• Journal of the Korea institute for structural maintenance and inspection
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• v.7 no.3
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• pp.231-239
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• 2003

Many foundation jobs have been designed and constructed in Korea with the sole information obtained from the SPT. The use of the CPT to estimate equivalent SPT values is becoming a common application for foundation design. The relationship between the CPT and the SPT has been determined in a number of studies over the past three decades. However a few papers have been published on the relationship between the CPT and the SPT in residual soil. Due to the large variation in published correlations between qt and N in residual soil, local correlations should be developed wherever possible. CPT tests have been carried out in the residual soil classified by SM in accordance with USCM and compared with SPT. Value of qt/N = 0.3 have been suggested for residual soil in Korea.

• Smart Structures and Systems
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• v.30 no.2
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• pp.159-172
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• 2022

To improve the accuracy of the standard penetration test (SPT) results, smart measurement system, which considers the energy transfer ratio into the sampler (ETR_Sampler), is required. The objective of this study is to evaluate the effects of joints and rod length on the transferred energy into the sampler. The energy transfer ratios into the rod head (ETR_Head) and ETR_Sampler, and the energy ratio from the head to the sampler (ER_HS) were obtained using energy modules, which were installed at the rod head and above the SPT sampler. Linear regression analyses are conducted to correlate the ER_HS with the number of joints, rod length, and SPT N-values. In addition, the dynamic resistances are calculated using both transferred energies into the rod head and into the sampler, and are compared with the corrected cone tip resistance measured from the cone penetration test (CPT). While the ETR_Head are generally constant, but the ETR_Sampler and ER_HS gradually decrease along the depth or the number of joints, except at certain depths with high SPT N-values. Thus, the ER_HS can be estimated using the number of joints, rod length, and SPT N-values. The dynamic resistance evaluated by E_Sampler produces a better correlation with the corrected cone tip resistance than that by E_Head. This study suggests that transferred energy into the SPT sampler may be effectively used for more accurate subsurface characterization.

• Journal of the Korean Geosynthetics Society
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• v.11 no.4
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• pp.55-62
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• 2012

In this application study, field pilot tests were performed to evaluate the validity of a proposed formula between the exerted electrical energy and SPT N-value based on the result of the basic study. Measurement sensors and recording system were developed to obtain exerted motor current and drilling depth in a field. By using the correlation formula proposed in the basic study, the measured motor current and boring speed were applied to predict SPT N-value and the predicted N-values were compared to SPT N-value of site exploration. From the comparisons it is verified that the exerted electrical energy to bore ground might be used to predict SPT N-value and pile tip location.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.385-386
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• 2023

In this application study, field pilot tests were performed to evaluate the validity of a proposed formula between the exerted electrical energy and SPT N-value based on the result of the basic study. Measurement sensors and recording system were developed to obtain exerted motor current and drilling depth in a field. By using the correlation formula proposed in the basic study, the measured motor current and boring speed were applied to predict SPT N-value and the predicted N-values were compared to SPT N-value of site exploration. From the comparisons it is verified that the exerted electrical energy to bore ground might be used to predict SPT N-value and pile tip location.

• Journal of the Korean GEO-environmental Society
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• v.21 no.6
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• pp.5-11
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• 2020

Recently, due to the liquefaction caused by earthquakes in Pohang and surrounding areas, the importance of researches on the liquefaction assessment has increased. The possibility of liquefaction can be assessed using the geotechnical information. The cyclic resistance ratio (CRR) value used in the assessment of liquefaction can be determined by using the SPT-N values or shear wave velocity, V_s value. A study was conducted to compare the accuracy of the liquefaction assessment using these two types of geotechnical information, and concluded that the results using SPT-N values are more accurate than those using V_s values. The previous study speculated that the used V_s value was measured at a depth of 12 m uniformly without considering the critical depth of liquefaction. Therefore, 10 empirical equations that convert SPT-N values measured at critical depth of liquefaction into V_s values to confirm the validity of geotechnical information measured at 12 m points uniformly are used to assess the liquefaction possibility and the results were compared with the actual liquefaction results to confirm the accuracy. As a result, 7 out of 10 cases considering critical depth for liquefaction show higher accuracy than those not considered.

• Journal of the Korean Geotechnical Society
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• v.29 no.12
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• pp.105-111
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• 2013

The standard penetration test (SPT) has been widely used because of its usability, economy, and many correlations with soil properties among other factors. In SPT, hammer energy is an important factor to evaluate and calibrate N values. To measure hammer energy, an instrumented SPT rod was developed considering that stress waves transferring on rods during SPT driving are the same as stress waves transferring on piles due to pile driving. Using this idea, an instrumented SPT rod with a pile driving analyzer was applied as a pile capacity prediction tool in this study. In order to evaluate this method, SPT and dynamic cone tests with the instrumented SPT rod were conducted and also 2 pile load tests were performed on pre-bored steel pipe piles at the same test site. End bearings were predicted by CAPWAP analysis on force and velocity waves from dynamic cone penetration tests and SPT. Comparing these predicted end bearings with static pile load tests, a new prediction method of the end bearing capacity using the instrumented SPT rod was proposed.

• Journal of the Korean Geotechnical Society
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• v.38 no.8
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• pp.53-66
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• 2022

The national ground survey database (GeoInfo) distributes numerous ground survey data nationwide. Many standard penetration test results exist in this database; however, the number of shear wave velocity (V_S) data is small. Hence, to use abundant standard penetration test-N values to predict V_S, this study proposed a new empirical N-V_S relationship model using GeoInfo data. The proposed N-V_S model is a single equation regardless of geological layer types; the layer type only specifies the upper limit of V_S. To validate the proposed model, residual analysis was performed using a test dataset that was not used for the model development. Therefore, this study's proposed model performed better than N-V_S models from previous studies. Since the N-V_S model in this study was developed using sufficient data from GeoInfo, we expect that it is the most applicable to GeoInfo dataset for V_S prediction.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.1168-1176
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• 2010

Currently drilling investigation and the SPT in parallel not only organization and peculation sincerity quality historian of test to be old the data was abundant with the site ground investigation test which is representative and the research of empirical formula in compliance with many scholar was accomplished and was come. The data which is like this wide is used with geotechnical engineering data of plan and space-time of the field which is various. SPT with tentative voluntary skillful degree record method of variety and technical expert of equipment, according to site conditional is consistent the quality of ground condition but cannot be made to show there is a tendency and specially the point whose is difficult actually accurately to follow the interval which decides in quality as a matter of tentative standard of drill and the test in parallel and a tentative method exists. From the research which sees consequently also the skill of variety and technical expert of equipment of SPT, strong point of the SPT automation logger will be able to complement the problem point of quality etc. of site condition under comparison analyzing should have been boiled about SPT of existing and tentative methods and N-value.

• Geomechanics and Engineering
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• v.28 no.6
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• pp.625-636
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• 2022

The standard penetration test (SPT) obtaining the N value of the number of blows has been widely used in various subsurface conditions, including in weathered soil and rock on fresh bedrock, in geotechnical studies pertaining to the design of foundations and earth structures. This study examined the applicability of SPTs terminated conventionally after 50 blows for a penetration of less than 30 cm, particularly in weathered strata, at four sites in Korea. The N values obtained during practical SPTs are typically extrapolated linearly at 30 cm penetration, despite the possibility of a nonlinear relationship between blow counts and penetration. Such nonlinearity in weathered strata has been verified by performing special SPTs ensuring 30 cm penetration. To quantify the nonlinearity in dense strata, we conducted statistical regression analyses comparing the differences (DN) between the N values measured by the special SPTs and those extrapolated using the practical approach with the differences (DP) between the 30 cm penetration and the penetration during 50 blows. Bi-linear relationship models between DN and DP were subsequently proposed for determining the N values at 30 cm penetration in weathered strata. The N values reflecting nonlinearity could be determined from the linearly extrapolated N values by adding a modeled DN value.

• Geotechnical Engineering
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• v.8 no.1
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• pp.59-66
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• 1992

The SPT If value has been known to be influenced by various factors, among which the actually delivered energy level of the falling ram has the most significant effect. If N values of different energy levels are to be applied in the general analysis which is based on N values of standard energy levee the safety of the foundation might be in danger or the design might be overestimated. In this study the actual falling velocity of the ram has been measured so that the energy level could be estimated. The results Indicated that the energy level should be considered in the analysis or the design in this country, since the measured values are different from the internationally accepted scandard value, N60