Influence of Matrices on Mechanical Properties of Miscellaneous Fillings

By using the medium-sized triaxial apparatus, the miscellaneous fill in the dump of the Jishan mining area in Nanjing was studied. Through the confining pressure tests of 100 kPa, 200 kPa and 400 kPa for miscellaneous fillings of silty clay, sand and silt with the stone content of 30%, the influence of matrixs on the mechanical properties of miscellaneous fillings was analyzed. The results showed that the (σ₁-σ₃)-ε₁ curves of miscellaneous fillings were hyperbolic and displayed a strain hardening tendency. Under the same confining pressure, when the confining pressure was low, with the change of the matrixs, the differences for deviation stress of miscellaneous fillings were very similar. When the confining pressure was high, with the change of the matrixs, the differences of deviation stress of miscellaneous fillings were significant. For the same matrix, with the increase of confining pressure, the deviation stress differences of miscellaneous fillings increased gradually, and the increase of deviation stress differences for miscellaneous fillings of silt was the largest. For the miscellaneous fillings of silty clay and silt, the volume was always in shear shrinkage. With the increase of axial strain, changes for the volume strain of miscellaneous fillings of sand were more complex. When the confining pressure was 100 kPa, the miscellaneous fillings of sand showed a shear shrinkage tendency first, and then dilatancy. When the confining pressure was 200 kPa and 400 kPa, sand was always in shear shrinkage. Based on comprehensive comparisons of strength parameters and constitutive model parameters, it indicated that the matrix was an important factor influencing the mechanical parameters of miscellaneous fillings.