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使用高压大型三轴仪,对某300 m级土石坝的砾质土心墙料进行了最高围压5 MPa的三轴试验。试验结果表明砾质土的应力-应变关系符合双曲线关系,抗剪强度包络线呈非线性。根据参数的物理意义,初始模量Ei应在尽可能小的应变范围内取值,最大主应力差(σ1-σ3)ult应在大应变范围内取值,且实际工程的应变在1%左右,建议在εa=0%～3%下取Ei值,在εa=5%～15%下取(σ1-σ3)ult值,数据拟合表明建议取值法比传统取值法拟合度高。由于试验的围压范围较大,提出把围压分0.2～1.0 MPa,1.5～3.0 MPa,3.5～5.0 MPa三段分别取切线模量,通过回归证明拟合较好。
A triaxial test with a maximum confining pressure of 5 MPa was performed on the gravelly core material of a 300 m earth-rock dam using a large-scale high-pressure triaxial apparatus. The test results show that the stress-strain relationship of gravelly soil conforms to the hyperbolic relationship, and the shear strength envelope is nonlinear. According to the physical meaning of the parameters, the initial modulus Ei should be as small as possible within the strain range, the maximum principal stress difference (σ1-σ3) ult should be within a large strain range, and the actual engineering strain of about 1% , It is suggested to take Ei values from 0% to 3% and take (σ1 to σ3) ult values from 5% to 15% of εa. The data fitting shows that the proposed method is better than the traditional method . Because of the large range of confining pressure, the tangential modulus of three sections with confining pressures of 0.2-1.0 MPa, 1.5-3.0 MPa and 3.5-5.0 MPa are proposed respectively, and the fitting is proved by regression.