Role of the coefficient of uniformity on the California bearing ratio, penetration resistance, and small strain stiffness of coarse arctic soils

Lee

et al. 2021

Sensors

Self Cite

Dynamic resistance, which can be used to express strength in the unit of stress and improve the reliability of the dynamic cone penetration test (DCPT), has been estimated by numerous methods. This study aims to compare different dynamic resistance estimation methods by using an instrumented dynamic cone penetrometer (IDCP). DCPTs are conducted using a standard dynamic cone penetrometer (DCP) and IDCP in the laboratory and field. Dynamic responses are obtained from the strain gauges and an accelerometer installed at the cone tip of the IDCP. The test results show that dynamic resistance is more efficient in distinguishing profiles than the dynamic cone penetration index. Among the methods to estimate the dynamic resistance at the cone tip, the force-velocity integration method and force integration method are more related to the conventional dynamic resistance considering the potential energy of the hammer than the force squared integration method. Additionally, the dynamic resistance estimated for a longer time period is more reliable, particularly for small driving rod lengths. Regarding the limitation of the dynamic response from an accelerometer in a previous study, the force-based dynamic resistance estimated for a longer time period can be used as the most reliable approach for further soil strength characterization.

Section: Dynamic Resistance At Cone Tipmentioning

confidence: 99%

where c and E denote the wave velocity through the steel rod and Young’s modulus of the rod, respectively.…”

Section: Experimental Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Comparative Study on Estimation Methods of Dynamic Resistance Using Dynamic Cone Penetrometer

Lee

et al. 2021

Sensors

Self Cite

“…During cold seasons, when heat is lost from the soil surface due to air temperature dropping, the soil water content begins to freeze [13], and after increasing the temperature, the upper layer of soil begins to thaw. The freezing-thawing cycle affects soil physical and chemical properties [20]. The snow and/or glacier melt water runs off the frozen soil and/or thawed soil surface in high erosion regions, which could affect surface or subsurface hydrology [24].…”

Section: Introductionmentioning

confidence: 99%

Effect of a Freezing-thawing Cycle on Overall and Inter-variability of Runoff and Soil Loss Components for a Loess Soil

Gharemahmudli

Sadeghi

Najafinejad

et al. 2021

Preprint

Background: Because control of runoff generation as well as soil loss is influenced by freezing-thawing, proper knowledge and insight into the freezing-thawing process in combination with other hydrological processes is essential for executives and planners. However, such dynamic phenomenon and corresponding consequences have not been studied adequately. The present study was therefore planned to comparatively analyze the effects of a freezing-thawing cycle on hydrologic behaviors of loess soil from northeast of Iran. Towards that, the small-size (0.5×0.50×0.30 m) erosion plots were subjected to a freezing-thawing cycle in accordance with governing conditions on the region of the origin soil. The plots were subjected to a freezing-thawing treatment through inducing cold air until temperature declined to below -20 °C and lasted for three days using a large cooling compartment system, and then were kept in the laboratory with ambient temperature of above 10 °C for two days. The treated plots as well as untreated (control) plots were then exposed to a simulated rainfall with an intensity of 72 mm h-1 and 0.5 h duration while they were placed on a slope of 20%. Results: The results indicated that the hybrid processes of freezing-thawing, and splash and interrill erosions significantly affected runoff generation and soil loss at small plots. So that the time to runoff reduced by 1.65 times in the freezing-thawing treatment compared to that reported for the control treatment. The runoff volume and soil loss also increased at tune of 1.38 and 2.90 times in treated plots in comparison with those measured for the untreated plots. Laboratorial results indicated significant differences (p< 0.006) between runoff and soil loss behaviors in plots subjected to a freezing-thawing cycle and those of control condition. Conclusion: The performance of ice lenses and freezing fronts and creating near-saturation moisture after completing the cycle were evaluated as the most important factors affecting the different soil behaviors under frozen-thawed cycle.

“…The standard DCP test provides the blow count per the desired depth, and in this test, a series of correlations between the DCP index and other engineering parameters of sandy soils have been observed [ 11 ]. For a more accurate characterization, an instrumented DCP was developed and used to evaluate the soil strength at a shallow depth [ 12 , 13 , 14 , 15 , 16 , 17 ]. However, the application of standard and instrumented DCPs is limited to fine-grained materials owing to their smaller cone diameter compared with coarse-grained materials.…”

Section: Introductionmentioning

confidence: 99%

Instrumented Cone Penetrometer for Dense Layer Characterization

Lee

Byun

2020

Sensors

Self Cite

Subsurface characterization is essential for a successful infrastructure design and construction. This paper demonstrates the use of an instrumented cone penetrometer (ICP) for a dense layer characterization at two sites. The ICP consists of a cone tip and rods equipped with an accelerometer and four strain gauges, which allow dynamic driving, in addition to quasi-static pushing of the cone. The force and velocity of the cone are measured using the ICP instrumentation and compared with the N value, dynamic cone penetration index, and static cone resistance. A strong correlation has been observed between the total cone resistance estimated from the ICP and the dynamic cone penetration index and static cone resistance. After the correction of the dynamic cone resistance effect, the static component of the total cone resistance can be used as an alternative to a static cone resistance. This novel approach of soil resistance estimation using the ICP may be useful for dense layer characterization.