Ground improvement technique for sustainable infrastructure

用于道路、铁路轨道、管道和土坝的柔性地基通常建在柔软的粘性土壤上。这些结构通常承受着承载能力低和过度沉降的问题，其表现形式是道路上的天坑和基础设施的灾难性倒塌和生命损失。对于这些类型的结构，石柱被认为具有成本效益，环保，易于安装和可持续的土壤改良技术（Wood et al., 2000; Hanna et al., 2013）。石柱还提供了额外的排水通道，这将加速固结过程，因此地面将抵抗地震（Sivakumar等人，2004）。此外，石柱用于改善天然边坡的稳定性，并在松散的无黏性土壤中安装时减少液化潜力（Etezad et al., 2015）。提出研究的目的是检查一组石柱上的柔性基础的性能。为了实现这些目标，将开发实验、数值和分析模型来模拟所述问题的土壤-结构-相互作用。实验：实验室原型装置由测试箱、加载架和测量装置组成。粘土样品将由干燥的高岭土粉末与约60%饱和度的水混合而成。从槽中取出直径为100mm的增强粘土芯样，置于三轴装置中进行试验。根据ASTM（2004）的规定，将在单元压力下进行固结不排水（CU）试验。测量装置的读数将由数据采集系统（DAS）定期记录，该系统将连接到个人计算机上。数值方面：将开发高保真三维数值模型来检验控制系统性能的参数的协同效应。建立了三个模型来模拟软土中石柱的安装过程，第二个模型是模拟（CU）三轴试验。从第一个模型测量的应力和变形将被用作第二个模型的输入数据。第二个模型的结果将与本实验研究的结果进行验证。第三个模型是模拟由石柱加固的软粘土层上的柔性基础。解析：将目前实验和数值研究推导出的破坏机制理想化，并将其划分为软粘土和砂片，采用非圆滑动面切片的Morgenstern-Price法和极限平衡技术对柱、非圆滑动面进行分析。该模型的结果将作为发展设计理论的基础，以预测系统的承载力，并为经济设计推荐柱的数量和间距。

Flexible foundations used for roads, railway tracks, pipelines, and earth dams are often built on soft cohesive soil. These structures usually suffer from low bearing capacity and excessive settlement, which are manifested in the form of sinkholes in roads and catastrophic collapses of the infrastructure and loss of life. Stone columns are known as cost-effective, environmentally friendly, easy to install and sustainable soil improvement technique for these types of structures (Wood et al., 2000; Hanna et al., 2013). Stone columns also provide additional drainage path, which will speed up the consolidation process, and accordingly the ground will resistance earthquakes (Sivakumar et al., 2004). Moreover, stone columns are used to improve the stability of natural slopes and to reduce liquefaction potential when installed in loose cohesionless soil (Etezad et al., 2015). The objective of the proposed research is to examine the performance of a flexible foundation overlying a group of stone columns. In order to achieve these objectives, experimental, numerical and analytical models will be developed to simulate the soil-structure-interaction of the problem stated. Experimentally: Laboratory prototype set-up consists of a testing tank, loading frame and measuring devices. The clay sample will be formed from a dry kaolin powder, mixed with water at about 60% saturation. Core samples of 100mm diameter of the reinforced clay will be extracted from the tank and placed in the triaxial set-up for testing. A consolidated undrained (CU) test will be carried out under cell pressure following ASTM, (2004). Reading of measuring devices will be recorded at a regular interval by data acquisition system (DAS), which will be attached to a personal computer. Numerically: High fidelity 3-D numerical models will be developed to examine the synergistic effect of the parameters govern the performance of this system. Three models will be developed to simulate the installation process of the stone columns in the soft soil and the second is to simulate the (CU) triaxial tests. The stresses and deformations measured from the first model will be used as an input data in the second model. The results of the second model will be validated with the results of the present experimental investigation. The third model is to simulate a flexible footing on a soft clay layer reinforced by stone columns. Analytically: The deduced failure mechanism from the present experimental and numerical investigations will be idealized and divided into slices of soft clay and sand, making the columns, a non-circular slip surface will be analyzed using Morgenstern-Price method of slice for non-circular slip surfaces, and the limit equilibrium technique. The results of this model will be used as the base to develop design theories to predict the bearing capacity of the system and to recommend on the number and spacing of the columns for economical design.