Standard Penetration Test Blow Counts Research Articles

Site-Specific correlation between geotechnical and geoelectrical properties of soil deposits in India

The combined application of geotechnical and geophysical methods provides an effective means of subsurface exploration. The insufficient correlation between geotechnical and geophysical methods prevents the conversion of geophysical data to geotechnical information and vice versa. In the present study, a correlation has been proposed between the geotechnical and geoelectrical properties of two soil deposits in India. Eleven boreholes along with a Standard Penetration Test (SPT) and different laboratory tests have been conducted to obtain the different engineering and physical properties of the soil layers. Twelve Electrical Resistivity Tomography (ERT) profiles have also been conducted to obtain the resistivity profile of the subsurface layers. The variation of the resistivity of the soil layers is analyzed and explained. Results show a strong linear correlation between resistivity and SPT blow counts (N′) of the soil layer for one site while a weak correlation for another site. A strong linear correlation between transverse resistivity (T) and N′ values has been observed for both sites. A comparison with the other existing correlation between resistivity/transverse resistivity and N′-values has also been presented. The range of resistivity values and engineering properties of soil layers are mentioned. The study is useful for the development of similar correlations and provides an approximate estimation of different geotechnical parameters for infrastructure design.

Correlating Measured SPT-N, Shear Wave Velocity and Liquid Limit Values in Melekli Region, Igdır (Türkiye)

Characterization of soil layers underneath or having interaction with structures is substantially critical for the overall stability of structures under static and dynamic conditions. The main objectives in characterizing soil are mainly to determine ultimate bearing capacity, settlement, and liquefaction potential. Additionally, the dynamic behavior of soil during seismic excitation, as well as its interaction with structures, should be determined. In these regards, Standard Penetration Test blow counts (SPT-N) and shear wave velocity (Vs) values of soils obtained directly through field tests are known to reflect the soil characteristics, strongly. Therefore, any correlation between these two soil parameters is always in utmost interest. This study assesses the correlation between Vs and SPT-N values measured in Melekli region, Igdır (Türkiye). Moreover, four existing correlations in the literature are presented. The best-fit curve for the measured data is shown to divert from the existing correlation curves, which are also significantly different from each other, for all soils, sand, and clay soils. This can be attributed to the uniqueness of correlation to the study site as geological conditions at one site differ extensively from another site. There seems to be valuable correlation between Vs and water content and liquid limit in the studied area.

Correlations between p-wave velocity and SPT-N for saturated and unsaturated alluvial clays using dimensional analysis

The aim of this research is to establish practical and robust correlations between dilatational wave velocities (p-wave velocities, Vp) and the Standard Penetration Test blow count (SPT-N). Very low levels of correlation are recorded with the conventional single variable approaches, in consequence, a multivariable study is needed for higher precision. A dimensional analysis was conducted including other soil parameters that condition this physical phenomenon, such as the void ratio (e), the degree of saturation (Sr), the effective overburden pressure (σ′v), and the particle density (γs), for greater precision with Vp and SPT-N correlations. Over 100 seismic and SPT tests were performed around the coastal city of Juchitán de Zaragoza (Oaxaca), Mexico, to gather information for this research. As a result, two dimensionless indexes -DSIu (Undrained Dilatational Stiffness Index) and MDSIu (Modified Undrained Dilatational Stiffness Index)- yielded two alternative expressions between both indexes and Vp. In this way, a strong relationship between Vp and SPT-N was obtained with an adjusted coefficient of determination R2 value of 0.93.

Liquefaction hazard mapping of the south-central coastal areas of Bangladesh

Liquefaction can cause significant damage to the built environment; therefore, assessing the liquefaction hazard in a seismically active region is essential to minimize the risk. This study attempted to evaluate the liquefaction potential of the south-central coastal areas of Bangladesh by calculating the liquefaction potential index (LPI) considering a scenario earthquake of Mw = 7.5 having a peak ground acceleration of 0.15g. For calculating LPI, both standard penetration test blow count (SPT-N) and shear wave velocity (Vs) data have been used in this study. The results show that the study area's LPI values vary from 0 to 37. A liquefaction hazard map is prepared for the area using the calculated LPI values from Vs data shows about 8% of the study area is very highly susceptible to liquefaction hazard, whereas 62% of the area falls under high hazard-prone area while about 28% and 2% area of the study have respectively low (0<LPI ≤5) and very low (LPI = 0) liquefaction potentiality. In addition, after analyzing the study area's fluctuating groundwater level (GWL) during the last 20 years, it has been observed that the GWL is likely to rise, thereby intensifying the potentiality of liquefaction hazards in the future. The outcome of this study will help engineers, urban planners, and policymakers to prepare a risk-sensitive land use plan and to develop a robust earthquake emergency response plan to reduce seismic risk.

Probabilistic Assessment of Standard Penetration Test Hammer Energy Efficiency and Rod Length Corrections

Despite the clearly stated procedures in current standards, and contrary to its name, nonstandard execution of the standard penetration test (SPT) has been common. The use of different equipment and procedures produces significantly different SPT blow counts. To minimize the effects of these differences, correction factors are applied. Two of these corrections factors, namely hammer energy efficiency ratio (CE) and rod length (CR) corrections, are the scope of this research study. With the intent of quantifying the effects of variabilities and reducing the uncertainties, SPT hammer efficiency measurements were compiled from available literature. Additionally, new hammer energy measurements were performed in the field, controlling the variables of the problem. The resulting database is used to probabilistically develop a set of new CE and CR recommendations. The recommended mean energy ratios for safety hammer and automatic hammers are estimated as 67%±11% and 78%±12%, respectively, which are higher than typically assumed values in engineering practice. The recommended rod length correction values at shallow depths, proven to be also a function of SPT blowcounts, N (SPT-N) values, are higher than typically used values. This suggests less pronounced rod length effects. Additionally, a modified procedure to assess the stress-wave energy at anvil and above the SPT sampler elevations is introduced.

Establishing competent ground conditions with the DPSH

Insufficient information is currently available to fully understand the mechanism of rod friction in DPSH (Dynamic Probe Super Heavy) probing. Consequently, a method is proposed to distinguish profiles in which friction results in excessive blow counts based on normalised profiles. While friction-impacted DPSH profiles are difficult to interpret, those unaffected by friction show better equivalence to SPT (Standard Penetration Test) profiles, especially if used to screen for competent (SPT blow counts &gt; 30) ground conditions.

A new approach to the correlation of SPT-CPT depending on the soil behavior type index

In this study, a model based on soil behavior type index (Ic) has been proposed for the conversion of field cone penetration test (CPT) data to the standard penetration test (SPT) blow counts (N). The field data used in the study were obtained from the fluvial soils formed by the Sakarya river in Adapazarı (Turkey). According to the proposed model, it is understood that there are exponential relationships between SPT-N and CPT data with varying coefficients (constant multipliers and exponents) for different Ic intervals. While the coefficients of the equations were kept constant in the previous formulations developed based on Ic, the current study revealed that the mentioned coefficients should be changed for different Ic intervals. The normalized cone resistance (qt/ Pa) or corrected SPT-N values (N60), found with the model created with the final coefficients, were evaluated. The results obtained by using the new model proposed in this paper were compared with other models generally accepted in the literature. It has been revealed that the results achieved by this new model are the closest ones to the measured values compared to the other methods. To verify the proposed model, CPT-SPT data pairs that were not used in the model generation were analyzed. Verification analyses confirmed that the developed method has given more realistic results than the other methods suggested in the literature. It was understood that the error rate in the model, in which conversion between CPT and SPT data can be made by considering the variability in the soil behavior type index, is lower than the others. As a result, the paper gives a new perspective by introducing a simple and newly updated form of estimating N60 values.

Liquefaction resistance evaluation of soils using artificial neural network for Dhaka City, Bangladesh

Soil liquefaction resistance evaluation is an important site investigation for seismically active areas. To minimize the loss of life and property, liquefaction hazard analysis is a prerequisite for seismic risk management. Liquefaction potential index (LPI) is widely used to determine the severity of liquefaction quantitatively and spatially. LPI is estimated from the factor of safety of liquefaction that is the ratio of cyclic resistance ratio (CRR) to cyclic stress ratio calculated applying simplified procedure. Artificial neural network (ANN) algorithm has been used in the present study to predict CRR directly from the normalized standard penetration test blow count (SPT-N) and near-surface shear wave velocity (Vs) data of Dhaka City. It is observed that ANN models have generated accurate CRR data. Three liquefaction hazard zones are identified in Dhaka City on the basis of the cumulative frequency (CF) distribution of the LPI of each geological unit. The liquefaction hazard maps have been prepared for the city using the liquefaction potential index (LPI) and its cumulative frequency (CF) distribution of each liquefaction hazard zone. The CF distribution of the SPT-N based LPI indicates that 15%, 53%, and 69% of areas, whereas the CF distribution of the Vs based LPI indicates that 11%, 48%, and 62% of areas of Zone 1, 2, and 3, respectively, show surface manifestation of liquefaction for an earthquake of moment magnitude, Mw 7.5 with a peak horizontal ground acceleration of 0.15 g.

Field Tests on Bearing Characteristics of Large-Diameter Combined Tip-and-Side Post Grouted Drilled Shafts

This paper presents a field study on the axial behavior of four large-diameter drilled shafts embedded in coarse sand. The grouting and loading test procedures were reported. The bearing capacity of shafts (TS1 and TS2) and grouted drilled shafts (TS3 and TS4) were herein determined by the bi-directional static test and top-down load test, respectively. The enhancement mechanism of bearing characteristics of the grouted shafts was discussed in detail. The test results indicate that the bearing characteristics and load transfer mechanisms of the test shafts were significantly affected by the quantity of pressurized cement slurry and the mechanical properties of the soil surrounding the shafts. Furthermore, the tip resistance of shaft can be mobilized more rapidly and fully after grouting, the side and tip resistance are mobilized in a more synchronized and coordinated manner due to the pre-mobilization of the grouted cement. Additionally, the standard penetration test (SPT) prediction model was introduced to calculate and predict the SPT blow counts of soil after grouting. The results show that the post grouting has a more obvious improvement on the strength of cohesionless soil.

Quality Assessment of Dry Soil Mixing Columns in Soft Soil Areas of Eastern China

To investigate the quality of dry soil mixing (DSM) columns in different soft soil areas of east China, a large number of laboratory test results and field test results of DSM columns were collected and analyzed statistically. Furthermore, a quality assessment method for DSM columns is proposed in this paper. The hardness description (HD), standard penetration test (SPT), unconfined compressive strength (UCS), and soil-cement column quality designation (SCQD) are used as assessment indexes. The statistical analysis showed that the test results of SPT, UCS, and SCQD were scattered, particularly in shallow ground. The mean values of the SPT blow count, UCS, and SCQD of the DSM columns decreased with depth: the greater the depth, the worse the quality of DSM columns. The quality assessment results showed that the proportion of the great quality columns was 64.84%, and the proportion of the unqualified columns was 1.4%. The proportion of DSM columns with great quality in the lagoon soft soil area was greater than in other areas. The proportion of unqualified columns in the lacustrine soft soil area was the largest. For all soft soil areas, the proportions of great quality, good quality, general quality, and unqualified soil decreased in that order. The quality assessment of 8627 DSM columns showed the proportions of great quality and unqualified were 64.84% and 1.4%, respectively. It was found that the greater the depth of the DSM column, the more unqualified DSM columns, and the more difficult it was to control the quality of DSM columns.

Liquefaction potential for the Kathmandu Valley, Nepal: a sensitivity study

An assessment of liquefaction potential for the Kathmandu Valley considering seasonal variability of the groundwater table has been conducted. To gain deeper understanding seven historical liquefaction records located adjacent to borehole datapoints (published in SAFER/GEO-591) were used to compare two methods for the estimation of liquefaction potential. Standard Penetration Test (SPT) blowcount data from 75 boreholes inform the new liquefaction potential maps. Various scenarios were modelled, i.e., seasonal variation of the groundwater table and peak ground acceleration. Ordinary kriging, implemented in ArcGIS, was used to prepare maps at urban scale. Liquefaction potential calculations using the methodology from (Sonmez, Environ Geol 44:862–871, 2003) provided a good match to the historical liquefaction records in the region. Seasonal variation of the groundwater table is shown to have a significant effect on the spatial distribution of calculated liquefaction potential across the valley. The less than anticipated liquefaction manifestations due to the Gorkha earthquake are possibly due to the seasonal water table level.

Correlation between field electrical resistivity and geotechnical SPT blow counts at tropical soils in Brazil

The joint application of geophysical investigations, non-invasive methods, and geotechnical investigations, invasive methods, in order to interpret the geological features in subsurface has been increasingly accepted, however, the correlation between the values collected by the geophysical methods and the direct investigative techniques have been developed in recent years. The obtained linear relationships are site specific and complementary studies are needed to establish their validation and limitations for each site. In this study, Electrical Resistivity Tomography (ERT) was used with Standard Penetration Test (SPT) for geotechnical investigation at three hillslope sites with different tropical soil properties in Bahia, Brazil. The results from thirteen boreholes were analyzed against data from 2D inverted sections. Linear fitting successfully correlates resistivity and NSPT for one borehole. Correlations of electrical resistivity and NSPT values were also performed using soils with similar compositions and physical characteristics, which showed good results. The coefficient of correlation (R) was 0.94. In addition, results the fitting slope coefficient seems to be dependent of soil genesis (lithology, texture and clay content variation) scription obtained in SPT surveys.

CORRELATION BETWEEN SPT AND PMT RESULTS FOR SANDY AND CLAYEY SOILS

Determination of soil deformation and strength properties is of great importance in geotechnical design. The disturbance that occurred during the sampling from the field affects the results obtained by the laboratory tests. Therefore, the lack of representation of the field conditions and in-situ soil features with laboratory tests leads the designers to carry out field tests. Standard penetration test (SPT) and the Menard pressuremeter test (PMT) are the most widely used geotechnical field tests in which the results are utilized to investigate soil properties and lateral deformation characteristics at a specified depth. In this study, a total of 102 data of sandy and clayey soils belonging to the geotechnical investigations carried out in Istanbul were compiled. The regression analysis between the corrected SPT blow count N60, pressuremeter modulus EPMT, limit pressure PL and EPMT/PL ratio is performed. Empirical equations were separately developed for sandy and clayey soils between the considered parameters. The developed equations showed that there are acceptable relationships between the parameters examined in the particular dataset. Moreover, a neural network (NN) based prediction model was developed to predict EPMT and PL using the available soil data. The highly accurate prediction performance of the proposed model demonstrated the availability of modern methods for the estimation of soil parameters.

A Simple and Sustainable Prediction Method of Liquefaction-Induced Settlement at Pohang Using an Artificial Neural Network

Conventionally, liquefaction-induced settlements have been predicted through numerical or analytical methods. In this study, a machine learning approach for predicting the liquefaction-induced settlement at Pohang was investigated. In particular, we examined the potential of an artificial neural network (ANN) algorithm to predict the earthquake-induced settlement at Pohang on the basis of standard penetration test (SPT) data. The performance of two ANN models for settlement prediction was studied and compared in terms of the R2 correlation. Model 1 (input parameters: unit weight, corrected SPT blow count, and cyclic stress ratio (CSR)) showed higher prediction accuracy than model 2 (input parameters: depth of the soil layer, corrected SPT blow count, and the CSR), and the difference in the R2 correlation between the models was about 0.12. Subsequently, an optimal ANN model was used to develop a simple predictive model equation, which was implemented using a matrix formulation. Finally, the liquefaction-induced settlement chart based on the predictive model equation was proposed, and the applicability of the chart was verified by comparing it with the interferometric synthetic aperture radar (InSAR) image.

Prediction of Pile Axial Bearing Capacity Using Artificial Neural Network and Random Forest

Axial bearing capacity of piles is the most important parameter in pile foundation design. In this paper, artificial neural network (ANN) and random forest (RF) algorithms were utilized to predict the ultimate axial bearing capacity of driven piles. An unprecedented database containing 2314 driven pile static load test reports were gathered, including the pile diameter, length of pile segments, natural ground elevation, pile top elevation, guide pile segment stop driving elevation, pile tip elevation, average standard penetration test (SPT) value along the embedded length of pile, and average SPT blow counts at the tip of pile as input variables, whereas the ultimate load on pile top was considered as output variable. The dataset was divided into the training (70%) and testing (30%) parts for the construction and validation phases, respectively. Various error criteria, namely mean absolute error (MAE), root mean squared error (RMSE), and the coefficient of determination (R2) were used to evaluate the performance of RF and ANN algorithms. In addition, the predicted results of pile load tests were compared with five empirical equations derived from the literature and with classical multi-variable regression. The results showed that RF outperformed ANN and other methods. Sensitivity analysis was conducted to reveal that the average SPT value and pile tip elevation were the most important factors in predicting the axial bearing capacity of piles.

Evaluation of Liquefaction Potential of Soil at a Power Plant Site in Chittagong, Bangladesh

This study presents an evaluation of liquefaction potential for combined cycle power plant site located in the Chittagong district, Bangladesh, using standard penetration test blow counts (SPT-N values). The peak ground acceleration (PGA) values at a bedrock level were estimated deterministically using both linear and point source models as well as different ground motion prediction equations (GMPEs). The surface level hazard was estimated using amplification factors for the soil conditions present and the response spectrum at the center of the plant site was plotted. The liquefaction potential for the site was arrived at by using the SPT-N values of 33 boreholes in the site and at every 3-meter interval from the ground level to a depth of 30 meters. The results from the LPI contours at successive depths indicate that in the majority of the borehole locations, the soil up to 15 meters depth had a significant hazard of liquefaction. These findings from the present study can prove to be crucial from the structural point of view, for any future construction activities in the area.

Effects of grain shape on the standard penetration test and particle packing

Coarse soils can contain flaky grains in addition to rounded or angular grains, along with a varying fines content. Depending on the regional geology, however, the mica grain content can be remarkable, reaching 30 % or higher. Therefore, it is reasonable to expect that mica grains would affect the soil behaviour. In this study, soils of a delta deposit that are known to involve mica grains were examined. The river sand was considered as the host material and the mica grain contents were determined by means of the flotation technique. A correlation between the mica content as found using the flotation technique and XRD count numbers obtained using an X-ray diffraction test method for each soil sample was established. The standard penetration test (SPT) blow counts from various boreholes were interpreted from the mica content’s influence point of view. The results showed that the mica grains would reduce the SPT resistance at certain fines-content, host-sand, mica-grain combinations. The reduction in the SPT resistance as a result of the presence of mica grains might reach eight units at depths close to the ground surface. This influence is expressed by means of a dimensionless parameter (MCef); however, it diminished with an increasing effective stress and fines content. The findings of the present study show that the influence of particle shape on the overall soil behaviour deserves further study.

Unified correlation between SPT–N and shear wave velocity for a wide range of soil types considering strain-dependent behavior

The shear wave velocity (Vs) of sediments plays a key role in seismic wave amplification and is required in site response analysis. Such information is usually lacking during field exploration, but standard penetration test blow count (N) is typically available. Therefore, several studies have established empirical correlations between N and Vs for engineering use. However, these empirical correlations significantly vary in terms of model form and are only applicable to specific soil types, such as sand or clay. A unified empirical correlation for a wide range of soil types, which contains several soil properties (e.g., liquid limit and plasticity index (PI)) in addition to the Vs and N of strata, is developed in this study using the Engineering Geological Database for the Taiwan Strong Motion Instrumentation Program. Influences of confining stress, fines content (FC), PI, and soil types on small-strain properties (i.e., Vs) and large-strain measurements (i.e., N) are first evaluated through the developed correlations with these parameters. The unified correlation between Vs and N that is dependent on confining stress, FC, and PI is then proposed through the conditional prediction approach. The model successfully applies to different regions in Taiwan that includes various types of soil deposits and, thus, is potentially used for the other regions.

Evaluation of strength distribution at cut slope of decomposed granite with the use of sounding method and geophysical exploration method

Natural slopes and cut slopes frequently collapse due to heavy rain and earthquakes, causing disasters. Countermeasures must be applied to mitigate such disasters. There is an especially high risk of a collapse at the surface layer of slopes, and thus, evaluating the strength distribution in the surface layer in detail is important to mitigating and preventing disasters. As simple investigation methods for these purposes, there are sounding methods and geophysical exploration methods. In the present study, dynamic cone penetration (DCP) is selected as the sounding method, and the surface wave method (SWM) is selected as the geophysical exploration method. The strength parameters are generally assumed based on standard penetration tests (SPTs), but DCP tests are simpler than SPTs and can be applied to narrow spaces. On the other hand, the SWM can be used to investigate wide spaces in a short time. We developed a synthesized approach to the geophysical exploration method and the sounding method. The two results obtained from the SWM and the DCP tests—namely the shear velocity and the DCP blow count, respectively—need to be converted to the standard penetration test blow count in order to be synthesized. An indicator simulation, one of the geostatistical methods, is employed to simulate the random field of N values by synthesizing the two results. The proposed procedure is applied to evaluate the strength of the weak surface layer of a cut slope composed of weathered granite, and its applicability for practical use is verified.

Estimating shear wave velocity of soil using standard penetration test (SPT) blow counts in Mashhad city

This study investigates the correlation between shear wave velocity ( $$V_{\mathrm{S}}$$ ) and standard penetration test blow counts (SPT-N value) in all soil types, gravelly soil, sandy soil and clayey soil for Mashhad city in the north eastern region of Iran. The $$V_{\mathrm{S}}$$ data used were measured through downhole method in 84 construction projects (in 88 boreholes). From among collected data, 424 pairs of $$V_{\mathrm{S}}$$ -SPT recorded in one depth were used for regression analysis. The obtained results showed that the N-value had a critical role in estimating $$V_{\mathrm{S}}$$ and soil type was less effective in this regard. These findings are in line with the findings of the previous studies. Regression equations obtained in this study were compared with correlations from previous studies. There was a relative similarity between the previously published and the new regression equations for Iranian soils. Although almost all correlations follow a similar trend, there are significant differences between new equations and correlations reported for other countries. The regression coefficients of the new equations show the acceptable capability of the suggested correlations in estimating $$V_{\mathrm{S}}$$ through SPT-N value. Therefore, these equations can be used to estimate $$V_{\mathrm{S}}$$ for the soils of the current study area and for other similar areas. Moreover, $$V_{\mathrm{S30}}$$ was used for site classification of the study area as per National Earthquake Hazard Reduction Program (NEHRP) guidelines and it was shown that a major portion of the city comes under site class C and other locations are categorised as site class D.