洱海泥炭质土动剪切模量和阻尼比试验研究

为探究洱海地域泥炭质土动力学特性,利用GDS动三轴仪对重塑土样进行循环加载试验,得到了一系列围压、固结比、频率控制条件下的泥炭质土动应力-应变关系曲线,分析了不同围压、固结比、频率对土体动剪切模量G_d、动剪切模量比G_d/G_dmax和阻尼比λ的影响规律。结果表明:动剪切模量G_d随剪应变γ_d增大而减小,γ_d较小时,衰减速率较小,随着γ_d继续增大,衰减速率先增大后减小;在同一剪应变下,G_d随围压、固结比增大而增大,G_d对频率变化表现不敏感;采用Hardin-Drnevich双曲线模型(H-D模型)对重塑泥炭质土动应力-应变曲线拟合效果较好,动剪切模量比G_d/G_dmax随剪应变γ_d增大而减小,围压、固结比和频率对G_d/G_dmax的衰减规律无明显的倾向性;阻尼比λ随剪应变γ_d增大而增大,围压对λ变化规律影响较复杂,γ_d较小时,λ随围压增大而减小,γ_d较大时,λ随围压增大而增大;固结比越大,λ越大,频率越大,λ越小,λ对频率变化表现更敏感,体现了循环加载下泥炭质土的速率效应。

Experimental Study on Dynamic Shear Modulus and Damping Ratio of Remoulded Peaty Soil in the Region of Erhai Lake

To explore the dynamic characteristics of peaty soil in the region of Erhai lake, cyclic loading test was conducted for remoulded sample via GDS triaxial shear equipment, and the dynamic stress-strain relation curve of peaty soil under a series of controlling conditions of confining pressure, concretion ratio and frequency was obtained, which is used to analyze the impact rules of different confining pressures, concretion ratios and frequencies on dynamic shear modulus of soil mass G_d, dynamic shear modulus ratio G_d/G_dmax and damping ratio λ. The result shows that the dynamic shear modulus G_d decreases along with the increasing of shearing strain, when γ_d was relatively small, decay rate was relatively small. And along with continuous increasing of γ_d, the decay rate increases after decreases; under the same shearing strain, G_d increases with the increase in confining pressure and concretion ratio, and G_d is not sensitive to the frequency variation performance; adopting Hardin-Drnevich double-curve model (H-D model) is of good imitative effect for dynamic stress-strain relation curve of remoulded peaty soil, and the dynamic shear modulus ratio G_d/G_dmax decreases with the increase of shearing strain γ_d, while confining pressure, concretion ratio and frequency are of not significant tendency for the attenuation laws of G_d/G_dmax; the damping ratio increases with the increase of shearing strain γ_d, and the confining pressure has complex influence on change laws of λ, when γ_d is relatively small, λ decreases with the increase in confining pressure, and when γ_d is relatively large, λ increases with the increase in confining pressure; the larger of concretion ratio, the larger of λ, the larger of frequency, and the smaller of λ, λ is more sensitive to the frequency change, which reflectes the rate effect of peaty soil under cyclic loading.