Investigations of vertical bearing capacity of open-ended piles in cohesive soils with respect to soil-plug formation

粘性土中开口桩竖向蓄水能力与土塞形成的研究

• 批准号: 495328022
• 负责人: Professor Dr.-Ing. Sascha Henke
• 金额: --
• 依托单位: Professur für Geotechnik
• 依托单位国家: 德国
• 项目类别: Research Grants
• 资助国家: 德国
• 项目状态: 未结题
• 来源: https://gepris.dfg.de/gepris/projekt/495328022?language=en
• 关键词: Investigations; vertical; bearing; capacity; open

Soil plugging in open-ended piles until now was mainly investigated regarding installation in granular soils. In the present research project, the aim is to investigate the mechanisms of soil plug formation during the installation of open-ended piles in cohesive soils.Thus, it is planned to carry out in-site as well as centrifuge tests regarding the installation of tubular piles into cohesive soils. On the one hand, during the in-site tests a realistic stress state can be considered at the best. On the other hand, centrifuge tests are used for tests under reproducible conditions as well as well defined soil mechanical boundary conditions. Especially, centrifuge tests are well suited for model testing in geotechnical engineering as the applied stress-state realistically reproduces in-site conditions. Furthermore, during centrifuge testing it is possible to investigate a wide range of influencing parameters (e.g. consolidation state, installation method, pile diameter) regarding soil plugging tendency.The tests are evaluated regarding the internal stress development inside the open-ended piles as indicator for arching and following a soil plug formation. Out of these results, general conclusions regarding the mechanisms of soil plugging in cohesive soils with respect to the main influencing parameters are drawn.Accompanying laboratory and element tests lead to better undestanding of the investigated cohesive soils especially in context with pile shaft-soil-interaction.Besides, a feasibility study regarding the possibilities to numerically simulating the soil plugging process during installation of open-ended piles into cohesive soils is carried out. In this framework, the results of centrifuge as well as in-site testing are used to investigate possibilities and limitations of different numerical modelling approaches (CEL, DEM, SPH) regarding soil plugging during pile installation in cohesive soils. Main aim of this work package is to validate the numerical models such that they can be used in future research.Finally, all results are consolidated to develop an analytical approach for prognosis of vertical pile resistance of open-ended piles installed in cohesive soils with respect to sthe oil plugging and its main influencing parameters. Thus, an approach will be developed to predict vertical capacity of a plug in cohesive soils based on an internal effective earth pressure coefficient in the area of a possible soil plug as it was succesfully developed by the applicant during a preceding DFG-research project regarding the installation of open-ended piles in granular material.

迄今为止，开口桩的土壤堵塞主要是针对颗粒土壤中的安装进行研究。本研究项目的目的是研究在粘性土中安装开口桩过程中土塞形成的机制。因此，计划对在粘性土中安装管桩进行现场和离心试验。一方面，在现场测试过程中，最好考虑真实的应力状态。另一方面，离心机测试用于在可重复的条件以及明确的土壤机械边界条件下进行测试。特别是，离心机测试非常适合岩土工程中的模型测试，因为所施加的应力状态真实地再现了现场条件。此外，在离心机测试过程中，可以研究有关土堵塞倾向的各种影响参数（例如固结状态、安装方法、桩直径）。测试根据开口桩内部的内应力发展作为拱形和土塞形成后的指标进行评估。根据这些结果，得出了关于粘性土中土堵塞机制的主要影响参数的一般性结论。伴随的实验室和元件测试可以更好地理解所研究的粘性土，特别是在桩身与土壤相互作用的情况下。此外，还对在开口桩安装期间对土堵塞过程进行数值模拟的可能性进行了可行性研究。 进行粘性土处理。在此框架中，离心机和现场测试的结果用于研究不同数值模拟方法（CEL、DEM、SPH）在粘性土壤中打桩过程中土壤堵塞的可能性和局限性。该工作包的主要目的是验证数值模型，以便它们可用于未来的研究。最后，整合所有结果以开发一种分析方法，用于预测安装在粘性土中的开口桩的垂直桩抗力与油堵及其主要影响参数的关系。因此，将开发一种方法来基于可能的土塞区域中的内部有效土压力系数来预测粘性土中的塞的垂直能力，正如申请人在之前的关于在粒状材料中安装开口桩的DFG研究项目期间成功开发的那样。