Numerical Analysis of Geosynthetic-Encased Stone Columns under Laterally Loads
Out of all methods for ground improvement, stone column became more popular these days due to its simple construction and economic consideration. Installation of stone column especially in loose fine graded soil causes increasing in load bearing capacity and settlement reduction. Encased granular stone columns (EGCs) are commonly subjected to vertical load. However, they may also be subjected to significant amount of shear loading. In this study, three-dimensional finite element (FE) analyses were conducted to estimate the shear load capacity of EGCs in sandy soil. Two types of different cases, stone column and geosynthetic encased stone column were studied at different normal pressures varying from 15 kPa to 75 kPa. Also, the effect of diameter in two cases was considered. A close agreement between the experimental and numerical curves of shear stress horizontal displacement trend line is observed. The obtained result showed that, by increasing the normal pressure and diameter of stone column, higher shear strength is mobilized by soil; however, in the case of encased stone column, increasing the diameter had more dominated effect in mobilized shear strength. Keywords—Ordinary stone column, validation, encased stone column, laterally load.
Analysis of Railway Embankment Supported with Geosynthetic-Encased Stone Columns in Soft Clays: A Case Study
Construction on soft soils is a promising task, as it is necessary for engineers to overcome challenges of excess settlements and possible bearing failure. This paper deals with proposing a suitable ground improvement technique as a remedy for an already failed railway embankment and evaluating the performance of the proposed technique both in short- and long-term periods. Based on the prevailing site conditions (i.e. poor shear strength) and obligatory to complete the work within the stipulated time, it is found that geosynthetic-encased stone column (ESC) is a preferred ground improvement technique. An extensive 2D finite element analysis has been undertaken to examine the improvement in bearing capacity concurrently addressing slope stability problem for different column spacing of 1.5, 2, 2.5, 3, 3.5, and 4 m. Interpretation of results revealed that bearing capacity and stability are critical in the short-term period. The results further demonstrated that ESCs by undergoing lateral deflection and bulging, which are found to predominate in the short-term period, sustained the failure against bearing capacity and stability. The spacing of 3 m when considered bearing capacity alone and 2.5 m corresponding to lateral deflection alone is found optimal. Based on the outcome of the study, it is demonstrated that the proposed ESC is an ideal solution of ground improvement for the present case study of failed railway embankment.
Time and Heritage
As a historian studying what can be considered a form of intellectual history, I have slowly come to adopt Michel de Certeau’s observation made at the end of the 1980s that ‘objectifying the past, for the last three centuries, has undoubtedly left unconsidered time within a discipline that has continued to use it as a taxonomic instrument’. To a certain degree, time has become commonplace for the historian who has preserved or instrumentalized it. It is not considered because it is inconceivable, but because we do not think of it or, more simply, we do not think about it. As a historian attempting to pay attention to the time I’m living in, I have thus, like many others, noticed the swift development of the category of the present until it has become obvious that the present is omnipresent. This is what I refer to here as ‘presentism’.