Retained soil and structures

Dynamic interaction of retaining walls and retained soil and structures... 

The scope of the present study was to investigate the dynamic interaction between retaining walls, retained soil and retained structures. In all cases examined it was proven that the characteristics of the wall as well as the seismic excitation affect substantially the dynamic behaviour of the whole system. The rigid wall imposes a boundary that clearly alters the 1-D conditions of the backfill, while the flexible wall does not transform the model into 2-D. Furthermore, it has been shown that the amplification of the acceleration levels on the retained soil and structure depends also on the seismic motion. In addition, it has been presented that the existence of a retaining wall may alter considerably the dynamic response of a structure founded on the retained soil. Moreover, the distress of the wall may be affected significantly by the presence of retained structures. 

The results of the present investigation provide a clear indication of the direct dynamic interaction between the wall, the retained soil, and the retained structures. That fact justifies the necessity for a more elaborate consideration, both in seismic codes and engineering practice, of this interrelated phenomenon during the seismic design, not only of the retaining walls but of the nearby structures as well. 

Retaining systems, such as cantilever walls, are widely used worldwide for serving various purposes in structures and infrastructures (embankments, bridges, ports, etc). In the chapter by Tsompanakis (Chapter 29) the dynamic interaction of the retaining walls with the retained soil and the retained structures is investigated. This so-called phenomenon of dynamic wall-soil-structure interaction (DWSSI) is a rather... 

Filtration installations include wrapping the trench of a pavement-edge drain system to prevent contamination of the underdrain placement behind retaining walls and bridge abutments to prevent contamination of the sand blanket placed against the structure to allow dissipation of pore pressures in order to avoid failure of the structure as silt fences to allow surface runoff from a site while retaining the soil suspended in the runoff and on earth slopes beneath larger stone or other overlay materials to prevent erosion of the slope as water escapes from the interior of the slope. 

The two most common natural textile fibers encountered in modern fabrics have contrasting responses to soil burial. Under most soil burial conditions cellulose will degrade rapidly whereas wool will decay at a slower rate. These phenomena are demonstrated by the degradation of textile fibers from the Experimental Earthworks Project (Janaway 1996a). Figures 7.9 and 7.10 compare wool and linen buried in the chalk environments at Overton Down for 32 years. The linen is denatured to the point that there is little surviving morphology, whereas the wool retained some fiber structure. 

At the root of an understanding of organic farming is an understanding of the soil. The structure of the soil determines what can be grown and how fertility can be maintained. The structure of the soil can be enhanced to increase the efficiency whereby nutrients are created, retained, and taken up by plants. Only when the quantity and fertility of the soil are maintained or increased can farming be truly called organic. 

Foliage can also be contaminated by actinides associated with resuspended soil particles deposited on foliar surfaces (38, 39). In arid, windy environments, dust and soil particles become airborne, deposit on foliar surfaces, and may be retained by hirsute structures or crevices of leaves (41). Concentration ratios for both Pu and Am that approach 10° (Fig. 3) are observed for these types of environments (e.g., the Nevada Test Site). Concentration ratios approaching 10-2 for Rocky Flats grassland species are also related to deposition of windblown Pu on foliar surfaces (38). 

When dead plant material is broken down by soil animals and microorganisms, it forms humus, which slowly releases minerals into the soil and makes nutrients available for plants. Humus can remain in the soil for hundreds of years. In a healthy soil, the organic humus and mineral particles stick together to form tiny crumbs a millimeter or so thick. These crumbs are held together by electrical attraction, and by organic glues produced by bacteria. The tiny pores in between this crumb structure form a kind of sponge that helps to retain water in the soil. 

Erosion control fabrics n. Fabrics used in the stabilization of embankments and the containment of silt run-off from erodible slopes. In embankment stabilization, the fabric functions as a filter medium behind stabilizing rip-rap revetments. In siltation control, the fabric acts as a filter to contain silt while allowing excess water to drain freely. In turf reinforcement, the mat is used to retain soil while allowing roots and stems to grow through. In fabric-forming systems for the construction of revetments, a double-layer, water-permeable fabric is positioned, then pumped full of structural grout. These systems are alternatives to rip-rap. 

TRM structures are composed of fused polymer nettings, made of randomly laid monofilaments, or yarns woven or tufted into an open, 3-dimensionally stable but flexible mat. Soil filling is carried out during installation and the weight of the soil fill ensures the mat conforms to undulations in the soil surface. They are designed to retain seed and soil cover, and therefore to entangle vith the root and stem of the plants as the vegetation becomes established. 

A) Agricultural uses. Water is a basic component of all plants and is taken up from the soil via the root system, flowing up the plant by the osmotic gradient between the soil and the air. The water consumption of a crop can be broken down into three parts (1) Constituent water, which is retained as a constituent part of the plant matter and used in combination with carbon dioxide to produce carbohydrates (photosynthesis), and to assist the uptake and transport of nutrients from the soil. (2) Transpiration water, which is taken up by the plant and lost as water vapor through the process of transpiration to provide cooling for aerial structures. (3) Evaporation water, which is lost by evaporation from the surface of the plant. 

Yu, C.P. Tuan, C.H. 2003. On the impact responses of retaining structures due to massive rocks in debris flows theory and analytical approaches. Journal of Chinese Soil and Water Conservation 34(l) 55-66 (in Chinese). 

---