Experimental study on the Effect of the Pile Installation on the Hydraulic Barrier Performance of Landfill Bottom Clay Layer

廃棄物処分場跡地の高度利用を図るためには構造物の基礎として支持杭を用いることが考えられるが、海成粘土層を底部遮水層としている場合が多く、構造物基礎として杭を打設することによる粘土層の遮水性能への影響について検討を行う必要がある。そこで本研究では、粘土と鋼管杭を想定した粘土-金属の界面における透水性を実験的に評価することを目的として、粘土に作用する鉛直応力および粘土-金属間の密着状態と透水性の関係について検討を行い、粘土と金属の間にフリクションが作用している状態では漏水は生じないことを明らかにした。さらに、実験結果を用いて、杭の打設が粘土層の遮水性能に及ぼす影響について定量的な評価を試み、その評価方法を提案した。
To promote the land use of the coastal landfill site after the waste reclamation, structures and facilities may require pile foundations to assure the sufficient baring capacity. Since the marine clay functions as bottom barrier in landfill sites, it is required to know how much leakage could occur due to the installed piles penetrating clay layer. This research is aimed to clarify the barrier performance with installed piles across the clay layer. Interface transmissivity between the clay and the steel is evaluated by using newly developed rigid-wall permeameter, which is able to determine the side-wall friction by measuring the soil pressures on the top and the bottom of the specimen. The more vertical stress increases, the larger friction between clay and steel occurs and the lower hydraulic conductivity is achieved. It was obvious that leakage could hardly occur from the interface between clay and steel, when friction could work. By using the methods proposed in this research, the hydraulic barrier performance of clay layer with pile foundation can be clearly seen.