上海黏性土的初始剪切模量试验研究

以上海天然沉积黏性土②~⑥层土为研究对象,利用共振柱仪器实现了各土层在不同固结压力下的弯曲元和共振柱试验,得到了各层土体小应变水平下的初始剪切模量。试验结果表明,利用弯曲元试验时域初达波法和时域峰值法能得到与现场单孔波速原位测试结果相一致的剪切波速;共振柱试验得到的土体小应变初始剪切模量与弯曲元试验结果基本一致。分析表明,在所试验的各层土中,第③层淤泥质粉质黏土和第④层淤泥质黏土的剪切模量相对较小,第⑥层土的剪切模量最大;第②、⑤层土的剪切模量接近,且大于③、④层,小于第⑥层土,这与土样的实际天然状态是相吻合的。利用Rampello公式可较好地拟合上海黏性土的初始剪切模量,所得的拟合曲线可用来确定各土层在不同深度处的初始剪切模量。

Laboratory Research on Initial Shear Modulus of Shanghai Cohesive Soil

A series of laboratory tests of natural Shanghai cohesive soils (layers ② ～ ⑥) were carried out by resonant column apparatus equipped with bender elements.The initial shear modulus of all the tested soil were obtained by the experiments.The start-to-start travel time and peak-to-peak travel time approaches in time domain were employed to calculate the shear wave velocities in bender element tests,and the results were consistent with those obtained from down hole velocity in-situ tests.The initial shear modulus obtained by the resonant column is consistent with that obtained from bender elements.Data analysis shows that the initial shear modulus of layer ③ and layer ④ are relatively smaller.The initial shear modulus of layer ⑥ is the largest among the tested soil.The initial shear modulus of layer ② and layer ⑤ is larger than those of layers ③ and ④ but smaller than that of layer ⑥.Relationship of the initial modulus of the tested soils is consistent with the soil natural state.The Rampello empirical expression was also proposed for practical use in estimating soil initial small strain stiffness.