The structure of the sedimentary clay influences its mechanical behavior in non-negligible ways. This paper proposes an effective approach for investigating the in-situ stiffness characteristics from shear modulus and strain decay curves (G–γ curves) based on self-boring pressuremeter and seismic dilatometer tests. To evaluate the excavation disturbance effects on the structured clay, the stiffness parameters from pre-bored pressuremeter tests are compared with the results of self-boring pressuremeter tests. The result indicates that the complete in-situ G–γ curves can be acquired by integrating the strain-dependent tangent shear modulus G_t from self-boring pressuremeter tests and the small-strain modulus G₀ from seismic dilatometer tests. Simultaneous observations of the G–γ curves with hyperbolic shapes in semi-logarithmic coordinates at the same strain scale show the similarity of the stiffness decay mode of the soil at different depths. The increase in the measured values of G_t and G₀ with depth can be attributed to the improved consolidation pressures and cemented strength in the structured clay. Additionally, the G/G₀–γ curves measured by the in-situ tests generally agree well with the results predicted by the Stokoe model. The excavation disturbance weakens the stiffness of the structured clay, as evidenced by G_t from the pre-bored pressuremeter data being significantly smaller than that from self-boring pressuremeter tests at the same depth. Based on quantitative analysis, the disturbance degree computed from the measured results has a low sensitivity to the soil depth and a strong negative correlation with the strain level of the soil. This study provides an effective method for predicting the stiffness parameters of structured soil based on in-situ tests.

沉积粘土的结构以不可忽略的方式影响其力学行为。本文提出了一种基于自钻压力计和地震膨胀计试验从剪切模量和应变衰减曲线（ G - γ曲线）研究原位刚度特性的有效方法。为了评估开挖扰动对结构化粘土的影响，将预钻孔压力计测试的刚度参数与自钻孔压力计测试的结果进行了比较。结果表明，通过对应变相关的切向剪切模量G _t积分可以获得完整的原位G - γ曲线。自钻孔压力计测试和地震膨胀计测试的小应变模量G ₀。同时观测同一应变尺度下半对数坐标中双曲线形状的G - γ曲线表明不同深度土壤刚度衰减模式的相似性。G _t和G ₀测量值随深度的增加可归因于结构粘土中固结压力和胶结强度的提高。此外，G/ G ₀ – γ现场测试测得的曲线与 Stokoe 模型预测的结果大体一致。开挖扰动削弱了结构化粘土的刚度，预钻孔压力计数据的G _t明显小于相同深度的自钻孔压力计测试数据。基于定量分析，由实测结果计算出的扰动程度对土壤深度的敏感性较低，与土壤的应变水平呈强负相关。该研究为基于原位试验的结构土刚度参数预测提供了一种有效的方法。