• Title/Summary/Keyword: soil penetration

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표준관입시험 수행 과정에서의 문제점과 개선방향

  • 백세환
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.10a
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    • pp.275-280
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    • 2001
  • Although important developments have taken place since ESOPT 1974 both with respect to the test method as well as the interpretation of the results, many uncertainties still remain in the Standard Penetration Test(SPT). The main pitfall of SPT is that it has not been standardized differing from its terminology and further, the possibility of standardization is very low in practice. Therefore, lack of knowledge on the equipment and method of SPT tends to cause some errors in interpretation of the results. It Is especially important to understand this tendency in domestic design, because most foundations are designed based on SPT results only. Many researchers have made an effort to minimize the uncertainties of SPf in Korea, it is not cleary defined what the most effective method of execution and interpretation of SPT Some uncertainties which many geotechnical engineers encounter in practice are introduced to discuss about improvement of test procedure and interpretation.

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The Evaluation of the Allowable Bearing Capacity of Foundations using N-Value (N-Value를 이용한 기초의 지지력 산정)

  • 이강운;박택규;정해운
    • Proceedings of the Korean Geotechical Society Conference
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    • 2001.10a
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    • pp.281-292
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    • 2001
  • The evaluation of the allowable bearing capacity is the most important step in the design of a foundation. An accurate evaluation of the effect of all factors such as the physical properties of the soil located beneath the area, the size of the area, the depth of foundation, and the position of the water table is impracticable Therefore, the designer is compelled to estimate the allowable bearing capacity on the basis of simple semiempirical rules under cohesionless soils. This paper deals with semiemperical rules for determining allowable bearing capacity based on observed relations between the results of standard penetration test. Additional comparisions between the results of the theoretical methods and the emperical rules are performed to suggest more conservative design for the engineer.

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Evaluation of the Natural Vibration Modes and Structural Strength of WTIV Legs based on Seabed Penetration Depth (해상풍력발전기 설치 선박 레그의 해저면 관입 깊이에 따른 고유 진동 모드와 구조 강도 평가)

  • Myung-Su Yi;Kwang-Cheol Seo;Joo-Shin Park
    • Journal of the Korean Society of Marine Environment & Safety
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    • v.30 no.1
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    • pp.127-134
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    • 2024
  • With the growth of offshore wind power generation market, the corresponding installation vessel market is also growing. It is anticipated that approximately 100 installation vessels will be required in the of shore wind power generation market by 2030. With a price range of 300 to 400 billion Korean won per vessel, this represents a high-value market compared to merchant vessels. Particularly, the demand for large installation vessels with a capacity of 11 MW or more is increasing. The rapid growth of the offshore wind power generation market in the Asia-Pacific region, centered around China, has led to several discussions on orders for operational installation vessels in this region. The seabed geology in the Asia-Pacific region is dominated by clay layers with low bearing capacity. Owing to these characteristics, during vessel operations, significant spudcan and leg penetration depths occur as the installation vessel rises and descends above the water surface. In this study, using penetration variables ranging from 3 to 21 m, the unique vibration period, structural safety of the legs, and conductivity safety index were assessed based on penetration depths. As the penetration depth increases, the natural vibration period and the moment length of the leg become shorter, increasing the margin of structural strength. It is safe against overturning moment at all angles of incidence, and the maximum value occurs at 270 degrees. The conditions reviewed through this study can be used as crucial data to determine the operation of the legs according to the penetration depth when developing operating procedures for WTIV in soft soil. In conclusion, accurately determining the safety of the leg structure according to the penetration depth is directly related to the safety of the WTIV.

Changes in the Soil Physical Properties of Vineyard Converted from Paddy Field (논에서 전환한 포도원의 토양물리적 특성변화)

  • Yun, Eul-Soo;Jung, Ki-Youl;Park, Ki-Do;Ko, Jee-Yeon;Lee, Jae-Saeng;Park, Sung-Tae
    • Korean Journal of Soil Science and Fertilizer
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    • v.42 no.3
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    • pp.145-151
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    • 2009
  • This study was conducted to develop rational soil management and enhance the productivity of lands converted from paddy soils. Specifically, the changes in the soil physical properties brought about by the change in land usage from paddy soil were evaluated. This was carried out from 1999 to 2001 at 50 site in large-scale converted paddy fields of Kimcheon, Youngcheon, Gyeongsan and Milyang in the Youngnam region, categorized according to soil texture and drainage class. The ridge height of converted paddy soils was higher in coarse-textured and poorly-drained soils than in fine-textured and well-drained soils. The gray color of the surface soil was of lesser degree in converted soils than paddy soils and more notable in welldrained soils. The porosity ratio and the formation of aggregate structure were higher, and the appearance of soil mottling was deeper in converted paddy fields than in paddy soils. The glaying layer "g" of surface soil degraded with time. The porosity and amount of water stable aggregate was found to increase with time after conversion. The penetration resistance of the converted paddy soil was lower and deeper with time after conversion. The soil aeration of the converted paddy soil was lower in sandy loam than in loamy soil. Furthermore, soil aeration was influenced by ridge height and drainage class in poorly-drained soils.

Effect of Soil Compaction Levels and Textures on Soybean (Glycine max L.) Root Elongation and Yield (토양 경반층 강도가 콩 뿌리신장 및 생육에 미치는 영향)

  • Jung, Ki-Yuol;Yun, Eul-Yoo;Park, Chang-Young;Hwang, Jae-Bok;Choi, Young-Dae;Jeon, Seung-Ho;Lee, Hwang-A
    • Korean Journal of Soil Science and Fertilizer
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    • v.45 no.3
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    • pp.332-338
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    • 2012
  • Soil compaction is one of the major problems facing modern agriculture. Overuse of machinery, intensive cropping, short crop rotations, intensive grazing and inappropriate soil management leads to compaction. This study was carried out evaluate of the effects soil texture and different compaction levels within the soil profile on the soybean root growth and productivity. The soybean plants were grown in $21cm{\o}{\times}30cm$ cylinder pots using three different soil textures (clay, fine loamy and coarse loamy) compacted at different compaction levels (1.25, 1.50, 1.75, and 2.00 MPa). Results revealed that soybean development is more sensitive on penetration resistance, irrespective of soil type. Soybean yield and root weight density significantly decreases with increasing levels of soil compaction in both clayey and fine loamy soils, but not in coarse loamy soil. The highest root weight density was recorded in coarse loamy soils, followed by fine loamy and clay soils, in descending order. The root growth by soil compaction levels started to decline from 1.16, 1.28 and 1.60 MPa for clay, fine loamy and coarse loamy soils. Soybean production in the field experiment decreased about 30% at compacted sub-soils compared to undisturbed soils.

Growth and yield responses of rice varieties to various soil water deficit conditions under different soil types

  • Kikuta, Mayumi;Samejima, Hiroaki;Magoti, Rahab;Kimani, John M.;Yamauchi, Akira;Makihara, Daigo
    • Proceedings of the Korean Society of Crop Science Conference
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    • 2017.06a
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    • pp.322-322
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    • 2017
  • To avoid drought stress under rainfed upland conditions, it is important for rice to efficiently utilize water at shallow soil layers supplied by rainfall, and access to water retained in deer soil layers. The root developmental characteristics of rice, which play important role in the adaptability to drought conditions, vary depending on the variety. Moreover, water availability for plant differs depending on the soil types that have different physical properties such as water holding capacity, permeability, capillary force, penetration resistance, etc. In this study, we evaluated growth and yield responses of rice varieties to various soil water deficit conditions under three different soil types. The experiment was conducted in a plastic greenhouse at the Kenya Agricultural and Livestock Research Organization-Mwea from October 2016 to January 2017. Two upland varieties (NERICA 1 and 4) and one lowland variety (Komboka) were grown in handmade PVC pots (15.2 cm diameter and 85.0 cm height) filled with three different types of soil collected from major rice-growing areas of the country, namely black cotton (BC), red clay (RC), and sandy clay (SC). Three watering methods, 1) supplying water only from the soil surface (W1), 2) supplying water only from the bottom of the pots (W2), and 3) supplying water both from the soil surface and the bottom of pots (W3), were imposed from 40 days after sowing to maturity. Soil water content (SWC) at 20, 40, and 60 cm depths was measured regularly. At the harvesting stage, aboveground and root samples were collected to determine total dry weight (TDW), grain yield, and root length at 0-20, 20-40, 40-60, and 60-80 cm soil layers. Irrespective of the watering methods, the greatest root development was obtained in RC, while that in BC was less than other two soils. In BC, the degree of yield reduction under W1 was less than that in RC and SC, which could be attributed to the higher water holding capacity of BC. In RC, the growth and yield reduction observed in all varieties under W1 was attributed to the severe drought stress. On the other hand, under W2, SWC at the shallow soil depth in RC was maintained because of its higher capillary force compared with BC and SC. As the result, growths and yields in RC were not suppressed under W2. In SC, deep root development was not promoted by W2 irrespective of the varieties, which resulted in significant yield losses. Under W1, the rice growth and yield in SC was decreased although shallow root development was enhanced, and the stomatal conductance was maintained higher than RC. It was suspected that W1 caused nutrients leaching in SC because of its higher permeability. Under rainfed conditions, growth and yield of rice can be strongly affected by soil types because dynamics of soil water conditions change according to soil physical properties.

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Comparison of Tn-situ Characteristics of Soft Deposits Using Piezocone and Dilatometer (피에조 콘과 딜라토메터 시험을 이용한 연약지반의 현장특성 비교)

  • 김영상;이승래;김동수
    • Geotechnical Engineering
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    • v.14 no.6
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    • pp.45-56
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    • 1998
  • In order to select a proper ground improvement technology and to assess the quality and rate of improvement in the soft deposits. it is essential to characterize in-situ properties of the soft marine clay layer that may have many thin silt or sand seams. In this paper, both piezocone and flat dilatometer tests were performed to characterize in situ properties of a marine clay. Both tests provided quite similar site classifications, and in both tests the penetration pore water pressure was the better indicator for the classification of marine clay layer, especially in which sand or silt seams are frequently interbedded. Undrained strengths determined by both the cone tip resistance and the excess pore water pressure measured from piezocone were very similar in clayey soil layers. And the untrained strength determined by dilatometer had an approximately average value of undiained strengths obtained from piezocone. In addition, the theoretical time factor that can consider pore pressure dissipation effect during cone penetration may provide a reliable estimation of the coefficient of consolidation, especially for a coastal site which includes many silt or sand fractions or seams.

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Analysis of Dynamically Penetrating Anchor based on Coupled Eulerian-Lagrangian (CEL) Method (Coupled Eulerian-Lagrangian (CEL) 방법을 이용한 Dynamically Penetrating Anchor의 동적 거동 분석)

  • Kim, Youngho;Jeong, Sang-Seom
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.34 no.3
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    • pp.895-906
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    • 2014
  • A fundamental study of the dynamically penetrating anchor (DPA - colloquially known as torpedo anchor) embedded into deep seabed was conducted using measurement data and numerical approaches. Numerical simulation of such a structure penetration was often suffered by severe mesh distortion arising from very large soil deformation, complex contact condition and nonlinear soil behavior. In recent years, a Coupled Eulerian-Lagrangian method (CEL) has been used to solve geomechanical boundary value problems involving large deformations. In this study, 3D finite element analyses using the CEL formulation are carried out to simulate the construction process of dynamic anchors. Through comparisons with results of field measurements, the CEL method in the present study is in good agreement with the general trend observed by in-situ measurements and thus, predicts a realistic large deformation movement for the dynamic anchors by free-fall dropping, which the conventional FE method cannot. Additionally, the appropriate parametric studies needed for verifying the characteristic of dynamic anchor are also discussed.

The Evaluation of the Field Applicability of the Soil Improving Method Using the Environment-friendly Organic Acid Material (친환경 유기산 재료를 활용한 지반개량 공법의 현장 적용성 평가)

  • Lee, Jong-Hwi;Hong, Jong-Ouk;Jin, Youngguo;Chun, Byung-Sik
    • Journal of the Korean Geotechnical Society
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    • v.28 no.9
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    • pp.85-95
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    • 2012
  • The method of using organic acid is more environment-friendly for it improves the strength of the ground. The method of proliferating microbes makes soil particle bonded, finally improves the strength of the ground and decreasing permeability. Although there has been the research on the effect of strength increasing, there has never been a research on the evaluation of field application. In this paper, through the light drop weight test, the dynamic cone penetration test, the field density test, the variation of strength was investigated in the mixed ground with organic acid for 56 days. As the results of the field test, it was found that the strength and stiffness of the ground increased with organic acid, and that through SEM-EDS, the precipitation of calcium carbonate made by specified microbe obviously increased with organic acid material and so the ground was improved. Therefore, the sustainable development of this method needs to be analysed more in the future.

Estimation of In-situ Stress State for NC Clays Using PCPT Results (정규압밀 점토지반에서 피에조콘관입 결과를 이용한 원위치 응력상태 평가)

  • Cho, Sung-Hwan;Seo, Kyung-Bum;Chang, Buhm-Soo;Lee, Jun-Hwan
    • Journal of the Korean Geotechnical Society
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    • v.26 no.10
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    • pp.15-25
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    • 2010
  • In this study, a method for estimating the in-situ stress state of NC clays using piezocone penetration test (PCPT) results is proposed. The proposed method is based on a correlation between the PCPT results and strength increment ratio. According to proposed method, no additional testing procedure for collecting undisturbed soil sample is required, which can reduce overall testing cost. To verify this method various analytical solutions were adopted and used. Measured result and predicted result are compared with each other. The verification sites consist of a variety of soil conditions. From the comparison, it is seen that predicted value of effective strcss using the proposed method match well those from measured results.