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为西昌昔格达组地层场地地震安全性评价提供基础性数据,对西昌经久乡昔格达组粉砂岩进行了一系列动三轴试验。研究结果表明:西昌昔格达组粉砂岩在一定条件下(σ3c=100、200、400kPa,kc=1.0、1.5、2.0)的骨干曲线符合幂函数模型;动剪应力随着固结围压σ3c或固结主压力比kc增大而增大;在偏压状态下产生相同动剪应变所需要的动剪应力比均压状态所需要的动剪应力大。不同固结应力条件下,动剪切模量随固结压力或固结主压力比增大而增大,随动剪应变增加而减小并趋于稳定;最大动剪切模量Gd0与σ3c/Pa、kc均有良好的幂函数关系。阻尼比随动剪应变增大而增大,但增大幅值随动剪应变增大而迅速减小;阻尼比随围压或固结主压力比增大而减小;不同固结应力条件下(λ/λmax)与(1-Gd/Gd0)有良好的幂函数关系并可归一化处理。西昌昔格达组饱和粉砂岩的动剪应力τd随固结围压σ3c或固结主压力比kc增大而增大,随振动次数增加而减小;τd/σm随固结围压σ3c增大而减小,随固结主压力比kc增大而增大;动剪应力τd与平均压力σm、固结主压力比kc有较好的线性关系。
This study provides basic data for the seismic safety assessment of the Xigeda Formation formation in Xichang. A series of dynamic triaxial tests were carried out on the Xigeda siltstone in the Jingjiageng Xichang. The results show that the backbone curve of the Xigeda siltstone in Xichang meets the power function model under certain conditions (σ3c = 100,200,400kPa, kc = 1.0,1.5,2.0). The dynamic shear stress increases with the consolidation confining pressure σ3c Or the consolidated main pressure ratio kc increases and increases; the dynamic shear stress required to generate the same dynamic shear strain under bias is larger than the dynamic shear stress required under the pressure equalization. Under different consolidation stress, the dynamic shear modulus increases with the consolidation pressure or consolidation main pressure ratio, decreases with the increase of dynamic shear strain and tends to be stable. The maximum dynamic shear modulus Gd0 and σ3c / Pa, kc have a good power function relationship. The damping ratio increases with the increase of dynamic shear strain, but the increase amplitude decreases rapidly with the increase of dynamic shear strain. The damping ratio decreases with the increase of confining pressure or consolidation main pressure ratio. Under different consolidation stress (λ / λmax) has a good power function relationship with (1-Gd / Gd0) and can be normalized. The dynamic shear stress τd of the Xigeda saturated siltstone in Xichang increases with the consolidation confining pressure σ3c or consolidation main pressure ratio kc and decreases with the increase of the vibration frequency. Τd / σm increases with the consolidation confining pressure σ3c Large and decreased, with the consolidation of the main pressure ratio kc increases and increases; dynamic shear stress τd and average pressure σm, consolidation of the main pressure ratio kc has a good linear relationship.