|Budget Amount *help
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2003: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2002: ¥700,000 (Direct Cost: ¥700,000)
Fiscal Year 2001: ¥2,100,000 (Direct Cost: ¥2,100,000)
The objective of this study is to establish a way of assessing shear strength characteristics of those soils to which current theories of soil mechanics would not be applied without difficulty. Those soils are characterized by that their stress histories are not known and that specimens will be difficult to prepare under specified conditions.
As representatives, of such soils, two volcanic soils, Daisen Matsue pumice (DMP) and Daisen Kurayoshi pumice (DKP), from Mt.Daisen in Tottor Prefecture, were studied. Triaxial and direct shear box tests were conducted on their undisturbed samples. In some direct shear box tests, the suction was measured, in the stage of consolidation prior to shearing, to examine the effects of suction on the shear strength.
Main conclusions are as follows :
(1)The interrelationship between shear strength, normal stress and void ratio are similar to those of sedimentary cohesive soils when the normal stress during shear is higher than the consolidation yield stress.
Using the interrelationship as a reference, the characteristics in shear tinder the normal stress lower than the consolidation yield stress were assessed. Results showed that, under the normal stress lower than the consolidation yield stress, the shear strength would possibly be higher than the reference value even with the void ratio higher than the reference value.
(2)Monotonous curves of particle size distribution might not be resulted in for soils without uniform water content, like samples used in this study. This problem was fixed by employing the method in which sieving was done in water and the total dry mass of sample was determined by direct measurement.
(3)The suction will decrease as the applied normal stress increases and will be null under the normal stress over the consolidation yield stress. Under an identical value of the normal stress, the shear strength can uniquely be related to the suction that specimens possess before the shearing. This indicates that the suction is an important factor controlling the shear strength. It will be crucial to consider the suction especially when the normal stress is lower than the consolidation yield stress. Less