Hydraulic uplift

Hydraulic uplift phenomena are associated with artesian conditions, that is, when water flowing under pressure through the ground is confined between two impermeable horizons (see the previous text). This can cause serious trouble in excavations, and both the position of the water table and the piezometric pressures should be determined before work commences. Otherwise, excavations that extend close to strata under artesian pressure may heave or, worse, may be severely damaged due to blow-outs taking place in the floors. Slopes also may fail. Indeed, such sites may have to be abandoned. 

The hydraulic impact shown as cones of depression and uplift around the wells. 

Another possibility for plants to influence the P cycle is the hydraulic redistribution of water. This is the redistribution of water from wet to dry soil areas via the roots, which has been suggested to have an impact on the availability of P due to better mobility of inorganic P in wet soil (Lambers et al. 2006). McCulley et al. (2004) found that the concentration of extractable P was greater at depth than in the top meter of the soil in several arid and semi-arid systems in the southwestern USA and that nutrients were uplifted from this depth. They proposed that hydraulic redistribution of water from the soil surface to depths up to 10 m by roots was the mechanism by which P and other nutrients were mobilized and could be taken up by plants. 

Regional uplift accompanying faulting in the late Carboniferous would have favoured hydraulic fracturing, and the sandstones would have been at relatively shallow burial depths (Fig. 3). This concurs both with the petrographic characteristics of intergranular dolomite cementation and with the isotopic data in terms of potential fluid sources. 

After tires are placed and fastened in designated construction area, various types of materials could be used to fill up voids in the structure for providing the required weight to overcome uplifting. Bases on laboratory direct shear strength tests and hydraulic resistance experiments [4], three types of fillings are recommended construction rubble, sand and gravel, and flowable mixture of loess, cement, and sand. 

This chapter is organized into sections on loadings, pile structures, gravity platforms, anchor uplift capacity, jack-up platforms, and hydraulic filled islands. 

Uplift pressure acts against the base of a dam and is caused by water seeping beneath it that is under hydrostatic head from the reservoir. Upiift pressure shouid be distinguished from the pore water pressure in the material beneath a dam. The uplift pressure on the heel of a dam is equal to the depth of the foundation below water level multiplied by the unit weight of the water. In the simplest case, it is assumed that the difference in hydraulic heads between the heel and the toe of the dam is dissipated uniformly between them. The uplift pressure can be reduced by allowing water to be conducted downstream by drains incorporated into the foundation and base of the dam. 

Hydraulic stability Uplift/flotation 1.5 2.0 design are high and/or consequences... 

Hydraulic stability Uplift — No FS values are specified. Investigation into uplift... 

With respect to the wave loads, it is seen that a substantial reduction of the horizontal and uplift forces is achieved, which would result in a reduction of about 50% of the required weight of the superstructure to ensure sliding stability. With respect to the hydraulic performance, it is seen that wave reflection is reduced by about 25%, and as a result of the reduction of wave overtopping the required crest level above still water level is reduced by about 40%. Even without using any splash reducer at the front and back wall of the concrete superstructure, the splash/spray heights are reduced by half. Further details on the results in Table 12.1 are given by Oumeraci and Muttray, Muttray et Oumeraci et Takahashi et Schiittrumpf et Muttray et al. and Oumeraci et al ... 

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