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2025 Vol.41, Issue 5 Preview Page
Development of Water Pressure-Compensated Self-Weighted Multiphysics Cone Penetration Apparatus for Investigation of Soft Offshore Sites

해상연약지반 탐사를 위한 수압보상형 자중관입식 다중물리 콘 관입시험기 개발

Juna Lee1
,
Junghee Park2*
이 준아1
,
박 정희2*
1Member, Graduate Student, Dept. of Civil and Environmental Engineering, Incheon National Univ.
2Member, Assistant Prof., Dept. of Civil and Environmental Engineering, Incheon National Univ.
1정회원, 인천대학교 건설환경공학과 석사과정
2정회원, 인천대학교 도시환경공학과 조교수
*Corresponding Author
31 October 2025. pp. 45-56
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Abstract

Offshore geotechnical projects require reliable design parameters for seabed structures such as wind turbine foundations, cables, tunnels, and pipelines, where such parameters must be estimated precisely and in an economical manner. However, conventional site investigation methods are sensitive to high pressure and are very expensive. This study proposes a water-pressure-compensated self-weighted multiphysics cone penetration apparatus for analyzing offshore soft ground. We designed a hydraulic compensation cone probe enabling high-resolution measurement of the resistance of the cone tip. The skin friction load cell designed in this study is separate from the cone tip module for pure skin friction measurements. A plastic circuit board (PCB) installed inside the body of the cone enables real-time data monitoring and storage during penetration. Furthermore, we conduct a preliminary laboratory test before field application of the multiphysics cone. The PCB successfully stored all measured data during the preliminary tests. The resistance of the cone tip appears to be higher in clay‒sand mixtures with a higher weight fraction of sand and captures the specimen heterogeneity. The resistance of the cone tip during the measurement evolves in three stages: The frictional resistance appears to be zero for very soft sediments. Acceleration data enable calculation of the cone inclination angle. Within the seafloor, the cone penetration rate is expected to exceed v = 2 cm/s, which will ensure combined undrained and unconsolidated conditions; therefore, the multiphysics cone apparatus can capture the resistance characteristics of the pure seafloor, which depend on the residual effective stress only under undrained and unconsolidated conditions. Indeed, the water-pressure-compensated self-weighted penetration multiphysics cone apparatus can be used for cost-effective and highly repeatable site investigation.

Keywords
Cone tip resistance
Hydraulic compensation
Offshore
Self-weight penetration
Site investigation
Skin friction

해저공간에 대한 발전가능성이 높아지는 가운데 해저 지반구조물의 중요성이 증가하고 있다. 본 연구에서는 기존의 해저지반조사 방법들의 한계점을 개선하기 위해 수압보상형 자중관입식 다중물리 콘 관입시험기를 개발하였다. 본 연구에서 제안한 새로운 콘 관입시험기는 콘 팁 모듈과 주면마찰력 로드셀을 구조적으로 분리한 설계를 통해 선단저항력과 주면마찰력을 독립적으로 측정한다. 특히, 수압보상형 선단부 콘 팁 모듈은 해수면 수심에 따라 증가하는 정수압의 영향을 최소화하여 선단저항력을 평가하도록 설계되었다. 콘 시험기 내부에 가속도계를 설치하여 콘 관입경사를 파악할 수 있도록 하였다. 본 연구에서 제안한 콘 관입시험기의 현장 적용성 평가를 위해 점토 – 모래 혼합시료를 조성하여 콘 자중에 의한 관입 실험을 수행하였다. 실험결과, 선단저항력은 콘 관입에 따라 뚜렷하게 구분되는 3가지 경향을 보여주었고 선단저항력은 모래 비중이 높은 시료에서 더 크게 나타났으며, 혼합시료의 불균질성을 보여주었다. 주면마찰력은 매우 연약한 시료 조건으로 인해 거의 0으로 나타났다. 측정된 가속도계 데이터는 콘 관입경사를 판단하기 위해 매우 효과적인 정보를 제공한다는 것을 보여주었다. 본 연구에서 수행한 배수/비배수 분석 및 향후 목표로 하는 해저지반 천층부의 비압밀 특성을 고려하였을 때 수압보상형 자중관입식 다중물리 콘 관입시험기는 2cm/sec 이상의 관입속도에 독립적이며 잔류유효응력에 의해 결정되는 해저 연약지반의 강도특성을 효율적으로 평가할 수 있다고 판단된다.

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Information
  • Publisher :The Korean Geotechnical Society
  • Publisher(Ko) :한국지반공학회
  • Journal Title :Journal of the Korean Geotechnical Society
  • Journal Title(Ko) :한국지반공학회 논문집
  • Volume : 41
  • No :5
  • Pages :45-56
  • Received Date : 2025-07-31
  • Revised Date : 2025-10-01
  • Accepted Date : 2025-10-01
  • DOI :https://doi.org/10.7843/kgs.2025.41.5.45
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