Journal of the Korean Geotechnical Society (한국지반공학회논문집)

Korean Geotechnical Society (한국지반공학회)
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Proposal of Mobilized Passive Earth Pressure to Allowable Wall Displacement and Movement Types in Sandy Soil

벽체 허용변위와 양상을 고려한 사질토지반에서 수동측토압 제안

  • Received : 2023.04.11
  • Accepted : 2023.07.12
  • Published : 2023.07.31
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Abstract

The evaluation of passive earth pressure plays a crucial role in the design of earth-retaining structures such as retaining walls and temporary earth-retaining walls to withstand horizontal earth pressure. In the earth pressure theory, active and passive earth pressures represent the earth pressures at the limit state, where the wall displacement reaches the maximum allowed displacement. In the design of earth-retaining structures, the passive earth pressure is considered as the resisting force. In this context, the limit displacement at which passive earth pressure occurs is significantly greater than that associated with the active earth pressure. Therefore, it is irrational to apply this displacement directly to the calculation of passive earth pressure. Instead, it is necessary to consider the mobilized passive earth pressure exerted at the allowable horizontal displacement to evaluate the structural stability. This study proposes an allowable wall displacement, denoted as 0.002 H (where H represents the excavation depth), based on a literature review that focuses on sandy soils. To calculate the mobilized passive earth pressure from the wall displacement, a semi-empirical equation is proposed. By analyzing the obtained data on mobilized passive earth pressure, a reduction factor applicable to Rankine's passive earth pressure is proposed for practical application in sandy soils under different wall movement types.

수평방향의 토압에 저항하는 흙막이 구조물(옹벽, 가시설 등) 설계에서 수동토압(Passive earth pressure) 산정은 중요한 요소이다. 토압이론에서 주동토압과 수동토압은 벽체 변위가 충분히 발생하여 한계변위에 도달한 한계상태에서의 토압이다. 흙막이 구조물설계에서 수동토압은 저항력으로 고려되는데, 이때, 수동토압이 발생하는 한계변위는 주동토압이 발생하는 한계변위의 10배 이상으로 이 변위를 수동토압산정에 적용하는 것은 비합리적이다. 그러므로 한계변위의 수동토압(Passive earth pressure)이 아닌 임의 크기의 수평변위에서 발생되는 임의 수동토압을 발현수동측토압(Mobilized passive earth pressure)으로 정의하고 흙막이 구조물의 안정성 검토에 발현수동측토압을 적용하는 것이 현실적으로 필요하다고 판단하였다. 본 연구에서는 모래지반에 대하여 문헌조사를 통해 흙막이 구조물의 안정성 확보가 가능한 허용수평변위를 0.002H(H:굴착깊이)로 제안하였으며, 임의수평변위에서 발생되는 발현수동측토압을 산정할 수 있는 반경험식을 사용하였다. 그리고 사질토 지반에서 구해진 발현수동측토압 자료를 바탕으로 실무에서 간단하게 적용할 수 있도록 벽체의 거동양상에 따른 Rankine의 수동토압에 적용 가능한 감소계수를 제안하였다.

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