Horizontal draining

Pradhan,T. B. S., Shiwakoti, D. R. and Imai, G. (1996), Effect of normal pressure and width of geosynthetic horizontal drain in pullout behaviour using saturated clay. Proceedings of the International Symposium on Earth Reinforcement, Kyushu, Japan, Vol. 1, pp. 133-138. 

Subhorizontal drains may be ineffective in clays and other fine-grained soils. Therefore, the possibility of poor performance should be considered when assessing the relative merits of subhorizontal drains to other remedial measures. Figure 11.13 illustrates some of the more common situations where subhorizontal drains can be used for slope stabilization (Cornforth, 2005). A case study of a large landslide on the southern Oregon coast, stabilized by a vertical shaft and horizontal drains, is discussed by Cornforth (2005) and illustrated in Figure 11.14. 

FIGURE 11.14 (a) Plane view and (b) cross section of a vertical shaft and horizontal drains applied to stabilize the Arizona Inn Slide, near Brookings, OR. (After Cornforth, D., Landslides in Practice, Investigation, Analysis, and Remedial/Preventative Options in Soils, Wiley, 2005.)... 

Similar to dynamic compaction except vertical or horizontal drains (or together with vacuum) are used to dissipate pore pressures generated in soil during compaction. 

The drains must be able to discharge the extracted pore water into a free-draining medium (sand or gravel layer, horizontal drains, etc.), usually—but not necessarily—located at the top of the vertical drain. It is essential to ensure that such a drainage blanket has sufficient permeability to handle the extracted water during all stages of the construction works. The hydraulic head within this horizontal layer or drain must be less than the hydrauhc head in the vertical drain in order to allow the pore water to be removed from the compressible soil mass. 

Regarding flow conditions, typical appUcaiions of unidirectional steady-flow conditions are earth dams, embankments, retaining walls, landfills, drainage trenches, and vertical and horizontal drains. The range of boundary conditions, in terms of vertical effective stress and applied hydraulic gradients, for these applications is shown in Table 8.3. 

Chai, J.-C., Horpibulsuk, S., Shen, S.-L., Carter, J.P., 2014. Consolidation analysis of clayey deposits under vacuum pressure with horizontal drains. Geotextiles and Geomembranes 42, 437-444. 

Nagahara, H., Fujiyama, T., Ishiguro, T., Ohta, H., 2004. FEM analysis of high airport embankment with horizontal drains. Geotextiles and Geomemhranes 22, 49—62. 

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