Slope stabilization drainage

Statement of provisional engineering comments on such aspects as foundation conditions and which methods appears most appropriate for structural foundations and ground slabs, road pavement subgrade conditions, drainage, excavatability of soils and rocks, suitability of local borrow materials for use in construction, slope stability considerations, nature and extent of any remedial works, temporary problems during construction... 

The responsible local authority may permit deviations from thickness and hydraulic conductivity of the drainage layer if it is verified that the necessaiy longterm water flow capacity and long-term slope stability are guaranteed... 

FIGURE 11.12 Various drainage measures applied to landslide stabilization. (After Bromhead, E.N., Slope Stability. 2nd Edition, Blackie Academic Professional, London, 411,1992.)... 

An example of using nonwoven geotextiles includes slope stabilization, in which the stability of the slope depends on the stresses that the geotextile can sustain and transmit the loads within the nonwoven stracture, for separation, filtration, drainage... 

Soil texture, especially clay content, has a significant influence on C sequestration (Parton et al., 1987 Burke et al., 1989 Beker-Heidmann and Scharpenseel, 1992 Schimel et al., 1994) by promoting the formation of physically stabilized and chemically stabilized SOC (Parton et al., 1994) and by controlling soil hydrologic properties (Schimel et al., 1994). The significance of the effects of individual site variables is in the order of soil taxon>drainage>texture>slope>elevation (Tan et al., 2004). 

All covers require a surface layer, but all of the six layers are not required at all sites. For example, a drainage layer may not be needed at an arid site. However, all of the layers that are used in a eover must have adeqirate shear strength to ensure stability against slope failure, and must be sufficiently durable to function adequately over the design life of the cap. More detail regarding the design and performance of covers can be fotmd in Rumer and Mitchell (1997). 

Drainage generally is the most applicable method for improving the stability of slopes or for the corrective treatment of slides, regardless of type, since it reduces the effectiveness of one of the principal causes of instability, namely, excess pore water pressure. The most likely zone of failure must be determined so that the extent of the slope mass that requires drainage treatment can be defined. 

Multi-layered liner systems (e.g. subgrade, geomembrane, protective layer, drainage layer, restoration layer) must be structurally stable especially on steep slopes. The issue of structural stability needs careful eonsideration, as is clearly illustrated by occasional, but sometime severe cases of failure and considerable damage due to sliding. The internal shear strength of the layers is usually quite large and the problems occur on the interfaces be-... 

Using the concept of limit equilibrium linear relationship c — tan cp, the effect of any remedial measure (drainage, modification of slope geometry, restraining structures) can easily be evaluated by considering the intercepts of the c — tan cp lines for the failed slope (Cg, tan (p ) and for the same slope after installing some remedial works (c j , tan cp nec), respectively (Figure 11.9). The safety factor of the stabilized slope is... 

Over the last several decades, there has been a notable shift toward soft engineering, nonstructural solutions, including classical methods such as drainage and modification of slope geometry, but also some novel methods such as lime/cement stabilization, grouting, or soil nailing. The cost of nonstructural remedial measures is considerably lower than the cost of structural solutions. In addition. 

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