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2026 Vol.27, Issue 9 Preview Page
Analysis of Transient Residual Pore Water Pressure in Cut-slope Retaining Walls due to Delayed Drainage during Rainfall

강우 시 배수 지연에 따른 절토부 옹벽의 일시적 잔류 수압 영향 분석

Youngcheol Hwang1*
황 영철1*
1Professor, Dept. of Civil Engineering, Sangji University
*Corresponding Author
1 September 2026. pp. 33-41
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Abstract

Recently, collapse accidents of cut-slope retaining walls have occurred repeatedly due to extreme rainfalls. The Korean Design Standard (KDS 11 80 05) assumes zero water pressure when drainage layers and weep holes are installed, prescribing only active earth pressure as the design load. However, weep holes behave as orifices with finite discharge capacities, exhibiting mechanical limitations against long-term clogging and heavy slope inflows. In this study, a water balance-based lumped-parameter numerical model combining hydraulic continuity, Darcy's law, and Terzaghi's effective stress theory was developed to quantitatively estimate peak transient pore water pressure. In particular, this model assumed a conservative bounding condition that excludes surface runoff and features the most direct drainage path to demonstrate the limit behavior of water pressure. The results revealed that even under 100% normal drainage, permeable sand ground generates a peak water head of 74 % of the wall height because rainfall inflow overwhelms orifice discharge capacity, increasing total lateral pressure by approximately 90 % over the design load. Through this conservative proof, this paper exposes the mechanical contradiction of assuming zero water pressure and proposes the imperative inclusion of dynamic residual pore water pressure in retaining wall design.

Keywords
Cut-slope retaining wall
Transient seepage
Residual pore water pressure
Delayed drainage
Drainage clogging

최근 기후변화에 따른 집중호우의 빈도와 강도가 증가하면서, 배수시설이 설치된 절토부 옹벽에서의 붕괴 사고가 반복적으로 발생하고 있다. 현행 국가건설기준(KDS 11 80 05)은 옹벽 배면에 배수층과 배수공을 설치하면 수압이 작용하지 않는 것으로 가정하여, 주동토압만을 설계 하중으로 고려하도록 규정하고 있다. 그러나 실제 현장에서 배수공은 유한한 통수 단면적을 가진 오리피스(Orifice) 개념의 거동을 하며, 장기적인 배수층의 막힘(Clogging) 현상과 배후 사면으로부터의 대량 유입수를 실시간으로 처리하는 데 역학적 한계를 지닌다. 본 연구에서는 수리학적 연속방정식과 Darcy의 법칙, Terzaghi의 유효응력 이론을 결합한 물수지 기반 집중정수형 수치모델(Water balance-based lumped-parameter numerical model)을 구축하여, 강우 시 옹벽 배면에 발생하는 동적 피크 수압(Peak Transient Pore Water Pressure)을 정량적으로 산정하였다. 특히 본 모델은 배수 경로가 가장 직선적이고 단순화된, 지표 유출을 배제한 보수적 한계조건을 가정하여 수압의 한계 거동을 증명하도록 하였다. 해석 결과, 배수 시스템이 100 % 정상 작동하는 조건에서도 배후 사면의 집수면적이 넓고 투수계수가 큰 사질토 지반에서는 배수공의 방류 한계를 초과하는 빗물 유입으로 인해 옹벽 높이의 74%에 해당하는 수두가 형성되며, 이로 인해 총 측압이 설계 하중 대비 약 90 % 증가하는 것으로 확인되었다. 본 논문은 이러한 보수적 경계 조건에서의 한계 입증을 통해, 배수시설 설계 시 수압을 고려하지 않는 것으로 가정하는 경우의 역학적 모순을 밝히고, 설계 수압의 동역학적 반영 필요성을 제언하였다.

키워드
절토부 옹벽
일시적 침투
잔류 간극수압
배수 지연
배수공 막힘
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Information
  • Publisher :Korean Geo-Environmental Society
  • Publisher(Ko) :한국지반환경공학회
  • Journal Title :Journal of the Korean Geo-Environmental Society
  • Journal Title(Ko) :한국지반환경공학회 논문집
  • Volume : 27
  • No :9
  • Pages :33-41
  • Received Date : 2026-07-22
  • Revised Date : 2026-07-27
  • Accepted Date : 2026-08-21
  • DOI :https://doi.org/10.14481/jkges.2026.27.9.33
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