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以我国引进的首台低温共振柱仪为依托,研究不同负温下冻结土的初始剪切模量、剪切模量比和阻尼比非线性曲线的变化规律和模式。对低温共振柱仪试验技术进行研究,结果显示,采用常温试验方法进行低温共振柱试验,会导致结果离散过大,通过试验确定围压介质、冻结时间等试验条件和参数。同时,采用更符合客观实际的围压、固结和冻结方式,以粉土为样本,在室温和不同负温下进行对比试验。结果表明:负温对土的初始模量和剪切模量比影响显著,0℃~-4.0℃为敏感段,-4.0℃后为平稳段;敏感段内,随负温增加,初始剪切模量呈Boltzmann函数形式急速增加,参考剪应变则呈Boltzmann函数形式迅速下降,平稳段上,二者随负温增加分别平稳上升和下降;负温下阻尼比曲线在剪应变小于一定值时高于常温曲线,而在大于该应变时常温试验曲线则超过负温曲线;负温对最大阻尼比有较大影响,随负温增大,最大阻尼比呈指数形式降低。该试验采用专门的低温共振柱仪完成,围压、固结和冻结条件更接近客观实际,得到的负温对土动剪切模量阻尼比的影响模式更真实可靠,可为季冻土区抗震规范中设计谱修正以及季冻土区重大工程抗震设计中获得合理地震动输入提供依据。
Based on the first low-temperature resonance column instrument imported from China, the variation regularities and modes of initial shear modulus, shear modulus ratio and damping ratio of frozen soil under different negative temperatures were studied. The research on low temperature resonance column test technique shows that using low temperature resonance column test at room temperature will cause the results to be too large and the test conditions and parameters such as confining medium and freezing time are determined through experiments. In the meantime, comparisons with confining pressure, consolidation and freezing which are more in line with objective reality, and silt were taken as samples were carried out at room temperature and different negative temperatures. The results show that the negative temperature has a significant effect on the initial modulus and shear modulus ratio of soil, 0 ℃ ~ -4.0 ℃ as sensitive section and -4.0 ℃ as stationary section. In the sensitive section, with the increase of negative temperature, the initial shear The modulus increases rapidly with Boltzmann function, while the reference shear strain decreases rapidly in the form of Boltzmann function. On the plateau, the two increase and decrease with the increase of negative temperature respectively. At negative temperature, the damping ratio curve decreases when the shear strain is less than a certain value At normal temperature, the test curve at room temperature exceeds the negative temperature curve. Negative temperature has a significant effect on the maximum damping ratio. As the negative temperature increases, the maximum damping ratio decreases exponentially. The experiment was carried out by a special low-temperature resonance column instrument. The confining pressure, consolidation and freezing conditions were closer to the objective reality. The effect of negative temperature on the dynamic shear modulus and damping ratio was more reliable and reliable. Seismic design code revision and seismic design of major projects in quarry area to provide a reasonable ground vibration input provide the basis.