Discharge Capacity Of Drains Research Articles

A vertical and radial consolidation analysis incorporating drain degradation based on the spectral method

The use of prefabricated vertical drains (PVDs) to improve soft soil has received much attention in the recent past, however, there is still a lack of rigorous analytical solutions that can incorporate the time- and depth-dependent behaviour of drains into the consolidation of multi-layered soil. This study thus presents a novel approach where the spectral method is used to capture the degradation in discharge capacity of drains over time and depth, while the average consolidation of different soil layers with regard to vertical and radial drainage is computed. In this approach, the excess pore water pressure profile across different soil layers is described as a single expression using matrix operations. This proposed method is then verified with laboratory and field investigations where the degradation of PVDs is captured and compared with other solutions. The results show that this method can predict the soil behaviour with greater accuracy and flexibility whereas there is a significant deviation in the predicted consolidation when the degradation of drains is not considered properly. A parametric investigation is also carried out using the proposed solution to further highlight its ability to evaluate the effect that drain degradation can have on the consolidation of multi-layered soil.

토낭 보강토 옹벽의 수평 배수재로서 PBD의 적용성 평가

흙 구조물의 안정성은 물과 직접적인 관련이 있고, 강우나 침투수에 대한 충분한 대책을 세우지 않는다면 구조물에 큰 피해를 입을 수 있다. 최근 이상기후로 인한 집중호우의 횟수가 잦아짐에 따라 흙 구조물의 안정성에 대한 관심이 커지고 있으며, 구조물의 배수에 대한 여러 가지 방법이 제시되고 있다. 본 연구에서는 연직 배수공법에 사용되는 PBD(Plastic Board Drain)를 보강토 옹벽의 수평 배수재로 이용했을 시 적용성 여부에 대해 평가 하였다. 특히 전면벽을 콘크리트 블록이 아닌 토낭으로 하여 시공성과 경제성을 높이고, 토낭과 연결재, PBD를 일체화 시켜 안정성을 확보하였다. PBD를 활용한 배면수의 투수능 시험결과 보강토체 사이에 자갈층을 포설한 것과 유사한 효과를 나타내었으며, 실제 현장에서의 수평배수재로 활용이 가능한 것으로 판단된다. Recently, construction of reinforced earth structure using geosynthetics has been increased because it has advantages such as construction efficient, cost effectiveness and appearance aspect against existing gravity or cantilever retaining wall. However due to the climate change in Korea excessive inflow of ground water and surface water from heavy rainfall could affect the stability of reinforced retaining wall seriously. So the discharge capacity of drains should be evaluated by using experimental method in the design of reinforced earth wall. In this study, instead of concrete block used in most of the retaining wall, eco-friendly porous soilbag was used. This paper describes the test method and result of the laboratory testing for determination of discharge capacity utilizing PBDs.

Reevaluation of the factors influencing the consolidation of ground by incorporating prefabricated vertical drains

In the consolidation of ground by incorporating prefabricated vertical drains, there are a number of rigorous and approximate solutions that can be utilized. These solutions are affected by many factors. Due to a high level of complexity, design and back analysis are generally inefficient in predicting the consolidation behaviour. In this study, the existing solutions for the combined vertical and radial consolidation and the recommended values of each parameter were reviewed. A parametric study was then performed to examine the appropriateness of the solutions and the effects of each factor on the total degree of consolidation Uvh to the combined consolidation. Results show that the effect of vertical drainage on Uvh is sufficiently insignificant, and the peak influence occurs at Uvh of less than 60%. All the solutions for the radial consolidation, except for Hansbo’s solution, gave rise to the almost identical results. Hansbo’s solution affected well resistance only. It was noted, however, that the significance of well resistance depends on soil permeability and the discharge capacity of drains which is compared to the effects of spacing and smear.