The correlation of the coefficients of Mohr-Coulomb equatoin, non-linear equation and the equation in which internal friction angle φ0 is given by function of normal stress σ are examined for compacted tuff and sand and gravel with drained triaxial compression tests. From these tests, the following results are obtained.
(1) Internal friction angle φ, internal friction angle φ1 at σ3=1.0kgf/<cm>^^^3 and basic shear strength (apparent cohesion) τ0 of Mohr-Coulomb equation are increased with increment of dry density ρd.
(2) The coefficient A of non-linear equation τ=A(σ/σ01)^b is increased with ρd and b is scatteringly distributed for ρd. Average value of b is 0.718 for sand and gravel and is 0.789 for tuff.
(3) Internal friction angle φ0 is expressed by φ0=φm-alog(σ/σ01). φm at σ=σ01=1.0kgf/<cm>^^^2 is increased with ρd and a is decreased with ρd but a is scatteringly, distributed. The average value of b is 14.4 for sand and gravel and is 14.0 for tuff.