Improvement of the load-deformation behavior of organic soils by means of sand compaction piles

利用压实砂桩改善有机土的荷载变形特性

基本信息

批准号：
262373812
负责人：
Professor Dr.-Ing. Frank Rackwitz
金额：
--
依托单位：
Fachgebiet Grundbau und Bodenmechanik
依托单位国家：
德国
项目类别：
Research Grants
财政年份：
2015
资助国家：
德国
起止时间：
2014-12-31 至 2022-12-31
项目状态：
已结题

来源：
https://gepris.dfg.de/gepris/projekt/262373812?language=en
关键词：
Improvement load deformation behavior organic

项目摘要

The aim of this research project is to investigate the load deformation behaviour of organic soils improved with uncased sand columns. Data available on the efficiency of organic soil improvement using compacted, uncased sand columns are currently very limited, especially on the influence of different installation methods of the sand columns. Creep, which occurs in particular in organic soils, is a time dependent process and develops over a long period of time. This behaviour has not yet been investigated and is therefore not part of any design model. The time dependent stress development after the installation of the displacement sand columns has also not been the topic of any previous investigations. Furthermore, the possibility of differential settlements between the organic soil and the sand column has also not yet satisfactorily been investigated. Based on the knowledge gained from 1g model testing as well as numerical analyses, different design approaches for these sand columns constructed by displacing the organic soil during their installation shall be developed. Testing in the laboratory will be divided into two parts. In one part the interaction between the subsoil and the sand columns will be analysed und evaluated. The behaviour of organic soils will be analysed in another part of the laboratory testing. The emphasis of these tests is to investigate the dependence of the load concentration to the cross-sectional area of the sand columns according to their spacing and their installation method. The main aim of the 1g model tests is to determine the influence of two different installation methods, namely the installation of the compacted sand columns by displacement or replacement of the organic soil. These tests on different scales shall than be compared against each other and also be used to make a judgement of the dimensions needed for a large scale prototype sand columns. The results from soil mechanical element tests are needed to gain a fundamental understanding of the soil mechanical behaviour of organic soils and to define the input parameters for the finite element analysis. These element tests shall include compression tests with restricted side deformation as well as consolidated, undrained triaxial tests. In order to investigate the behaviour of anisotropic, organic soils, a Rowe cell will be used which has to be purchased in the frame of this research project. Using this equipment, the load-deformation behaviour for different drainage and loading conditions can be accurately measured. Combining the results from all the laboratory tests, a prognosis for the deformation behaviour of prototype sand columns will be possible according to their installation method and cross-sectional area. A validation of this forecast will then be possible using the pre-defined finite element model.

该研究项目的目的是研究用无套管砂柱改良的有机土壤的荷载变形行为。目前，关于使用压实的无套管砂柱改良有机土壤的效率的数据非常有限，特别是关于砂柱不同安装方法的影响的数据。蠕变，尤其发生在有机土壤中，是一个依赖于时间的过程，并且会在很长一段时间内发展。此行为尚未经过研究，因此不属于任何设计模型的一部分。安装位移砂柱后随时间变化的应力发展也不是以前任何研究的主题。此外，有机土和沙柱之间差异沉降的可能性也尚未得到令人满意的研究。基于 1g 模型测试和数值分析获得的知识，应开发这些在安装过程中通过置换有机土壤建造的沙柱的不同设计方法。实验室的测试将分为两个部分。其中一部分将分析和评估底土和沙柱之间的相互作用。有机土壤的行为将在实验室测试的另一部分进行分析。这些试验的重点是根据砂柱的间距和安装方法，研究荷载集中对砂柱横截面积的依赖性。 1g模型试验的主要目的是确定两种不同安装方法的影响，即通过移动或更换有机土来安装压实砂柱。这些不同规模的试验应相互比较，并用于判断大型原型砂柱所需的尺寸。需要土壤力学元素测试的结果来基本了解有机土壤的土壤力学行为并定义有限元分析的输入参数。这些元件试验应包括限制侧面变形的压缩试验以及固结、不排水三轴试验。为了研究各向异性有机土壤的行为，将使用 Rowe 池，该池必须在本研究项目的框架内购买。使用该设备，可以准确测量不同排水和负载条件下的负载变形行为。结合所有实验室测试的结果，可以根据其安装方法和横截面积对原型砂柱的变形行为进行预测。然后可以使用预定义的有限元模型验证该预测。