In the sewer pipes, reinforced concrete pipes and concrete pipes are mostly used. However, it is difficult to ensure the long-term durability of the pipe due to the corrosion of the rebar which is used for the reinforcement of the concrete. Also, reinforced concrete pipes are difficult to secure watertightness due to deterioration and corrosion by hydrogen sulfide. In order to solve such problems, research on using sewer pipes made of plastic materials is being actively conducted. When soil pressure and live load act on the buried flexible pipe, the load acting on the pipe is transferred to the surrounding soil. So, the flexible pipe will support the load with the surrounding soil together. It is difficult to predict these behaviors theoretically and clearly. Therefore, the design equation for the buried flexible pipe is analyzed by adopting theoretically idealized assumptions and it is estimated through experimental studies that it is similar to the actual structural behavior. In this paper, the mechanical properties of the soil and the polyethylene pipe were considered in application of the method proposed in ASTM D 2412 to design the buried polyethylene pipe. Also, structural behavior of the pipe resisting external loads such as soil pressure was investigated to use a polyethylene pipe as the buried pipe and the long-term behavior of the polyethylene pipe was predicted by the compaction rate of surrounding backfill soil through the field test.

Most of existing buried pipes are composed of reinforced concrete. Reinforced concrete pipes have many problems such as aging, corrosion, leaking, etc. The polyethylene (PE) pipes have advantages to solve these problems. The plastic pipes buried underground are classified into a flexible pipe. National standard that has limited the long-term vertical deformation of the pipe to 5% for flexible pipes including PE pipe. This study presents a prediction for the long-term behavior of the polyethylene pipe based on ASTM D 5365. This prediction method is presented to estimate by using the statistical method from the initial deflection measurement data. We predict the behavior of long-term performance on the double-wall pipe and multi-wall pipe. As a result, it was found that the PE pipe will be sound enough more than 50 years if the compaction of soil around the pipe is more than 95% of the standard soil compaction density.

This study was performed to develop a new process technology for advanced wastewater treatment using a modified Rotating Activated Bacillus Contactor (RABC) process that adopts anoxic-oxic suspended biomass tanks to enhance nutrients removal. A modified lab-scale RABC process was applied to examine its applicability and to obtain the design factors for the optimum operation of the system. The modified RABC process showed a little more stable and high nutrients removal efficiency than the prototype RABC process: about 70% of nitrogen and 55% of phosphorous removal when the low organic loading (influent COD 200mg/L). However, the processing efficiency of nutrients removal rates was enhanced to great extent when high organic loading: nitrogen 90% and phosphorous 85% (influent COD 500mg/L). High organic loading stimulated extremely good biomass attachment on the reticular carrier RABC stage and the excellent nutrients removal, nevertheless with almost no offensive odor.

The industrialization and urbanization forced to increase the density of pipelines such as water supply, sewers, and gas pipelines. The materials used for the existing pipe lines are mostly composed of concretes and steels, but it is true that the development for more durable and efficient materials has been continued performed to produce long lasting pipe lines. Recently, underground pipes serve in diverse applications such as sewer lines, drain lines, water mains, gas lines, telephone and electrical conduits, culverts, oil lines, etc. In this paper, we present the result of investigation pertaining to the structural behavior of unplasticized polyvinyl chloride (PVC-U) flexible pipes buried underground. In the investigation of structural behavior such as a ring deflection, pipe stiffness, 4-point bending test, experimental and analytical studies are conducted. In addition, pipe stiffness is determined by the parallel plate loading tests and the finite element analysis. The difference between test and analysis is about 8% although there are significant variations in the mechanical properties of the pipe material. In addition, it was found by the 4-point bending test there is no problem in the connection between the pipes by coupler.

Recently, the use of buried flexible pipes is widespread and ever increasing trend in the construction field. In this paper, we present the result of an investigation pertaining to the pipe stiffness of buried unplasticized polyvinyl chloride (PVC-U) pipes. To estimate the mechanical properties of PVC pipe produced by the domestic manufacturers, tensile test specimens were prepared and tested. In addition, parallel plate loading tests for the pipes with 150mm and 400mm inside diameters were conducted. From the test result, the pipe stiffness according to the ASTM D 2412 (2008) is estimated.

최근 지중매설 유리섬유복합관(GRP관)은 유해한 환경에서 뛰어난 성능을 보유하고 있어 하수관거용으로서 사용이 증가 되고 있다. 또한 지중에 매설되어 있는 조건에서 기존의 콘크리트관 등 강성관에 비해 구조적 성능이 뛰어나 다. 지중매설 GRP관은 주로 상부에 작용하는 상부토압과 활하중에 의한 압축응력에 의해 원주방향으로 변형이 일 어나게 된다. GRP관의 구조적 거동은 매설토와 주변의 지반의 성질에 따라 다르게 설계되어야 한다. GRP관의 설 계는 Spangler 의 변형량 계산식을 Watkins에 의해 수정되어 사용되고 있다. 이 연구에서는 Watkins의 관변형 추정 식에 GRP관의 재료적 특성을 고려하여 관변형량을 예측하였다.

본 연구에서는 경수로 사용후핵연료로부터 다시 핵연료 물질로 재사용할 수 있는 우라늄과 초우라늄원소군을 분리/회수하기 위한 고온전해분리 공정(Pyroprocessing)의 기술적 타당성을 조사하였으며, 나아가서 핵비확산 측면에서 기존 핵연료주기기술의 대체기술로서 적합성이 있는지를 검토하였다. 먼저 고온전해분리 공정에 편입될 각종 단위공정을 조합하여 전체 공정을 구성하였다. 그리고 사용후핵연료에 들어 있는 여러 가지 물질들의 분리 과정에서, 본 연구에서 확보한 실험결과와 관련 문헌에 발표된 각종 분리도 자료를 바탕으로 문제의 원소군들 즉, 우라늄, 초우라늄원소군, 희토류, 귀금속류, 그리고 열발생원소군들이 공정흐름도에서 어떤 경로를 따라 흘러가는지 그 향방을 추적하여 보았다. 결과적으로 전체 공정의 물질수지 산출 결과에 의하면 우라늄과 초우라늄원소군(TRU)은 각각 98.0wt%, 97.0wt%가 제품으로 회수될 수 있으며 나머지 원소군들은 대부분 제거되어 방사성폐기물로 분리될 수 있음을 파악하였다. 게다가 초우라늄원소군 제품이 상당한 -방사선과 중성자선을 방출하고 있어 핵비확산에 유리하게 작용하고 있음을 알 수 있었다.