• Title, Summary, Keyword: 콘관입시험

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Influence of Penetration Rate on Piezocone Penetration Test (변형율 속도가 콘관입시험에 미치는 영향)

  • Kim, Dae-kyu
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.59-70
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    • 2000
  • 본 연구에서는 콘관입속도가 콘관입시험 결과에 미치는 영향을 연구하기 위하여 LSU/CALCHAS(Louisiana State University Calibration Chamber System)를 이용한 미니 Piezocone의 관입시험이 수행되었으며 그 결과를 비교 분석하였다. 10회의 미니 Piezocone 관입시험이 Ko 조건에서 수행되었으며 33% kaolin, 67% sand mixture가 시료로 사용되었고, 콘관입속도 0.3, 0.6cm/sec, U1(filter element at the cone tip), U2(filter element above the cone base), OCR=1, 10 의 조건이 다양하게 적용되었다. 시험결과 Cone Resistance, Excess Pore Water Pressure, Sleeve Friction 은 U1, U2 두 종류의 콘에 대해서 모두 관입속도가 커짐에 따라 증가하였으나 OCR의 증가에 따라서는 감소하였으며 U1의 Excess Pore Water Pressure가 U2 경우보다 크게 측정되었다.

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Advanced Evaluation of In-situ Strength using CPT results (콘관입시험을 이용한 지반강도의 상세평가해석)

  • Lee, Jun-Hwan;Kang, Byung-Jun;Kyung, Doo-Hyun;Hong, Jung-Mu
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.111-116
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    • 2008
  • 콘관입시험(CPT)은 의사정적상태로 수행되는 현장시험방법으로서, 각종 기초구조물의 설계와 더불어 지반조사를 위한 대표적 방법으로 널리 적용되고 있다. 본 논문에서는 콘관입시험결과를 이용하여 사질토 지반에 있어서 지반강도의 상세평가법을 제안하고자 한다. 사질토의 강도는 상대밀도와 응력상태에 따라 변하는 상태의존적 성질을 나타내고 있으나, 이러한 역학적 성질은 실험실 내에서만 측정이 가능한 상태이며, 현장강도의 경험식이나, 대표강도의 평가만이 제안되어 있는 실정이다. 따라서 본 연구에서는 대표적 현장시험방법인 CPT를 이용하여 다이러턴시 특성 평가가 가능하며, 다양한 지반특성치가 반영될 수 있는 현장강도의 상세평가법을 제안하고자 한다. 이를 위해 실내삼축압축시험을 통해 얻어진 강도특성과 역학특성치들을 분석하였으며, 이를 토대로 수정 다일러턴시 평가법을 제안하였다. 제안된 방법의 검증을 위해 가압토조를 이용한 콘관입시험을 수행하였으며, 측정값과의 비교분석을 수행하였다.

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Consolidation characteristics of Soft Clay from Piezocone Dissipation Tests (피조콘 소산시험을 이용한 연약지반의 압밀특성)

  • 윤길림;구자갑
    • Journal of the Korean Geotechnical Society
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    • v.16 no.2
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    • pp.13-22
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    • 2000
  • 서해안에 위치한 특정 연구현장에서 연약지반의 압밀거동을 파악하기 위한 소산시험을 포함한 콘관입시험을 수행했다. 연구현장에서 시험시공으로 적용한 연약지반개량공법으로는 압성토공법, 두 종류의 페이퍼드레인 공법, 팩드레인 공법이었으며 각각의 공법들에 있어 현장에서의 지반개량에 따른 압밀거동을 판정하기 위해서 적용되었다. 콘관입시험은 근본적으로 지반개량 전과 후에 보링, 표준관입시험, 압밀시험과 함께 수행되었다. 실내실험과 피조콘관입시험을 비교한 결과, 연약지반의 표층에서는 상당한 지반개량효과가 있었으나 표층아래 심층지반에서는 그렇치 않았다. 그리고 지반개량 후, 10개월이 지난 시점에 압밀시험과 소산시험 결과를 통하여 분석한 수평압밀계수는 압성토 방법을 제외한 3가지 개량공법을 적용한 지점에서 압밀계수는 감소하여 개량효과를 간접적으로 판단할 수 있었다.

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Evaluation of Maximum Shear Modulus of Silty Sand in Songdo Area in the West Coast of Korea Using Various Testing Methods (다양한 시험 방법을 이용한 서해안 송도 지역에 분포하는 실트질 모래의 최대 전단탄성계수 평가)

  • Jung Young-Hoon;Lee Kang-Won;Kim Myoung-Mo;Kwon Hyung-Min;Chung Choong-Ki
    • Journal of the Korean Geotechnical Society
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    • v.21 no.9
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    • pp.65-75
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    • 2005
  • Maximum shear modulus of soil is a principal parameter for the design of earth structures under static and dynamic loads. In this study, the statistical data of maximum shear moduli of silty sands in Songdo area in the west coast of Korea evaluated by various field and laboratory tests - standard penetration test (SPT), cone penetration test (CPT), self-boring pressuremeter test (SBPT), downhole test (DH), seismic cone penetration test (SCPT) and resonant column test (RC) were analyzed. Based on the measurement of shear moduli using DH which is known as maximum value at very small strain, the new empirical correlations between shear moduli and SPT or CPT values were proposed. Predictions of maximum shear moduli using the proposed correlations were compared with the data obtained from DH. The good agreement confirmed that the proposed correlations reasonably predicted the maximum shear moduli of silty sands in the area.

Scale Effects and Field Applications for Continuous Intrusion Miniature Cone Penetrometer (연속관입형 소형콘관입시험기에 대한 크기효과 및 현장적용)

  • Yoon, Sungsoo;Kim, Kyu-Sun;Lee, Jin Hyung;Shin, Dong-Hyun
    • Journal of The Korean Society of Civil Engineers
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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.

Numerical Simulation of Cone Penetration Tests in Sand Ground Using Critical State Mohr Coulomb Plasticity Model (한계상태 Mohr Coulomb 소성 모델을 활용한 콘관입시험의 수치적 모사)

  • Woo, Sang Inn;Chung, Choong-Ki
    • Journal of the Korean Geotechnical Society
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    • v.35 no.2
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    • pp.37-51
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    • 2019
  • This study focuses on the numerical simulations of the cone penetration tests in a sand ground. The mechanical responses of sand were described using the modified Mohr Coulomb plasticity model based on the critical state soil mechanics. In the plasticity model, the dilatancy angle was not a constant, but a function of the distance to the critical state line from the current state of void ratio and mean effective stress. To simulate cone penetration tests numerically, this study relied on Lagrangian finite element method under the axisymmetric condition. To enable penetration of the cone penetrometer without tearing elements along the symmetric axis, the penetration guide concept was adopted in this study. The results of numerical simulations on the calibration chamber cone penetration tests had good agreement with the experimental results.

Estimation of Pile Resistance Factor by CPT Based Pile Capacity (CPT결과를 이용한 항타말뚝 지지력 평가를 위한 저항계수 산정)

  • Kim Dae-Ho;Lee Jun-Hwan;Kim Bum-Joo
    • Journal of the Korean Geotechnical Society
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    • v.21 no.10
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    • pp.113-122
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    • 2005
  • Application of Limit State Design in geotechnical engineering has become world-widely popular. While LRFD code in the North America presents geotechnical load and resistance factors, the values of resistance factors proposed by these methods are still unstable with limited application. CPT has been widely used for the pile design and various methods have been proposed to estimate the bearing capacity of piles. In this paper, resistance factors for representative pile design methods based on CPT results are evaluated. Field pile load test and CPT results were collected and analyzed in order to obtain necessary statistical data and resistance factors. Resistance factors of the base, shaft, and total capacity are estimated. From fisrt order second moment (FOSM) analysis, resistance factors of $0.30{\sim}0.55$ are estimated for total load capacity.

Characteristics of Undrained Shear Strength and Development of Modified SPT on Very Soft Ground in Korea (국내 초연약지반의 비배수전단강도 특성 및 개량표준관입시험기 개발)

  • Jung, Hyuksang;Cho, Changkoo;Chun, Byungsik
    • Journal of the Korean Geoenvironmental Society
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    • v.10 no.6
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    • pp.105-115
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    • 2009
  • In this study, SPT, FV, and CPT tests were performed at five very soft grounds in southern coast of Korea to characterize the $S_u$ of very soft ground. In addition, a new modified SPT that is applicable to very soft ground was developed. Tests results showed that in very soft ground (N<2), the $S_u$ was lower than 12.5 kPa using the empirical N-Su correlation, and lower than 50 kPa and 65 kPa using vane shear test and CPT, respectively. It was shown that the results of in-situ tests were higher than those estimated from the N-Su correlation, and it was also demonstrated that the range of estimated $S_u$ was quite wide. New correlations that relate the modified SPT $N_m$ with Su from FV and CPT were developed, which are $S_u=1.76N_m-10.47$ and $S_u=1.82N_m-9.71$, respectively.

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Correlations between the CPT and the SPT for the Residual Soil in Korea (국내 잔류토층에서 CPT와 SPT와의 상관관계에 대한 연구)

  • Koo, Ja-Kap;Yi, Chang-Tok
    • 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.