Search

A technique for the analysis of 1D pollutant migration through a clay layer of finite depth is presented. This formulation includes dispersive and advective transport in the clay as well as geochemical reactions and permits consideration of the depletion of contaminant in the landfill with time as well as the effect of groundwater flow in a permeable stratum beneath the clay layer. A limited parametric study is presented to illustrate the effect of considering these factors in the analysis. It is shown that for most practical situations the concentration of contaminant within the ground water beneath the landfill will reach a peak value at a specific time and will then decrease with subsequent time. It is shown that the magnitude of this peak concentration and the time required for it to occur are highly dependent upon the mass of contaminant within the landfill and the sorption capacity of the clay. Other important factors which are examined include the thickness of the clay layer, the advection velocity relative to the dispersivity, and the groundwater flow velocity in any permeable strata beneath the clay layer. The implications of these results for optimizing the design of clay liners is then discussed.

A technique for the analysis of periodically layered soil deposits is developed. This technique requires minimal data preparation and is compu tationally very efficient. The technique is used to determine the deformations of a periodically layered half space subjected to a uniform circular applied pres sure. Consideration is given to the center settlement, edge settlement and hor izontal displacement at the edge. Results are presented for a wide range of geometries and soil conditions. The validity of two approximate approaches which represent the deposit as a single homogeneous layer are then evaluated. It is shown that simple approaches will suffice for a wide range of conditions, and parametric solutions are provided for certain situations where simple ap proaches are not appropriate.

A numerical technique for the analysis of geotextile reinforced em bankments is outlined. This technique permits consideration of soilreinforcement interaction, slip at the soilfabric interface, plastic failure within the soil and large deformations. The applicability of the approach has been assessed by examining the observed and predicted performance of a number of reinforced embankments constructed on soft foundations. In this paper, the application of the approach is illustrated by reference to an embankment constructed on a soft peat deposit. Finally, the paper presents a practical design procedure which involves the use of simple design charts. The use of this design procedure is illustrated by means of a worked example using a typical set of design charts.