• 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 Geosynthetics Society
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• v.18 no.3
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• pp.1-9
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• 2019

In this study, the effect of ground improvement was to be verified by granular compaction pile from the ground reclaimed with Fly Ash landfill site. The depth and strength parameters of the Fly ash layer was determined using the ground investigation and cone penetration test. And the STONE C program was used to predict the strength parameter, bearing capacity and settlement of the improved ground. As a result of the plate bearing test, the bearing capacity of improvement ground was higher than the design load and the settlement was smaller than the reference value. After the construction, the improvement effect by the cone penetration test was confirmed. The cone penetration resistance value($q_c$) increased by 250% to 500% and the effect was excellent.

• 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.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.6
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• pp.2359-2368
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• 2013

Cone penetration tests (CPTs) have been increasingly used for site characterizations. However, the site investigations using CPTs are often limited due to soil conditions depending on the cone size and capacity of the CPT system. The small sectional area of a miniature cone improves the applicability of the CPT system due to the increased capacity of the CPT system. A continuous intrusion system using a coiled rod allows fast and cost effective site investigation. In this study, the performance of the continuous intrusion miniature cone penetration test (CIMCPT) system has been evaluated by comparison tests with the standard CPT system at several construction sites in Korea. The results show that the CIMCPT system has a same performance with the CPT system and has advantages on the mobility and applicability. According to field verification tests for scale effect evaluation, the cone tip resistance evaluated by CIMCPT overestimates by 10% comparing to standard CPTs. A crawler mounted with the CIMCPT system has been implemented to improve accessibility to soft ground, and has shown improvement over the truck type CIMCPT system. Therefore, the improved CIMCPT system can be utilized as a cost effective and highly reliable soil investigation methodology to detect the depth of soft ground and to evaluate soil classification.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.13 no.11
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• pp.5572-5577
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• 2012

Results of in-situ test, laboratory test and strength prediction method for the soft soil underlain by failed road embankment were compared each other. Comparing cone penetration test results with the field vane test results it can be seen that cone factor is 12. Undrained shear strengths determined from the cone factor which was predicted by prediction equation were smaller than those obtained from field vane tests. Among the prediction methods Jamiolkowsky's method gave close strengths to the measured undrained shear strengths by field vane tests and strength ratio were 0.88~1.23.

• Geomechanics and Engineering
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• v.14 no.1
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• pp.99-105
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• 2018

Soils are generally classified as fine-grained or coarse-grained depending on the percentage content of the primary constituents. In reality, soils are actually made up of mixed and composite constituents. Soils primarily classified as fine-grained, still consists of a range of coarse particles as secondary constituents in between 0% to 50%. A laboratory scale model test was conducted to investigate the influence of coarse particles on the physical (e.g., density, water content, and void ratio) and mechanical (e.g., quick undrained shear strength) properties of primarily classified fine-grained cohesive soils. Pure kaolinite clay and sand-mixed kaolinite soil (e.g., sand content: 10%, 20%, and 30%) having various water contents (60%, 65%, and 70%) were preconsolidated at different stress levels (0, 13, 17.5, 22 kPa). The quick undrained shear strength properties were determined using the conventional Static Cone Penetration Test (SCPT) method and the new Fall Cone Test (FCT) method. The corresponding void ratios and densities with respect to the quick undrained shear strength were also observed. Correlations of the physical properties and quick undrained shear strengths derived from the SCPT and FCT were also established. Comparison of results showed a significant relationship between the two methods. From the results of FCT and SCPT, there is a decreasing trend of quick undrained shear strength, strength increase ratio ($S_u/P_o$), and void ratio (e) as the sand content is increased. The quick undrained shear strength generally decreases with increased water content. For the same water content, increasing the sand content resulted to a decrease in quick undrained shear strength due to reduced adhesion, and also, resulted to an increase in density. Similarly, it is observed that the change in density is distinctively noticeable at sand content greater than 20%. However, for sand content lower than 10%, there is minimal change in density with respect to water content. In general, the results showed a decrease in quick undrained shear strength for soils with higher amounts of sand content. Therefore, as the soil adhesion is reduced, the cone penetration resistances of the FCT and SCPT reflects internal friction and density of sand in the total shear strength.

• Journal of the Korean Geotechnical Society
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• v.36 no.10
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• pp.57-71
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• 2020

Liquefaction-induced sand boils were observed during the Pohang earthquake (Moment magnitude, 5.4) on November 15, 2017, specifically in the region of agricultural fields and park areas near the epicenter. This was recorded as the first observed liquefaction phenomenon in Korea. This paper analyzes liquefaction potentials at the key sites at Pohang area. The simplified methods and current design standard were used to evaluate the occurrence of liquefaction. The seismic demand was estimated based on the NGA-WEST2 ground motion prediction equations (GMPEs). The liquefaction resistance of the ground was determined using the in-situ tests: standard penetration test (SPT) and cone penetration test (CPT). The liquefaction potentials were quantified by liquefaction potential index (LPI), which were compared with those from the previous studies.

• Journal of the Korean Geotechnical Society
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• v.39 no.7
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• pp.49-56
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• 2023

Gravel is commonly employed to enhance the bearing capacity of foundations and provide stable support for structures. However, effectively assessing the ground characteristics in the presence of gravel poses significant challenges. This study aims to compare the resolution of ground containing gravel using electrical resistivity, elastic wave surveys, and ground penetration radar (GPR). Nondestructive methods are applied at construction sites where soil improvement is carried out using gravel. The experiments focus on shallow depths, and the obtained results cover depths up to 2 m. Both the electrical resistivity and elastic wave techniques exhibit similar behavior in their findings, indicating comparable outcomes. However, GPR has limitations in observing the characteristics of ground with gravel. Dynamic cone-penetration tests were conducted to validate these findings. The electrical resistivity and elastic wave profiles exhibited similar behaviors in localized areas, further supporting their compatibility and reliability.

• Journal of the Korean Geotechnical Society
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• v.23 no.12
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• pp.13-23
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• 2007

Weathered soils appear from the rock and its weathering result. In accordance with the degree of weathering the roch may become soft rock, weathered rock and residual soil. In general, classification method for determining the degree of weathering are performed by chemical method and N-value. But these method have some problems. So, this research is to suggest an appropriate physical method to determine the degree of weathering of weathered soils. A new classification method for determining the degree of weathering is suggested, based upon the results from fall cone test. According to the proposed physical method using fall cone apparatus, the measured values of the samples from the same area show distinctive difference of weathering. For the checking, we selected two areas. As a result, the relationship between CWI and water content according to penetration is expressed as an equation in Ilsan and Incheon area. And it proved to be a good method to determine the degree of weathering.

• Journal of the Korean Geotechnical Society
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• v.24 no.11
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• pp.133-141
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• 2008

In this study, a new method for estimating the undrained shear strength $s_u$ of saturated clays using piezocone penetration test (CPTu) result is proposed. This is to develop more effective CPTu-based $s_u$ estimation method at lower cost with less uncertainty. For this purpose, a marine clay deposit is selected and tested through extensive experimental testing program including both in-situ and fundamental laboratory tests. The proposed method is based on a correlation between the undrained shear strength $s_u$ and the cone resistance $q_t$, without introduction of the total overburden stress into the $s_u-q_t$ correlation. As a result, no additional testing procedure for collecting undisturbed soils samples is required, which can reduce overall testing cost. To verify the proposed method, 4 test sites, which consist of a variety of soil conditions, are selected and used for comparison between measured and predicted undrained shear strength. From comparison, it is seen that predicted values of $s_u$ using the proposed method match well those from measured results.