.

Stabilization Effectiveness of Treatment with T-Shaped Deep-Mixing Column for Low-Volume Roads

Deep-soil mixing using column elements is a widely used technology for improving soft soil properties for low-volume roads in China. The deep-mixing method has some limitations, because a high-treatment area over the entire column length makes this method expensive and impractical. On the basis of a stabilization mechanism and factors that affect column construction quality, a T-shaped bidirectional soil–cement deep-mixing column has been successfully developed and proved to be effective and economical. As part of quality control of field improvement of these columns, seismic piezocone penetration tests (SCPTUs) were used. The tests can provide near-continuous measurements of tip resistance, sleeve friction, and pore pressure induced during the penetration. This paper discusses field SCPTUs that were performed in the untreated soils and the interpile soils between the T-shaped bidirectional soil–cement deep-mixing columns at the Huzhou lacustrine clay site in China. Soil properties estimated from the SCPTU data both before and after improvement methods were compared to assess the effectiveness of soil improvement. These results indicate that the use of SCPTUs will improve understanding of the changes in soil behavior achieved by this novel deep-soil mixing method for low-volume roads.

Interpretation of Seismic Piezocone Results for the Estimation of Hydraulic Conductivity in Clays

Abstract Seismic piezocone penetration tests with dissipation phases provide sufficient data for outlining the geostratigraphy, soil strength, stiffness, and flow characteristics in fine-grained soils. The dissipation of excess pore water pressures with time can be monitored at regular intervals (e.g., at 1-m rod breaks) and provides information on the coefficient of consolidation (ch). Monotonic and/or dilatory responses of Δu decay can be accommodated. The shear wave velocity (Vs) provides a measure of the small-strain stiffness (G0), or surrogate evaluation of the constrained modulus (D′). A sampling of data from ten clay sites was used to assess the derived magnitude of hydraulic conductivity, as determined from k = chγw/D′.

Undrained Anisotropic Monotonic Behavior of Sand from In Situ Tests

A procedure for estimating the undrained stress-strain behavior of sand from drained self-boring pressuremeter and seismic piezocone penetration tests is proposed in this paper. The procedure offers an inexpensive alternative to laboratory testing and avoids the uncertainty of the empirical methods based on index measurements such as the Standard Penetration Test blow count and the tip resistance in a Piezocone Penetration Test (CPTU). To check its validity, the proposed procedure was used to infer the undrained triaxial stress-strain curves and the results were compared with laboratory triaxial tests on undisturbed samples. The undrained limit equilibrium stability of a dike was also assessed using the inferred stress-strain behavior to illustrate the usefulness of the procedure. The result of the stability analysis was found to be in qualitative agreement with the observed performance of the dike during a recent field experiment attempting to trigger static liquefaction.

Assessment of the coefficient of the earth pressure at rest from shear wave velocity measurements

The paper presents an attempt to evaluate the feasibility of predicting the value of the coefficient of the earth pressure at rest K. of natural soil deposits on the basis of the measured velocities of the seismic shear waves. The experimental data presented were obtained from seismic tests performed in a calibration chamber on laboratory prepared specimens of seven granular materials, with grades ranging from fine sand to gravelly sand. The relationship between K. and the shear wave velocity established using the calibration chamber results was used successfully to predict K. at two well-documented sites for which both cross-hole seismic and seismic piezocone penetration test results are available Cet exposé dicrit un essai destiné à évaluer la faisabilité dune pr6vision de la valeur du coefficient de pression au sol au repos (Ko) des dépôts de sol naturels en se basant sur les vélociés mesurées des ondes sismiques transversales. Les donn6es expérimentales qui sont présentées dans cet expos&aute; viennent d'essais sismiques effectués dans une chambre de calibrage sur les spécimens préparés en laboratoire de sept matières en grains allant du sable fin au sable graveleux. La relation entre K. et la vitesse d'onde transversale établie d'après les résultats de la chambre de calibrage a 6t6 utilisée avec succés pour préd1re K. sur deux sites bien documentés oùi des essais de forage transversal sismique et de pénétration piéocone sismique sont disponibles.