Ground improvement technique for sustainable infrastructure

用于道路、铁路轨道、管道和土坝的柔性基础通常建在软粘性土上。这些结构通常承受能力低和过度沉降，表现为道路上的天坑和基础设施的灾难性倒塌以及生命损失。对于这些类型的结构，石柱被认为是具有成本效益、环境友好、易于安装和可持续的土壤改良技术（Wood等人，2000; Hanna等人，2013年）。石柱还提供了额外的排水路径，这将加速固结过程，因此地面将抵抗地震（Sivakumar等人，2004年）。此外，当安装在松散的无粘性土壤中时，使用石柱来提高天然斜坡的稳定性并降低液化可能性（Etezad等人，2015年）。建议的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-结构相互作用。实验方面：实验室原型装置包括一个试验箱、装载架和测量装置。粘土样品将由干燥的高岭土粉末形成，与水以约60%的饱和度混合。将从罐中提取直径为100 mm的加固粘土芯样，并置于三轴装置中进行测试。根据ASTM（2004），在单元压力下进行固结不排水（CU）试验。测量装置的阅读将通过数据采集系统（DAS）定期记录，该系统将连接到个人计算机上。 数字上：将开发高保真三维数值模型，以检查控制该系统性能的参数的协同效应。建立了三个模型来模拟碎石桩在软土中的安装过程，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。第三个模型是模拟一个柔性基础上的软粘土层加固的石柱。 分析：从目前的实验和数值研究中推导出的破坏机制将被理想化，并分为软粘土和砂的切片，使柱，非圆形滑动面将使用Morgenstern-Price非圆形滑动面切片法和极限平衡技术进行分析。 该模型的结果将被用作开发设计理论的基础，以预测系统的承载能力，并推荐经济设计的柱的数量和间距。

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.