tailieunhanh - DEVELOPMENTS IN HYDRAULIC CONDUCTIVITY RESEARCH Phần 4

Tham khảo tài liệu 'developments in hydraulic conductivity research phần 4', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 76 Developments in Hydraulic Conductivity Research the AEV. Nevertheless we infer in this chapter that for materials that are highly compressible E cap may be sufficient to keep on inducing compression for suction values greater than the AEV. Hence the shrinkage limit may be observed for suction values higher than the AEV. From the compression energy concept it can be inferred that x v may be somehow related to S r . Indeed the pore water pressure component of the effective stress x v V should null when the porous media is saturated v 0 and x 1 and also be null when it is dry y 106 kPa - the theoretical suction value that corresponds to a null water content Fredlund Xing 1994 - and x 0 .Hence the pore water pressure component of the effective stress in unsaturated state - . x v V - reaches a maximal value at a certain suction value between complete and null saturation. This behavior can be easily observed when wet and dry beach sands flows through our fingers but when the sand is partially saturated particles stick together making possible the construction of a sand castle. However not supported by a mechanistic model Bishop 1959 s approach was used by Khalili Khabbaz 1998 who proposed an exponential empirical relationship between X and ratio t yav where aev is the AEV allowing the determination of x for most soils with an equation similar to the one proposed by Brooks Corey 1964 for WRC curve fitting Kev 7 . 1 if w waev where paev is the suction at the air-entry value AEV and is an empirical parameter estimated to be equal to by Khalili Khabbaz 1998 . It is possible to force parameter X to reach a null value at 106 kPa using the function C i in Equation 10 presented after. 17. V 1-----z----X if w 8 I 1 if The optimum of compression capability by means of suction using X is coherent with Fredlund 1967 s conceptual behavior that was treated later on by Toll 1995 . The latter suggested that void ratio of a normally consolidated soil decreases as suction .