To date, investigations of soils in Shanghai have mainly focused on upper clays, namely, Layer 2–6, generally within 30–40 m depth. Knowledge of the deep clays of Layer 8 and 10, at depths of approximately 50 m and 100 m, respectively, is very limited. In this study, the detailed geotechnical properties of the deep Shanghai clays of these two layers were investigated through a series of field and laboratory tests. Physical property tests showed that both clays can be classified as low-plasticity silty clay. For the first time in Shanghai, high-quality intact clay samples were retrieved from the deep soil using a double-tube rotary sampler. High-pressure oedometer tests and consolidated undrained (CU) triaxial tests were conducted to evaluate the compressibility and shear strength of intact samples. The oedometer tests indicate that Layer 8 is an overconsolidated clay with an overconsolidation ratio (OCR) of 2–3, and Layer 10 is a normally consolidated clay with a light degree of structure. CU triaxial tests further confirmed the above findings. The compressibility of the Layer 8 clay is lower, and its undrained shear strength and effective friction angle are larger than those of Layer 10, with the latter being deeper. The sensitivity framework, based on Burland's intrinsic compression line (ICL) and sedimentary compression line (SCL), can be used to characterize the overconsolidation/structure nature of the deep Shanghai clays. The strain energy method was found to be more suitable than the Casagrande method for determining the preconsolidation pressure of the deep Shanghai clays.

迄今为止，上海的土壤调查主要集中在上层粘土，即第2-6层，一般在30-40米深度范围内。对深度分别约为 50 m 和 100 m 的第 8 层和第 10 层深层粘土的了解非常有限。在这项研究中，通过一系列现场和实验室测试，研究了这两层深部上海粘土的详细岩土特性。物性试验表明，这两种粘土都属于低塑性粉质粘土。在上海，首次使用双管旋转取样器从深层土壤中采集到高质量的完整粘土样品。进行了高压固结试验和固结不排水 (CU) 三轴试验，以评估完整样品的可压缩性和剪切强度。固结仪测试表明，第 8 层为超固结比（OCR）为 2-3 的超固结粘土，第 10 层为结构较轻的正常固结粘土。CU 三轴试验进一步证实了上述发现。8层粘土的压缩性较低，其不排水剪切强度和有效摩擦角大于10层，后者更深。基于 Burland 的固有压缩线 (ICL) 和沉积压缩线 (SCL) 的敏感性框架可用于表征上海深部粘土的超固结/结构性质。发现应变能法比卡萨格兰德法更适用于确定上海深部粘土的预固结压力。