Applicability of "Full-Flow" Penetration Probes for Characterizing Soft Soil Deposits

软土沉积物，主要是由于其高敏感性、欠固结和非常低的强度，在其特性和作为工程材料的使用方面对岩土工程界提出了独特的挑战。传统的钻井和原位测试方法不能精确和可靠地量化软沉积物，这是许多岩土工程项目所需要的。虽然可以进行性能修改，但这些原位装置受其测试程序和/或几何设计的固有特性的限制，不能通过微小的改进来克服。陆上、近岸和近海软沉积物应用（如隧道、桥梁、风力涡轮机、海底斜坡稳定性、埋地管道和石油和天然气平台）的数量和复杂性不断增加，加剧了这些方法的不足。该项目专注于一个独特而重要的机会，通过利用五个现有的高度表征的国际试验场的资源，验证“全流”贯入仪表征软土沉积物的能力。“全流”贯深仪提供了一种测量压力差的方法，这种压力差是在对称几何探针周围引起土壤流动所必需的。原则上，穿透仪类似于粘度测量，因为它们在穿透过程中引起几何探针周围土壤的塑性流动。这种独特的流量测量不受现有设备精度的校正因素的限制，因此在上述应用中具有很大的潜力。迄今为止，通过分析、数值、实验室和离心机研究，已经评估了三种类型的“全流”贯入仪（t型棒、球型和板式）。从这些分析中，“全流”穿透仪显示出分别获得不排水剪切强度（su）和重塑剪切强度（su-remolded）剖面的潜力，这反过来又提供了原位灵敏度（St）的估计。通过进行“抽动”试验，一系列连续的短贯入，其中贯入速度依次减半，可以获得固结系数（cv）的原位估计。“全流量”穿透仪将以经济有效的方式在五个高度特征的测试地点进行广泛的现场调查，以全面验证，其中三个在北美，一个在挪威，一个在澳大利亚。每个地点的现场测试计划将包括进行至少13次探测，选择穿透仪的挖掘以验证流动模式，以及有限的抽样以验证现有数据的适用性。最终将验证/开发“全流量”渗透探针的解释方法和程序指南。该提案的广泛影响包括可能影响全球土壤工程实践，涉及现场调查和岸上、近岸和离岸地质系统的设计，包括上面列出的应用。使用国际试验场并与国际专家就现场试验进行合作，确保了研究成果的广泛适用性和传播。本研究结果将在PIs网站上发布，在会议上展示，并及时在期刊上发表。

Soft soil sediments, primarily due to their high sensitivity, underconsolidation and very low strength, present a unique challenge to the geotechnical community in both their characterization and use as an engineering material. Conventional drilling and in situ testing methods do not quantify soft sediments at a level of accuracy and reliability now required for many geotechnical projects. While performance modifications can be made, these in situ devices are restricted by inherent characteristics of their test procedure and/or geometric design that cannot be overcome through minor improvements. The insufficiency of these methods is compounded by steady increases in the quantity and complexity of on-shore, near-shore, and off-shore soft sediment applications such as tunnels, bridges, wind turbines, submarine slope stability, buried pipelines, and oil and gas platforms. This project is focused on a unique and important opportunity to validate the ability of "full-flow" penetrometers to characterize soft soil deposits through leveraging the resources of five existing highly characterized international test sites. "Full-flow" penetrometers provide a measure of the pressure differential necessary to induce soil flow around a symmetric geometric probe. In principal, the penetrometers are akin to a viscosity measurement as they induce plastic flow of the soil around a geometric probe during penetration. This unique flow measurement is free from the correction factors that limit the accuracy of state-of-practice devices and therefore have strong potential in the applications mentioned above. To date, three types of "full-flow" penetrometers have been evaluated (T-bar, ball, and plate) though analytical, numerical, laboratory, and centrifuge investigations. From these analyses, "full-flow" penetrometers demonstrate potential to obtain profiles of the undrained shear strength (su) and the remolded shear strength (su-remolded) respectively, which in turn provide an in situ estimate of sensitivity (St). Through performing "twitch" tests, a series of consecutive short penetrations where the penetration rate is sequentially halved, an in situ estimate of the coefficient of consolidation (cv) may be obtained. "Full-flow" penetrometers will be validated at full-scale through an extensive field investigation at five highly characterized test sites, three in North America, one in Norway, and one in Australia, in a cost-effective manner. The field testing program at each site will consist of performing a minimum of 13 soundings, selected excavation of the penetrometers to verify flow patterns, and limited sampling for validation of the applicability of existing data. This will culminate in the validation/development of interpretation methods and procedural guidelines for "full-flow" penetration probes. The broader impacts of this proposal include the potential to affect worldwide soil engineering practice with respect to site investigations and the design of geosystems on-shore, near-shore, and off-shore including the applications listed above. The use of international test sites and collaboration with international experts on in situ testing ensures broad applicability and dissemination of the research findings. The results of this research will be posted on the PIs website, presented at conferences, and published in journals in a timely manner.