Investigations on deep vibratory compaction in sandy soils for desgin optimization and execution quality with respect to effectivity, simulation and control of the achieved soil densification

设想的项目的科学目标是通过深层振动压实方法模拟土壤改良，因此，这种类型的压实设计需要根据要达到的密度、深层振动器的功率和直径以及土壤的颗粒性质来确定地面上密实点的网格间距。所有这些参数都对致密化结果有显著影响。1136研究单位的科学方法和成果将在本项目中使用，尽管1136研究单位的主要工作集中在振动沉桩这一岩土施工过程上，并得到了广泛的处理。在这一设想的工程实践移交项目中，高循环累积模型(HCA)将用于计算深部可控震源周围松散散粒土的变形累积(体积和偏差)，其中该HCA模型优先扩展到大应变幅度(在应变振幅的几个百分比范围内)。众所周知，现有的HCA模型只能适用于每毫耳范围内的应变幅度。振动压实的数值模拟一方面将采用有限元形式的HCA模型，以确定深部可控震源周围大范围可压实区域内的变形，由此将使用用于估计变形幅度的亚塑性模型作为整个场的HCA模型的输入。对于多相介质(土壤骨架、水)的模拟，采用多材料任意拉格朗日-欧拉(MMALE)公式来描述振子与振子附近的即时流态化土壤以及流态化和压实带之间的过渡区之间的相互作用。在所提出的项目中，将进行振动压实物理模型试验作为仿真模型验证的第一步。作为进一步的验证步骤，将与负责应用程序的合作伙伴进行现场实验。这些现场测试将在工业合作伙伴选定的建筑工地上进行，以验证模拟的准确性，并验证旨在本项目范围内开发的另一个简化模型。最后，这个简化的模型应该作为一个工程模型。它应该能够指示所需的密实点之间的距离以及深度压实后可获得的最终密度，作为土壤的粒度和先前存在的体积密度的函数，以及所使用的深层振动器的功率。

The scientific target of the envisaged project is the simulation of soil improvement by the deep vibro compaction method, whereby the design of this type of compaction requires the grid spacing of the densification points on the ground surface based on the density to be achieved, on the power and the diameter of the deep vibrator and on the granulometric soil properties. All these parameters have a significant influence on the densification results. The scientific methods and results of the research unit FOR 1136 will be used within this project although the main efforts within the FOR 1136 were concentrated on the vibro-installation of piles as a geotechnical construction process, which has been treated extensively.Within this envisaged transfer project for the engineering practice, the high cyclic accumulation model (HCA) will be used for the calculation of the deformation accumulation (volumetric as well as deviatoric) of the loose granular soil around the deep vibrator, wherein the extension of this HCA model for large strain amplitudes (in the range of a few percent of strain amplitude) has priority. It is well known that the existing HCA model can only be adapted for strain amplitudes in the per mille range. The numerical simulation of vibro compaction will be conducted on the one hand with the HCA model in a finite element formulation to determine the deformations within a large compactable area around the deep vibrator, whereby the hypoplastic model for the estimation of the deformation amplitudes as input to the HCA model for the entire field will be used. For the simulation of the multiphase medium (soil skeleton, water) the Multi-Material Arbitrary Lagrangian-Eulerian (MMALE) formulation is used to describe the interaction of the vibrator with the immediate fluidized soil close to the vibrator as well as the transition area in the soil between fluidized and compacted zone.Within the proposed project physical model testing of vibro compaction will be performed as a first step of validation of the simulation model. As a further validation step field experiments with the partner responsible for the application will be performed. These field tests will be conducted on selected construction sites of the industrial partner in order to verify the accuracy of the simulation and to validate an additional simplified model, which is aimed to be developed within this project. Finally, this simplified model should serve as an engineering model. It should be able to indicate the required distance between the densification points as well as the accessible final density after the deep compaction as a function of granulometry of the soil and the pre-existing bulk density as well as the power of the used deep vibrator.